/* field.c - Don Yang (uguu.org)

   11/09/08
                                                                           */

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<time.h>
#include<math.h>

#define RAND() ((double)rand() / (double)RAND_MAX)

static void GenerateImage(int width, int height, FILE *outfile)
{
   double x_phase, y_phase, d_phase, x_period, y_period, d_period;
   double pi, sx, sy, sd;
   int pscale, x, y, pixel;

   pscale = width;
   if( height > width )
      pscale = height;

   srand((unsigned)time(NULL));
   pi = atan2(0.0, -1.0);
   x_phase = 2.0 * pi * RAND();
   y_phase = 2.0 * pi * RAND();
   d_phase = 2.0 * pi * RAND();
   x_period = (8.0 + (8.0 * RAND())) / pscale;
   y_period = (8.0 + (8.0 * RAND())) / pscale;
   d_period = (8.0 + (8.0 * RAND())) / pscale;
   for(y = 0; y < height; y++)
   {
      sy = sin((y + y_phase) * y_period);
      for(x = 0; x < width; x++)
      {
         sx = sin((x + x_phase) * x_period);
         sd = sin((x + y + d_phase) * d_period);
         pixel = (int)(255.0 * (sx + sy + sd + 3.0) / 6.0);
         (void)fputc(pixel, outfile);
      }
   }
}

int main(int argc, char **argv)
{
   char header[32];
   int width, height;
   FILE *outfile;

   if( argc < 4 )
   {
      printf("%s <width> <height> <output>\n", *argv);
      return 1;
   }
   width = atoi(argv[1]);
   height = atoi(argv[2]);
   if( width < 1 || height < 1 )
   {
      printf("Invalid image size: %s %s\n", argv[1], argv[2]);
      return 1;
   }
   if( (outfile = fopen(argv[3], "wb")) == NULL )
   {
      printf("Error writing %s\n", argv[3]);
      return 1;
   }

   /*@i1@*/sprintf(header, "P5\n%d %d\n255\n", width, height);
   (void)fwrite(header, strlen(header), 1, outfile);
   GenerateImage(width, height, outfile);
   (void)fclose(outfile);
   return 0;
}