/* Circular moire pattern generator.

   ./circular_moire_dither_bayer <width> <height> > output.pgm

   Forked from circular_moire.c to use ordered dither pattern.

   https://en.wikipedia.org/wiki/Ordered_dithering
                                                               */
#include<math.h>
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#ifdef _WIN32
   #include<fcntl.h>
   #include<io.h>
#endif

#define CIRCLE_COUNT  3

#if 0
   #define PATTERN_SIZE 4
   static const int pattern[PATTERN_SIZE][PATTERN_SIZE] =
   {
      { 0,  8,  2, 10},
      {12,  4, 14,  6},
      { 3, 11,  1,  9},
      {15,  7, 13,  5}
   };
#else
   #define PATTERN_SIZE 8
   static const int pattern[PATTERN_SIZE][PATTERN_SIZE] =
   {
      { 0, 32,  8, 40,  2, 34, 10, 42},
      {48, 16, 56, 24, 50, 18, 58, 26},
      {12, 44,  4, 36, 14, 46,  6, 38},
      {60, 28, 52, 20, 62, 30, 54, 22},
      { 3, 35, 11, 43,  1, 33,  9, 41},
      {51, 19, 59, 27, 49, 17, 57, 25},
      {15, 47,  7, 39, 13, 45,  5, 37},
      {63, 31, 55, 23, 61, 29, 53, 21}
   };
#endif

int main(int argc, char **argv)
{
   int width, height, x, y, i;
   double cx[CIRCLE_COUNT], cy[CIRCLE_COUNT], scale[CIRCLE_COUNT], a;

   if( argc != 3 ||
       (width = atoi(argv[1])) <= 0 ||
       (height = atoi(argv[2])) <= 0 )
   {
      return printf("%s <width> <height>\n", *argv);
   }
   if( width >= 0x8000 || height >= 0x8000 )
      return !puts("Output size too large.");

   #ifdef _WIN32
      setmode(STDOUT_FILENO, O_BINARY);
   #endif

   srand(time(NULL));

   for(i = 0; i < CIRCLE_COUNT; i++)
   {
      cx[i] = (double)rand() / RAND_MAX * width;
      cy[i] = (double)rand() / RAND_MAX * height;
      scale[i] = ((double)rand() / RAND_MAX * 30.0 + 6.0)
                  / (width < height ? width : height);
   }

   printf("P5\n%d %d\n255\n", width, height);
   for(y = 0; y < height; y++)
   {
      for(x = 0; x < width; x++)
      {
         a = 0;
         for(i = 0; i < CIRCLE_COUNT; i++)
            a += sin(hypot(x - cx[i], y - cy[i]) * scale[i]) + 1.0;

         a /= 2.0 * CIRCLE_COUNT;
         a = a + (pattern[y % PATTERN_SIZE][x % PATTERN_SIZE] / 
                  (double)(PATTERN_SIZE * PATTERN_SIZE) - 0.5);
         fputc(a > 0.5 ? 255 : 0, stdout);
      }
   }
   return 0;
}