#define USAGE "Usage: %s [OPTION]... PSFILE [PNGFILE]\n" \
"Converts a PostScript file to PNG using GhostScript (gs).\n" \
"\n" \
"\n" \
"  -h, --help         Prints this usage information\n" \
"  -H, --description  Prints a description of the program\n" \
"  -d, -D, -s, -S     Defines names or strings within gs\n" \
"  -r RES             Specifies image resolution\n" \
"  -g SIZE            Specifies image size\n" \
"  -I DIR             Specifies search directories\n" \
"\n" \
"This program executes %s with the options -dBATCH,\n" \
"-dNOPAUSE, -dEPSCrop, -sDEVICE=pngalpha, and -sOutputFile=PNGFILE,\n" \
"with any other options passed directly on to GhostScript.  Of\n" \
"particular note: the default resolution is 72 pixels per \"inch\";\n" \
"this can be changed with the -rRES or -rXRESxYRES option.\n" \
"\n"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

#define CMD "/usr/bin/gs"         /* GhostScript command (full path) */
#define ARGV0 "gs"                /* GhostScript command (name only) */
#define ARGV1 "-dBATCH"           /* GhostScript argument */
#define ARGV2 "-dNOPAUSE"         /* GhostScript argument */
#define ARGV3 "-dEPSCrop"         /* GhostScript argument */
#define ARGV4 "-sDEVICE=pngalpha" /* GhostScript argument */
#define ARGV5 "-sOutputFile="     /* GhostScript destination stub */

int
main( int argc, char **argv )
{
  int i;           /* index over argument list */
  char **argv_new; /* argv array for new argument list */

  /* Check input arguments. */
  if ( argc < 3 ) {
    fprintf( stderr, USAGE, argv[0], CMD );
    return -1;
  }

  /* Assign new argv array. */
  if ( !( argv_new = (char **)malloc( ( argc + 5 )*sizeof(char *) ) ) ||
       !( argv_new[5] = (char *)
	  malloc( strlen( argv[argc-1] ) + strlen( ARGV5 ) + 1 ) ) ) {
    fprintf( stderr, "%s: memory error\n", argv[0] );
    return -2;
  }
  argv_new[0] = ARGV0;
  argv_new[1] = ARGV1;
  argv_new[2] = ARGV2;
  argv_new[3] = ARGV3;
  argv_new[4] = ARGV4;
  sprintf( argv_new[5], "%s%s", ARGV5, argv[argc-1] );
  for ( i = 1; i < argc - 2; i++ )
    argv_new[i+5] = argv[i];
  argv_new[argc+3] = argv[argc-2];
  argv_new[argc+4] = NULL;

  /* Execute GhostScript. */
  execvp( CMD, argv_new );
  fprintf( stderr, "%s: execvp() failed with errno=%i\n", argv[0],
	   errno );
  return -3;
}