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WebP/Lossy: Add test for lossy webp with uncompressed alpha

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The alpha channel of a lossy webp is always stored separately from
the (lossy) RGB data. Alpha is either compressed in a lossless webp
that stores just the alpha data, or it's stored completely
uncompressed. (But again, even if it's compressed, it's losslessly
compressed.)

This adds a test for uncompressed alpha, which I hadn't tested before.
It seems to work correctly, though :^)

I generated the test image by running:

    ~/Downloads/libwebp-1.3.0-mac-arm64/bin/cwebp \
      -alpha_method 0 \
      Tests/LibGfx/test-inputs/extended-lossless.webp \
      -o Tests/LibGfx/test-inputs/extended-lossy-uncompressed-alpha.webp
This commit is contained in:
Nico Weber 2023-05-29 19:19:29 -04:00 • committed by Andreas Kling
parent a22cbc9a28
commit b7e31ba194
2 changed files with 25 additions and 0 deletions
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25
Tests/LibGfx/TestImageDecoder.cpp
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@ -379,6 +379,31 @@ 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_uncompressed_alpha)
{
auto file = MUST(Core::MappedFile::map(TEST_INPUT("extended-lossy-uncompressed-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(417, 223));
auto frame = MUST(plugin_decoder->frame(0));
EXPECT_EQ(frame.image->size(), Gfx::IntSize(417, 223));
// 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.
EXPECT_EQ(frame.image->get_pixel(89, 72), Gfx::Color(255, 0, 4, 255));
EXPECT_EQ(frame.image->get_pixel(174, 69), Gfx::Color(4, 255, 0, 255));
EXPECT_EQ(frame.image->get_pixel(245, 84), Gfx::Color(0, 0, 255, 255));
EXPECT_EQ(frame.image->get_pixel(352, 125), Gfx::Color(0, 0, 0, 128));
EXPECT_EQ(frame.image->get_pixel(355, 106), Gfx::Color(0, 0, 0, 0));
}
TEST_CASE(test_webp_lossy_5)
{
// This is https://commons.wikimedia.org/wiki/File:Fr%C3%BChling_bl%C3%BChender_Kirschenbaum.jpg,