/* Circular moire pattern generator.

   ./circular_moire <width> <height> > output.pgm
                                                  */
#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

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;
         fputc((int)(a * 255.0 / (2.0 * CIRCLE_COUNT)), stdout);
      }
   }
   return 0;
}