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LibGfx/WebPWriter: Extract compute_and_write_prefix_code_group()

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Pure code move, no behavior change.
This commit is contained in:
Nico Weber 2024-06-30 14:03:24 +02:00
parent 2627721e0b
commit f5bbc69e6a
1 changed files with 28 additions and 24 deletions
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52
Userland/Libraries/LibGfx/ImageFormats/WebPWriterLossless.cpp
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@ -263,25 +263,8 @@ static ErrorOr<Vector<Symbol>> bitmap_to_symbols(Bitmap const& bitmap)
return symbols;
}
static ErrorOr<void> write_VP8L_coded_image(ImageKind image_kind, LittleEndianOutputBitStream& bit_stream, Bitmap const& bitmap, IsOpaque& is_fully_opaque)
static ErrorOr<PrefixCodeGroup> compute_and_write_prefix_code_group(Vector<Symbol> const& symbols, LittleEndianOutputBitStream& bit_stream, IsOpaque& is_fully_opaque)
{
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#5_image_data
// spatially-coded-image = color-cache-info meta-prefix data
// entropy-coded-image = color-cache-info data
// color-cache-info = %b0
// color-cache-info =/ (%b1 4BIT) ; 1 followed by color cache size
dbgln_if(WEBP_DEBUG, "writing has_color_cache_info false");
TRY(bit_stream.write_bits(0u, 1u)); // No color cache for now.
if (image_kind == ImageKind::SpatiallyCoded) {
// meta-prefix = %b0 / (%b1 entropy-image)
dbgln_if(WEBP_DEBUG, "writing has_meta_prefix false");
TRY(bit_stream.write_bits(0u, 1u)); // No meta prefix for now.
}
// data = prefix-codes lz77-coded-image
// prefix-codes = prefix-code-group *prefix-codes
// prefix-code-group =
// 5prefix-code ; See "Interpretation of Meta Prefix Codes" to
// ; understand what each of these five prefix
@ -304,11 +287,6 @@ static ErrorOr<void> write_VP8L_coded_image(ImageKind image_kind, LittleEndianOu
if (alphabet_sizes[0] > 288)
return Error::from_string_literal("Invalid alphabet size");
auto symbols = TRY(bitmap_to_symbols(bitmap));
// We do use huffman coding by writing a single prefix-code-group for the entire image.
// FIXME: Consider using a meta-prefix image and using one prefix-code-group per tile.
Array<Array<u16, 256>, 4> symbol_frequencies {};
static constexpr auto saturating_increment = [](u16& value) {
@ -353,7 +331,33 @@ static ErrorOr<void> write_VP8L_coded_image(ImageKind image_kind, LittleEndianOu
// For code #5, use a simple empty code, since we don't use this yet.
prefix_code_group[4] = TRY(write_simple_code_lengths(bit_stream, {}));
// Image data.
return prefix_code_group;
}
static ErrorOr<void> write_VP8L_coded_image(ImageKind image_kind, LittleEndianOutputBitStream& bit_stream, Bitmap const& bitmap, IsOpaque& is_fully_opaque)
{
// https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification#5_image_data
// spatially-coded-image = color-cache-info meta-prefix data
// entropy-coded-image = color-cache-info data
// color-cache-info = %b0
// color-cache-info =/ (%b1 4BIT) ; 1 followed by color cache size
dbgln_if(WEBP_DEBUG, "writing has_color_cache_info false");
TRY(bit_stream.write_bits(0u, 1u)); // No color cache for now.
if (image_kind == ImageKind::SpatiallyCoded) {
// meta-prefix = %b0 / (%b1 entropy-image)
dbgln_if(WEBP_DEBUG, "writing has_meta_prefix false");
// We do huffman coding by writing a single prefix-code-group for the entire image.
// FIXME: Consider using a meta-prefix image and using one prefix-code-group per tile.
TRY(bit_stream.write_bits(0u, 1u));
}
// data = prefix-codes lz77-coded-image
// prefix-codes = prefix-code-group *prefix-codes
auto symbols = TRY(bitmap_to_symbols(bitmap));
auto prefix_code_group = TRY(compute_and_write_prefix_code_group(symbols, bit_stream, is_fully_opaque));
TRY(write_image_data(bit_stream, symbols.span(), prefix_code_group));
return {};