nuclear@0: /*
nuclear@0: A simple interactive mandelbrot fractal explorer
nuclear@0: Copyright (C) John Tsiombikas <nuclear@member.fsf.org>
nuclear@0: 
nuclear@0: This program is free software: you can redistribute it and/or modify
nuclear@0: it under the terms of the GNU General Public License as published by
nuclear@0: the Free Software Foundation, either version 3 of the License, or
nuclear@0: (at your option) any later version.
nuclear@0: 
nuclear@0: This program is distributed in the hope that it will be useful,
nuclear@0: but WITHOUT ANY WARRANTY; without even the implied warranty of
nuclear@0: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
nuclear@0: GNU General Public License for more details.
nuclear@0: 
nuclear@0: You should have received a copy of the GNU General Public License
nuclear@0: along with this program.  If not, see <http://www.gnu.org/licenses/>.
nuclear@0: */
nuclear@0: #include "mbrot.h"
nuclear@0: #include "palette.h"
nuclear@0: 
nuclear@0: static int mandelbrot(double cx, double cy, int iter);
nuclear@0: 
nuclear@0: void draw_mandelbrot(unsigned char *pix, int xsz, int ysz, struct area *area, int iter)
nuclear@0: {
nuclear@0: 	int i, j;
nuclear@0: 	double x, y, dx, dy;
nuclear@0: 
nuclear@0: 	dx = area->width / (double)xsz;
nuclear@0: 	dy = area->height / (double)ysz;
nuclear@0: 
nuclear@0: 	y = area->y;
nuclear@0: 	for(i=0; i<ysz; i++) {
nuclear@0: 		x = area->x;
nuclear@0: 		for(j=0; j<xsz; j++) {
nuclear@0: 			int res = mandelbrot(x, y, iter);
nuclear@0: 			/* visualize according to the number of iterations
nuclear@0: 			 * required to determine membership in the mandelbrot set.
nuclear@0: 			 * Members of the set will have res = iter and so col = PAL_SIZE-1
nuclear@0: 			 */
nuclear@0: 			int col = (PAL_SIZE - 1) * res / iter;
nuclear@0: 			*pix++ = palette[col].r;
nuclear@0: 			*pix++ = palette[col].g;
nuclear@0: 			*pix++ = palette[col].b;
nuclear@0: 			*pix++ = 0;
nuclear@0: 
nuclear@0: 			x += dx;
nuclear@0: 		}
nuclear@0: 		y += dy;
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: static int mandelbrot(double cx, double cy, int iter)
nuclear@0: {
nuclear@0: 	int i;
nuclear@0: 	double zx, zy;	/* complex number Z */
nuclear@0: 
nuclear@0: 	/* start with Z0 = C */
nuclear@0: 	zx = cx;
nuclear@0: 	zy = cy;
nuclear@0: 
nuclear@0: 	for(i=0; i<iter; i++) {
nuclear@0: 		/* calculate Zn+1 = Zn * Zn + C */
nuclear@0: 		double x = (zx * zx - zy * zy) + cx;
nuclear@0: 		double y = (zy * zx + zx * zy) + cy;
nuclear@0: 		zx = x;
nuclear@0: 		zy = y;
nuclear@0: 
nuclear@0: 		/* escape if ||Z|| > 2 */
nuclear@0: 		if((x * x + y * y) > 4.0) {
nuclear@0: 			break;
nuclear@0: 		}
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	return i;
nuclear@0: }