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LibGfx/TIFF: Decode all PackedBits beforehand

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This change doesn't change much on its own. The idea behind this
refactoring is to separate the sample reading from the decoding step.
The decoder returning data byte per byte was fine as we only support
8 bits images, but this assumption won't hold for a long time. So let's
decode everything beforehand and strictly partition the sample reading
code somewhere else.
This commit is contained in:
Lucas CHOLLET 2023-11-30 23:00:41 -05:00 committed by Andreas Kling
parent 4994609af0
commit 1ede4f249d
Notes: sideshowbarker 2024-07-17 18:46:30 +09:00 
Author: https://github.com/LucasChollet
Commit: https://github.com/SerenityOS/serenity/commit/1ede4f249d
Pull-request: https://github.com/SerenityOS/serenity/pull/22109
Reviewed-by: https://github.com/nico ✅
1 changed files with 28 additions and 11 deletions
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39
Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.cpp
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@ -156,20 +156,31 @@ private:
}
case Compression::PackBits: {
// Section 9: PackBits Compression
Optional<i8> n;
Optional<u8> saved_byte;
auto read_packed_byte = [&]() -> ErrorOr<u8> {
while (true) {
OwnPtr<FixedMemoryStream> strip_stream;
ByteBuffer decoded_bytes {};
u32 read_head {};
auto initializer = [&](u32 num_bytes) -> ErrorOr<void> {
strip_stream = make<FixedMemoryStream>(TRY(m_stream->read_in_place<u8 const>(num_bytes)));
decoded_bytes.clear();
read_head = 0;
Optional<i8> n {};
Optional<u8> saved_byte {};
while (strip_stream->remaining() > 0 || saved_byte.has_value()) {
if (!n.has_value())
n = TRY(read_value<i8>());
n = TRY(strip_stream->read_value<i8>());
if (n.value() >= 0 && !saved_byte.has_value()) {
n.value() = n.value() - 1;
if (n.value() == -1)
n.clear();
return read_value<u8>();
decoded_bytes.append(TRY(strip_stream->read_value<u8>()));
continue;
}
if (n.value() == -128) {
@ -178,22 +189,28 @@ private:
}
if (!saved_byte.has_value())
saved_byte = TRY(read_value<u8>());
saved_byte = TRY(strip_stream->read_value<u8>());
n.value() = n.value() + 1;
auto const byte_backup = *saved_byte;
decoded_bytes.append(*saved_byte);
if (n == 1) {
saved_byte.clear();
n.clear();
}
return byte_backup;
}
return {};
};
TRY(loop_over_pixels(move(read_packed_byte)));
auto read_packed_byte = [&]() -> ErrorOr<u8> {
if (read_head < decoded_bytes.size())
return decoded_bytes[read_head++];
return Error::from_string_literal("TIFFImageDecoderPlugin: Reached end of PackedBits stream");
};
TRY(loop_over_pixels(move(read_packed_byte), move(initializer)));
break;
}
default: