text: /* pbmtopgm.c - convert bitmap to greymap by totalling pixels over sample area
   * AJCD 12/12/90
   */
  
  #include <stdio.h>
  #include "pgm.h"
  
  int
  main(argc, argv)
       int argc;
       char *argv[];
  {
     register gray *outrow, maxval;
     register int right, left, down, up;
     register bit **inbits;
     int rows, cols;
     FILE *ifd;
     int col, row, width, height;
     char *usage = "<w> <h> [pbmfile]";
     
  
     pgm_init( &argc, argv );
  
     if (argc > 4 || argc < 3)
        pm_usage(usage);
  
     width = atoi(argv[1]);
     height = atoi(argv[2]);
     if (width < 1 || height < 1)
        pm_error("width and height must be > 0");
     left=width/2; right=width-left;
     up=width/2; down=height-up;
  
     if (argc == 4)
        ifd = pm_openr(argv[3]);
     else
        ifd = stdin ;
  
     inbits = pbm_readpbm(ifd, &cols, &rows) ;
  
     if (width > cols || height > rows)
        pm_error("sample size greater than bitmap size");
  
     outrow = pgm_allocrow(cols) ;
     maxval = width*height;
     pgm_writepgminit(stdout, cols, rows, maxval, 0) ;
  
     for (row = 0; row < rows; row++) {
        int t = (row > up) ? (row-up) : 0;
        int b = (row+down < rows) ? (row+down) : rows;
        int onv = height - (t-row+up) - (row+down-b);
        for (col = 0; col < cols; col++) {
  	 int l = (col > left) ? (col-left) : 0;
  	 int r = (col+right < cols) ? (col+right) : cols;
  	 int onh = width - (l-col+left) - (col+right-r);
  	 int value = 0, x, y;
  	 for (x = l; x < r; x++)
  	    for (y = t; y < b; y++)
  	       if (inbits[y][x] == PBM_WHITE) value++;
  	 outrow[col] = maxval*value/(onh*onv);
        }
        pgm_writepgmrow(stdout, outrow, cols, maxval, 0) ;
     }
     pm_close(ifd);
     exit(0);
  }
  