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LibGfx/JBIG2: Call decode_immediate_generic_region for lossless regions

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It seems to do the right thing already, and nothing in the spec says
not to do this as far as I can tell.

With this, we can finally decode
Tests/LibGfx/test-inputs/jbig2/bitmap.jbig2 and add a test for
decoding simple arithmetic-coded images.
This commit is contained in:
Nico Weber 2024-03-14 22:00:01 -04:00 committed by Tim Flynn
parent 6788a82ec5
commit f391c7822d
2 changed files with 23 additions and 8 deletions
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17
Tests/LibGfx/TestImageDecoder.cpp
View file

@ -336,6 +336,23 @@ TEST_CASE(test_jbig2_white_47x23)
EXPECT_EQ(pixel, Gfx::Color(Gfx::Color::White).value());
}
TEST_CASE(test_jbig2_generic_region_arithmetic_code)
{
auto file = TRY_OR_FAIL(Core::MappedFile::map(TEST_INPUT("jbig2/bitmap.jbig2"sv)));
EXPECT(Gfx::JBIG2ImageDecoderPlugin::sniff(file->bytes()));
auto plugin_decoder = TRY_OR_FAIL(Gfx::JBIG2ImageDecoderPlugin::create(file->bytes()));
auto bmp_file = TRY_OR_FAIL(Core::MappedFile::map(TEST_INPUT("bmp/bitmap.bmp"sv)));
auto bmp_plugin_decoder = TRY_OR_FAIL(Gfx::JBIG2ImageDecoderPlugin::create(file->bytes()));
auto frame = TRY_OR_FAIL(expect_single_frame_of_size(*plugin_decoder, { 399, 400 }));
auto bmp_frame = TRY_OR_FAIL(expect_single_frame_of_size(*bmp_plugin_decoder, { 399, 400 }));
for (int y = 0; y < frame.image->height(); ++y)
for (int x = 0; x < frame.image->width(); ++x)
EXPECT_EQ(frame.image->get_pixel(x, y), bmp_frame.image->get_pixel(x, y));
}
TEST_CASE(test_jbig2_arithmetic_decoder)
{
// https://www.itu.int/rec/T-REC-T.88-201808-I

14
Userland/Libraries/LibGfx/ImageFormats/JBIG2Loader.cpp
View file

@ -922,11 +922,6 @@ static ErrorOr<void> decode_immediate_generic_region(JBIG2LoadingContext& contex
return {};
}
static ErrorOr<void> decode_immediate_lossless_generic_region(JBIG2LoadingContext&, SegmentData const&)
{
return Error::from_string_literal("JBIG2ImageDecoderPlugin: Cannot decode immediate lossless generic region yet");
}
static ErrorOr<void> decode_intermediate_generic_refinement_region(JBIG2LoadingContext&, SegmentData const&)
{
return Error::from_string_literal("JBIG2ImageDecoderPlugin: Cannot decode intermediate generic refinement region yet");
@ -1118,10 +1113,13 @@ static ErrorOr<void> decode_data(JBIG2LoadingContext& context)
TRY(decode_intermediate_generic_region(context, segment));
break;
case SegmentType::ImmediateGenericRegion:
TRY(decode_immediate_generic_region(context, segment));
break;
case SegmentType::ImmediateLosslessGenericRegion:
TRY(decode_immediate_lossless_generic_region(context, segment));
// 7.4.6 Generic region segment syntax
// "The data parts of all three of the generic region segment types ("intermediate generic region", "immediate generic region" and
// "immediate lossless generic region") are coded identically, but are acted upon differently, see 8.2."
// But 8.2 only describes a difference between intermediate and immediate regions as far as I can tell,
// and calling the immediate generic region handler for immediate generic lossless regions seems to do the right thing (?).
TRY(decode_immediate_generic_region(context, segment));
break;
case SegmentType::IntermediateGenericRefinementRegion:
TRY(decode_intermediate_generic_refinement_region(context, segment));