#include "stdio.h"
 
putbyte(outf,val)
FILE *outf;
unsigned char val;
{
    unsigned char buf[1];
 
    buf[0] = val;
    fwrite(buf,1,1,outf);
}
 
putshort(outf,val)
FILE *outf;
unsigned short val;
{
    unsigned char buf[2];
 
    buf[0] = (val>>8);
    buf[1] = (val>>0);
    fwrite(buf,2,1,outf);
}
 
static int putlong(outf,val)
FILE *outf;
unsigned long val;
{
    unsigned char buf[4];
 
    buf[0] = (val>>24);
    buf[1] = (val>>16);
    buf[2] = (val>>8);
    buf[3] = (val>>0);
    return fwrite(buf,4,1,outf);
}

unsigned short getshort()
{
 unsigned char buf[2];
 fread(buf, 2, 1, inf);
 return (buf[0]<<8) + (buf[1]<<0);
}

static long getlong()
{
 unsigned char buf[4];
 fread(buf, 4, 1, inf);
 return (buf[0]<<24) + (buf[1]<<16)+ (buf[2]<<8) + (buf[3]<<0);
}

#define IXSIZE      (800)
#define IYSIZE      (800)
#define IZZIZE  (3)

main(argc, argv)
int   argc;
char **argv;
{
    FILE *of, *inf;
    char iname[80];
 unsigned char inbuf[IXSIZE][IYSIZE][IZSIZE];
    int i, x, y,z;
 unsigned short ixsi, iysi, izsi, ixsi1, iysi1;
 
 /* make sure the user invokes this program properly */
 if(argc != 5) {
  fprintf(stderr, "Usage: merge red.bw green.bw blue.bw out.rgb\n");
  exit(1);
 }

 /* Read the input BW files*/
    /*red channel */
 if ((inf=fopen(argv[1], "r"))==NULL)
 {
  fprintf(stderr, "readImage: Can't open file %s\n", argv[1]);
  exit(1);
 }
 else
 {
 ixsi1 = getshort();
 ixsi = getshort();
 iysi1 = getshort();
 iysi = getshort();

 for (y=0; y < iysi; y++)
  for (x=0; x < ixsi; x++)
   fread(&inbuf[x][y][0], 1, 1, inf);
 }
 fclose(inf);

    /*green channel */
 if ((inf=fopen(argv[2], "r"))==NULL)
 {
  fprintf(stderr, "readImage: Can't open file %s\n", argv[1]);
  exit(1);
 }
 else
 {
 ixsi1 = getshort();
 ixsi = getshort();
 iysi1 = getshort();
 iysi = getshort();

 for (y=0; y < iysi; y++)
  for (x=0; x < ixsi; x++)
   fread(&inbuf[x][y][1], 1, 1, inf);
 }
 fclose(inf);

    /*blue channel */
 if ((inf=fopen(argv[3], "r"))==NULL)
 {
  fprintf(stderr, "readImage: Can't open file %s\n", argv[1]);
  exit(1);
 }
 else
 {
 ixsi1 = getshort();
 ixsi = getshort();
 iysi1 = getshort();
 iysi = getshort();

 for (y=0; y < iysi; y++)
  for (x=0; x < ixsi; x++)
   fread(&inbuf[x][y][2], 1, 1, inf);
 }
 fclose(inf);

/*Begin to write output files */
    of = fopen(argv[4],"w");
    if(!of) {
        fprintf(stderr,"sgiimage: can't open output file\n");
        exit(1);
    }
    putshort(of,474);       /* MAGIC                       */
    putbyte(of,0);          /* STORAGE is VERBATIM         */
    putbyte(of,1);          /* BPC is 1                    */
    putshort(of,2);         /* DIMENSION is 2              */
    putshort(of,ixsi);    /* XSIZE                       */
    putshort(of,iysi);    /* YSIZE                       */
    putshort(of,3);         /* ZSIZE                       */
    putlong(of,0);          /* PIXMIN is 0                 */
    putlong(of,255);        /* PIXMAX is 255               */
    for(i=0; i<4; i++)      /* DUMMY 4 bytes       */
        putbyte(of,0);
    strcpy(iname,"No Name");
    fwrite(iname,80,1,of);  /* IMAGENAME           */
    putlong(of,0);          /* COLORMAP is 0       */
    for(i=0; i<404; i++)    /* DUMMY 404 bytes     */
        putbyte(of,0);
 
 for (z=0; z < 3; z++)
  for(y=0; y<iysi; y++)
   for(x=0; x<ixsi; x++)
    fwrite(&inbuf[x][y][z],1,1, of);
 
    fclose(of);
}