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LibGfx/CCITT: Abstract the code to read a single CCITT 2D line
This commit is contained in:
Lucas CHOLLET
Jelle Raaijmakers
parent
e8133c8297
commit
e9dd1cda3e
Notes:
sideshowbarker
2024-07-17 09:49:48 +09:00
Author: https://github.com/LucasChollet
Commit: e9dd1cda3e
Pull-request: https://github.com/SerenityOS/serenity/pull/23281
Reviewed-by: https://github.com/nico ✅
1 changed files with 86 additions and 81 deletions
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@ -413,6 +413,89 @@ enum class Search : u8 {
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B2,
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};
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ErrorOr<ReferenceLine> decode_single_ccitt_2d_line(BigEndianInputBitStream& input_bit_stream, BigEndianOutputBitStream& decoded_bits, ReferenceLine&& reference_line, u32 image_width)
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{
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ReferenceLine current_line {};
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Color current_color { ccitt_white };
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u32 column {};
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auto const next_change_on_reference_line = [&](Search search = Search::B1) -> ErrorOr<Change> {
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// 4.2.1.3.1 Definition of changing picture elements
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Optional<Change> next_change {}; // This is referred to as b1 in the spec.
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while (!next_change.has_value()) {
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if (reference_line.is_empty())
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return Error::from_string_literal("CCITTDecoder: Corrupted stream");
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auto const change = reference_line.take_first();
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if (change.column < column)
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continue;
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if ((search == Search::B1 && change.color != current_color)
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|| (search == Search::B2 && change.color == current_color))
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next_change = change;
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}
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return *next_change;
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};
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auto const encode_for = [&](Change change, i8 offset = 0) -> ErrorOr<void> {
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auto const to_encode = change.column - column + offset;
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for (u32 i {}; i < to_encode; ++i)
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TRY(decoded_bits.write_bits(current_color == ccitt_white ? 0u : 1u, 1));
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column += to_encode;
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current_color = change.color;
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TRY(current_line.try_empend(change.color, change.column + offset));
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return {};
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};
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while (column < image_width) {
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auto const mode = TRY(read_mode(input_bit_stream));
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// Behavior are described here 4.2.1.3.2 Coding modes.
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switch (mode.mode) {
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case Mode::Pass:
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TRY(next_change_on_reference_line(Search::B2));
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break;
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case Mode::Horizontal: {
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// a0a1
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auto run_length = TRY(read_run_length(input_bit_stream, OptionalNone {}, current_color, image_width, column));
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TRY(encode_for({ invert(current_color), column + run_length }));
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// a1a2
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run_length = TRY(read_run_length(input_bit_stream, OptionalNone {}, current_color, image_width, column));
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TRY(encode_for({ invert(current_color), column + run_length }));
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break;
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}
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case Mode::Vertical_0:
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TRY(encode_for(TRY(next_change_on_reference_line())));
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break;
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case Mode::Vertical_R1:
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TRY(encode_for(TRY(next_change_on_reference_line()), 1));
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break;
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case Mode::Vertical_R2:
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TRY(encode_for(TRY(next_change_on_reference_line()), 2));
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break;
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case Mode::Vertical_R3:
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TRY(encode_for(TRY(next_change_on_reference_line()), 3));
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break;
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case Mode::Vertical_L1:
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TRY(encode_for(TRY(next_change_on_reference_line()), -1));
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break;
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case Mode::Vertical_L2:
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TRY(encode_for(TRY(next_change_on_reference_line()), -2));
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break;
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case Mode::Vertical_L3:
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TRY(encode_for(TRY(next_change_on_reference_line()), -3));
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break;
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default:
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return Error::from_string_literal("CCITTDecoder: Unsupported mode for 2D decoding");
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}
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}
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TRY(decoded_bits.align_to_byte_boundary());
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return current_line;
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}
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ErrorOr<void> decode_single_ccitt3_2d_block(BigEndianInputBitStream& input_bit_stream, BigEndianOutputBitStream& decoded_bits, u32 image_width, u32 image_height, Group3Options::UseFillBits use_fill_bits)
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{
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ReferenceLine reference_line;
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@ -420,90 +503,12 @@ ErrorOr<void> decode_single_ccitt3_2d_block(BigEndianInputBitStream& input_bit_s
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TRY(read_eol(input_bit_stream, use_fill_bits));
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bool const next_is_1D = TRY(input_bit_stream.read_bit()) == 1;
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if (next_is_1D) {
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if (next_is_1D)
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reference_line = TRY(decode_single_ccitt3_1d_line(input_bit_stream, decoded_bits, image_width));
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} else {
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ReferenceLine current_line {};
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Color current_color { ccitt_white };
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u32 column {};
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auto const next_change_on_reference_line = [&](Search search = Search::B1) -> ErrorOr<Change> {
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// 4.2.1.3.1 Definition of changing picture elements
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Optional<Change> next_change {}; // This is referred to as b1 in the spec.
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while (!next_change.has_value()) {
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if (reference_line.is_empty())
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return Error::from_string_literal("CCITTDecoder: Corrupted stream");
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auto const change = reference_line.take_first();
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if (change.column < column)
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continue;
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if ((search == Search::B1 && change.color != current_color)
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|| (search == Search::B2 && change.color == current_color))
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next_change = change;
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}
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return *next_change;
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};
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auto const encode_for = [&](Change change, i8 offset = 0) -> ErrorOr<void> {
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auto const to_encode = change.column - column + offset;
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for (u32 i {}; i < to_encode; ++i)
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TRY(decoded_bits.write_bits(current_color == ccitt_white ? 0u : 1u, 1));
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column += to_encode;
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current_color = change.color;
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TRY(current_line.try_empend(change.color, change.column + offset));
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return {};
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};
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while (column < image_width) {
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auto const mode = TRY(read_mode(input_bit_stream));
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// Behavior are described here 4.2.1.3.2 Coding modes.
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switch (mode.mode) {
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case Mode::Pass:
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TRY(next_change_on_reference_line(Search::B2));
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break;
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case Mode::Horizontal: {
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// a0a1
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auto run_length = TRY(read_run_length(input_bit_stream, OptionalNone {}, current_color, image_width, column));
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TRY(encode_for({ invert(current_color), column + run_length }));
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// a1a2
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run_length = TRY(read_run_length(input_bit_stream, OptionalNone {}, current_color, image_width, column));
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TRY(encode_for({ invert(current_color), column + run_length }));
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break;
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}
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case Mode::Vertical_0:
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TRY(encode_for(TRY(next_change_on_reference_line())));
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break;
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case Mode::Vertical_R1:
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TRY(encode_for(TRY(next_change_on_reference_line()), 1));
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break;
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case Mode::Vertical_R2:
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TRY(encode_for(TRY(next_change_on_reference_line()), 2));
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break;
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case Mode::Vertical_R3:
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TRY(encode_for(TRY(next_change_on_reference_line()), 3));
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break;
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case Mode::Vertical_L1:
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TRY(encode_for(TRY(next_change_on_reference_line()), -1));
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break;
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case Mode::Vertical_L2:
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TRY(encode_for(TRY(next_change_on_reference_line()), -2));
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break;
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case Mode::Vertical_L3:
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TRY(encode_for(TRY(next_change_on_reference_line()), -3));
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break;
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default:
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return Error::from_string_literal("CCITTDecoder: Unsupported mode for 2D decoding");
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}
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}
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reference_line = move(current_line);
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}
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else
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reference_line = TRY(decode_single_ccitt_2d_line(input_bit_stream, decoded_bits, move(reference_line), image_width));
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}
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TRY(decoded_bits.align_to_byte_boundary());
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return {};
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}
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