RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-05-31 22:58:11 +00:00
Code Issues Activity Actions

LibGfx/JPEG: Decode the App14 segment

Browse source 
This half-standardized application specific segment is used for color
transform information. It means that the decoder is know informed if the
image uses YCbCr, RGB, CMYK or even YCCK.
This commit is contained in:
Lucas CHOLLET 2023-03-04 17:22:16 -05:00 • committed by Andreas Kling
parent 00808c5eba
commit c60338e187
1 changed files with 57 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

58
Userland/Libraries/LibGfx/JPEGLoader.cpp
View file

@ -214,6 +214,14 @@ struct Scan {
}
};
enum class ColorTransform {
// https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-T.872-201206-I!!PDF-E&type=items
// 6.5.3 - APP14 marker segment for colour encoding
CmykOrRgb = 0,
YCbCr = 1,
YCCK = 2,
};
struct JPEGLoadingContext {
enum State {
NotDecoded = 0,
@ -243,6 +251,8 @@ struct JPEGLoadingContext {
MacroblockMeta mblock_meta;
OwnPtr<FixedMemoryStream> stream;
Optional<ColorTransform> color_transform {};
Optional<ICCMultiChunkState> icc_multi_chunk_state;
Optional<ByteBuffer> icc_data;
};
@ -557,7 +567,7 @@ static inline bool is_supported_marker(Marker const marker)
{
if (marker >= JPEG_APPN0 && marker <= JPEG_APPN15) {
if (marker != JPEG_APPN0)
if (marker != JPEG_APPN0 && marker != JPEG_APPN14)
dbgln_if(JPEG_DEBUG, "{:#04x} not supported yet. The decoder may fail!", marker);
return true;
}
@ -787,6 +797,50 @@ static ErrorOr<void> read_icc_profile(SeekableStream& stream, JPEGLoadingContext
return {};
}
static ErrorOr<void> read_colour_encoding(SeekableStream& stream, [[maybe_unused]] JPEGLoadingContext& context, int bytes_to_read)
{
// The App 14 segment is application specific in the first JPEG standard.
// However, the Adobe implementation is globally accepted and the value of the color transform
// was latter standardized as a JPEG-1 extension.
// For the structure of the App 14 segment, see:
// https://www.pdfa.org/norm-refs/5116.DCT_Filter.pdf
// 18 Adobe Application-Specific JPEG Marker
// For the value of color_transform, see:
// https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-T.872-201206-I!!PDF-E&type=items
// 6.5.3 - APP14 marker segment for colour encoding
if (bytes_to_read < 6)
return Error::from_string_literal("App14 segment too small");
[[maybe_unused]] auto const version = TRY(stream.read_value<u8>());
[[maybe_unused]] u16 const flag0 = TRY(stream.read_value<BigEndian<u16>>());
[[maybe_unused]] u16 const flag1 = TRY(stream.read_value<BigEndian<u16>>());
auto const color_transform = TRY(stream.read_value<u8>());
if (bytes_to_read > 6) {
dbgln_if(JPEG_DEBUG, "Unread bytes in App14 segment: {}", bytes_to_read - 1);
TRY(stream.discard(bytes_to_read - 1));
}
switch (color_transform) {
case 0:
context.color_transform = ColorTransform::CmykOrRgb;
break;
case 1:
context.color_transform = ColorTransform::YCbCr;
break;
case 2:
context.color_transform = ColorTransform::YCCK;
break;
default:
dbgln("0x{:x} is not a specified transform flag value, ignoring", color_transform);
}
return {};
}
static ErrorOr<void> read_app_marker(SeekableStream& stream, JPEGLoadingContext& context, int app_marker_number)
{
i32 bytes_to_read = TRY(stream.read_value<BigEndian<u16>>());
@ -814,6 +868,8 @@ static ErrorOr<void> read_app_marker(SeekableStream& stream, JPEGLoadingContext&
if (app_marker_number == 2 && app_id == "ICC_PROFILE"sv)
return read_icc_profile(stream, context, bytes_to_read);
if (app_marker_number == 14 && app_id == "Adobe"sv)
return read_colour_encoding(stream, context, bytes_to_read);
return stream.discard(bytes_to_read);
}