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WebP: Add test for horizontal ALPH chunk filtering_method

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This commit is contained in:
Nico Weber 2023-06-08 17:28:59 -04:00 • committed by Tim Flynn
parent 737786f9a8
commit 816674de36
2 changed files with 25 additions and 1 deletions
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25
Tests/LibGfx/TestImageDecoder.cpp
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@ -348,6 +348,7 @@ TEST_CASE(test_webp_simple_lossless)
TEST_CASE(test_webp_extended_lossy)
{
// This extended lossy image has an ALPH chunk for (losslessly compressed) alpha data.
auto file = MUST(Core::MappedFile::map(TEST_INPUT("extended-lossy.webp"sv)));
EXPECT(Gfx::WebPImageDecoderPlugin::sniff(file->bytes()));
auto plugin_decoder = MUST(Gfx::WebPImageDecoderPlugin::create(file->bytes()));
@ -379,6 +380,30 @@ TEST_CASE(test_webp_extended_lossy)
EXPECT_EQ(frame.image->get_pixel(341, 75), Gfx::Color(0, 0, 0, 128));
}
TEST_CASE(test_webp_extended_lossy_alpha_horizontal_filter)
{
// Also lossy rgb + lossless alpha, but with a horizontal alpha filtering method.
// The image should look like smolkling.webp, but with a horizontal alpha gradient.
auto file = MUST(Core::MappedFile::map(TEST_INPUT("smolkling-horizontal-alpha.webp"sv)));
EXPECT(Gfx::WebPImageDecoderPlugin::sniff(file->bytes()));
auto plugin_decoder = MUST(Gfx::WebPImageDecoderPlugin::create(file->bytes()));
MUST(plugin_decoder->initialize());
EXPECT_EQ(plugin_decoder->frame_count(), 1u);
EXPECT(!plugin_decoder->is_animated());
EXPECT(!plugin_decoder->loop_count());
EXPECT_EQ(plugin_decoder->size(), Gfx::IntSize(264, 264));
auto frame = MUST(plugin_decoder->frame(0));
EXPECT_EQ(frame.image->size(), Gfx::IntSize(264, 264));
// While VP8 YUV contents are defined bit-exact, the YUV->RGB conversion isn't.
// So pixels changing by 1 or so below is fine if you change code.
// The important component in this test is alpha, and that shouldn't change even by 1 as it's losslessly compressed and doesn't use YUV.
EXPECT_EQ(frame.image->get_pixel(131, 131), Gfx::Color(0x8f, 0x51, 0x2f, 0x4b));
}
TEST_CASE(test_webp_extended_lossy_uncompressed_alpha)
{
auto file = MUST(Core::MappedFile::map(TEST_INPUT("extended-lossy-uncompressed-alpha.webp"sv)));

1
Userland/Libraries/LibGfx/ImageFormats/WebPLoader.cpp
View file

@ -276,7 +276,6 @@ static ErrorOr<void> decode_webp_chunk_ALPH(Chunk const& alph_chunk, Bitmap& bit
// "Method 1: predictor = A"
// "The top-left value at location (0, 0) uses 0 as predictor value. Otherwise,
// For horizontal or gradient filtering methods, the left-most pixels at location (0, y) are predicted using the location (0, y-1) just above."
// FIXME: This branch is untested.
for (int y = 1; y < bitmap.height(); ++y)
alpha[y * bitmap.width()] += alpha[(y - 1) * bitmap.width()];
for (int y = 0; y < bitmap.height(); ++y) {