CompressedImageSaver improvements

Cargo.toml

@@ -431,7 +431,12 @@ 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
+# 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

_release-content/migration-guides/compressed_image_saver.md

@@ -0,0 +1,20 @@
+---
+title: "`CompressedImageSaver` improvements"
+pull_requests: [23567]
+---
+
+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.
+
+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`:
+
+```toml
+# Before
+bevy = { version = "0.18", features = ["compressed_image_saver"] }
+
+# 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 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.

_release-content/release-notes/compressed_image_saver.md

@@ -0,0 +1,21 @@
+---
+title: CompressedImageSaver Improvements
+authors: ["@JMS55", "@cwfitzgerald"]
+pull_requests: [23567]
+---
+
+Bevy's `CompressedImageSaver` asset processor has been significantly upgraded with a new compression backend powered by the [`ctt`](https://github.com/cwfitzgerald/ctt) library.
+
+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.
+
+## Automatic Mipmap Generation
+
+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.
+
+## ASTC for Mobile
+
+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.

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 (cross-platform, transcodes to any GPU format at load time)
+compressed_image_saver_universal = ["basis-universal"]
+
+# Texture compression asset processor (BCn for desktop, ASTC for mobile via env var)
+compressed_image_saver = ["dep:ctt", "ktx2"]
 
 [dependencies]
 # bevy
@@ -79,7 +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 }
@@ -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 = { git = "https://github.com/cwfitzgerald/ctt", rev = "0ac0748fc25fd0cdee2794a43d1617cc5b776e05", optional = true }
 
 [dev-dependencies]
 bevy_ecs = { path = "../bevy_ecs", version = "0.19.0-dev" }