text: #include <qpdf/Pl_PNGFilter.hh>
  #include <qpdf/Pl_TIFFPredictor.hh>
  #include <qpdf/Pl_StdioFile.hh>
  #include <qpdf/QUtil.hh>
  #include <qpdf/QIntC.hh>
  
  #include <iostream>
  #include <errno.h>
  #include <assert.h>
  #include <string.h>
  #include <stdlib.h>
  
  void run(char const* filename, char const* filter,
           bool encode, unsigned int columns,
           unsigned int bits_per_sample, unsigned int samples_per_pixel)
  {
      FILE* in = QUtil::safe_fopen(filename, "rb");
      FILE* o1 = QUtil::safe_fopen("out", "wb");
      Pipeline* out = new Pl_StdioFile("out", o1);
      Pipeline* pl = 0;
      if (strcmp(filter, "png") == 0)
      {
          pl = new Pl_PNGFilter(
              "png", out,
              encode ? Pl_PNGFilter::a_encode : Pl_PNGFilter::a_decode,
              columns, samples_per_pixel, bits_per_sample);
      }
      else if (strcmp(filter, "tiff") == 0)
      {
          pl = new Pl_TIFFPredictor(
              "png", out,
              encode ? Pl_TIFFPredictor::a_encode : Pl_TIFFPredictor::a_decode,
              columns, samples_per_pixel, bits_per_sample);
      }
      else
      {
          std::cerr << "unknown filter " << filter << std::endl;
          exit(2);
      }
      assert((2 * (columns + 1)) < 1024);
      unsigned char buf[1024];
      size_t len;
      while (true)
      {
  	len = fread(buf, 1, (2 * columns) + 1, in);
  	if (len == 0)
  	{
  	    break;
  	}
  	pl->write(buf, len);
  	len = fread(buf, 1, 1, in);
  	if (len == 0)
  	{
  	    break;
  	}
  	pl->write(buf, len);
  	len = fread(buf, 1, 1, in);
  	if (len == 0)
  	{
  	    break;
  	}
  	pl->write(buf, len);
      }
  
      pl->finish();
      delete pl;
      delete out;
      fclose(o1);
      fclose(in);
  
      std::cout << "done" << std::endl;
  }
  
  int main(int argc, char* argv[])
  {
      if (argc != 7)
      {
  	std::cerr << "Usage: predictor {png|tiff} {en,de}code filename"
                    << " columns samples-per-pixel bits-per-sample"
                    << std::endl;
  	exit(2);
      }
      char* filter = argv[1];
      bool encode = (strcmp(argv[2], "encode") == 0);
      char* filename = argv[3];
      int columns = QUtil::string_to_int(argv[4]);
      int samples_per_pixel = QUtil::string_to_int(argv[5]);
      int bits_per_sample = QUtil::string_to_int(argv[6]);
  
      try
      {
  	run(filename, filter, encode,
              QIntC::to_uint(columns),
              QIntC::to_uint(bits_per_sample),
              QIntC::to_uint(samples_per_pixel));
      }
      catch (std::exception& e)
      {
  	std::cout << e.what() << std::endl;
      }
      return 0;
  }
  