add support for Sixel

Project.toml

@@ -12,13 +12,14 @@ ImageCore = "a09fc81d-aa75-5fe9-8630-4744c3626534"
 LazyModules = "8cdb02fc-e678-4876-92c5-9defec4f444e"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 SHA = "ea8e919c-243c-51af-8825-aaa63cd721ce"
+Sixel = "45858cf5-a6b0-47a3-bbea-62219f50df47"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 XTermColors = "c8c2cc18-de81-4e68-b407-38a3a0c0491f"
 
 [compat]
 BSON = "0.3"
-Colors = "0.10 - 0.13"
 CSVFiles = "1"
+Colors = "0.10 - 0.13"
 DataFrames = "0.21 - 0.22, 1"
 DeepDiffs = "1"
 Distances = "0.7 - 0.10"
@@ -28,6 +29,7 @@ ImageMagick = "0.7, 1"
 ImageTransformations = "0.8 - 0.10"
 LazyModules = "0.3"
 Plots = "= 1.39.0"
+Sixel = "0.1.3"
 TestImages = "0.6, 1"
 XTermColors = "0.2"
 julia = "1.6"

src/ReferenceTests.jl

@@ -11,6 +11,7 @@ using FileIO
 using SHA
 using DeepDiffs
 using Random
+using Sixel
 
 export
     @withcolor,

src/render.jl

@@ -30,13 +30,17 @@ function render_item(::BeforeAfterImage, item)
     println(io, "eltype: ", eltype(item))
     println(io, "size: ", map(length, axes(item)))
     println(io, "thumbnail:")
-    strs = @withcolor XTermColors.ascii_show(
-        item,
-        Base.invokelatest(XTermColors.TermColor8bit),
-        :small,
-        (20, 40)
-    )
-    print(io, join(strs, '\n'))
+    if Base.get_bool_env("REFERENCETESTS_SIXEL", false)
+        sixel_encode(io, item)
+    else
+        strs = @withcolor XTermColors.ascii_show(
+            item,
+            Base.invokelatest(XTermColors.TermColor8bit),
+            :small,
+            (20, 40)
+        )
+        print(io, join(strs, '\n'))
+    end
     read(io, String)
 end