/*********************************************************/
/*   program 27: SGI RGB read/write functions            */
/*********************************************************/

typedef struct        /* SGI RGB header structure */
  {
  short int  magic;
  short int  type;
  short int  dim;
  short int  xsize;
  short int  ysize;
  short int  zsize;
  long  int  min;
  long  int  max;
  long  int  waste;
  char       name[80];
  long  int  space[102];
  }  SGI_HEADER;

void read_sgi_header ( fp, xs, ys, pl, type )
/*
 *******************************************************
*/

  long int  fp;          /* file pointer */
  long int *xs,*ys;     /* x,y size */
  long int *pl;         /* plane count */
  long int *type;       /* file type */
{
  SGI_HEADER header;

  read ( fp, &header, sizeof(header) );

  if (header.magic != 474) {
    printf("INVALID SGI MAGIC NUMBER: %d\n",header.magic);
  }
  else {
    *xs = (long)header.xsize;
    *ys = (long)header.ysize;
    *pl = (long)header.zsize;
    *type = (long)header.type;
    if (*type != 1) {
      printf("SGI TYPE NOT 1: %d\n",header.type);
    }
  }
  return;
}

void read_sgi_data ( fp, xs, ys, pl, type, r, g, b )
/*
 *******************************************************
*/
  long int fp;          /* file pointer */
  long int xs,ys;       /* x,y size */
  long int pl;          /* plane count */
  long int type;        /* file type */
  unsigned char *r,*g,*b; /* data buffer pointers */
{
  long int c;
  unsigned char *d;
  long int y;

  for ( c = 0; c < pl; c++ ) {

    if (c == 0) d = r;
    if (c == 1) d = g;
    if (c == 2) d = b;
    d = d + ((ys - 1) * xs);

    for ( y = 0; y < ys; y++ ) {
      read ( fp, d, xs );
      d = d - xs;
    }

  }
  return;
}

void write_sgi_header ( fp, xs, ys, pl, type )
/*
 *******************************************************
*/
  long int fp;          /* file pointer */
  long int xs,ys;       /* x,y size */
  long int pl;          /* plane count */
  long int type;        /* file type */
{
  SGI_HEADER header;
  long int  i;

  header.magic = 474;
  header.type  = type;
  header.dim   = 3;
  header.xsize = xs;
  header.ysize = ys;
  header.zsize = pl;
  header.min   = 0;
  header.max   = 255;
  header.waste = 0;

  for ( i = 0; i < 80; i++ ) {
    header.name[i] = 0;
  }

  for ( i = 0; i < 102; i++ ) {
    header.space[i] = 0;
  }

  write ( fp, &header, sizeof(header) );

  return;
}

void write_sgi_data ( fp, xs, ys, pl, r, g, b, type )
/*
 *******************************************************
*/
  long int fp;          /* file pointer */
  long int xs,ys;       /* x,y size */
  long int pl;          /* plane count */
  unsigned char *r,*g,*b; /* data buffer pointers */
  long int type;        /* file type */
{
  long int c;
  unsigned char *d;
  long int y;

  for ( c = 0; c < pl; c++ ) {

    if (c == 0) d = r;
    if (c == 1) d = g;
    if (c == 2) d = b;
    d = d + ((ys - 1) * xs);

    for ( y = 0; y < ys; y++ ) {
      write ( fp, d, xs );
      d = d - xs;
    }

  }
  return;
}