From f28892cb16d2f12f84278bd8f829f20dc51219b2 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sat, 28 Mar 2026 22:15:00 -0400
Subject: [PATCH 01/21] WIP

---
 Cargo.toml                                    |  9 +++-
 .../compressed_image_saver.md                 | 14 ++++++
 .../release-notes/compressed_image_saver.md   | 19 ++++++++
 crates/bevy_image/Cargo.toml                  |  8 +++-
 .../bevy_image/src/compressed_image_saver.rs  | 46 ++++++++++++++++++-
 crates/bevy_image/src/image.rs                | 22 ++++-----
 crates/bevy_image/src/lib.rs                  | 10 +++-
 crates/bevy_internal/Cargo.toml               |  7 ++-
 docs/cargo_features.md                        |  3 +-
 9 files changed, 116 insertions(+), 22 deletions(-)
 create mode 100644 _release-content/migration-guides/compressed_image_saver.md
 create mode 100644 _release-content/release-notes/compressed_image_saver.md

diff --git a/Cargo.toml b/Cargo.toml
index d3e301b23f43d..8b082adadeb07 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -431,8 +431,13 @@ trace = ["bevy_internal/trace", "dep:tracing"]
 # Basis Universal compressed texture support
 basis-universal = ["bevy_internal/basis-universal"]
 
-# Enables compressed KTX2 UASTC texture output on the asset processor
-compressed_image_saver = ["bevy_internal/compressed_image_saver"]
+# Texture compression asset processor (for web)
+compressed_image_saver_web = ["bevy_internal/compressed_image_saver_web"]
+
+# Texture compression asset processor (for desktop)
+compressed_image_saver_desktop = [
+  "bevy_internal/compressed_image_saver_desktop",
+]
 
 # BMP image format support
 bmp = ["bevy_internal/bmp"]
diff --git a/_release-content/migration-guides/compressed_image_saver.md b/_release-content/migration-guides/compressed_image_saver.md
new file mode 100644
index 0000000000000..c15a30710e1f7
--- /dev/null
+++ b/_release-content/migration-guides/compressed_image_saver.md
@@ -0,0 +1,14 @@
+---
+title: Feature that broke
+pull_requests: [14791, 15458, 15269]
+---
+
+Copy the contents of this file into a new file in `./migration-guides`, update the metadata, and add migration guide content here.
+
+Remember, your aim is to communicate:
+
+- What has changed since the last release?
+- Why did we make this breaking change?
+- How can users migrate their existing code?
+
+For more specifics about style and content, see the [instructions](./migration_guides.md).
diff --git a/_release-content/release-notes/compressed_image_saver.md b/_release-content/release-notes/compressed_image_saver.md
new file mode 100644
index 0000000000000..0a4110a5cb015
--- /dev/null
+++ b/_release-content/release-notes/compressed_image_saver.md
@@ -0,0 +1,19 @@
+---
+title: Feature name
+authors: ["@FerrisTheCrab", "@BirdObsessed"]
+pull_requests: [14791, 15458, 15269]
+---
+
+Copy the contents of this file into `./release-notes`, update the metadata, and add release note content here.
+
+## Goals
+
+Answer the following:
+
+- What has been changed or added?
+- Why is this a big deal for users?
+- How can they use it?
+
+## Style Guide
+
+You may use markdown headings levels two and three, and must not start with a heading. Prose is appreciated, but bullet points are acceptable. Copying the introduction from your PR is often a good place to start.
diff --git a/crates/bevy_image/Cargo.toml b/crates/bevy_image/Cargo.toml
index f45a92afee3db..0bf3ac5278932 100644
--- a/crates/bevy_image/Cargo.toml
+++ b/crates/bevy_image/Cargo.toml
@@ -45,8 +45,11 @@ zstd_rust = ["zstd", "dep:ruzstd"]
 # Binding to zstd C implementation (faster)
 zstd_c = ["zstd", "dep:zstd"]
 
-# Enables compressed KTX2 UASTC texture output on the asset processor
-compressed_image_saver = ["basis-universal"]
+# Texture compression asset processor (for web)
+compressed_image_saver_web = ["basis-universal"]
+
+# Texture compression asset processor (for desktop)
+compressed_image_saver_desktop = ["dep:ctt", "ktx2"]
 
 [dependencies]
 # bevy
@@ -88,6 +91,7 @@ ruzstd = { version = "0.8.0", optional = true }
 basis-universal = { version = "0.3.0", optional = true }
 tracing = { version = "0.1", default-features = false, features = ["std"] }
 half = { version = "2.4.1" }
+ctt = { version = "0.1", optional = true }
 
 [dev-dependencies]
 bevy_ecs = { path = "../bevy_ecs", version = "0.19.0-dev" }
diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 6b6348a1a3c30..5b658585bdd30 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -8,11 +8,17 @@ use bevy_reflect::TypePath;
 use futures_lite::AsyncWriteExt;
 use thiserror::Error;
 
-/// An [`AssetSaver`] that writes compressed basis universal (.ktx2) files.
+/// An [`AssetSaver`] for [`Image`] that compresses texture files.
+///
+/// Compressed textures both take up less space on disk, and use less VRAM.
+///
+/// TODO: Document what platforms are supported, how feature flags work,
+/// required native dependencies (https://github.com/cwfitzgerald/ctt?tab=readme-ov-file#prerequisites),
+/// and what compression types exist
 #[derive(TypePath)]
 pub struct CompressedImageSaver;
 
-/// Errors encountered when writing compressed images.
+/// Errors encountered when writing compressed images via [`CompressedImageSaverError`].
 #[non_exhaustive]
 #[derive(Debug, Error, TypePath)]
 pub enum CompressedImageSaverError {
@@ -31,6 +37,42 @@ impl AssetSaver for CompressedImageSaver {
     type OutputLoader = ImageLoader;
     type Error = CompressedImageSaverError;
 
+    #[cfg(feature = "compressed_image_saver_desktop")]
+    async fn save(
+        &self,
+        writer: &mut bevy_asset::io::Writer,
+        image: SavedAsset<'_, '_, Self::Asset>,
+        _settings: &Self::Settings,
+        _asset_path: AssetPath<'_>,
+    ) -> Result<ImageLoaderSettings, Self::Error> {
+        let is_srgb = image.texture_descriptor.format.is_srgb();
+
+        let config = ctt::config::CompressConfig {
+            format: todo!(),
+            output_format: ctt::config::OutputFormat::Ktx2,
+            swizzle: None,
+            color_space: if is_srgb {
+                ctt::format::ColorSpace::Srgb
+            } else {
+                ctt::format::ColorSpace::Linear
+            },
+            encode_settings: None,
+        };
+
+        let compressed_bytes = ctt::pipeline::run(&config, todo!())?;
+        writer.write_all(&compressed_bytes).await?;
+
+        Ok(ImageLoaderSettings {
+            format: ImageFormatSetting::Format(ImageFormat::Ktx2),
+            is_srgb,
+            sampler: image.sampler.clone(),
+            asset_usage: image.asset_usage,
+            texture_format: None,
+            array_layout: None,
+        })
+    }
+
+    #[cfg(feature = "compressed_image_saver_web")]
     async fn save(
         &self,
         writer: &mut bevy_asset::io::Writer,
diff --git a/crates/bevy_image/src/image.rs b/crates/bevy_image/src/image.rs
index 456c61406f2b0..149b502a51dd1 100644
--- a/crates/bevy_image/src/image.rs
+++ b/crates/bevy_image/src/image.rs
@@ -219,21 +219,21 @@ impl Plugin for ImagePlugin {
             .insert(&TRANSPARENT_IMAGE_HANDLE, Image::transparent())
             .unwrap();
 
-        #[cfg(feature = "compressed_image_saver")]
+        #[cfg(any(
+            feature = "compressed_image_saver_desktop",
+            feature = "compressed_image_saver_web"
+        ))]
         if let Some(processor) = app
             .world()
             .get_resource::<bevy_asset::processor::AssetProcessor>()
         {
-            processor.register_processor::<bevy_asset::processor::LoadTransformAndSave<
-                ImageLoader,
-                bevy_asset::transformer::IdentityAssetTransformer<Image>,
-                crate::CompressedImageSaver,
-            >>(crate::CompressedImageSaver.into());
-            processor.set_default_processor::<bevy_asset::processor::LoadTransformAndSave<
-                ImageLoader,
-                bevy_asset::transformer::IdentityAssetTransformer<Image>,
-                crate::CompressedImageSaver,
-            >>("png");
+            for file_extension in ["png", "jpeg", "jpg"] {
+                processor.set_default_processor::<bevy_asset::processor::LoadTransformAndSave<
+                    ImageLoader,
+                    bevy_asset::transformer::IdentityAssetTransformer<Image>,
+                    crate::CompressedImageSaver,
+                >>(file_extension);
+            }
         }
 
         app.preregister_asset_loader::<ImageLoader>(ImageLoader::SUPPORTED_FILE_EXTENSIONS);
diff --git a/crates/bevy_image/src/lib.rs b/crates/bevy_image/src/lib.rs
index 8f47a238a852b..32d13b1917825 100644
--- a/crates/bevy_image/src/lib.rs
+++ b/crates/bevy_image/src/lib.rs
@@ -24,7 +24,10 @@ mod serialized_image;
 pub use self::serialized_image::*;
 #[cfg(feature = "basis-universal")]
 mod basis;
-#[cfg(feature = "compressed_image_saver")]
+#[cfg(any(
+    feature = "compressed_image_saver_desktop",
+    feature = "compressed_image_saver_web"
+))]
 mod compressed_image_saver;
 #[cfg(feature = "dds")]
 mod dds;
@@ -40,7 +43,10 @@ mod saver;
 mod texture_atlas;
 mod texture_atlas_builder;
 
-#[cfg(feature = "compressed_image_saver")]
+#[cfg(any(
+    feature = "compressed_image_saver_desktop",
+    feature = "compressed_image_saver_web"
+))]
 pub use compressed_image_saver::*;
 #[cfg(feature = "dds")]
 pub use dds::*;
diff --git a/crates/bevy_internal/Cargo.toml b/crates/bevy_internal/Cargo.toml
index a4f5c3d13d883..e11bbcb2bdcdd 100644
--- a/crates/bevy_internal/Cargo.toml
+++ b/crates/bevy_internal/Cargo.toml
@@ -29,8 +29,11 @@ detailed_trace = ["bevy_ecs/detailed_trace", "bevy_render?/detailed_trace"]
 
 sysinfo_plugin = ["bevy_diagnostic/sysinfo_plugin"]
 
-# Enables compressed KTX2 UASTC texture output on the asset processor
-compressed_image_saver = ["bevy_image/compressed_image_saver"]
+# Texture compression asset processor (for web)
+compressed_image_saver_web = ["bevy_image/compressed_image_saver_web"]
+
+# Texture compression asset processor (for desktop)
+compressed_image_saver_desktop = ["bevy_image/compressed_image_saver_desktop"]
 
 # For ktx2 supercompression
 zlib = ["bevy_image/zlib"]
diff --git a/docs/cargo_features.md b/docs/cargo_features.md
index 30b19f33a1ef2..1486b03c27f9e 100644
--- a/docs/cargo_features.md
+++ b/docs/cargo_features.md
@@ -110,7 +110,8 @@ This is the complete `bevy` cargo feature list, without "profiles" or "collectio
 |bevy_winit|winit window and input backend|
 |bluenoise_texture|Include spatio-temporal blue noise KTX2 file used by generated environment maps, Solari and atmosphere|
 |bmp|BMP image format support|
-|compressed_image_saver|Enables compressed KTX2 UASTC texture output on the asset processor|
+|compressed_image_saver_desktop|Texture compression asset processor (for desktop)|
+|compressed_image_saver_web|Texture compression asset processor (for web)|
 |critical-section|`critical-section` provides the building blocks for synchronization primitives on all platforms, including `no_std`.|
 |custom_cursor|Enable winit custom cursor support|
 |dds|DDS compressed texture support|

From 18cfdbb7317c30fbb38903a70756b725bfc5bb9e Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sat, 28 Mar 2026 22:15:30 -0400
Subject: [PATCH 02/21] add todo

---
 crates/bevy_image/src/compressed_image_saver.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 5b658585bdd30..3a5b22b1e63ab 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -14,7 +14,7 @@ use thiserror::Error;
 ///
 /// TODO: Document what platforms are supported, how feature flags work,
 /// required native dependencies (https://github.com/cwfitzgerald/ctt?tab=readme-ov-file#prerequisites),
-/// and what compression types exist
+/// what compression types exist, and mipmap generation?
 #[derive(TypePath)]
 pub struct CompressedImageSaver;
 

From ef98abdeadae2351b0fdf4984c098b0a25449eea Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sat, 28 Mar 2026 22:57:05 -0400
Subject: [PATCH 03/21] WIP

---
 crates/bevy_image/src/compressed_image_saver.rs | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 3a5b22b1e63ab..f52233ca275e5 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -18,13 +18,16 @@ use thiserror::Error;
 #[derive(TypePath)]
 pub struct CompressedImageSaver;
 
-/// Errors encountered when writing compressed images via [`CompressedImageSaverError`].
+/// Errors encountered when writing compressed images via [`CompressedImageSaver`].
 #[non_exhaustive]
 #[derive(Debug, Error, TypePath)]
 pub enum CompressedImageSaverError {
     /// I/O error.
     #[error(transparent)]
     Io(#[from] std::io::Error),
+    /// The underlying compression library returned an error.
+    #[error(transparent)]
+    CompressionFailed(Box<dyn std::error::Error + Send + Sync>),
     /// Attempted to save an image with uninitialized data.
     #[error("Cannot compress an uninitialized image")]
     UninitializedImage,
@@ -47,6 +50,11 @@ impl AssetSaver for CompressedImageSaver {
     ) -> Result<ImageLoaderSettings, Self::Error> {
         let is_srgb = image.texture_descriptor.format.is_srgb();
 
+        let layout = ctt::image::ImageLayout {
+            layers: todo!(),
+            is_cubemap: todo!(),
+        };
+
         let config = ctt::config::CompressConfig {
             format: todo!(),
             output_format: ctt::config::OutputFormat::Ktx2,
@@ -59,7 +67,10 @@ impl AssetSaver for CompressedImageSaver {
             encode_settings: None,
         };
 
-        let compressed_bytes = ctt::pipeline::run(&config, todo!())?;
+        let compressed_bytes = ctt::pipeline::run(&config, layout)
+            .await
+            .map_err(|e| CompressedImageSaver::CompressionFailed(Box::new(e)))?;
+
         writer.write_all(&compressed_bytes).await?;
 
         Ok(ImageLoaderSettings {

From ad31db5acf5b74d8a940fc4be2a42ff49b9b8355 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sat, 28 Mar 2026 23:00:32 -0400
Subject: [PATCH 04/21] Disable selector RDO for linear, based on
 tune_for_normal_maps

---
 crates/bevy_image/src/compressed_image_saver.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index f52233ca275e5..00ef912e35fb8 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -100,6 +100,7 @@ impl AssetSaver for CompressedImageSaver {
             let color_space = if is_srgb {
                 basis_universal::ColorSpace::Srgb
             } else {
+                compressor_params.set_no_selector_rdo(true);
                 basis_universal::ColorSpace::Linear
             };
             compressor_params.set_color_space(color_space);

From a0d83131e7b0d53d49ff193b9b8b5d8b0b4ef57a Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 29 Mar 2026 10:35:29 -0400
Subject: [PATCH 05/21] WIP

---
 .../bevy_image/src/compressed_image_saver.rs  | 34 +++++++++++++++----
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 00ef912e35fb8..0850c8e7b9e0e 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -48,13 +48,33 @@ impl AssetSaver for CompressedImageSaver {
         _settings: &Self::Settings,
         _asset_path: AssetPath<'_>,
     ) -> Result<ImageLoaderSettings, Self::Error> {
-        let is_srgb = image.texture_descriptor.format.is_srgb();
-
-        let layout = ctt::image::ImageLayout {
-            layers: todo!(),
-            is_cubemap: todo!(),
+        let Some(ref data) = image.data else {
+            return Err(CompressedImageSaverError::UninitializedImage);
         };
 
+        let is_srgb = image.texture_descriptor.format.is_srgb();
+        let is_cubemap = matches!(
+            image.texture_view_descriptor,
+            Some(wgpu_types::TextureViewDescriptor {
+                dimension: Some(wgpu_types::TextureViewDimension::Cube),
+                ..
+            })
+        );
+
+        let layers = (0..image.texture_descriptor.array_layer_count())
+            .into_iter()
+            .map(|layer| {
+                vec![ctt::image::RawImage {
+                    data: todo!(),
+                    width: image.width(),
+                    height: image.height(),
+                    stride: todo!(),
+                    pixel_format: todo!(),
+                }];
+            })
+            .collect();
+        let layout = ctt::image::ImageLayout { layers, is_cubemap };
+
         let config = ctt::config::CompressConfig {
             format: todo!(),
             output_format: ctt::config::OutputFormat::Ktx2,
@@ -122,7 +142,9 @@ impl AssetSaver for CompressedImageSaver {
             // library bindings note that invalid params might produce undefined behavior.
             unsafe {
                 compressor.init(&compressor_params);
-                compressor.process().unwrap();
+                compressor
+                    .process()
+                    .map_err(|e| CompressedImageSaver::CompressionFailed(Box::new(e)))?;
             }
             compressor.basis_file().to_vec()
         };

From 23f25b2b8e0e7b3d97d34ae2f51b6c077cbe617f Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 29 Mar 2026 10:37:03 -0400
Subject: [PATCH 06/21] Misc

---
 crates/bevy_image/src/compressed_image_saver.rs | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 0850c8e7b9e0e..4cff61cb261ad 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -53,6 +53,12 @@ impl AssetSaver for CompressedImageSaver {
         };
 
         let is_srgb = image.texture_descriptor.format.is_srgb();
+        let color_space = if is_srgb {
+            ctt::format::ColorSpace::Srgb
+        } else {
+            ctt::format::ColorSpace::Linear
+        };
+
         let is_cubemap = matches!(
             image.texture_view_descriptor,
             Some(wgpu_types::TextureViewDescriptor {
@@ -79,11 +85,7 @@ impl AssetSaver for CompressedImageSaver {
             format: todo!(),
             output_format: ctt::config::OutputFormat::Ktx2,
             swizzle: None,
-            color_space: if is_srgb {
-                ctt::format::ColorSpace::Srgb
-            } else {
-                ctt::format::ColorSpace::Linear
-            },
+            color_space,
             encode_settings: None,
         };
 

From bd2ed87e7fccc6dda108fe511043409e6f2ceb1f Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 29 Mar 2026 10:37:53 -0400
Subject: [PATCH 07/21] WIP

---
 crates/bevy_image/src/compressed_image_saver.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 4cff61cb261ad..b3a8cc7e62be1 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -75,7 +75,11 @@ impl AssetSaver for CompressedImageSaver {
                     width: image.width(),
                     height: image.height(),
                     stride: todo!(),
-                    pixel_format: todo!(),
+                    pixel_format: ctt::format::PixelFormat {
+                        components: todo!(),
+                        channel_type: todo!(),
+                        color_space,
+                    },
                 }];
             })
             .collect();

From fa171ae6ef3b1b04054f1dfd23f744e8debd31f0 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 29 Mar 2026 10:40:57 -0400
Subject: [PATCH 08/21] Assert

---
 crates/bevy_image/src/compressed_image_saver.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index b3a8cc7e62be1..ec853e5631669 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -27,7 +27,7 @@ pub enum CompressedImageSaverError {
     Io(#[from] std::io::Error),
     /// The underlying compression library returned an error.
     #[error(transparent)]
-    CompressionFailed(Box<dyn std::error::Error + Send + Sync>),
+    CompressionFailed(Box<dyn std::error::Error>),
     /// Attempted to save an image with uninitialized data.
     #[error("Cannot compress an uninitialized image")]
     UninitializedImage,
@@ -52,6 +52,12 @@ impl AssetSaver for CompressedImageSaver {
             return Err(CompressedImageSaverError::UninitializedImage);
         };
 
+        if image.texture_descriptor.mip_level_count != 1 {
+            return Err(CompressedImageSaverError::CompressionFailed(
+                "Expected texture_descriptor.mip_level_count to be 1".into(),
+            ));
+        }
+
         let is_srgb = image.texture_descriptor.format.is_srgb();
         let color_space = if is_srgb {
             ctt::format::ColorSpace::Srgb

From c2454e1ed272afcca6417a1eaa1b895498581a48 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 29 Mar 2026 10:46:29 -0400
Subject: [PATCH 09/21] WIP

---
 crates/bevy_image/src/compressed_image_saver.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index ec853e5631669..980b13b2b96fa 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -82,7 +82,13 @@ impl AssetSaver for CompressedImageSaver {
                     height: image.height(),
                     stride: todo!(),
                     pixel_format: ctt::format::PixelFormat {
-                        components: todo!(),
+                        components: match image.texture_descriptor.format.components() {
+                            1 => ctt::format::PixelComponents::R,
+                            2 => ctt::format::PixelComponents::Rg,
+                            3 => ctt::format::PixelComponents::Rgb,
+                            4 => ctt::format::PixelComponents::Rgba,
+                            _ => unreachable!(),
+                        },
                         channel_type: todo!(),
                         color_space,
                     },

From 542d427b902a20b4aaf55dad5a6f25f4ecae6e9e Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 10:56:15 -0400
Subject: [PATCH 10/21] WIP

---
 crates/bevy_image/Cargo.toml                  |   2 +-
 .../bevy_image/src/compressed_image_saver.rs  | 323 ++++++++++++++++--
 2 files changed, 291 insertions(+), 34 deletions(-)

diff --git a/crates/bevy_image/Cargo.toml b/crates/bevy_image/Cargo.toml
index 0bf3ac5278932..21d8c190edc28 100644
--- a/crates/bevy_image/Cargo.toml
+++ b/crates/bevy_image/Cargo.toml
@@ -91,7 +91,7 @@ ruzstd = { version = "0.8.0", optional = true }
 basis-universal = { version = "0.3.0", optional = true }
 tracing = { version = "0.1", default-features = false, features = ["std"] }
 half = { version = "2.4.1" }
-ctt = { version = "0.1", optional = true }
+ctt = { git = "https://github.com/cwfitzgerald/ctt", rev = "fd41d518a557803bd1eda1bcc6fbbcd4e07757c5", optional = true }
 
 [dev-dependencies]
 bevy_ecs = { path = "../bevy_ecs", version = "0.19.0-dev" }
diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 980b13b2b96fa..c49462fe51cc7 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -1,12 +1,14 @@
 use crate::{Image, ImageFormat, ImageFormatSetting, ImageLoader, ImageLoaderSettings};
 
 use bevy_asset::{
+    io::Writer,
     saver::{AssetSaver, SavedAsset},
     AssetPath,
 };
 use bevy_reflect::TypePath;
 use futures_lite::AsyncWriteExt;
 use thiserror::Error;
+use wgpu_types::TextureFormat;
 
 /// An [`AssetSaver`] for [`Image`] that compresses texture files.
 ///
@@ -27,10 +29,13 @@ pub enum CompressedImageSaverError {
     Io(#[from] std::io::Error),
     /// The underlying compression library returned an error.
     #[error(transparent)]
-    CompressionFailed(Box<dyn std::error::Error>),
+    CompressionFailed(Box<dyn std::error::Error + Send + Sync>),
     /// Attempted to save an image with uninitialized data.
     #[error("Cannot compress an uninitialized image")]
     UninitializedImage,
+    /// The texture format is not supported for compression.
+    #[error("Unsupported texture format for compression: {0:?}")]
+    UnsupportedFormat(TextureFormat),
 }
 
 impl AssetSaver for CompressedImageSaver {
@@ -43,7 +48,7 @@ impl AssetSaver for CompressedImageSaver {
     #[cfg(feature = "compressed_image_saver_desktop")]
     async fn save(
         &self,
-        writer: &mut bevy_asset::io::Writer,
+        writer: &mut Writer,
         image: SavedAsset<'_, '_, Self::Asset>,
         _settings: &Self::Settings,
         _asset_path: AssetPath<'_>,
@@ -58,11 +63,14 @@ impl AssetSaver for CompressedImageSaver {
             ));
         }
 
+        let input_format = map_to_ctt_texture_format(image.texture_descriptor.format)?;
+        let output_format = choose_ctt_compressed_format(image.texture_descriptor.format)?;
+
         let is_srgb = image.texture_descriptor.format.is_srgb();
         let color_space = if is_srgb {
-            ctt::format::ColorSpace::Srgb
+            ctt::ColorSpace::Srgb
         } else {
-            ctt::format::ColorSpace::Linear
+            ctt::ColorSpace::Linear
         };
 
         let is_cubemap = matches!(
@@ -73,43 +81,54 @@ impl AssetSaver for CompressedImageSaver {
             })
         );
 
-        let layers = (0..image.texture_descriptor.array_layer_count())
-            .into_iter()
-            .map(|layer| {
-                vec![ctt::image::RawImage {
-                    data: todo!(),
+        let bytes_per_pixel =
+            crate::TextureFormatPixelInfo::pixel_size(&image.texture_descriptor.format).map_err(
+                |_| CompressedImageSaverError::UnsupportedFormat(image.texture_descriptor.format),
+            )? as u32;
+
+        let surfaces = data
+            .chunks_exact((image.width() * image.height() * bytes_per_pixel) as usize)
+            .map(|layer_data| {
+                vec![ctt::Surface {
+                    data: layer_data.to_vec(),
                     width: image.width(),
                     height: image.height(),
-                    stride: todo!(),
-                    pixel_format: ctt::format::PixelFormat {
-                        components: match image.texture_descriptor.format.components() {
-                            1 => ctt::format::PixelComponents::R,
-                            2 => ctt::format::PixelComponents::Rg,
-                            3 => ctt::format::PixelComponents::Rgb,
-                            4 => ctt::format::PixelComponents::Rgba,
-                            _ => unreachable!(),
-                        },
-                        channel_type: todo!(),
-                        color_space,
-                    },
-                }];
+                    stride: image.width() * bytes_per_pixel,
+                    format: input_format,
+                    color_space,
+                    alpha: ctt::AlphaMode::Straight, // TODO: User-configurable?
+                }]
             })
             .collect();
-        let layout = ctt::image::ImageLayout { layers, is_cubemap };
+        let ctt_image = ctt::Image {
+            surfaces,
+            is_cubemap,
+        };
 
-        let config = ctt::config::CompressConfig {
-            format: todo!(),
-            output_format: ctt::config::OutputFormat::Ktx2,
+        let settings = ctt::ConvertSettings {
+            format: Some(output_format),
+            container: ctt::Container::Ktx2,
+            quality: ctt::Quality::default(),
+            output_color_space: None,
+            output_alpha: None,
             swizzle: None,
-            color_space,
-            encode_settings: None,
+            mipmap: true,
+            mipmap_count: None,
+            mipmap_filter: ctt::MipmapFilter::default(),
+            allow_lossy: true,
+            encoder_settings: None,
+            registry: None,
         };
 
-        let compressed_bytes = ctt::pipeline::run(&config, layout)
-            .await
-            .map_err(|e| CompressedImageSaver::CompressionFailed(Box::new(e)))?;
+        let output = ctt::convert(ctt_image, settings)
+            .map_err(|e| CompressedImageSaverError::CompressionFailed(Box::new(e)))?;
+        let ctt::ConvertOutput::Encoded(compressed_bytes) = &output else {
+            return Err(CompressedImageSaverError::CompressionFailed(
+                "Expected encoded output from ctt".into(),
+            ));
+        };
 
-        writer.write_all(&compressed_bytes).await?;
+        writer.write_all(compressed_bytes).await?;
 
         Ok(ImageLoaderSettings {
             format: ImageFormatSetting::Format(ImageFormat::Ktx2),
@@ -124,7 +143,7 @@ impl AssetSaver for CompressedImageSaver {
     #[cfg(feature = "compressed_image_saver_web")]
     async fn save(
         &self,
-        writer: &mut bevy_asset::io::Writer,
+        writer: &mut Writer,
         image: SavedAsset<'_, '_, Self::Asset>,
         _settings: &Self::Settings,
         _asset_path: AssetPath<'_>,
@@ -178,3 +197,241 @@ impl AssetSaver for CompressedImageSaver {
         })
     }
 }
+
+#[cfg(feature = "compressed_image_saver_desktop")]
+fn choose_ctt_compressed_format(
+    input: TextureFormat,
+) -> Result<ctt::TargetFormat, CompressedImageSaverError> {
+    use ktx2::Format;
+
+    let format = match input {
+        // 1-channel snorm -> BC4 snorm
+        TextureFormat::R8Snorm | TextureFormat::R16Snorm => Format::BC4_SNORM_BLOCK,
+
+        // 1-channel -> BC4
+        TextureFormat::R8Unorm
+        | TextureFormat::R8Uint
+        | TextureFormat::R8Sint
+        | TextureFormat::R16Uint
+        | TextureFormat::R16Sint
+        | TextureFormat::R16Unorm
+        | TextureFormat::R16Float
+        | TextureFormat::R32Uint
+        | TextureFormat::R32Sint
+        | TextureFormat::R32Float
+        | TextureFormat::R64Uint => Format::BC4_UNORM_BLOCK,
+
+        // 2-channel snorm -> BC5 snorm
+        TextureFormat::Rg8Snorm | TextureFormat::Rg16Snorm => Format::BC5_SNORM_BLOCK,
+
+        // 2-channel -> BC5
+        TextureFormat::Rg8Unorm
+        | TextureFormat::Rg8Uint
+        | TextureFormat::Rg8Sint
+        | TextureFormat::Rg16Uint
+        | TextureFormat::Rg16Sint
+        | TextureFormat::Rg16Unorm
+        | TextureFormat::Rg16Float
+        | TextureFormat::Rg32Uint
+        | TextureFormat::Rg32Sint
+        | TextureFormat::Rg32Float => Format::BC5_UNORM_BLOCK,
+
+        // HDR / float RGB formats -> BC6H
+        TextureFormat::Rgb9e5Ufloat
+        | TextureFormat::Rg11b10Ufloat
+        | TextureFormat::Rgba16Float
+        | TextureFormat::Rgba32Float => Format::BC6H_UFLOAT_BLOCK,
+
+        // 4-channel LDR -> BC7
+        TextureFormat::Rgba8Unorm
+        | TextureFormat::Rgba8Uint
+        | TextureFormat::Rgba8Sint
+        | TextureFormat::Rgba8Snorm
+        | TextureFormat::Rgba16Uint
+        | TextureFormat::Rgba16Sint
+        | TextureFormat::Rgba16Unorm
+        | TextureFormat::Rgba16Snorm
+        | TextureFormat::Rgba32Uint
+        | TextureFormat::Rgba32Sint
+        | TextureFormat::Bgra8Unorm
+        | TextureFormat::Rgb10a2Uint
+        | TextureFormat::Rgb10a2Unorm => Format::BC7_UNORM_BLOCK,
+        TextureFormat::Rgba8UnormSrgb | TextureFormat::Bgra8UnormSrgb => Format::BC7_SRGB_BLOCK,
+
+        // Already compressed -> pass through
+        TextureFormat::Bc1RgbaUnorm
+        | TextureFormat::Bc1RgbaUnormSrgb
+        | TextureFormat::Bc2RgbaUnorm
+        | TextureFormat::Bc2RgbaUnormSrgb
+        | TextureFormat::Bc3RgbaUnorm
+        | TextureFormat::Bc3RgbaUnormSrgb
+        | TextureFormat::Bc4RUnorm
+        | TextureFormat::Bc4RSnorm
+        | TextureFormat::Bc5RgUnorm
+        | TextureFormat::Bc5RgSnorm
+        | TextureFormat::Bc6hRgbUfloat
+        | TextureFormat::Bc6hRgbFloat
+        | TextureFormat::Bc7RgbaUnorm
+        | TextureFormat::Bc7RgbaUnormSrgb
+        | TextureFormat::Etc2Rgb8Unorm
+        | TextureFormat::Etc2Rgb8UnormSrgb
+        | TextureFormat::Etc2Rgb8A1Unorm
+        | TextureFormat::Etc2Rgb8A1UnormSrgb
+        | TextureFormat::Etc2Rgba8Unorm
+        | TextureFormat::Etc2Rgba8UnormSrgb
+        | TextureFormat::EacR11Unorm
+        | TextureFormat::EacR11Snorm
+        | TextureFormat::EacRg11Unorm
+        | TextureFormat::EacRg11Snorm
+        | TextureFormat::Astc { .. } => map_to_ctt_texture_format(input)?,
+
+        // Depth/stencil and video formats cannot be compressed
+        TextureFormat::Stencil8
+        | TextureFormat::Depth16Unorm
+        | TextureFormat::Depth24Plus
+        | TextureFormat::Depth24PlusStencil8
+        | TextureFormat::Depth32Float
+        | TextureFormat::Depth32FloatStencil8
+        | TextureFormat::NV12
+        | TextureFormat::P010 => {
+            return Err(CompressedImageSaverError::UnsupportedFormat(input));
+        }
+    };
+
+    Ok(ctt::TargetFormat::Compressed {
+        encoder_name: None,
+        format,
+    })
+}
+
+#[cfg(feature = "compressed_image_saver_desktop")]
+fn map_to_ctt_texture_format(
+    input: TextureFormat,
+) -> Result<ctt::Format, CompressedImageSaverError> {
+    use ctt::Format;
+    use wgpu_types::{AstcBlock, AstcChannel, TextureFormat};
+
+    Ok(match input {
+        TextureFormat::R8Unorm => Format::R8_UNORM,
+        TextureFormat::R8Snorm => Format::R8_SNORM,
+        TextureFormat::R8Uint => Format::R8_UINT,
+        TextureFormat::R8Sint => Format::R8_SINT,
+        TextureFormat::R16Uint => Format::R16_UINT,
+        TextureFormat::R16Sint => Format::R16_SINT,
+        TextureFormat::R16Unorm => Format::R16_UNORM,
+        TextureFormat::R16Snorm => Format::R16_SNORM,
+        TextureFormat::R16Float => Format::R16_SFLOAT,
+        TextureFormat::Rg8Unorm => Format::R8G8_UNORM,
+        TextureFormat::Rg8Snorm => Format::R8G8_SNORM,
+        TextureFormat::Rg8Uint => Format::R8G8_UINT,
+        TextureFormat::Rg8Sint => Format::R8G8_SINT,
+        TextureFormat::R32Uint => Format::R32_UINT,
+        TextureFormat::R32Sint => Format::R32_SINT,
+        TextureFormat::R32Float => Format::R32_SFLOAT,
+        TextureFormat::Rg16Uint => Format::R16G16_UINT,
+        TextureFormat::Rg16Sint => Format::R16G16_SINT,
+        TextureFormat::Rg16Unorm => Format::R16G16_UNORM,
+        TextureFormat::Rg16Snorm => Format::R16G16_SNORM,
+        TextureFormat::Rg16Float => Format::R16G16_SFLOAT,
+        TextureFormat::Rgba8Unorm => Format::R8G8B8A8_UNORM,
+        TextureFormat::Rgba8UnormSrgb => Format::R8G8B8A8_SRGB,
+        TextureFormat::Rgba8Snorm => Format::R8G8B8A8_SNORM,
+        TextureFormat::Rgba8Uint => Format::R8G8B8A8_UINT,
+        TextureFormat::Rgba8Sint => Format::R8G8B8A8_SINT,
+        TextureFormat::Bgra8Unorm => Format::B8G8R8A8_UNORM,
+        TextureFormat::Bgra8UnormSrgb => Format::B8G8R8A8_SRGB,
+        TextureFormat::Rgb9e5Ufloat => Format::E5B9G9R9_UFLOAT_PACK32,
+        TextureFormat::Rgb10a2Uint => Format::A2B10G10R10_UINT_PACK32,
+        TextureFormat::Rgb10a2Unorm => Format::A2B10G10R10_UNORM_PACK32,
+        TextureFormat::Rg11b10Ufloat => Format::B10G11R11_UFLOAT_PACK32,
+        TextureFormat::R64Uint => Format::R64_UINT,
+        TextureFormat::Rg32Uint => Format::R32G32_UINT,
+        TextureFormat::Rg32Sint => Format::R32G32_SINT,
+        TextureFormat::Rg32Float => Format::R32G32_SFLOAT,
+        TextureFormat::Rgba16Uint => Format::R16G16B16A16_UINT,
+        TextureFormat::Rgba16Sint => Format::R16G16B16A16_SINT,
+        TextureFormat::Rgba16Unorm => Format::R16G16B16A16_UNORM,
+        TextureFormat::Rgba16Snorm => Format::R16G16B16A16_SNORM,
+        TextureFormat::Rgba16Float => Format::R16G16B16A16_SFLOAT,
+        TextureFormat::Rgba32Uint => Format::R32G32B32A32_UINT,
+        TextureFormat::Rgba32Sint => Format::R32G32B32A32_SINT,
+        TextureFormat::Rgba32Float => Format::R32G32B32A32_SFLOAT,
+        TextureFormat::Stencil8 => Format::S8_UINT,
+        TextureFormat::Depth16Unorm => Format::D16_UNORM,
+        TextureFormat::Depth24Plus => Format::X8_D24_UNORM_PACK32,
+        TextureFormat::Depth24PlusStencil8 => Format::D24_UNORM_S8_UINT,
+        TextureFormat::Depth32Float => Format::D32_SFLOAT,
+        TextureFormat::Depth32FloatStencil8 => Format::D32_SFLOAT_S8_UINT,
+        TextureFormat::NV12 | TextureFormat::P010 => {
+            return Err(CompressedImageSaverError::UnsupportedFormat(input));
+        }
+        TextureFormat::Bc1RgbaUnorm => Format::BC1_RGBA_UNORM_BLOCK,
+        TextureFormat::Bc1RgbaUnormSrgb => Format::BC1_RGBA_SRGB_BLOCK,
+        TextureFormat::Bc2RgbaUnorm => Format::BC2_UNORM_BLOCK,
+        TextureFormat::Bc2RgbaUnormSrgb => Format::BC2_SRGB_BLOCK,
+        TextureFormat::Bc3RgbaUnorm => Format::BC3_UNORM_BLOCK,
+        TextureFormat::Bc3RgbaUnormSrgb => Format::BC3_SRGB_BLOCK,
+        TextureFormat::Bc4RUnorm => Format::BC4_UNORM_BLOCK,
+        TextureFormat::Bc4RSnorm => Format::BC4_SNORM_BLOCK,
+        TextureFormat::Bc5RgUnorm => Format::BC5_UNORM_BLOCK,
+        TextureFormat::Bc5RgSnorm => Format::BC5_SNORM_BLOCK,
+        TextureFormat::Bc6hRgbUfloat => Format::BC6H_UFLOAT_BLOCK,
+        TextureFormat::Bc6hRgbFloat => Format::BC6H_SFLOAT_BLOCK,
+        TextureFormat::Bc7RgbaUnorm => Format::BC7_UNORM_BLOCK,
+        TextureFormat::Bc7RgbaUnormSrgb => Format::BC7_SRGB_BLOCK,
+        TextureFormat::Etc2Rgb8Unorm => Format::ETC2_R8G8B8_UNORM_BLOCK,
+        TextureFormat::Etc2Rgb8UnormSrgb => Format::ETC2_R8G8B8_SRGB_BLOCK,
+        TextureFormat::Etc2Rgb8A1Unorm => Format::ETC2_R8G8B8A1_UNORM_BLOCK,
+        TextureFormat::Etc2Rgb8A1UnormSrgb => Format::ETC2_R8G8B8A1_SRGB_BLOCK,
+        TextureFormat::Etc2Rgba8Unorm => Format::ETC2_R8G8B8A8_UNORM_BLOCK,
+        TextureFormat::Etc2Rgba8UnormSrgb => Format::ETC2_R8G8B8A8_SRGB_BLOCK,
+        TextureFormat::EacR11Unorm => Format::EAC_R11_UNORM_BLOCK,
+        TextureFormat::EacR11Snorm => Format::EAC_R11_SNORM_BLOCK,
+        TextureFormat::EacRg11Unorm => Format::EAC_R11G11_UNORM_BLOCK,
+        TextureFormat::EacRg11Snorm => Format::EAC_R11G11_SNORM_BLOCK,
+        TextureFormat::Astc { block, channel } => match (block, channel) {
+            (AstcBlock::B4x4, AstcChannel::Unorm) => Format::ASTC_4x4_UNORM_BLOCK,
+            (AstcBlock::B4x4, AstcChannel::UnormSrgb) => Format::ASTC_4x4_SRGB_BLOCK,
+            (AstcBlock::B4x4, AstcChannel::Hdr) => Format::ASTC_4x4_SFLOAT_BLOCK,
+            (AstcBlock::B5x4, AstcChannel::Unorm) => Format::ASTC_5x4_UNORM_BLOCK,
+            (AstcBlock::B5x4, AstcChannel::UnormSrgb) => Format::ASTC_5x4_SRGB_BLOCK,
+            (AstcBlock::B5x4, AstcChannel::Hdr) => Format::ASTC_5x4_SFLOAT_BLOCK,
+            (AstcBlock::B5x5, AstcChannel::Unorm) => Format::ASTC_5x5_UNORM_BLOCK,
+            (AstcBlock::B5x5, AstcChannel::UnormSrgb) => Format::ASTC_5x5_SRGB_BLOCK,
+            (AstcBlock::B5x5, AstcChannel::Hdr) => Format::ASTC_5x5_SFLOAT_BLOCK,
+            (AstcBlock::B6x5, AstcChannel::Unorm) => Format::ASTC_6x5_UNORM_BLOCK,
+            (AstcBlock::B6x5, AstcChannel::UnormSrgb) => Format::ASTC_6x5_SRGB_BLOCK,
+            (AstcBlock::B6x5, AstcChannel::Hdr) => Format::ASTC_6x5_SFLOAT_BLOCK,
+            (AstcBlock::B6x6, AstcChannel::Unorm) => Format::ASTC_6x6_UNORM_BLOCK,
+            (AstcBlock::B6x6, AstcChannel::UnormSrgb) => Format::ASTC_6x6_SRGB_BLOCK,
+            (AstcBlock::B6x6, AstcChannel::Hdr) => Format::ASTC_6x6_SFLOAT_BLOCK,
+            (AstcBlock::B8x5, AstcChannel::Unorm) => Format::ASTC_8x5_UNORM_BLOCK,
+            (AstcBlock::B8x5, AstcChannel::UnormSrgb) => Format::ASTC_8x5_SRGB_BLOCK,
+            (AstcBlock::B8x5, AstcChannel::Hdr) => Format::ASTC_8x5_SFLOAT_BLOCK,
+            (AstcBlock::B8x6, AstcChannel::Unorm) => Format::ASTC_8x6_UNORM_BLOCK,
+            (AstcBlock::B8x6, AstcChannel::UnormSrgb) => Format::ASTC_8x6_SRGB_BLOCK,
+            (AstcBlock::B8x6, AstcChannel::Hdr) => Format::ASTC_8x6_SFLOAT_BLOCK,
+            (AstcBlock::B8x8, AstcChannel::Unorm) => Format::ASTC_8x8_UNORM_BLOCK,
+            (AstcBlock::B8x8, AstcChannel::UnormSrgb) => Format::ASTC_8x8_SRGB_BLOCK,
+            (AstcBlock::B8x8, AstcChannel::Hdr) => Format::ASTC_8x8_SFLOAT_BLOCK,
+            (AstcBlock::B10x5, AstcChannel::Unorm) => Format::ASTC_10x5_UNORM_BLOCK,
+            (AstcBlock::B10x5, AstcChannel::UnormSrgb) => Format::ASTC_10x5_SRGB_BLOCK,
+            (AstcBlock::B10x5, AstcChannel::Hdr) => Format::ASTC_10x5_SFLOAT_BLOCK,
+            (AstcBlock::B10x6, AstcChannel::Unorm) => Format::ASTC_10x6_UNORM_BLOCK,
+            (AstcBlock::B10x6, AstcChannel::UnormSrgb) => Format::ASTC_10x6_SRGB_BLOCK,
+            (AstcBlock::B10x6, AstcChannel::Hdr) => Format::ASTC_10x6_SFLOAT_BLOCK,
+            (AstcBlock::B10x8, AstcChannel::Unorm) => Format::ASTC_10x8_UNORM_BLOCK,
+            (AstcBlock::B10x8, AstcChannel::UnormSrgb) => Format::ASTC_10x8_SRGB_BLOCK,
+            (AstcBlock::B10x8, AstcChannel::Hdr) => Format::ASTC_10x8_SFLOAT_BLOCK,
+            (AstcBlock::B10x10, AstcChannel::Unorm) => Format::ASTC_10x10_UNORM_BLOCK,
+            (AstcBlock::B10x10, AstcChannel::UnormSrgb) => Format::ASTC_10x10_SRGB_BLOCK,
+            (AstcBlock::B10x10, AstcChannel::Hdr) => Format::ASTC_10x10_SFLOAT_BLOCK,
+            (AstcBlock::B12x10, AstcChannel::Unorm) => Format::ASTC_12x10_UNORM_BLOCK,
+            (AstcBlock::B12x10, AstcChannel::UnormSrgb) => Format::ASTC_12x10_SRGB_BLOCK,
+            (AstcBlock::B12x10, AstcChannel::Hdr) => Format::ASTC_12x10_SFLOAT_BLOCK,
+            (AstcBlock::B12x12, AstcChannel::Unorm) => Format::ASTC_12x12_UNORM_BLOCK,
+            (AstcBlock::B12x12, AstcChannel::UnormSrgb) => Format::ASTC_12x12_SRGB_BLOCK,
+            (AstcBlock::B12x12, AstcChannel::Hdr) => Format::ASTC_12x12_SFLOAT_BLOCK,
+        },
+    })
+}

From a027777a2dbf1a8ec07aa44ab9f71502dc209c5c Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 10:58:53 -0400
Subject: [PATCH 11/21] Add TODO

---
 crates/bevy_image/src/compressed_image_saver.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index c49462fe51cc7..02fbf9a578a1f 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -204,6 +204,7 @@ fn choose_ctt_compressed_format(
 ) -> Result<ctt::TargetFormat, CompressedImageSaverError> {
     use ktx2::Format;
 
+    // TODO: ASTC support
     let format = match input {
         // 1-channel snorm -> BC4 snorm
         TextureFormat::R8Snorm | TextureFormat::R16Snorm => Format::BC4_SNORM_BLOCK,

From f1346ba4dc215c33468341bdde6ae394414e06b3 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 10:59:07 -0400
Subject: [PATCH 12/21] Misc

---
 crates/bevy_image/src/compressed_image_saver.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 02fbf9a578a1f..99634e6cdc744 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -310,7 +310,7 @@ fn map_to_ctt_texture_format(
     input: TextureFormat,
 ) -> Result<ctt::Format, CompressedImageSaverError> {
     use ctt::Format;
-    use wgpu_types::{AstcBlock, AstcChannel, TextureFormat};
+    use wgpu_types::{AstcBlock, AstcChannel};
 
     Ok(match input {
         TextureFormat::R8Unorm => Format::R8_UNORM,

From 48f9c44dfab4f76d6c3c365d0ec6cdd41ca9b1b0 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 11:14:53 -0400
Subject: [PATCH 13/21] Docs

---
 .../bevy_image/src/compressed_image_saver.rs  | 54 +++++++++++++++++--
 1 file changed, 49 insertions(+), 5 deletions(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 99634e6cdc744..b54b971bdc923 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -12,11 +12,55 @@ use wgpu_types::TextureFormat;
 
 /// An [`AssetSaver`] for [`Image`] that compresses texture files.
 ///
-/// Compressed textures both take up less space on disk, and use less VRAM.
+/// Compressed textures both take up less space on disk, and use less GPU VRAM.
 ///
-/// TODO: Document what platforms are supported, how feature flags work,
-/// required native dependencies (https://github.com/cwfitzgerald/ctt?tab=readme-ov-file#prerequisites),
-/// what compression types exist, and mipmap generation?
+/// Mipmaps are also generated, which prevents aliasing when textures are viewed at a distance,
+/// and increases GPU cache hits, improving rendering performance.
+///
+/// # Platform support
+///
+/// Two mutually exclusive feature flags control which compression backend is used:
+///
+/// - **`compressed_image_saver_desktop`** — Uses the [`ctt`](https://github.com/cwfitzgerald/ctt)
+///   library to compress textures into BCn formats, output as KTX2. Requires a C++ compiler;
+///   see the [ctt readme](https://github.com/cwfitzgerald/ctt?tab=readme-ov-file#prebuilt-binaries).
+///   Best for desktop (Windows, macOS, Linux) where BCn hardware support is universal.
+///
+/// - **`compressed_image_saver_web`** — Uses [`basis-universal`] to compress textures into UASTC
+///   (Basis Universal) format. This is a GPU-agnostic supercompressed format that can be
+///   transcoded at load time to whatever format the target GPU supports, making it suitable for
+///   WebGPU and cross-platform distribution.
+///
+/// # Runtime feature flags
+///
+/// The compressed output must also be loadable at runtime. Enable the corresponding feature:
+///
+/// - **`ktx2`** — Required to load KTX2 files produced by the desktop backend.
+/// - **`basis-universal`** — Required to load Basis Universal files produced by the web backend.
+///
+/// # Compression format selection (desktop)
+///
+/// The output format is chosen automatically based on the input texture's channel count and type:
+///
+/// | Input channels | Output format |
+/// |---|---|
+/// | 1-channel (R) | BC4 |
+/// | 1-channel snorm | BC4 snorm |
+/// | 2-channel (RG) | BC5 |
+/// | 2-channel snorm | BC5 snorm |
+/// | HDR / float (e.g. `Rgba16Float`) | BC6H |
+/// | 4-channel LDR (e.g. `Rgba8Unorm`) | BC7 |
+/// | 4-channel sRGB (e.g. `Rgba8UnormSrgb`) | BC7 sRGB |
+/// | Already compressed (BCn, ETC2, EAC, ASTC) | Re-encoded to the same format |
+///
+/// Depth, stencil, and video formats (`NV12`, `P010`) are not supported and will return
+/// [`CompressedImageSaverError::UnsupportedFormat`].
+///
+/// # Mipmap generation
+///
+/// Mipmaps are generated automatically during compression. The desktop backend requires
+/// input images to have a `mip_level_count` of 1 (i.e., no pre-existing mip chain);
+/// the compressor will produce a full mip chain in the output.
 #[derive(TypePath)]
 pub struct CompressedImageSaver;
 
@@ -181,7 +225,7 @@ impl AssetSaver for CompressedImageSaver {
                 compressor.init(&compressor_params);
                 compressor
                     .process()
-                    .map_err(|e| CompressedImageSaver::CompressionFailed(Box::new(e)))?;
+                    .map_err(|e| CompressedImageSaverError::CompressionFailed(Box::new(e)))?;
             }
             compressor.basis_file().to_vec()
         };

From 5b90771310aed8d216ef3d8c2ff02ed844ee1f68 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 12:03:45 -0400
Subject: [PATCH 14/21] Fix docs

---
 crates/bevy_image/src/compressed_image_saver.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index b54b971bdc923..4ce036d09eccd 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -12,7 +12,7 @@ use wgpu_types::TextureFormat;
 
 /// An [`AssetSaver`] for [`Image`] that compresses texture files.
 ///
-/// Compressed textures both take up less space on disk, and use less GPU VRAM.
+/// Compressed textures use less GPU VRAM.
 ///
 /// Mipmaps are also generated, which prevents aliasing when textures are viewed at a distance,
 /// and increases GPU cache hits, improving rendering performance.
@@ -26,7 +26,7 @@ use wgpu_types::TextureFormat;
 ///   see the [ctt readme](https://github.com/cwfitzgerald/ctt?tab=readme-ov-file#prebuilt-binaries).
 ///   Best for desktop (Windows, macOS, Linux) where BCn hardware support is universal.
 ///
-/// - **`compressed_image_saver_web`** — Uses [`basis-universal`] to compress textures into UASTC
+/// - **`compressed_image_saver_web`** — Uses `basis-universal` to compress textures into UASTC
 ///   (Basis Universal) format. This is a GPU-agnostic supercompressed format that can be
 ///   transcoded at load time to whatever format the target GPU supports, making it suitable for
 ///   WebGPU and cross-platform distribution.
@@ -51,7 +51,7 @@ use wgpu_types::TextureFormat;
 /// | HDR / float (e.g. `Rgba16Float`) | BC6H |
 /// | 4-channel LDR (e.g. `Rgba8Unorm`) | BC7 |
 /// | 4-channel sRGB (e.g. `Rgba8UnormSrgb`) | BC7 sRGB |
-/// | Already compressed (BCn, ETC2, EAC, ASTC) | Re-encoded to the same format |
+/// | Already compressed (BCn, ASTC, ETC2, EAC) | Re-encoded to the same format |
 ///
 /// Depth, stencil, and video formats (`NV12`, `P010`) are not supported and will return
 /// [`CompressedImageSaverError::UnsupportedFormat`].

From f92fb42256687304aaf87c9fbca6e98c3ee08008 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 12:23:49 -0400
Subject: [PATCH 15/21] ASTC support

---
 Cargo.toml                                    |  12 +-
 crates/bevy_image/Cargo.toml                  |   8 +-
 .../bevy_image/src/compressed_image_saver.rs  | 213 +++++++++++++++---
 crates/bevy_image/src/image.rs                |   4 +-
 crates/bevy_image/src/lib.rs                  |   8 +-
 crates/bevy_internal/Cargo.toml               |  10 +-
 docs/cargo_features.md                        |   4 +-
 7 files changed, 210 insertions(+), 49 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 31f26c4c682b0..c7f90aa4d4dce 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -431,14 +431,14 @@ trace = ["bevy_internal/trace", "dep:tracing"]
 # Basis Universal compressed texture support
 basis-universal = ["bevy_internal/basis-universal"]
 
-# Texture compression asset processor (for web)
-compressed_image_saver_web = ["bevy_internal/compressed_image_saver_web"]
-
-# Texture compression asset processor (for desktop)
-compressed_image_saver_desktop = [
-  "bevy_internal/compressed_image_saver_desktop",
+# Texture compression asset processor (cross-platform, transcodes to any GPU format at load time)
+compressed_image_saver_universal = [
+  "bevy_internal/compressed_image_saver_universal",
 ]
 
+# Texture compression asset processor (BCn for desktop, ASTC for mobile via env var)
+compressed_image_saver = ["bevy_internal/compressed_image_saver"]
+
 # BMP image format support
 bmp = ["bevy_internal/bmp"]
 
diff --git a/crates/bevy_image/Cargo.toml b/crates/bevy_image/Cargo.toml
index 21d8c190edc28..3d3e3ea92dc8a 100644
--- a/crates/bevy_image/Cargo.toml
+++ b/crates/bevy_image/Cargo.toml
@@ -45,11 +45,11 @@ zstd_rust = ["zstd", "dep:ruzstd"]
 # Binding to zstd C implementation (faster)
 zstd_c = ["zstd", "dep:zstd"]
 
-# Texture compression asset processor (for web)
-compressed_image_saver_web = ["basis-universal"]
+# Texture compression asset processor (cross-platform, transcodes to any GPU format at load time)
+compressed_image_saver_universal = ["basis-universal"]
 
-# Texture compression asset processor (for desktop)
-compressed_image_saver_desktop = ["dep:ctt", "ktx2"]
+# Texture compression asset processor (BCn for desktop, ASTC for mobile via env var)
+compressed_image_saver = ["dep:ctt", "ktx2"]
 
 [dependencies]
 # bevy
diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 4ce036d09eccd..18f36bebde717 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -21,12 +21,13 @@ use wgpu_types::TextureFormat;
 ///
 /// Two mutually exclusive feature flags control which compression backend is used:
 ///
-/// - **`compressed_image_saver_desktop`** — Uses the [`ctt`](https://github.com/cwfitzgerald/ctt)
-///   library to compress textures into BCn formats, output as KTX2. Requires a C++ compiler;
-///   see the [ctt readme](https://github.com/cwfitzgerald/ctt?tab=readme-ov-file#prebuilt-binaries).
-///   Best for desktop (Windows, macOS, Linux) where BCn hardware support is universal.
+/// - **`compressed_image_saver`** — Uses the [`ctt`](https://github.com/cwfitzgerald/ctt)
+///   library to compress textures into BCn or ASTC formats, output as KTX2. Requires a C++
+///   compiler; see the [ctt readme](https://github.com/cwfitzgerald/ctt?tab=readme-ov-file#prebuilt-binaries).
+///   Outputs BCn by default (for desktop targets). Set
+///   `BEVY_COMPRESSED_IMAGE_SAVER_ASTC` to output ASTC instead (for mobile targets).
 ///
-/// - **`compressed_image_saver_web`** — Uses `basis-universal` to compress textures into UASTC
+/// - **`compressed_image_saver_universal`** — Uses `basis-universal` to compress textures into UASTC
 ///   (Basis Universal) format. This is a GPU-agnostic supercompressed format that can be
 ///   transcoded at load time to whatever format the target GPU supports, making it suitable for
 ///   WebGPU and cross-platform distribution.
@@ -35,10 +36,10 @@ use wgpu_types::TextureFormat;
 ///
 /// The compressed output must also be loadable at runtime. Enable the corresponding feature:
 ///
-/// - **`ktx2`** — Required to load KTX2 files produced by the desktop backend.
-/// - **`basis-universal`** — Required to load Basis Universal files produced by the web backend.
+/// - **`ktx2`** — Required to load KTX2 files produced by `compressed_image_saver`.
+/// - **`basis-universal`** — Required to load Basis Universal files produced by `compressed_image_saver_universal`.
 ///
-/// # Compression format selection (desktop)
+/// # Compression format selection
 ///
 /// The output format is chosen automatically based on the input texture's channel count and type:
 ///
@@ -56,9 +57,28 @@ use wgpu_types::TextureFormat;
 /// Depth, stencil, and video formats (`NV12`, `P010`) are not supported and will return
 /// [`CompressedImageSaverError::UnsupportedFormat`].
 ///
+/// # ASTC override
+///
+/// Set the `BEVY_COMPRESSED_IMAGE_SAVER_ASTC` environment variable to compress into ASTC
+/// instead of BCn. ASTC is natively supported on mobile GPUs (Android, iOS) and some
+/// desktop GPUs, while BCn is typically only supported on desktop GPUs.
+///
+/// The value specifies the block size. Larger blocks compress more aggressively (smaller
+/// files, less VRAM) at the cost of quality. If set to an empty string or `1`, defaults
+/// to `4x4`.
+///
+/// | Block size | Bits per pixel | Notes |
+/// |---|---|---|
+/// | `4x4` | 8.00 | Highest quality, same bit rate as BC7 |
+/// | `6x6` | 3.56 | Good balance of quality and size |
+/// | `8x8` | 2.00 | Aggressive, suitable for base_color_texture |
+///
+/// All 14 ASTC block sizes are supported: `4x4`, `5x4`, `5x5`, `6x5`, `6x6`, `8x5`,
+/// `8x6`, `8x8`, `10x5`, `10x6`, `10x8`, `10x10`, `12x10`, `12x12`.
+///
 /// # Mipmap generation
 ///
-/// Mipmaps are generated automatically during compression. The desktop backend requires
+/// Mipmaps are generated automatically during compression. The `compressed_image_saver` feature requires
 /// input images to have a `mip_level_count` of 1 (i.e., no pre-existing mip chain);
 /// the compressor will produce a full mip chain in the output.
 #[derive(TypePath)]
@@ -89,7 +109,7 @@ impl AssetSaver for CompressedImageSaver {
     type OutputLoader = ImageLoader;
     type Error = CompressedImageSaverError;
 
-    #[cfg(feature = "compressed_image_saver_desktop")]
+    #[cfg(feature = "compressed_image_saver")]
     async fn save(
         &self,
         writer: &mut Writer,
@@ -184,7 +204,7 @@ impl AssetSaver for CompressedImageSaver {
         })
     }
 
-    #[cfg(feature = "compressed_image_saver_web")]
+    #[cfg(feature = "compressed_image_saver_universal")]
     async fn save(
         &self,
         writer: &mut Writer,
@@ -242,18 +262,121 @@ impl AssetSaver for CompressedImageSaver {
     }
 }
 
-#[cfg(feature = "compressed_image_saver_desktop")]
+/// Returns `Some((unorm, srgb, hdr))` ASTC format triple if the env var is set, `None` otherwise.
+#[cfg(feature = "compressed_image_saver")]
+fn parse_astc_env_var(
+) -> Result<Option<(ktx2::Format, ktx2::Format, ktx2::Format)>, CompressedImageSaverError> {
+    use ktx2::Format;
+
+    let val = match std::env::var("BEVY_COMPRESSED_IMAGE_SAVER_ASTC") {
+        Ok(v) => v,
+        Err(std::env::VarError::NotPresent) => return Ok(None),
+        Err(std::env::VarError::NotUnicode(_)) => return Ok(None),
+    };
+
+    let val = val.trim();
+    let (unorm, srgb, hdr) = match val {
+        "" | "1" | "4x4" => (
+            Format::ASTC_4x4_UNORM_BLOCK,
+            Format::ASTC_4x4_SRGB_BLOCK,
+            Format::ASTC_4x4_SFLOAT_BLOCK,
+        ),
+        "5x4" => (
+            Format::ASTC_5x4_UNORM_BLOCK,
+            Format::ASTC_5x4_SRGB_BLOCK,
+            Format::ASTC_5x4_SFLOAT_BLOCK,
+        ),
+        "5x5" => (
+            Format::ASTC_5x5_UNORM_BLOCK,
+            Format::ASTC_5x5_SRGB_BLOCK,
+            Format::ASTC_5x5_SFLOAT_BLOCK,
+        ),
+        "6x5" => (
+            Format::ASTC_6x5_UNORM_BLOCK,
+            Format::ASTC_6x5_SRGB_BLOCK,
+            Format::ASTC_6x5_SFLOAT_BLOCK,
+        ),
+        "6x6" => (
+            Format::ASTC_6x6_UNORM_BLOCK,
+            Format::ASTC_6x6_SRGB_BLOCK,
+            Format::ASTC_6x6_SFLOAT_BLOCK,
+        ),
+        "8x5" => (
+            Format::ASTC_8x5_UNORM_BLOCK,
+            Format::ASTC_8x5_SRGB_BLOCK,
+            Format::ASTC_8x5_SFLOAT_BLOCK,
+        ),
+        "8x6" => (
+            Format::ASTC_8x6_UNORM_BLOCK,
+            Format::ASTC_8x6_SRGB_BLOCK,
+            Format::ASTC_8x6_SFLOAT_BLOCK,
+        ),
+        "8x8" => (
+            Format::ASTC_8x8_UNORM_BLOCK,
+            Format::ASTC_8x8_SRGB_BLOCK,
+            Format::ASTC_8x8_SFLOAT_BLOCK,
+        ),
+        "10x5" => (
+            Format::ASTC_10x5_UNORM_BLOCK,
+            Format::ASTC_10x5_SRGB_BLOCK,
+            Format::ASTC_10x5_SFLOAT_BLOCK,
+        ),
+        "10x6" => (
+            Format::ASTC_10x6_UNORM_BLOCK,
+            Format::ASTC_10x6_SRGB_BLOCK,
+            Format::ASTC_10x6_SFLOAT_BLOCK,
+        ),
+        "10x8" => (
+            Format::ASTC_10x8_UNORM_BLOCK,
+            Format::ASTC_10x8_SRGB_BLOCK,
+            Format::ASTC_10x8_SFLOAT_BLOCK,
+        ),
+        "10x10" => (
+            Format::ASTC_10x10_UNORM_BLOCK,
+            Format::ASTC_10x10_SRGB_BLOCK,
+            Format::ASTC_10x10_SFLOAT_BLOCK,
+        ),
+        "12x10" => (
+            Format::ASTC_12x10_UNORM_BLOCK,
+            Format::ASTC_12x10_SRGB_BLOCK,
+            Format::ASTC_12x10_SFLOAT_BLOCK,
+        ),
+        "12x12" => (
+            Format::ASTC_12x12_UNORM_BLOCK,
+            Format::ASTC_12x12_SRGB_BLOCK,
+            Format::ASTC_12x12_SFLOAT_BLOCK,
+        ),
+        other => {
+            return Err(CompressedImageSaverError::CompressionFailed(
+                format!("Invalid BEVY_COMPRESSED_IMAGE_SAVER_ASTC block size: {other:?}. \
+                    Expected one of: 4x4, 5x4, 5x5, 6x5, 6x6, 8x5, 8x6, 8x8, 10x5, 10x6, 10x8, 10x10, 12x10, 12x12")
+                    .into(),
+            ));
+        }
+    };
+
+    Ok(Some((unorm, srgb, hdr)))
+}
+
+#[cfg(feature = "compressed_image_saver")]
 fn choose_ctt_compressed_format(
     input: TextureFormat,
 ) -> Result<ctt::TargetFormat, CompressedImageSaverError> {
     use ktx2::Format;
 
-    // TODO: ASTC support
+    let astc_block = parse_astc_env_var()?;
+
     let format = match input {
-        // 1-channel snorm -> BC4 snorm
-        TextureFormat::R8Snorm | TextureFormat::R16Snorm => Format::BC4_SNORM_BLOCK,
+        // 1-channel snorm
+        TextureFormat::R8Snorm | TextureFormat::R16Snorm => {
+            if let Some((unorm, _, _)) = astc_block {
+                unorm
+            } else {
+                Format::BC4_SNORM_BLOCK
+            }
+        }
 
-        // 1-channel -> BC4
+        // 1-channel
         TextureFormat::R8Unorm
         | TextureFormat::R8Uint
         | TextureFormat::R8Sint
@@ -264,12 +387,24 @@ fn choose_ctt_compressed_format(
         | TextureFormat::R32Uint
         | TextureFormat::R32Sint
         | TextureFormat::R32Float
-        | TextureFormat::R64Uint => Format::BC4_UNORM_BLOCK,
+        | TextureFormat::R64Uint => {
+            if let Some((unorm, _, _)) = astc_block {
+                unorm
+            } else {
+                Format::BC4_UNORM_BLOCK
+            }
+        }
 
-        // 2-channel snorm -> BC5 snorm
-        TextureFormat::Rg8Snorm | TextureFormat::Rg16Snorm => Format::BC5_SNORM_BLOCK,
+        // 2-channel snorm
+        TextureFormat::Rg8Snorm | TextureFormat::Rg16Snorm => {
+            if let Some((unorm, _, _)) = astc_block {
+                unorm
+            } else {
+                Format::BC5_SNORM_BLOCK
+            }
+        }
 
-        // 2-channel -> BC5
+        // 2-channel
         TextureFormat::Rg8Unorm
         | TextureFormat::Rg8Uint
         | TextureFormat::Rg8Sint
@@ -279,15 +414,27 @@ fn choose_ctt_compressed_format(
         | TextureFormat::Rg16Float
         | TextureFormat::Rg32Uint
         | TextureFormat::Rg32Sint
-        | TextureFormat::Rg32Float => Format::BC5_UNORM_BLOCK,
+        | TextureFormat::Rg32Float => {
+            if let Some((unorm, _, _)) = astc_block {
+                unorm
+            } else {
+                Format::BC5_UNORM_BLOCK
+            }
+        }
 
-        // HDR / float RGB formats -> BC6H
+        // HDR / float RGB formats
         TextureFormat::Rgb9e5Ufloat
         | TextureFormat::Rg11b10Ufloat
         | TextureFormat::Rgba16Float
-        | TextureFormat::Rgba32Float => Format::BC6H_UFLOAT_BLOCK,
+        | TextureFormat::Rgba32Float => {
+            if let Some((_, _, hdr)) = astc_block {
+                hdr
+            } else {
+                Format::BC6H_UFLOAT_BLOCK
+            }
+        }
 
-        // 4-channel LDR -> BC7
+        // 4-channel LDR
         TextureFormat::Rgba8Unorm
         | TextureFormat::Rgba8Uint
         | TextureFormat::Rgba8Sint
@@ -300,8 +447,20 @@ fn choose_ctt_compressed_format(
         | TextureFormat::Rgba32Sint
         | TextureFormat::Bgra8Unorm
         | TextureFormat::Rgb10a2Uint
-        | TextureFormat::Rgb10a2Unorm => Format::BC7_UNORM_BLOCK,
-        TextureFormat::Rgba8UnormSrgb | TextureFormat::Bgra8UnormSrgb => Format::BC7_SRGB_BLOCK,
+        | TextureFormat::Rgb10a2Unorm => {
+            if let Some((unorm, _, _)) = astc_block {
+                unorm
+            } else {
+                Format::BC7_UNORM_BLOCK
+            }
+        }
+        TextureFormat::Rgba8UnormSrgb | TextureFormat::Bgra8UnormSrgb => {
+            if let Some((_, srgb, _)) = astc_block {
+                srgb
+            } else {
+                Format::BC7_SRGB_BLOCK
+            }
+        }
 
         // Already compressed -> pass through
         TextureFormat::Bc1RgbaUnorm
@@ -349,7 +508,7 @@ fn choose_ctt_compressed_format(
     })
 }
 
-#[cfg(feature = "compressed_image_saver_desktop")]
+#[cfg(feature = "compressed_image_saver")]
 fn map_to_ctt_texture_format(
     input: TextureFormat,
 ) -> Result<ctt::Format, CompressedImageSaverError> {
diff --git a/crates/bevy_image/src/image.rs b/crates/bevy_image/src/image.rs
index 149b502a51dd1..f6cc9464cb944 100644
--- a/crates/bevy_image/src/image.rs
+++ b/crates/bevy_image/src/image.rs
@@ -220,8 +220,8 @@ impl Plugin for ImagePlugin {
             .unwrap();
 
         #[cfg(any(
-            feature = "compressed_image_saver_desktop",
-            feature = "compressed_image_saver_web"
+            feature = "compressed_image_saver",
+            feature = "compressed_image_saver_universal"
         ))]
         if let Some(processor) = app
             .world()
diff --git a/crates/bevy_image/src/lib.rs b/crates/bevy_image/src/lib.rs
index 32d13b1917825..20400a1b066fd 100644
--- a/crates/bevy_image/src/lib.rs
+++ b/crates/bevy_image/src/lib.rs
@@ -25,8 +25,8 @@ pub use self::serialized_image::*;
 #[cfg(feature = "basis-universal")]
 mod basis;
 #[cfg(any(
-    feature = "compressed_image_saver_desktop",
-    feature = "compressed_image_saver_web"
+    feature = "compressed_image_saver",
+    feature = "compressed_image_saver_universal"
 ))]
 mod compressed_image_saver;
 #[cfg(feature = "dds")]
@@ -44,8 +44,8 @@ mod texture_atlas;
 mod texture_atlas_builder;
 
 #[cfg(any(
-    feature = "compressed_image_saver_desktop",
-    feature = "compressed_image_saver_web"
+    feature = "compressed_image_saver",
+    feature = "compressed_image_saver_universal"
 ))]
 pub use compressed_image_saver::*;
 #[cfg(feature = "dds")]
diff --git a/crates/bevy_internal/Cargo.toml b/crates/bevy_internal/Cargo.toml
index 23607751347dc..3aa21b2e3068f 100644
--- a/crates/bevy_internal/Cargo.toml
+++ b/crates/bevy_internal/Cargo.toml
@@ -29,11 +29,13 @@ detailed_trace = ["bevy_ecs/detailed_trace", "bevy_render?/detailed_trace"]
 
 sysinfo_plugin = ["bevy_diagnostic/sysinfo_plugin"]
 
-# Texture compression asset processor (for web)
-compressed_image_saver_web = ["bevy_image/compressed_image_saver_web"]
+# Texture compression asset processor (cross-platform, transcodes to any GPU format at load time)
+compressed_image_saver_universal = [
+  "bevy_image/compressed_image_saver_universal",
+]
 
-# Texture compression asset processor (for desktop)
-compressed_image_saver_desktop = ["bevy_image/compressed_image_saver_desktop"]
+# Texture compression asset processor (BCn for desktop, ASTC for mobile via env var)
+compressed_image_saver = ["bevy_image/compressed_image_saver"]
 
 # For ktx2 supercompression
 zlib = ["bevy_image/zlib"]
diff --git a/docs/cargo_features.md b/docs/cargo_features.md
index 360b757c2c347..142e7fad7d53e 100644
--- a/docs/cargo_features.md
+++ b/docs/cargo_features.md
@@ -110,8 +110,8 @@ This is the complete `bevy` cargo feature list, without "profiles" or "collectio
 |bevy_world_serialization|Provides ECS serialization functionality|
 |bluenoise_texture|Include spatio-temporal blue noise KTX2 file used by generated environment maps, Solari and atmosphere|
 |bmp|BMP image format support|
-|compressed_image_saver_desktop|Texture compression asset processor (for desktop)|
-|compressed_image_saver_web|Texture compression asset processor (for web)|
+|compressed_image_saver|Texture compression asset processor (BCn for desktop, ASTC for mobile via env var)|
+|compressed_image_saver_universal|Texture compression asset processor (cross-platform, transcodes to any GPU format at load time)|
 |critical-section|`critical-section` provides the building blocks for synchronization primitives on all platforms, including `no_std`.|
 |custom_cursor|Enable winit custom cursor support|
 |dds|DDS compressed texture support|

From 8b721defe783be80258e92c457618ea21d87af06 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 12:31:22 -0400
Subject: [PATCH 16/21] Docs

---
 .../compressed_image_saver.md                 | 22 ++++++++++-------
 .../release-notes/compressed_image_saver.md   | 24 ++++++++++---------
 .../bevy_image/src/compressed_image_saver.rs  | 15 ++++++------
 3 files changed, 35 insertions(+), 26 deletions(-)

diff --git a/_release-content/migration-guides/compressed_image_saver.md b/_release-content/migration-guides/compressed_image_saver.md
index c15a30710e1f7..e33a5d8c949a7 100644
--- a/_release-content/migration-guides/compressed_image_saver.md
+++ b/_release-content/migration-guides/compressed_image_saver.md
@@ -1,14 +1,20 @@
 ---
-title: Feature that broke
-pull_requests: [14791, 15458, 15269]
+title: `CompressedImageSaver` improvements
+pull_requests: [23567]
 ---
 
-Copy the contents of this file into a new file in `./migration-guides`, update the metadata, and add migration guide content here.
+The `compressed_image_saver` Cargo feature has been reworked. The old behavior (Basis Universal UASTC compression) has been moved to a new feature called `compressed_image_saver_universal`, and the `compressed_image_saver` feature now uses the `ctt` library to compress textures into BCn (desktop) or ASTC (mobile) formats instead.
 
-Remember, your aim is to communicate:
+If you were using the `compressed_image_saver` feature and want to keep the previous Basis Universal behavior, rename the feature in your `Cargo.toml`:
 
-- What has changed since the last release?
-- Why did we make this breaking change?
-- How can users migrate their existing code?
+```toml
+# Before
+bevy = { version = "0.18", features = ["compressed_image_saver"] }
 
-For more specifics about style and content, see the [instructions](./migration_guides.md).
+# After (keeps old Basis Universal behavior)
+bevy = { version = "0.19", features = ["compressed_image_saver_universal"] }
+```
+
+Alternatively, keep using `compressed_image_saver` to get the new BCn/ASTC compression backend. This produces higher-quality output and supports a wider range of input formats, but does not support web.
+
+`CompressedImageSaverError` has a new variant `CompressionFailed`. If you were matching exhaustively on this enum, add a branch for it.
diff --git a/_release-content/release-notes/compressed_image_saver.md b/_release-content/release-notes/compressed_image_saver.md
index 0a4110a5cb015..358317f05990e 100644
--- a/_release-content/release-notes/compressed_image_saver.md
+++ b/_release-content/release-notes/compressed_image_saver.md
@@ -1,19 +1,21 @@
 ---
-title: Feature name
-authors: ["@FerrisTheCrab", "@BirdObsessed"]
-pull_requests: [14791, 15458, 15269]
+title: CompressedImageSaver Improvements
+authors: ["@JMS55", "@cwfitzgerald"]
+pull_requests: [23567]
 ---
 
-Copy the contents of this file into `./release-notes`, update the metadata, and add release note content here.
+Bevy's `CompressedImageSaver` asset processor has been significantly upgraded with a new compression backend powered by the [`ctt`](https://github.com/cwfitzgerald/ctt) library.
 
-## Goals
+The new `compressed_image_saver` feature compresses textures into BCn formats (for desktop GPUs) or ASTC formats (for mobile GPUs), producing higher-quality output than the previous Basis Universal approach. The compressor automatically selects the best output format based on the input texture's channel count and type — for example, single-channel textures get BC4, HDR textures get BC6H, and standard RGBA textures get BC7.
 
-Answer the following:
+## Automatic Mipmap Generation
 
-- What has been changed or added?
-- Why is this a big deal for users?
-- How can they use it?
+No more manually generating mipmaps! The new backend automatically produces a full mip chain during compression. This means less aliasing when textures are viewed at a distance and better GPU cache utilization — all for free, just by running your textures through the asset processor.
 
-## Style Guide
+## ASTC for Mobile
 
-You may use markdown headings levels two and three, and must not start with a heading. Prose is appreciated, but bullet points are acceptable. Copying the introduction from your PR is often a good place to start.
+To target mobile GPUs, set the `BEVY_COMPRESSED_IMAGE_SAVER_ASTC` environment variable with your desired block size (e.g. `4x4`, `6x6`, `8x8`). Larger blocks give smaller files at the cost of quality. All 14 ASTC block sizes are supported.
+
+## Basis Universal is Still Available
+
+The previous Basis Universal compression behavior has been moved to the `compressed_image_saver_universal` feature. This remains the best choice for cross-platform distribution (including WebGPU), since UASTC can be transcoded at load time to whatever format the target GPU supports.
diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 18f36bebde717..043efced5c056 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -14,9 +14,6 @@ use wgpu_types::TextureFormat;
 ///
 /// Compressed textures use less GPU VRAM.
 ///
-/// Mipmaps are also generated, which prevents aliasing when textures are viewed at a distance,
-/// and increases GPU cache hits, improving rendering performance.
-///
 /// # Platform support
 ///
 /// Two mutually exclusive feature flags control which compression backend is used:
@@ -76,11 +73,15 @@ use wgpu_types::TextureFormat;
 /// All 14 ASTC block sizes are supported: `4x4`, `5x4`, `5x5`, `6x5`, `6x6`, `8x5`,
 /// `8x6`, `8x8`, `10x5`, `10x6`, `10x8`, `10x10`, `12x10`, `12x12`.
 ///
-/// # Mipmap generation
+/// # Mipmap generation (`compressed_image_saver` only)
+///
+/// When using the `compressed_image_saver` backend, mipmaps are generated automatically
+/// during compression. This prevents aliasing when textures are viewed at a distance and
+/// increases GPU cache hits, improving rendering performance. Input images must have a
+/// `mip_level_count` of 1 (i.e., no pre-existing mip chain); the compressor will produce
+/// a full mip chain in the output.
 ///
-/// Mipmaps are generated automatically during compression. The `compressed_image_saver` feature requires
-/// input images to have a `mip_level_count` of 1 (i.e., no pre-existing mip chain);
-/// the compressor will produce a full mip chain in the output.
+/// The `compressed_image_saver_universal` backend does not generate mipmaps.
 #[derive(TypePath)]
 pub struct CompressedImageSaver;
 

From f71c5856680f170c4f4452d5b4fcc491382eb499 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 12:46:55 -0400
Subject: [PATCH 17/21] Feedback

---
 .../compressed_image_saver.md                 |   2 +-
 .../bevy_image/src/compressed_image_saver.rs  | 104 +++++++++---------
 2 files changed, 56 insertions(+), 50 deletions(-)

diff --git a/_release-content/migration-guides/compressed_image_saver.md b/_release-content/migration-guides/compressed_image_saver.md
index e33a5d8c949a7..2098d312607f6 100644
--- a/_release-content/migration-guides/compressed_image_saver.md
+++ b/_release-content/migration-guides/compressed_image_saver.md
@@ -1,5 +1,5 @@
 ---
-title: `CompressedImageSaver` improvements
+title: "`CompressedImageSaver` improvements"
 pull_requests: [23567]
 ---
 
diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 043efced5c056..540eb4ea478b8 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -42,13 +42,14 @@ use wgpu_types::TextureFormat;
 ///
 /// | Input channels | Output format |
 /// |---|---|
-/// | 1-channel (R) | BC4 |
-/// | 1-channel snorm | BC4 snorm |
-/// | 2-channel (RG) | BC5 |
-/// | 2-channel snorm | BC5 snorm |
-/// | HDR / float (e.g. `Rgba16Float`) | BC6H |
+/// | 1-channel (`R8Unorm`) | BC4 |
+/// | 1-channel snorm (`R8Snorm`) | BC4 snorm |
+/// | 2-channel (`Rg8Unorm`) | BC5 |
+/// | 2-channel snorm (`Rg8Snorm`) | BC5 snorm |
+/// | HDR / packed float (e.g. `Rgb9e5Ufloat`) | BC6H |
 /// | 4-channel LDR (e.g. `Rgba8Unorm`) | BC7 |
 /// | 4-channel sRGB (e.g. `Rgba8UnormSrgb`) | BC7 sRGB |
+/// | Integer or high-precision (16-bit+) formats | Uncompressed KTX2 (passthrough) |
 /// | Already compressed (BCn, ASTC, ETC2, EAC) | Re-encoded to the same format |
 ///
 /// Depth, stencil, and video formats (`NV12`, `P010`) are not supported and will return
@@ -161,7 +162,7 @@ impl AssetSaver for CompressedImageSaver {
                     stride: image.width() * bytes_per_pixel,
                     format: input_format,
                     color_space,
-                    alpha: ctt::AlphaMode::Straight, // TODO: User-configurable?
+                    alpha: ctt::AlphaMode::Straight, // TODO: User-configurable
                 }]
             })
             .collect();
@@ -175,12 +176,12 @@ impl AssetSaver for CompressedImageSaver {
             container: ctt::Container::Ktx2,
             quality: ctt::Quality::default(),
             output_color_space: None,
-            output_alpha: None,
+            output_alpha: Some(ctt::AlphaMode::Premultiplied), // TODO: User-configurable
             swizzle: None,
             mipmap: true,
             mipmap_count: None,
             mipmap_filter: ctt::MipmapFilter::default(),
-            allow_lossy: true,
+            allow_lossy: false,
             encoder_settings: None,
             registry: None,
         };
@@ -369,7 +370,7 @@ fn choose_ctt_compressed_format(
 
     let format = match input {
         // 1-channel snorm
-        TextureFormat::R8Snorm | TextureFormat::R16Snorm => {
+        TextureFormat::R8Snorm => {
             if let Some((unorm, _, _)) = astc_block {
                 unorm
             } else {
@@ -378,17 +379,7 @@ fn choose_ctt_compressed_format(
         }
 
         // 1-channel
-        TextureFormat::R8Unorm
-        | TextureFormat::R8Uint
-        | TextureFormat::R8Sint
-        | TextureFormat::R16Uint
-        | TextureFormat::R16Sint
-        | TextureFormat::R16Unorm
-        | TextureFormat::R16Float
-        | TextureFormat::R32Uint
-        | TextureFormat::R32Sint
-        | TextureFormat::R32Float
-        | TextureFormat::R64Uint => {
+        TextureFormat::R8Unorm => {
             if let Some((unorm, _, _)) = astc_block {
                 unorm
             } else {
@@ -397,7 +388,7 @@ fn choose_ctt_compressed_format(
         }
 
         // 2-channel snorm
-        TextureFormat::Rg8Snorm | TextureFormat::Rg16Snorm => {
+        TextureFormat::Rg8Snorm => {
             if let Some((unorm, _, _)) = astc_block {
                 unorm
             } else {
@@ -406,16 +397,7 @@ fn choose_ctt_compressed_format(
         }
 
         // 2-channel
-        TextureFormat::Rg8Unorm
-        | TextureFormat::Rg8Uint
-        | TextureFormat::Rg8Sint
-        | TextureFormat::Rg16Uint
-        | TextureFormat::Rg16Sint
-        | TextureFormat::Rg16Unorm
-        | TextureFormat::Rg16Float
-        | TextureFormat::Rg32Uint
-        | TextureFormat::Rg32Sint
-        | TextureFormat::Rg32Float => {
+        TextureFormat::Rg8Unorm => {
             if let Some((unorm, _, _)) = astc_block {
                 unorm
             } else {
@@ -424,10 +406,7 @@ fn choose_ctt_compressed_format(
         }
 
         // HDR / float RGB formats
-        TextureFormat::Rgb9e5Ufloat
-        | TextureFormat::Rg11b10Ufloat
-        | TextureFormat::Rgba16Float
-        | TextureFormat::Rgba32Float => {
+        TextureFormat::Rgb9e5Ufloat | TextureFormat::Rg11b10Ufloat => {
             if let Some((_, _, hdr)) = astc_block {
                 hdr
             } else {
@@ -436,19 +415,7 @@ fn choose_ctt_compressed_format(
         }
 
         // 4-channel LDR
-        TextureFormat::Rgba8Unorm
-        | TextureFormat::Rgba8Uint
-        | TextureFormat::Rgba8Sint
-        | TextureFormat::Rgba8Snorm
-        | TextureFormat::Rgba16Uint
-        | TextureFormat::Rgba16Sint
-        | TextureFormat::Rgba16Unorm
-        | TextureFormat::Rgba16Snorm
-        | TextureFormat::Rgba32Uint
-        | TextureFormat::Rgba32Sint
-        | TextureFormat::Bgra8Unorm
-        | TextureFormat::Rgb10a2Uint
-        | TextureFormat::Rgb10a2Unorm => {
+        TextureFormat::Rgba8Unorm | TextureFormat::Bgra8Unorm | TextureFormat::Rgb10a2Unorm => {
             if let Some((unorm, _, _)) = astc_block {
                 unorm
             } else {
@@ -463,7 +430,7 @@ fn choose_ctt_compressed_format(
             }
         }
 
-        // Already compressed -> pass through
+        // Already compressed -> pass through as compressed
         TextureFormat::Bc1RgbaUnorm
         | TextureFormat::Bc1RgbaUnormSrgb
         | TextureFormat::Bc2RgbaUnorm
@@ -490,6 +457,45 @@ fn choose_ctt_compressed_format(
         | TextureFormat::EacRg11Snorm
         | TextureFormat::Astc { .. } => map_to_ctt_texture_format(input)?,
 
+        // Integer, high-precision, and float formats -> pass through uncompressed
+        TextureFormat::R8Uint
+        | TextureFormat::R8Sint
+        | TextureFormat::R16Uint
+        | TextureFormat::R16Sint
+        | TextureFormat::R16Unorm
+        | TextureFormat::R16Snorm
+        | TextureFormat::R16Float
+        | TextureFormat::R32Uint
+        | TextureFormat::R32Sint
+        | TextureFormat::R32Float
+        | TextureFormat::R64Uint
+        | TextureFormat::Rg8Uint
+        | TextureFormat::Rg8Sint
+        | TextureFormat::Rg16Uint
+        | TextureFormat::Rg16Sint
+        | TextureFormat::Rg16Unorm
+        | TextureFormat::Rg16Snorm
+        | TextureFormat::Rg16Float
+        | TextureFormat::Rg32Uint
+        | TextureFormat::Rg32Sint
+        | TextureFormat::Rg32Float
+        | TextureFormat::Rgba8Uint
+        | TextureFormat::Rgba8Sint
+        | TextureFormat::Rgba8Snorm
+        | TextureFormat::Rgba16Uint
+        | TextureFormat::Rgba16Sint
+        | TextureFormat::Rgba16Unorm
+        | TextureFormat::Rgba16Snorm
+        | TextureFormat::Rgba16Float
+        | TextureFormat::Rgba32Uint
+        | TextureFormat::Rgba32Sint
+        | TextureFormat::Rgba32Float
+        | TextureFormat::Rgb10a2Uint => {
+            return Ok(ctt::TargetFormat::Uncompressed(map_to_ctt_texture_format(
+                input,
+            )?));
+        }
+
         // Depth/stencil and video formats cannot be compressed
         TextureFormat::Stencil8
         | TextureFormat::Depth16Unorm

From 595ebf4863a9337c435dfe1c70a82ee61a4ee146 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 14:30:24 -0400
Subject: [PATCH 18/21] Doc tweaks

---
 _release-content/migration-guides/compressed_image_saver.md | 2 +-
 crates/bevy_image/src/compressed_image_saver.rs             | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/_release-content/migration-guides/compressed_image_saver.md b/_release-content/migration-guides/compressed_image_saver.md
index 2098d312607f6..40ede9f0d0050 100644
--- a/_release-content/migration-guides/compressed_image_saver.md
+++ b/_release-content/migration-guides/compressed_image_saver.md
@@ -15,6 +15,6 @@ bevy = { version = "0.18", features = ["compressed_image_saver"] }
 bevy = { version = "0.19", features = ["compressed_image_saver_universal"] }
 ```
 
-Alternatively, keep using `compressed_image_saver` to get the new BCn/ASTC compression backend. This produces higher-quality output and supports a wider range of input formats, but does not support web.
+Alternatively, keep using `compressed_image_saver` to get the new BCn/ASTC compression backend. This produces higher-quality output and supports a wider range of input formats, but does not support all platforms in a single file like UASTC does. We reccomend sticking to `compressed_image_saver_universal` when targeting the web.
 
 `CompressedImageSaverError` has a new variant `CompressionFailed`. If you were matching exhaustively on this enum, add a branch for it.
diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 540eb4ea478b8..5e4c729d3d763 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -12,7 +12,7 @@ use wgpu_types::TextureFormat;
 
 /// An [`AssetSaver`] for [`Image`] that compresses texture files.
 ///
-/// Compressed textures use less GPU VRAM.
+/// Compressed textures use less GPU VRAM and are faster to sample.
 ///
 /// # Platform support
 ///
@@ -27,7 +27,7 @@ use wgpu_types::TextureFormat;
 /// - **`compressed_image_saver_universal`** — Uses `basis-universal` to compress textures into UASTC
 ///   (Basis Universal) format. This is a GPU-agnostic supercompressed format that can be
 ///   transcoded at load time to whatever format the target GPU supports, making it suitable for
-///   WebGPU and cross-platform distribution.
+///   WebGPU and cross-platform distribution in a single file.
 ///
 /// # Runtime feature flags
 ///

From 3978fbf19381c0bf0b644f04af8c98b5d88aea75 Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 14:32:50 -0400
Subject: [PATCH 19/21] Typo

---
 _release-content/migration-guides/compressed_image_saver.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/_release-content/migration-guides/compressed_image_saver.md b/_release-content/migration-guides/compressed_image_saver.md
index 40ede9f0d0050..1d39a165e249a 100644
--- a/_release-content/migration-guides/compressed_image_saver.md
+++ b/_release-content/migration-guides/compressed_image_saver.md
@@ -15,6 +15,6 @@ bevy = { version = "0.18", features = ["compressed_image_saver"] }
 bevy = { version = "0.19", features = ["compressed_image_saver_universal"] }
 ```
 
-Alternatively, keep using `compressed_image_saver` to get the new BCn/ASTC compression backend. This produces higher-quality output and supports a wider range of input formats, but does not support all platforms in a single file like UASTC does. We reccomend sticking to `compressed_image_saver_universal` when targeting the web.
+Alternatively, keep using `compressed_image_saver` to get the new BCn/ASTC compression backend. This produces higher-quality output and supports a wider range of input formats, but does not support all platforms in a single file like UASTC does. We recommend sticking to `compressed_image_saver_universal` when targeting the web.
 
 `CompressedImageSaverError` has a new variant `CompressionFailed`. If you were matching exhaustively on this enum, add a branch for it.

From 5f0f2b227ed32d3e6c2071a2ce4cc3bcee6aa0ca Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Sun, 12 Apr 2026 18:12:55 -0400
Subject: [PATCH 20/21] Use BC6H for rgba16float

---
 crates/bevy_image/src/compressed_image_saver.rs | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 5e4c729d3d763..463d85f03a980 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -46,10 +46,10 @@ use wgpu_types::TextureFormat;
 /// | 1-channel snorm (`R8Snorm`) | BC4 snorm |
 /// | 2-channel (`Rg8Unorm`) | BC5 |
 /// | 2-channel snorm (`Rg8Snorm`) | BC5 snorm |
-/// | HDR / packed float (e.g. `Rgb9e5Ufloat`) | BC6H |
+/// | HDR / float (e.g. `Rgba16Float`) | BC6H |
 /// | 4-channel LDR (e.g. `Rgba8Unorm`) | BC7 |
 /// | 4-channel sRGB (e.g. `Rgba8UnormSrgb`) | BC7 sRGB |
-/// | Integer or high-precision (16-bit+) formats | Uncompressed KTX2 (passthrough) |
+/// | Integer or high-precision (>16-bit) formats | Uncompressed KTX2 (passthrough) |
 /// | Already compressed (BCn, ASTC, ETC2, EAC) | Re-encoded to the same format |
 ///
 /// Depth, stencil, and video formats (`NV12`, `P010`) are not supported and will return
@@ -405,8 +405,12 @@ fn choose_ctt_compressed_format(
             }
         }
 
-        // HDR / float RGB formats
-        TextureFormat::Rgb9e5Ufloat | TextureFormat::Rg11b10Ufloat => {
+        // HDR / float formats
+        TextureFormat::Rgb9e5Ufloat
+        | TextureFormat::Rg11b10Ufloat
+        | TextureFormat::R16Float
+        | TextureFormat::Rg16Float
+        | TextureFormat::Rgba16Float => {
             if let Some((_, _, hdr)) = astc_block {
                 hdr
             } else {
@@ -464,7 +468,6 @@ fn choose_ctt_compressed_format(
         | TextureFormat::R16Sint
         | TextureFormat::R16Unorm
         | TextureFormat::R16Snorm
-        | TextureFormat::R16Float
         | TextureFormat::R32Uint
         | TextureFormat::R32Sint
         | TextureFormat::R32Float
@@ -475,7 +478,6 @@ fn choose_ctt_compressed_format(
         | TextureFormat::Rg16Sint
         | TextureFormat::Rg16Unorm
         | TextureFormat::Rg16Snorm
-        | TextureFormat::Rg16Float
         | TextureFormat::Rg32Uint
         | TextureFormat::Rg32Sint
         | TextureFormat::Rg32Float
@@ -486,7 +488,6 @@ fn choose_ctt_compressed_format(
         | TextureFormat::Rgba16Sint
         | TextureFormat::Rgba16Unorm
         | TextureFormat::Rgba16Snorm
-        | TextureFormat::Rgba16Float
         | TextureFormat::Rgba32Uint
         | TextureFormat::Rgba32Sint
         | TextureFormat::Rgba32Float

From 6e1255cc37f2b64470b9d631e3a5c07250286fff Mon Sep 17 00:00:00 2001
From: JMS55 <47158642+JMS55@users.noreply.github.com>
Date: Mon, 13 Apr 2026 22:27:56 -0400
Subject: [PATCH 21/21] Zstd supercompression

---
 crates/bevy_image/Cargo.toml                    | 4 ++--
 crates/bevy_image/src/compressed_image_saver.rs | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/crates/bevy_image/Cargo.toml b/crates/bevy_image/Cargo.toml
index 3d3e3ea92dc8a..62a725eb1b16f 100644
--- a/crates/bevy_image/Cargo.toml
+++ b/crates/bevy_image/Cargo.toml
@@ -82,7 +82,7 @@ futures-lite = "2.0.1"
 guillotiere = "0.6.0"
 rectangle-pack = "0.4"
 ddsfile = { version = "0.5.2", optional = true }
-ktx2 = { version = "0.4.0", optional = true }
+ktx2 = { git = "https://github.com/BVE-Reborn/ktx2.git", rev = "49e6fed", optional = true }
 # For ktx2 supercompression
 flate2 = { version = "1.0.22", optional = true }
 zstd = { version = "0.13.3", optional = true }
@@ -91,7 +91,7 @@ ruzstd = { version = "0.8.0", optional = true }
 basis-universal = { version = "0.3.0", optional = true }
 tracing = { version = "0.1", default-features = false, features = ["std"] }
 half = { version = "2.4.1" }
-ctt = { git = "https://github.com/cwfitzgerald/ctt", rev = "fd41d518a557803bd1eda1bcc6fbbcd4e07757c5", optional = true }
+ctt = { git = "https://github.com/cwfitzgerald/ctt", rev = "0ac0748fc25fd0cdee2794a43d1617cc5b776e05", optional = true }
 
 [dev-dependencies]
 bevy_ecs = { path = "../bevy_ecs", version = "0.19.0-dev" }
diff --git a/crates/bevy_image/src/compressed_image_saver.rs b/crates/bevy_image/src/compressed_image_saver.rs
index 463d85f03a980..f797657939232 100644
--- a/crates/bevy_image/src/compressed_image_saver.rs
+++ b/crates/bevy_image/src/compressed_image_saver.rs
@@ -33,7 +33,7 @@ use wgpu_types::TextureFormat;
 ///
 /// The compressed output must also be loadable at runtime. Enable the corresponding feature:
 ///
-/// - **`ktx2`** — Required to load KTX2 files produced by `compressed_image_saver`.
+/// - **`ktx2` and `zstd`** — Required to load KTX2 files produced by `compressed_image_saver`.
 /// - **`basis-universal`** — Required to load Basis Universal files produced by `compressed_image_saver_universal`.
 ///
 /// # Compression format selection
@@ -173,7 +173,7 @@ impl AssetSaver for CompressedImageSaver {
 
         let settings = ctt::ConvertSettings {
             format: Some(output_format),
-            container: ctt::Container::Ktx2,
+            container: ctt::Container::ktx2_zstd(0),
             quality: ctt::Quality::default(),
             output_color_space: None,
             output_alpha: Some(ctt::AlphaMode::Premultiplied), // TODO: User-configurable
@@ -188,7 +188,7 @@ impl AssetSaver for CompressedImageSaver {
 
         let output = ctt::convert(ctt_image, settings)
             .map_err(|e| CompressedImageSaverError::CompressionFailed(Box::new(e)))?;
-        let ctt::ConvertOutput::Encoded(compressed_bytes) = &output else {
+        let ctt::PipelineOutput::Encoded(compressed_bytes) = &output else {
             return Err(CompressedImageSaverError::CompressionFailed(
                 "Expected encoded output from ctt".into(),
             ));