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LibGfx: Put the code to reset the encoder in its own function

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With it, we can also add a spec reference. And it will remind to anyone
who wants to add support for a new coding to not forget to update it.
This commit is contained in:
Lucas CHOLLET 2023-02-20 00:28:17 -05:00 • committed by Andreas Kling
parent 3fefb696a3
commit 8ed630a7ec
1 changed files with 26 additions and 3 deletions
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29
Userland/Libraries/LibGfx/JPEGLoader.cpp
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@ -363,6 +363,31 @@ static ErrorOr<void> build_macroblocks(JPEGLoadingContext& context, Vector<Macro
return {};
}
static bool is_dct_based(StartOfFrame::FrameType frame_type)
{
return frame_type == StartOfFrame::FrameType::Baseline_DCT
|| frame_type == StartOfFrame::FrameType::Extended_Sequential_DCT
|| frame_type == StartOfFrame::FrameType::Progressive_DCT
|| frame_type == StartOfFrame::FrameType::Differential_Sequential_DCT
|| frame_type == StartOfFrame::FrameType::Differential_Progressive_DCT
|| frame_type == StartOfFrame::FrameType::Progressive_DCT_Arithmetic
|| frame_type == StartOfFrame::FrameType::Differential_Sequential_DCT_Arithmetic
|| frame_type == StartOfFrame::FrameType::Differential_Progressive_DCT_Arithmetic;
}
static void reset_decoder(JPEGLoadingContext& context)
{
// E.2.4 Control procedure for decoding a restart interval
if (is_dct_based(context.frame.type)) {
context.previous_dc_values[0] = 0;
context.previous_dc_values[1] = 0;
context.previous_dc_values[2] = 0;
return;
}
VERIFY_NOT_REACHED();
}
static ErrorOr<void> decode_huffman_stream(JPEGLoadingContext& context, Vector<Macroblock>& macroblocks)
{
if constexpr (JPEG_DEBUG) {
@ -385,9 +410,7 @@ static ErrorOr<void> decode_huffman_stream(JPEGLoadingContext& context, Vector<M
u32 i = vcursor * context.mblock_meta.hpadded_count + hcursor;
if (context.dc_restart_interval > 0) {
if (i != 0 && i % (context.dc_restart_interval * context.vsample_factor * context.hsample_factor) == 0) {
context.previous_dc_values[0] = 0;
context.previous_dc_values[1] = 0;
context.previous_dc_values[2] = 0;
reset_decoder(context);
// Restart markers are stored in byte boundaries. Advance the huffman stream cursor to
// the 0th bit of the next byte.