Fix #613, 24-bit PNG files with a zero alpha channel are now properly…

… encoded when using lossy PNG and when no transparency-inducing operations are performed.
imazen · Nov 21, 2022 · d5f439c · d5f439c
1 parent c6039b4
commit d5f439c
Show file tree

Hide file tree

Showing 3 changed files with 8 additions and 3 deletions.
diff --git a/imageflow_core/src/codecs/pngquant.rs b/imageflow_core/src/codecs/pngquant.rs
@@ -56,6 +56,11 @@ impl Encoder for PngquantEncoder {
         let mut bitmap = bitmaps.try_borrow_mut(bitmap_key)
             .map_err(|e| e.at(here!()))?;
 
+        {
+            let mut bitmap_bgra = unsafe { bitmap.get_window_u8().unwrap().to_bitmap_bgra()? };
+            bitmap_bgra.normalize_alpha().map_err(|e| e.at(here!()))?;
+        }
+
         unsafe {
             let (vec,w,h) = bitmap.get_window_u8()
                 .ok_or_else(|| nerror!(ErrorKind::InvalidBitmapType))?

diff --git a/imageflow_core/tests/visuals.rs b/imageflow_core/tests/visuals.rs
@@ -92,12 +92,12 @@ fn test_transparent_png_to_png() {
 #[test]
 fn test_problematic_png_lossy() {
     compare_encoded(
-        Some(IoTestEnum::Url("https://imageflow-resources.s3.us-west-2.amazonaws.com/test_inputs/png_turns_empty.png".to_owned())),
+        Some(IoTestEnum::Url("https://imageflow-resources.s3.us-west-2.amazonaws.com/test_inputs/png_turns_empty_2.png".to_owned())),
         "test_problematic_png_lossy",
         POPULATE_CHECKSUMS,
         DEBUG_GRAPH,
         Constraints {
-            similarity: Similarity::AllowOffByOneBytesCount(100),
+            similarity: Similarity::AllowDssimMatch(0.0, 0.002),
             max_file_size: None
         },
         vec![

diff --git a/imageflow_core/tests/visuals/checksums.json b/imageflow_core/tests/visuals/checksums.json
@@ -78,7 +78,7 @@
   "test_branching_crop_whitespace_gradient_output_1": "01864661ED8AB31EF.png",
   "test_branching_crop_whitespace_gradient_output_2": "0B3D16EB972FE0DBB.png",
   "test_negatives_in_command_string": "0BA85F7DC751DD69E_0726847C75419A20C",
-  "test_problematic_png_lossy": "0E5E63543D35A149D.png",
+  "test_problematic_png_lossy": "03B9493B2F3806A45.png",
   "test_rot_90_and_red_dot": "0176FBE641002F3ED_0AE4839D1D9B04C57",
   "test_rot_90_and_red_dot_command_string": "0C790C6600AFBBADA_0AE4839D1D9B04C57",
   "test_round_corners_command_string": "05218274046A5989B_0BF80F0AE71CD9A63",