RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-26 09:07:35 +00:00
Code Issues Activity Actions

LibGfx/JPEG: Support refinement scans

Browse source 
These scans are only present in progressive JPEGs and contains bits to
increase the precision of values acquired in previous scans.
This commit is contained in:
Lucas CHOLLET 2023-03-17 22:14:11 -04:00 • committed by Linus Groh
parent 8806e66f66
commit fbad9a70fc
1 changed files with 66 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

78
Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.cpp
View file

@ -321,6 +321,17 @@ static inline i32* get_component(Macroblock& block, unsigned component)
} }
} }
static ErrorOr<void> refine_coefficient(Scan& scan, i32& coefficient)
{
// G.1.2.3 - Coding model for subsequent scans of successive approximation
// See the correction bit from rule b.
u8 const bit = TRY(read_huffman_bits(scan.huffman_stream, 1));
if (bit == 1)
coefficient |= 1 << scan.successive_approximation_low;
return {};
}
static ErrorOr<void> add_dc(JPEGLoadingContext& context, Macroblock& macroblock, ScanComponent const& scan_component) static ErrorOr<void> add_dc(JPEGLoadingContext& context, Macroblock& macroblock, ScanComponent const& scan_component)
{ {
auto maybe_table = context.dc_tables.get(scan_component.dc_destination_id); auto maybe_table = context.dc_tables.get(scan_component.dc_destination_id);
@ -332,6 +343,14 @@ static ErrorOr<void> add_dc(JPEGLoadingContext& context, Macroblock& macroblock,
auto& dc_table = maybe_table.value(); auto& dc_table = maybe_table.value();
auto& scan = context.current_scan; auto& scan = context.current_scan;
auto* select_component = get_component(macroblock, scan_component.component.index);
auto& coefficient = select_component[0];
if (context.current_scan.successive_approximation_high > 0) {
TRY(refine_coefficient(scan, coefficient));
return {};
}
// For DC coefficients, symbol encodes the length of the coefficient. // For DC coefficients, symbol encodes the length of the coefficient.
auto dc_length = TRY(get_next_symbol(scan.huffman_stream, dc_table)); auto dc_length = TRY(get_next_symbol(scan.huffman_stream, dc_table));
if (dc_length > 11) { if (dc_length > 11) {
@ -346,9 +365,9 @@ static ErrorOr<void> add_dc(JPEGLoadingContext& context, Macroblock& macroblock,
if (dc_length != 0 && dc_diff < (1 << (dc_length - 1))) if (dc_length != 0 && dc_diff < (1 << (dc_length - 1)))
dc_diff -= (1 << dc_length) - 1; dc_diff -= (1 << dc_length) - 1;
auto* select_component = get_component(macroblock, scan_component.component.index);
auto& previous_dc = context.previous_dc_values[scan_component.component.index]; auto& previous_dc = context.previous_dc_values[scan_component.component.index];
select_component[0] = previous_dc += dc_diff; previous_dc += dc_diff;
coefficient = previous_dc << scan.successive_approximation_low;
return {}; return {};
} }
@ -375,6 +394,14 @@ static ErrorOr<bool> read_eob(Scan& scan, u32 symbol)
return false; return false;
} }
static bool is_progressive(StartOfFrame::FrameType frame_type)
{
return frame_type == StartOfFrame::FrameType::Progressive_DCT
|| frame_type == StartOfFrame::FrameType::Progressive_DCT_Arithmetic
|| frame_type == StartOfFrame::FrameType::Differential_Progressive_DCT
|| frame_type == StartOfFrame::FrameType::Differential_Progressive_DCT_Arithmetic;
}
static ErrorOr<void> add_ac(JPEGLoadingContext& context, Macroblock& macroblock, ScanComponent const& scan_component) static ErrorOr<void> add_ac(JPEGLoadingContext& context, Macroblock& macroblock, ScanComponent const& scan_component)
{ {
auto maybe_table = context.ac_tables.get(scan_component.ac_destination_id); auto maybe_table = context.ac_tables.get(scan_component.ac_destination_id);
@ -395,9 +422,12 @@ static ErrorOr<void> add_ac(JPEGLoadingContext& context, Macroblock& macroblock,
u32 to_skip = 0; u32 to_skip = 0;
Optional<u8> saved_symbol; Optional<u8> saved_symbol;
Optional<u8> saved_bit_for_rule_a;
bool in_zrl = false; bool in_zrl = false;
for (int j = first_coefficient; j <= scan.spectral_selection_end; ++j) { for (int j = first_coefficient; j <= scan.spectral_selection_end; ++j) {
auto& coefficient = select_component[zigzag_map[j]];
// AC symbols encode 2 pieces of information, the high 4 bits represent // AC symbols encode 2 pieces of information, the high 4 bits represent
// number of zeroes to be stuffed before reading the coefficient. Low 4 // number of zeroes to be stuffed before reading the coefficient. Low 4
// bits represent the magnitude of the coefficient. // bits represent the magnitude of the coefficient.
@ -412,9 +442,20 @@ static ErrorOr<void> add_ac(JPEGLoadingContext& context, Macroblock& macroblock,
to_skip++; to_skip++;
saved_symbol.clear(); saved_symbol.clear();
} }
if (!in_zrl && is_progressive(context.frame.type) && scan.successive_approximation_high != 0) {
// G.1.2.3 - Coding model for subsequent scans of successive approximation
// Bit sign from rule a
saved_bit_for_rule_a = TRY(read_huffman_bits(scan.huffman_stream, 1));
}
} }
} }
if (coefficient != 0) {
TRY(refine_coefficient(scan, coefficient));
continue;
}
if (to_skip > 0) { if (to_skip > 0) {
--to_skip; --to_skip;
if (to_skip == 0) if (to_skip == 0)
@ -425,18 +466,31 @@ static ErrorOr<void> add_ac(JPEGLoadingContext& context, Macroblock& macroblock,
if (scan.end_of_bands_run_count > 0) if (scan.end_of_bands_run_count > 0)
continue; continue;
u8 coeff_length = *saved_symbol & 0x0F; if (is_progressive(context.frame.type) && scan.successive_approximation_high != 0) {
if (coeff_length > 10) { // G.1.2.3 - Coding model for subsequent scans of successive approximation
dbgln_if(JPEG_DEBUG, "AC coefficient too long: {}!", coeff_length); if (auto const low_bits = *saved_symbol & 0x0F; low_bits != 1) {
return Error::from_string_literal("AC coefficient too long"); dbgln_if(JPEG_DEBUG, "AC coefficient low bits isn't equal to 1: {}!", low_bits);
} return Error::from_string_literal("AC coefficient low bits isn't equal to 1");
}
if (coeff_length != 0) { coefficient = (*saved_bit_for_rule_a == 0 ? -1 : 1) << scan.successive_approximation_low;
i32 ac_coefficient = TRY(read_huffman_bits(scan.huffman_stream, coeff_length)); saved_bit_for_rule_a.clear();
if (ac_coefficient < (1 << (coeff_length - 1))) } else {
ac_coefficient -= (1 << coeff_length) - 1; // F.1.2.2 - Huffman encoding of AC coefficients
u8 const coeff_length = *saved_symbol & 0x0F;
select_component[zigzag_map[j]] = ac_coefficient; if (coeff_length > 10) {
dbgln_if(JPEG_DEBUG, "AC coefficient too long: {}!", coeff_length);
return Error::from_string_literal("AC coefficient too long");
}
if (coeff_length != 0) {
i32 ac_coefficient = TRY(read_huffman_bits(scan.huffman_stream, coeff_length));
if (ac_coefficient < (1 << (coeff_length - 1)))
ac_coefficient -= (1 << coeff_length) - 1;
coefficient = ac_coefficient * (1 << scan.successive_approximation_low);
}
} }
saved_symbol.clear(); saved_symbol.clear();