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LibGfx/JBIG2: Add an initial decode_segment_header()

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With `#define JBIG2_DEBUG 1` at the top of the file:

    % Build/lagom/bin/image --no-output \
        .../JBIG2_ConformanceData-A20180829/F01_200_TT10.jb2
    JBIG2LoadingContext: Organization: 0 (Sequential)
    JBIG2LoadingContext: Number of pages: 1
    Segment number: 0
    Segment type: 48
    Referred to segment count: 0
    Segment page association: 1
    Segment data length: 19
    Runtime error: JBIG2ImageDecoderPlugin: Draw the rest of the owl
This commit is contained in:
Nico Weber 2024-03-03 20:38:30 -05:00 • committed by Andreas Kling
parent 5cefcad2fe
commit 177664cfae
1 changed files with 112 additions and 0 deletions
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112
Userland/Libraries/LibGfx/ImageFormats/JBIG2Loader.cpp
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@ -9,12 +9,39 @@
// Spec: ITU-T_T_88__08_2018.pdf in the zip file here:
// https://www.itu.int/rec/T-REC-T.88-201808-I
// Annex H has a datastream example.
namespace Gfx {
// JBIG2 spec, Annex D, D.4.1 ID string
static constexpr u8 id_string[] = { 0x97, 0x4A, 0x42, 0x32, 0x0D, 0x0A, 0x1A, 0x0A };
// 7.3 Segment types
enum SegmentType {
SymbolDictionary = 0,
IntermediateTextRegion = 4,
ImmediateTextRegion = 6,
ImmediateLosslessTextRegion = 7,
PatternDictionary = 16,
IntermediateHalftoneRegion = 20,
ImmediateHalftoneRegion = 22,
ImmediateLosslessHalftoneRegion = 23,
IntermediateGenericRegion = 36,
ImmediateGenericRegion = 38,
ImmediateLosslessGenericRegion = 39,
IntermediateGenericRefinementRegion = 40,
ImmediateGenericRefinementRegion = 42,
ImmediateLosslessGenericRefinementRegion = 43,
PageInformation = 48,
EndOfPage = 49,
EndOfStripe = 50,
EndOfFile = 51,
Profiles = 52,
Tables = 53,
ColorPalette = 54,
Extension = 62,
};
// Annex D
enum class Organization {
// D.1 Sequential organization
@ -27,6 +54,14 @@ enum class Organization {
Embedded,
};
struct SegmentHeader {
u32 segment_number;
SegmentType type;
Vector<u32> referred_to_segment_numbers;
u32 page_association;
Optional<u32> data_length;
};
struct JBIG2LoadingContext {
enum class State {
NotDecoded = 0,
@ -53,6 +88,7 @@ static ErrorOr<void> decode_jbig2_header(JBIG2LoadingContext& context)
if (header_flags & 0b11110000)
return Error::from_string_literal("JBIG2LoadingContext: Invalid header flags");
context.organization = (header_flags & 1) ? Organization::Sequential : Organization::RandomAccess;
dbgln_if(JBIG2_DEBUG, "JBIG2LoadingContext: Organization: {} ({})", (int)context.organization, context.organization == Organization::Sequential ? "Sequential" : "Random-access");
bool has_known_number_of_pages = (header_flags & 2) ? false : true;
bool uses_templates_with_12_AT_pixels = (header_flags & 4) ? true : false;
bool contains_colored_region_segments = (header_flags & 8) ? true : false;
@ -70,6 +106,81 @@ static ErrorOr<void> decode_jbig2_header(JBIG2LoadingContext& context)
return {};
}
static ErrorOr<SegmentHeader> decode_segment_header(JBIG2LoadingContext& context)
{
ReadonlyBytes data = context.data.slice(sizeof(id_string) + sizeof(u8) + (context.number_of_pages.has_value() ? sizeof(u32) : 0));
FixedMemoryStream stream(data);
// 7.2.2 Segment number
u32 segment_number = TRY(stream.read_value<BigEndian<u32>>());
dbgln_if(JBIG2_DEBUG, "Segment number: {}", segment_number);
// 7.2.3 Segment header flags
u8 flags = TRY(stream.read_value<u8>());
SegmentType type = static_cast<SegmentType>(flags & 0b11'1111);
dbgln_if(JBIG2_DEBUG, "Segment type: {}", (int)type);
bool segment_page_association_size_is_32_bits = (flags & 0b100'0000) != 0;
bool segment_retained_only_by_itself_and_extension_segments = (flags & 0b1000'00000) != 0;
// FIXME: Do something with these.
(void)segment_page_association_size_is_32_bits;
(void)segment_retained_only_by_itself_and_extension_segments;
// 7.2.4 Referred-to segment count and retention flags
u8 referred_to_segment_count_and_retention_flags = TRY(stream.read_value<u8>());
u32 count_of_referred_to_segments = referred_to_segment_count_and_retention_flags >> 5;
if (count_of_referred_to_segments == 5 || count_of_referred_to_segments == 6)
return Error::from_string_literal("JBIG2ImageDecoderPlugin: Invalid count_of_referred_to_segments");
u32 extra_count = 0;
if (count_of_referred_to_segments == 7) {
TRY(stream.seek(-1, SeekMode::FromCurrentPosition));
count_of_referred_to_segments = TRY(stream.read_value<BigEndian<u32>>()) & 0x1FFF'FFFF;
extra_count = ceil_div(count_of_referred_to_segments + 1, 8);
TRY(stream.seek(extra_count, SeekMode::FromCurrentPosition));
}
dbgln_if(JBIG2_DEBUG, "Referred-to segment count: {}", count_of_referred_to_segments);
// 7.2.5 Referred-to segment numbers
Vector<u32> referred_to_segment_numbers;
for (u32 i = 0; i < count_of_referred_to_segments; ++i) {
u32 referred_to_segment_number;
if (segment_number <= 256)
referred_to_segment_number = TRY(stream.read_value<u8>());
else if (segment_number <= 65536)
referred_to_segment_number = TRY(stream.read_value<BigEndian<u16>>());
else
referred_to_segment_number = TRY(stream.read_value<BigEndian<u32>>());
referred_to_segment_numbers.append(referred_to_segment_number);
dbgln_if(JBIG2_DEBUG, "Referred-to segment number: {}", referred_to_segment_number);
}
// 7.2.6 Segment page association
u32 segment_page_association;
if (segment_page_association_size_is_32_bits) {
segment_page_association = TRY(stream.read_value<BigEndian<u32>>());
} else {
segment_page_association = TRY(stream.read_value<u8>());
}
dbgln_if(JBIG2_DEBUG, "Segment page association: {}", segment_page_association);
// 7.2.7 Segment data length
u32 data_length = TRY(stream.read_value<BigEndian<u32>>());
dbgln_if(JBIG2_DEBUG, "Segment data length: {}", data_length);
// FIXME: Add some validity checks:
// - data_length can only be 0xffff'ffff for type ImmediateGenericRegion
// - check type is valid
// - check referred_to_segment_numbers are smaller than segment_number
// - 7.3.1 Rules for segment references
// - 7.3.2 Rules for page associations
Optional<u32> opt_data_length;
if (data_length != 0xffff'ffff)
opt_data_length = data_length;
return SegmentHeader { segment_number, type, move(referred_to_segment_numbers), segment_page_association, opt_data_length };
}
JBIG2ImageDecoderPlugin::JBIG2ImageDecoderPlugin(ReadonlyBytes data)
{
m_context = make<JBIG2LoadingContext>();
@ -90,6 +201,7 @@ ErrorOr<NonnullOwnPtr<ImageDecoderPlugin>> JBIG2ImageDecoderPlugin::create(Reado
{
auto plugin = TRY(adopt_nonnull_own_or_enomem(new (nothrow) JBIG2ImageDecoderPlugin(data)));
TRY(decode_jbig2_header(*plugin->m_context));
TRY(decode_segment_header(*plugin->m_context));
return plugin;
}