text: /* pgmkernel.c - generate a portable graymap convolution kernel
  **
  ** Creates a Portable Graymap file containing a convolution filter
  ** with max value = 255 and minimum value > 127 that can be used as a 
  ** smoothing kernel for pnmconvol.
  **
  ** Copyright (C) 1992 by Alberto Accomazzi, Smithsonian Astrophysical
  ** Observatory.
  **
  ** Permission to use, copy, modify, and distribute this software and its
  ** documentation for any purpose and without fee is hereby granted, provided
  ** that the above copyright notice appear in all copies and that both that
  ** copyright notice and this permission notice appear in supporting
  ** documentation.  This software is provided "as is" without express or
  ** implied warranty.
  */
  
  #include <math.h>
  #include "pgm.h"
  #include "mallocvar.h"
  
  int
  main ( argc, argv )
      int argc;
      char *argv[];
  {
      register    int i, j;
      int     argn = 1, ixsize, iysize, maxval = 255;
      double  fxsize = 0.0, fysize = 0.0, w = 6.0, kxcenter, kycenter, 
          tmax = 0, *fkernel;
      const char  *usage = "[-weight f] width [height]";
  
      pgm_init( &argc, argv );
  
      while ( argn < argc && argv[argn][0] == '-' && argv[argn][1] != '\0' )
      {
          if ( pm_keymatch( argv[argn], "-weight", 2 )) {
              if (++argn >= argc)
                  pm_usage( usage );
              else if (sscanf(argv[argn], "%lf", &w) != 1)
                  pm_usage( usage );
          }
          else
              pm_usage( usage );
          argn++;
      }
  
      if (argn == argc)
          pm_usage( usage );
      
      if (sscanf(argv[argn], "%lf", &fxsize) != 1) 
          pm_error( "error reading input kernel x size, (%s)\n", argv[argn]);
  
      ++argn;
      if (argn == argc - 1) {
          if (sscanf(argv[argn], "%lf", &fysize) != 1)
              pm_error( "error reading input kernel y size, (%s)\n", argv[argn]);
      }
      else if (argn == argc)
          fysize = fxsize;
      else
          pm_usage( usage );
  
      if (fxsize <= 1 || fysize <= 1)
          pm_usage( usage );
  
      kxcenter = (fxsize - 1) / 2.0;
      kycenter = (fysize - 1) / 2.0;
      ixsize = fxsize + 0.999;
      iysize = fysize + 0.999;
      MALLOCARRAY(fkernel, ixsize * iysize);
      for (i = 0; i < iysize; i++) 
          for (j = 0; j < ixsize; j++) {
              fkernel[i*ixsize+j] = 1.0 / (1.0 + w * sqrt((double)
                                                          (i-kycenter)*(i-kycenter)+
                                                          (j-kxcenter)*(j-kxcenter)));
              if (tmax < fkernel[i*ixsize+j])
                  tmax = fkernel[i*ixsize+j];
          }
  
      /* output PGM header + data (ASCII format only) */
      printf("P2\n%d %d\n%d\n", ixsize, iysize, maxval);
      
      for (i = 0; i < iysize; i++, printf("\n"))
          for (j = 0; j < ixsize; j++)
              printf(" %3d", (int)(maxval * (fkernel[i*ixsize+j] / 
                                             (2*tmax) + 0.5)));
      
      exit(0);
  }
  
  