#include <stdio.h>
#include <stdlib.h>

typedef enum { FALSE, TRUE } boolean;

typedef unsigned char BYTE;


   /* Interface to John Logajan's gray-level display routines. */

extern void grayinit(void), grayexit(void), grayshow(void);
extern void gray22(BYTE *address, long span);


boolean read_file(FILE *fp, BYTE *mem, int w, int h)
{
   BYTE *rbuf, *rover;
   int x, y;
   long conv;

   if ((rbuf = calloc((size_t)w, (size_t)3)) == NULL)
      return FALSE;

   for (y = 0; y < h; ++y) {
      if (fread(rbuf, (size_t)3, (size_t)w, fp) < (size_t)w) {
         free(rbuf);
         return FALSE;
      }

      for (x = 0, rover = rbuf; x < w; ++x) {
         conv   = *rover++ * 299l       /* calc luminance (NTSC Y formula) */
                + *rover++ * 587l
                + *rover++ * 114l;
         *mem++ = (BYTE)(conv / 11591); /* scale to range 0..21 */
      }
   }

   free(rbuf);

   return TRUE;
}

void main(int argc, char **argv)
{
   FILE *file;
   int width, height;
   BYTE *buffer;

   if (argc != 2) {
      printf("Usage: viewmtv filename\n");
      exit(1);
   }

   if ((file = fopen(argv[1], "rb")) == NULL) {
      printf("Can't open '%s'\n", argv[1]);
      exit(1);
   }

   if (fscanf(file, "%d %d", &width, &height) != 2) {
      fclose(file);
      printf("'%s' is not in MTV format\n");
      exit(1);
   }

   while (getc(file) != '\n') /* skip MTV `header' line */
      ;

   if ((buffer = malloc((long)width * (long)height)) == NULL) {
      fclose(file);
      printf("Not enough memory for %dx%d pixels\n", width, height);
      exit(1);
   }

   if (! read_file(file, buffer, width, height)) {
      fclose(file);
      printf("Error while reading '%s'\n", argv[1]);
      exit(1);
   }

   fclose(file);

   /* ### */
   grayinit();
   gray22(buffer, width);
   grayexit();
   /* ### */

   free(buffer);
   exit(0);
}