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LibGfx/JPEGXL: Implement the ANS decoder
This allows us to read many more images. This decoder is one of the two possibilities (along Brotli) that can be used for modular images. All the logic is directly taken from the spec. One of the image that can now be decoded is "Lucifer's Dominion: Synthesis" that can be found on `https://jpegxl.info/art/`, it also makes us pass one more test of the conformance test suite, namely "alpha_triangles".
This commit is contained in:
Lucas CHOLLET
Jelle Raaijmakers
parent
4da8c45e43
commit
e83b04417b
Notes:
sideshowbarker
2024-07-17 04:41:05 +09:00
Author: https://github.com/LucasChollet Commit: https://github.com/SerenityOS/serenity/commit/e83b04417b Pull-request: https://github.com/SerenityOS/serenity/pull/20305 Reviewed-by: https://github.com/gmta ✅
@ -810,10 +810,277 @@ static ErrorOr<LfChannelDequantization> read_lf_channel_dequantization(LittleEnd
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///
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/// C - Entropy decoding
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class ANSHistogram {
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public:
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static ErrorOr<ANSHistogram> read_histogram(LittleEndianInputBitStream& stream, u8 log_alphabet_size)
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{
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ANSHistogram histogram;
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auto const alphabet_size = TRY(histogram.read_ans_distribution(stream, log_alphabet_size));
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// C.2.6 - Alias mapping
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histogram.m_log_bucket_size = 12 - log_alphabet_size;
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histogram.m_bucket_size = 1 << histogram.m_log_bucket_size;
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auto const table_size = 1 << log_alphabet_size;
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Optional<u64> index_of_unique_symbol {};
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for (u64 i {}; i < histogram.m_distribution.size(); ++i) {
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if (histogram.m_distribution[i] == 1 << 12)
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index_of_unique_symbol = i;
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}
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TRY(histogram.m_symbols.try_resize(table_size));
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TRY(histogram.m_offsets.try_resize(table_size));
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TRY(histogram.m_cutoffs.try_resize(table_size));
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if (index_of_unique_symbol.has_value()) {
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auto const s = *index_of_unique_symbol;
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for (i32 i = 0; i < table_size; i++) {
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histogram.m_symbols[i] = s;
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histogram.m_offsets[i] = histogram.m_bucket_size * i;
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histogram.m_cutoffs[i] = 0;
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}
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return histogram;
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}
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Vector<u16> overfull;
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Vector<u16> underfull;
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for (u16 i {}; i < alphabet_size; i++) {
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histogram.m_cutoffs[i] = histogram.m_distribution[i];
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histogram.m_symbols[i] = i;
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if (histogram.m_cutoffs[i] > histogram.m_bucket_size)
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TRY(overfull.try_append(i));
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else if (histogram.m_cutoffs[i] < histogram.m_bucket_size)
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TRY(underfull.try_append(i));
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}
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for (u16 i = alphabet_size; i < table_size; i++) {
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histogram.m_cutoffs[i] = 0;
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TRY(underfull.try_append(i));
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}
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while (overfull.size() > 0) {
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VERIFY(underfull.size() > 0);
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auto const o = overfull.take_last();
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auto const u = underfull.take_last();
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auto const by = histogram.m_bucket_size - histogram.m_cutoffs[u];
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histogram.m_cutoffs[o] -= by;
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histogram.m_symbols[u] = o;
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histogram.m_offsets[u] = histogram.m_cutoffs[o];
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if (histogram.m_cutoffs[o] < histogram.m_bucket_size)
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TRY(underfull.try_append(o));
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else if (histogram.m_cutoffs[o] > histogram.m_bucket_size)
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TRY(overfull.try_append(o));
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}
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for (u16 i {}; i < table_size; i++) {
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if (histogram.m_cutoffs[i] == histogram.m_bucket_size) {
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histogram.m_symbols[i] = i;
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histogram.m_offsets[i] = 0;
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histogram.m_cutoffs[i] = 0;
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} else {
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histogram.m_offsets[i] -= histogram.m_cutoffs[i];
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}
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}
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return histogram;
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}
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ErrorOr<u16> read_symbol(LittleEndianInputBitStream& stream, Optional<u32>& state) const
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{
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if (!state.has_value())
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state = TRY(stream.read_bits(32));
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auto const index = *state & 0xFFF;
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auto const symbol_and_offset = alias_mapping(index);
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state = m_distribution[symbol_and_offset.symbol] * (*state >> 12) + symbol_and_offset.offset;
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if (*state < (1 << 16))
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state = (*state << 16) | TRY(stream.read_bits(16));
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return symbol_and_offset.symbol;
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}
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private:
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static ErrorOr<u8> U8(LittleEndianInputBitStream& stream)
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{
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if (TRY(stream.read_bit()) == 0)
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return 0;
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auto const n = TRY(stream.read_bits(3));
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return TRY(stream.read_bits(n)) + (1 << n);
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}
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struct SymbolAndOffset {
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u16 symbol {};
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u16 offset {};
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};
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SymbolAndOffset alias_mapping(u32 x) const
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{
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// C.2.6 - Alias mapping
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auto const i = x >> m_log_bucket_size;
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auto const pos = x & (m_bucket_size - 1);
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u16 const symbol = pos >= m_cutoffs[i] ? m_symbols[i] : i;
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u16 const offset = pos >= m_cutoffs[i] ? m_offsets[i] + pos : pos;
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return { symbol, offset };
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}
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static ErrorOr<u16> read_with_prefix(LittleEndianInputBitStream& stream)
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{
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auto const prefix = TRY(stream.read_bits(3));
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switch (prefix) {
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case 0:
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return 10;
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case 1:
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for (auto const possibility : { 4, 0, 11, 13 }) {
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if (TRY(stream.read_bit()))
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return possibility;
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}
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return 12;
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case 2:
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return 7;
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case 3:
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return TRY(stream.read_bit()) ? 1 : 3;
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case 4:
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return 6;
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case 5:
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return 8;
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case 6:
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return 9;
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case 7:
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return TRY(stream.read_bit()) ? 2 : 5;
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default:
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VERIFY_NOT_REACHED();
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}
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}
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ErrorOr<u16> read_ans_distribution(LittleEndianInputBitStream& stream, u8 log_alphabet_size)
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{
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// C.2.5 ANS distribution decoding
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auto const table_size = 1 << log_alphabet_size;
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m_distribution = TRY(FixedArray<i32>::create(table_size));
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if (TRY(stream.read_bit())) {
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u16 alphabet_size {};
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if (TRY(stream.read_bit())) {
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auto const v1 = TRY(U8(stream));
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auto const v2 = TRY(U8(stream));
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VERIFY(v1 != v2);
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m_distribution[v1] = TRY(stream.read_bits(12));
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m_distribution[v2] = (1 << 12) - m_distribution[v1];
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alphabet_size = 1 + max(v1, v2);
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} else {
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auto const x = TRY(U8(stream));
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m_distribution[x] = 1 << 12;
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alphabet_size = 1 + x;
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}
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return alphabet_size;
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}
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if (TRY(stream.read_bit())) {
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auto const alphabet_size = TRY(U8(stream)) + 1;
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for (u16 i = 0; i < alphabet_size; i++)
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m_distribution[i] = (1 << 12) / alphabet_size;
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for (u16 i = 0; i < ((1 << 12) % alphabet_size); i++)
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m_distribution[i]++;
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return alphabet_size;
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}
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u8 len = 0;
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while (len < 3) {
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if (TRY(stream.read_bit()))
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len++;
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else
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break;
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}
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u8 const shift = TRY(stream.read_bits(len)) + (1 << len) - 1;
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VERIFY(shift <= 13);
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auto const alphabet_size = TRY(U8(stream)) + 3;
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i32 omit_log = -1;
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i32 omit_pos = -1;
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auto same = TRY(FixedArray<i32>::create(alphabet_size));
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auto logcounts = TRY(FixedArray<i32>::create(alphabet_size));
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u8 rle {};
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for (u16 i = 0; i < alphabet_size; i++) {
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logcounts[i] = TRY(read_with_prefix(stream));
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if (logcounts[i] == 13) {
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rle = TRY(U8(stream));
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same[i] = rle + 5;
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i += rle + 3;
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continue;
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}
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if (logcounts[i] > omit_log) {
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omit_log = logcounts[i];
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omit_pos = i;
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}
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}
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VERIFY(m_distribution[omit_pos] >= 0);
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VERIFY(omit_pos + 1 >= alphabet_size || logcounts[omit_pos + 1] != 13);
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i32 prev = 0;
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i32 numsame = 0;
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i64 total_count {};
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for (u16 i = 0; i < alphabet_size; i++) {
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if (same[i] != 0) {
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numsame = same[i] - 1;
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prev = i > 0 ? m_distribution[i - 1] : 0;
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}
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if (numsame > 0) {
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m_distribution[i] = prev;
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numsame--;
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} else {
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auto const code = logcounts[i];
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if (i == omit_pos || code == 0)
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continue;
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if (code == 1) {
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m_distribution[i] = 1;
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} else {
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auto const bitcount = min(max(0, shift - ((12 - code + 1) >> 1)), code - 1);
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m_distribution[i] = (1 << (code - 1)) + (TRY(stream.read_bits(bitcount)) << (code - 1 - bitcount));
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}
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}
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total_count += m_distribution[i];
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}
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m_distribution[omit_pos] = (1 << 12) - total_count;
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VERIFY(m_distribution[omit_pos] >= 0);
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return alphabet_size;
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}
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Vector<u16> m_symbols;
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Vector<u16> m_offsets;
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Vector<u16> m_cutoffs;
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FixedArray<i32> m_distribution;
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u16 m_log_bucket_size {};
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u16 m_bucket_size {};
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};
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class EntropyDecoder {
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using BrotliCanonicalCode = Compress::Brotli::CanonicalCode;
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AK_MAKE_NONCOPYABLE(EntropyDecoder);
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AK_MAKE_DEFAULT_MOVABLE(EntropyDecoder);
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public:
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EntropyDecoder() = default;
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~EntropyDecoder()
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{
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if (m_state.has_value() && *m_state != 0x130000)
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dbgln("JPEGXLLoader: ANS decoder left in invalid state");
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}
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static ErrorOr<EntropyDecoder> create(LittleEndianInputBitStream& stream, u8 initial_num_distrib)
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{
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EntropyDecoder entropy_decoder;
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@ -863,7 +1130,12 @@ public:
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distributions[i] = BrotliCanonicalCode { { 1 }, { 0 } };
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}
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} else {
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TODO();
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entropy_decoder.m_distributions = Vector<ANSHistogram> {};
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auto& distributions = entropy_decoder.m_distributions.get<Vector<ANSHistogram>>();
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TRY(distributions.try_ensure_capacity(entropy_decoder.m_configs.size()));
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for (u32 i = 0; i < entropy_decoder.m_configs.size(); ++i)
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distributions.empend(TRY(ANSHistogram::read_histogram(stream, entropy_decoder.m_log_alphabet_size)));
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}
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return entropy_decoder;
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@ -882,6 +1154,10 @@ public:
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[&](Vector<BrotliCanonicalCode> const& distributions) -> ErrorOr<void> {
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token = TRY(distributions[m_clusters[context]].read_symbol(stream));
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return {};
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},
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[&](Vector<ANSHistogram> const& distributions) -> ErrorOr<void> {
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token = TRY(distributions[m_clusters[context]].read_symbol(stream, m_state));
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return {};
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}));
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auto r = TRY(read_uint(stream, m_configs[m_clusters[context]], token));
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@ -889,6 +1165,8 @@ public:
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}
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private:
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using BrotliCanonicalCode = Compress::Brotli::CanonicalCode;
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struct HybridUint {
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u32 split_exponent {};
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u32 split {};
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@ -972,7 +1250,8 @@ private:
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u8 m_log_alphabet_size { 15 };
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Variant<Vector<BrotliCanonicalCode>> m_distributions { Vector<BrotliCanonicalCode> {} }; // D in the spec
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Variant<Vector<BrotliCanonicalCode>, Vector<ANSHistogram>> m_distributions { Vector<BrotliCanonicalCode> {} }; // D in the spec
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Optional<u32> m_state {};
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};
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///
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