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LibGfx/GIF: Only parse global color table if header flag is set

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This fixes an issue where GIF images without a global color table would
have the first segment incorrectly interpreted as color table data.

Makes many more screenshots appear on https://virtuallyfun.com/ :^)
This commit is contained in:
Andreas Kling 2024-01-04 21:19:53 +01:00
parent a1d669fe63
commit 182a2b0c3a
2 changed files with 75 additions and 10 deletions
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59
Tests/LibGfx/TestImageDecoder.cpp
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@ -100,6 +100,65 @@ TEST_CASE(test_gif)
EXPECT(frame.duration == 400);
}
TEST_CASE(test_gif_without_global_color_table)
{
Array<u8, 35> gif_data {
// Header (6 bytes): "GIF89a"
0x47,
0x49,
0x46,
0x38,
0x39,
0x61,
// Logical Screen Descriptor (7 bytes)
0x01,
0x00, // Width (1)
0x01,
0x00, // Height (1)
0x00, // Packed fields (NOTE: the MSB here is the Global Color Table flag!)
0x00, // Background Color Index
0x00, // Pixel Aspect Ratio
// Image Descriptor (10 bytes)
0x2C,
0x00,
0x00,
0x00,
0x00,
0x01,
0x00,
0x01,
0x00,
0x80,
// Local Color Table (6 bytes: 2 colors, 3 bytes per color)
0x00,
0x00,
0x00, // Color 1: Black (RGB: 0, 0, 0)
0xff,
0x00,
0x00, // Color 2: Red (RGB: 255, 0, 0)
// Image Data (8 bytes)
0x02, // LZW Minimum Code Size
0x02, // Data Sub-block size (2 bytes)
0x4C,
0x01, // Image Data
0x00, // Data Sub-block Terminator
// Trailer (1 byte)
0x3B,
};
auto plugin_decoder = TRY_OR_FAIL(Gfx::GIFImageDecoderPlugin::create(gif_data));
EXPECT_EQ(plugin_decoder->frame_count(), 1u);
auto frame = TRY_OR_FAIL(plugin_decoder->frame(0));
EXPECT(frame.image);
EXPECT_EQ(frame.image->size(), Gfx::IntSize(1, 1));
EXPECT_EQ(frame.image->get_pixel(0, 0), Gfx::Color::NamedColor::Red);
}
TEST_CASE(test_not_ico)
{
auto file = MUST(Core::MappedFile::map(TEST_INPUT("png/buggie.png"sv)));