commit 38cd721a7a515460c2a752a5bd0e5bbbd7ea8923
author Wan-Teh Chang <wtc@google.com> Mon Apr 10 16:19:48 2023 -0700
committer Wan-Teh Chang <wtc@google.com> Tue Apr 11 12:07:58 2023 -0700
tree 49d1e3b74266671cd3ed7d2db4848e41ffa235d2
parent d7d05ec3c5aecbc14090eec6e432346a56c5e9a4

avifPNGRead: Don't add alpha filler if no alpha

If the PNG input has no alpha, don't add fully-opaque alpha filler.
Although avifEncoderAddImage() ignores a fully-opaque alpha plane, it
does so only when encoding a single image. When we encode a progressive
image, the current implementation encodes the layers as potentially
different images, so the avifImageIsOpaque() check for a single image is
skipped and the alpha plane is encoded.

apps/shared/avifpng.c

diff --git a/apps/shared/avifpng.c b/apps/shared/avifpng.c
index 4bbe8d6..bcd908a 100644
--- a/apps/shared/avifpng.c
+++ b/apps/shared/avifpng.c
@@ -294,10 +294,6 @@
         png_set_tRNS_to_alpha(png);
     }
 
-    if ((rawColorType == PNG_COLOR_TYPE_RGB) || (rawColorType == PNG_COLOR_TYPE_GRAY) || (rawColorType == PNG_COLOR_TYPE_PALETTE)) {
-        png_set_filler(png, 0xFFFF, PNG_FILLER_AFTER);
-    }
-
     if ((rawColorType == PNG_COLOR_TYPE_GRAY) || (rawColorType == PNG_COLOR_TYPE_GRAY_ALPHA)) {
         png_set_gray_to_rgb(png);
     }
@@ -339,6 +335,9 @@
     avifRGBImageSetDefaults(&rgb, avif);
     rgb.chromaDownsampling = chromaDownsampling;
     rgb.depth = imgBitDepth;
+    if ((rawColorType == PNG_COLOR_TYPE_RGB) || (rawColorType == PNG_COLOR_TYPE_GRAY) || (rawColorType == PNG_COLOR_TYPE_PALETTE)) {
+        rgb.format = AVIF_RGB_FORMAT_RGB;
+    }
     if (avifRGBImageAllocatePixels(&rgb) != AVIF_RESULT_OK) {
         fprintf(stderr, "Conversion to YUV failed: %s (out of memory)\n", inputFilename);
         goto cleanup;