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LibGfx/JPEGLoader: Check earlier for quantization tables presence

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This patch brings few small QoL improvements:
 - We don't need to read the Huffman stream before returning an error
   due to a missing quantization table.
 - We check the table presence only once per scan instead of once per
   MCU.
 - `dequantize()` is now infallible.
This commit is contained in:
Lucas CHOLLET 2024-02-26 12:44:40 -05:00 • committed by Sam Atkins
parent c41b359ca5
commit fb81668d8f
1 changed files with 18 additions and 16 deletions
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34
Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.cpp
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@ -454,7 +454,8 @@ struct JPEGLoadingContext {
State state { State::NotDecoded };
Array<Optional<Array<u16, 64>>, 4> quantization_tables {};
Array<Array<u16, 64>, 4> quantization_tables {};
Array<bool, 4> registered_quantization_tables {};
StartOfFrame frame;
SamplingFactors sampling_factors {};
@ -917,6 +918,15 @@ static ErrorOr<u16> read_effective_chunk_size(JPEGStream& stream)
return stored_size - 2;
}
static ErrorOr<void> ensure_quantization_tables_are_present(JPEGLoadingContext& context)
{
for (auto const& component : context.current_scan->components) {
if (!context.registered_quantization_tables[component.component.quantization_table_id])
return Error::from_string_literal("Unknown quantization table id");
}
return {};
}
static ErrorOr<void> read_start_of_scan(JPEGStream& stream, JPEGLoadingContext& context)
{
// B.2.3 - Scan header syntax
@ -984,6 +994,8 @@ static ErrorOr<void> read_start_of_scan(JPEGStream& stream, JPEGLoadingContext&
context.current_scan = move(current_scan);
TRY(ensure_quantization_tables_are_present(context));
return {};
}
@ -1367,12 +1379,9 @@ static ErrorOr<void> read_quantization_table(JPEGStream& stream, JPEGLoadingCont
return Error::from_string_literal("Unsupported quantization table id");
}
auto& maybe_table = context.quantization_tables[table_id];
context.registered_quantization_tables[table_id] = true;
if (!maybe_table.has_value())
maybe_table = Array<u16, 64> {};
auto& table = maybe_table.value();
auto& table = context.quantization_tables[table_id];
for (int i = 0; i < 64; i++) {
if (element_unit_hint == 0)
@ -1398,19 +1407,14 @@ static ErrorOr<void> skip_segment(JPEGStream& stream)
return {};
}
static ErrorOr<void> dequantize(JPEGLoadingContext& context, Vector<Macroblock>& macroblocks)
static void dequantize(JPEGLoadingContext& context, Vector<Macroblock>& macroblocks)
{
for (u32 vcursor = 0; vcursor < context.mblock_meta.vcount; vcursor += context.sampling_factors.vertical) {
for (u32 hcursor = 0; hcursor < context.mblock_meta.hcount; hcursor += context.sampling_factors.horizontal) {
for (u32 i = 0; i < context.components.size(); i++) {
auto const& component = context.components[i];
if (!context.quantization_tables[component.quantization_table_id].has_value()) {
dbgln_if(JPEG_DEBUG, "Unknown quantization table id: {}!", component.quantization_table_id);
return Error::from_string_literal("Unknown quantization table id");
}
auto const& table = context.quantization_tables[component.quantization_table_id].value();
auto const& table = context.quantization_tables[component.quantization_table_id];
for (u32 vfactor_i = 0; vfactor_i < component.sampling_factors.vertical; vfactor_i++) {
for (u32 hfactor_i = 0; hfactor_i < component.sampling_factors.horizontal; hfactor_i++) {
@ -1424,8 +1428,6 @@ static ErrorOr<void> dequantize(JPEGLoadingContext& context, Vector<Macroblock>&
}
}
}
return {};
}
static void inverse_dct_8x8(i16* block_component)
@ -1967,7 +1969,7 @@ static ErrorOr<Vector<Macroblock>> construct_macroblocks(JPEGLoadingContext& con
static ErrorOr<void> decode_jpeg(JPEGLoadingContext& context)
{
auto macroblocks = TRY(construct_macroblocks(context));
TRY(dequantize(context, macroblocks));
dequantize(context, macroblocks);
inverse_dct(context, macroblocks);
undo_subsampling(context, macroblocks);
TRY(handle_color_transform(context, macroblocks));