Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 9378948f645655b1eb35f0058adc14aecd566d32
https://github.com/WebKit/WebKit/commit/9378948f645655b1eb35f0058adc14aecd566d32
Author: Ahmad Saleem <[email protected]>
Date: 2026-09-13 (Sun, 13 Sep 2026)
Changed paths:
M Source/WebCore/platform/graphics/cv/CVUtilities.mm
M Tools/TestWebKitAPI/Tests/WebCore/cocoa/ImageRotationSessionVT.cpp
Log Message:
-----------
createBlackPixelBuffer produces super-black instead of legal black for
video-range buffers
https://bugs.webkit.org/show_bug.cgi?id=324081
rdar://187309125
Reviewed by Jean-Yves Avenard.
createBlackPixelBuffer() zeroed the Y (luma) plane unconditionally for
both supported formats. That is correct for kCVPixelFormatType_420YpCbCr8-
BiPlanarFullRange, where black is Y=0, but wrong for the video-range
format kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange, whose legal luma
range is 16-235 and whose black is the luma floor Y=16. Writing Y=0 there
produces "super-black" / footroom below the legal floor. Video range is
the default format on macOS (preferedPixelBufferFormat()), so black frames
generated on macOS were out of range. The chroma fill (UV=128) was already
correct for both formats.
Fill the luma plane with the format-appropriate black: 16 for video range,
0 for full range.
Test: Tools/TestWebKitAPI/Tests/WebCore/cocoa/ImageRotationSessionVT.cpp
* Source/WebCore/platform/graphics/cv/CVUtilities.mm:
(WebCore::createBlackPixelBuffer): Select the luma value based on the
pixel format instead of always zeroing the Y plane.
* Tools/TestWebKitAPI/Tests/WebCore/cocoa/ImageRotationSessionVT.cpp:
(TestWebKitAPI::TEST(CVUtilities, CreateBlackPixelBuffer)): Verify the Y
plane matches the buffer's legal black for its actual pixel format and
that chroma is neutral (128).
Canonical link: https://commits.webkit.org/321040@main
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