mirror of https://github.com/qpdf/qpdf.git
52 lines
1.3 KiB
C++
52 lines
1.3 KiB
C++
#ifndef PL_PNGFILTER_HH
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#define PL_PNGFILTER_HH
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// This pipeline applies or reverses the application of a PNG filter as described in the PNG
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// specification.
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// NOTE: In its current implementation, this filter always encodes using the "up" filter, but it
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// decodes all the filters.
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#include <qpdf/Pipeline.hh>
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class Pl_PNGFilter: public Pipeline
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{
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public:
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// Encoding is only partially supported
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enum action_e { a_encode, a_decode };
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Pl_PNGFilter(
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char const* identifier,
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Pipeline* next,
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action_e action,
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unsigned int columns,
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unsigned int samples_per_pixel = 1,
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unsigned int bits_per_sample = 8);
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~Pl_PNGFilter() override = default;
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void write(unsigned char const* data, size_t len) override;
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void finish() override;
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private:
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void decodeSub();
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void decodeUp();
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void decodeAverage();
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void decodePaeth();
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void processRow();
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void encodeRow();
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void decodeRow();
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int PaethPredictor(int a, int b, int c);
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action_e action;
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unsigned int bytes_per_row;
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unsigned int bytes_per_pixel;
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unsigned char* cur_row; // points to buf1 or buf2
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unsigned char* prev_row; // points to buf1 or buf2
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std::shared_ptr<unsigned char> buf1;
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std::shared_ptr<unsigned char> buf2;
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size_t pos;
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size_t incoming;
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};
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#endif // PL_PNGFILTER_HH
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