commit 5bdead578d3ad9772e27317b10a2e1d86eea116d
author Wan-Teh Chang <wtc@google.com> Wed Aug 12 17:02:22 2020 -0700
committer Joe Drago <joedrago@gmail.com> Wed Aug 12 18:02:12 2020 -0700
tree a01712d757860c2c9aa330854b91104f13b4565d
parent bc35a5f0123ab00f7515ad5b10f56a37dc3bf16b

Fix avifDecoderDataFillImageGrid for alpha images

Require all tiles in the image grid to have the same alphaRange.

Guard the (dstImage->yuvFormat != firstTile->image->yuvFormat) check
with !alpha. avifDecoderDataFillImageGrid() is called twice, first for
color, then for alpha. In the first call (alpha=false),
dstImage->yuvRange is set to the correct value. In the second call
(alpha=true), firstTile->image->yuvFormat is AVIF_PIXEL_FORMAT_NONE (the
default value), so (dstImage->yuvFormat != firstTile->image->yuvFormat)
is always true.

Call avifGetPixelFormatInfo(firstTile->image->yuvFormat, &formatInfo)
if 'alpha' is false because formatInfo is only used when 'alpha' is
false.

src/read.c

diff --git a/src/read.c b/src/read.c
index a4517c0..4c76efd 100644
--- a/src/read.c
+++ b/src/read.c
@@ -694,7 +694,8 @@
             (tile->image->yuvRange != firstTile->image->yuvRange) || (uvPresent != firstTileUVPresent) ||
             (tile->image->colorPrimaries != firstTile->image->colorPrimaries) ||
             (tile->image->transferCharacteristics != firstTile->image->transferCharacteristics) ||
-            (tile->image->matrixCoefficients != firstTile->image->matrixCoefficients)) {
+            (tile->image->matrixCoefficients != firstTile->image->matrixCoefficients) ||
+            (tile->image->alphaRange != firstTile->image->alphaRange)) {
             return AVIF_FALSE;
         }
     }
@@ -736,7 +737,7 @@
     // Lazily populate dstImage with the new frame's properties. If we're decoding alpha,
     // these values must already match.
     if ((dstImage->width != grid->outputWidth) || (dstImage->height != grid->outputHeight) ||
-        (dstImage->depth != firstTile->image->depth) || (dstImage->yuvFormat != firstTile->image->yuvFormat)) {
+        (dstImage->depth != firstTile->image->depth) || (!alpha && (dstImage->yuvFormat != firstTile->image->yuvFormat))) {
         if (alpha) {
             // Alpha doesn't match size, just bail out
             return AVIF_FALSE;
@@ -762,7 +763,9 @@
     avifImageAllocatePlanes(dstImage, alpha ? AVIF_PLANES_A : AVIF_PLANES_YUV);
 
     avifPixelFormatInfo formatInfo;
-    avifGetPixelFormatInfo(firstTile->image->yuvFormat, &formatInfo);
+    if (!alpha) {
+        avifGetPixelFormatInfo(firstTile->image->yuvFormat, &formatInfo);
+    }
 
     unsigned int tileIndex = firstTileIndex;
     size_t pixelBytes = avifImageUsesU16(dstImage) ? 2 : 1;