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LibPDF: Be more forgiving about trailing image data

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The predictor code assumed that all stream data is image data
(...which would make sense: trailing data there is wasted space).

But some PDFs have trailing data there, e.g. 0000257.pdf, so be
forgiving about it.
This commit is contained in:
Nico Weber 2024-01-15 21:11:26 -05:00 • committed by Tim Flynn
parent 55b971e133
commit 0e91682283
1 changed files with 8 additions and 4 deletions
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12
Userland/Libraries/LibPDF/Filter.cpp
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@ -240,17 +240,21 @@ PDFErrorOr<ByteBuffer> Filter::handle_lzw_and_flate_parameters(ByteBuffer buffer
return AK::Error::from_string_literal("Invalid predictor value");
// Rows are always a whole number of bytes long, for PNG starting with an algorithm tag.
auto buffer_bytes = buffer.bytes();
size_t bytes_per_row = ceil_div(columns * colors * bits_per_component, 8);
if (predictor != 2)
bytes_per_row++;
if (buffer.size() % bytes_per_row)
return AK::Error::from_string_literal("Predictor input data is not divisible into columns");
if (buffer.size() % bytes_per_row) {
// Rarely, there is some trailing data after the image data. Ignore the part of it that doesn't fit into a row.
dbgln_if(PDF_DEBUG, "Predictor input data length {} is not divisible into columns {}, dropping {} bytes", buffer.size(), bytes_per_row, buffer.size() % bytes_per_row);
buffer_bytes = buffer_bytes.slice(0, buffer.size() - buffer.size() % bytes_per_row);
}
if (predictor == 2)
return decode_tiff_prediction(buffer, columns, colors, bits_per_component);
return decode_tiff_prediction(buffer_bytes, columns, colors, bits_per_component);
size_t bytes_per_pixel = ceil_div(colors * bits_per_component, 8);
return decode_png_prediction(buffer, bytes_per_row, bytes_per_pixel);
return decode_png_prediction(buffer_bytes, bytes_per_row, bytes_per_pixel);
}
PDFErrorOr<ByteBuffer> Filter::decode_lzw(ReadonlyBytes bytes, int predictor, int columns, int colors, int bits_per_component, int early_change)