/**  mandel.c   by Eric R. Weeks   written 9-28-96
 **  weeks@physics.emory.edu
 **  http://www.physics.emory.edu/~weeks/
 **  
 **  This program is public domain, but this header must be left intact
 **  and unchanged.
 **  
 **  to compile:  cc -o mand mandel.c
 ** 
 **/

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
void color();

main()
{
	double x,xx,y,cx,cy;
	int iteration,hx,hy;
	int itermax = 100;		/* how many iterations to do	*/
	double magnify=1.0;		/* no magnification		*/
	int hxres = 500;		/* horizonal resolution		*/
	int hyres = 500;		/* vertical resolution		*/

	/* header for PPM output */
	printf("P6\n# CREATOR: Eric R Weeks / mandel program\n");
	printf("%d %d\n255\n",hxres,hyres);

	for (hy=1;hy<=hyres;hy++)  {
		for (hx=1;hx<=hxres;hx++)  {
			cx = (((float)hx)/((float)hxres)-0.5)/magnify*3.0-0.7;
			cy = (((float)hy)/((float)hyres)-0.5)/magnify*3.0;
			x = 0.0; y = 0.0;
			for (iteration=1;iteration<itermax;iteration++)  {
				xx = x*x-y*y+cx;
				y = 2.0*x*y+cy;
				x = xx;
				if (x*x+y*y>100.0)  iteration = 999999;
			}
			if (iteration<99999)  color(0,255,255);
			else color(180,0,0);
		}
	}
}

void color(int red, int green, int blue)  {
	fputc((char)red,stdout);
	fputc((char)green,stdout);
	fputc((char)blue,stdout);
}