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LibGfx/CCITT: Consider the UseFillBits option

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This commit is contained in:
Lucas CHOLLET 2024-01-18 00:29:46 -05:00 • committed by Jelle Raaijmakers
parent cbfea68ed8
commit b9afac0a06
3 changed files with 26 additions and 2 deletions
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14
Userland/Libraries/LibGfx/ImageFormats/CCITTDecoder.cpp
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@ -318,9 +318,19 @@ ErrorOr<void> decode_single_ccitt3_1d_line(BigEndianInputBitStream& input_bit_st
return {};
}
static ErrorOr<void> read_eol(BigEndianInputBitStream& bit_stream)
static ErrorOr<void> read_eol(BigEndianInputBitStream& bit_stream, Group3Options::UseFillBits use_fill_bits)
{
constexpr u16 EOL = 0b0000'0000'0001;
if (use_fill_bits == Group3Options::UseFillBits::Yes) {
// TIFF specification, description of the T4Options tag:
// "Fill bits have been added as necessary before EOL codes such that
// EOL always ends on a byte boundary, thus ensuring an EOL-sequence of 1 byte
// preceded by a zero nibble: xxxx-0000 0000-0001."
auto const to_skip = (12 + bit_stream.bits_until_next_byte_boundary()) % 8;
TRY(bit_stream.read_bits(to_skip));
}
auto const read = TRY(bit_stream.read_bits<u16>(12));
if (read != EOL)
return Error::from_string_literal("CCITTDecoder: Invalid EndOfLine code");
@ -368,7 +378,7 @@ ErrorOr<ByteBuffer> decode_ccitt_group3(ReadonlyBytes bytes, u32 image_width, u3
// NOTE: For whatever reason, the last EOL doesn't seem to be included
for (u32 i = 0; i < image_height; ++i) {
TRY(read_eol(*bit_stream));
TRY(read_eol(*bit_stream, options.use_fill_bits));
TRY(decode_single_ccitt3_1d_line(*bit_stream, *decoded_bits, image_width));
}