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#ifndef __PL_PNGFILTER_HH__
#define __PL_PNGFILTER_HH__
// This pipeline applies or reverses the application of a PNG filter
// as described in the PNG specification.
// NOTE: In its initial implementation, it only encodes and decodes
// filters "none" and "up". The primary motivation of this code is to
// encode and decode PDF 1.5+ XRef streams which are often encoded
// with Flate predictor 12, which corresponds to the PNG up filter.
// At present, the bytes_per_pixel parameter is ignored, and an
// exception is thrown if any row of the file has a filter of other
// than 0 or 2. Finishing the implementation would not be difficult.
// See chapter 6 of the PNG specification for a description of the
// filter algorithms.
#include <qpdf/Pipeline.hh>
class Pl_PNGFilter: public Pipeline
{
public:
class Exception: public Pipeline::Exception
{
public:
Exception(std::string const& message) :
Pipeline::Exception(message)
{
}
virtual ~Exception() throw ()
{
}
};
// Encoding is not presently supported
enum action_e { a_encode, a_decode };
Pl_PNGFilter(char const* identifier, Pipeline* next,
action_e action, unsigned int columns,
unsigned int bytes_per_pixel);
virtual ~Pl_PNGFilter();
virtual void write(unsigned char* data, int len);
virtual void finish();
private:
void processRow();
void encodeRow();
void decodeRow();
action_e action;
unsigned int columns;
unsigned char* cur_row;
unsigned char* prev_row;
unsigned char* buf1;
unsigned char* buf2;
int pos;
int incoming;
};
#endif // __PL_PNGFILTER_HH__
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