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89 lines
1.9 KiB
C
89 lines
1.9 KiB
C
#include "SDL.h"
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#include <complex.h>
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#include <stdbool.h>
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/* The maximum iteration count. */
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const int max_it = 170;
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/* Compute the out-coloring based on the iteration counter. */
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Uint32 outcolor(int it) {
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return 0x00010001 * ((it * 0xff) / max_it);
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}
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/* "Compute" the in-coloring. */
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Uint32 incolor() {
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return 0x00000000; /* black */
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}
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void drawmandelbrot(SDL_Surface * surface) {
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if (SDL_MUSTLOCK(surface)) {
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SDL_LockSurface(surface);
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}
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Uint32 *pixels = (Uint32 *) surface->pixels;
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for (int i = 0; i < surface->w * surface->h; i++) {
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int y = i / surface->w;
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int x = i % surface->w;
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float complex c = ((3.0f * x / surface->w) - 2.0f)
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+ I * ((2.0f * y / surface->h) - 1.0f);
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bool diverges = false;
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float complex z = 0;
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int it;
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for (it = 1; it <= max_it; it++) {
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/* z = z² + c */
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z = cpowf(z, 2) + c;
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/* If |z| ever gets greater than 2, it diverges. */
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if (cabsf(z) > 2) {
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diverges = true;
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break;
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}
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}
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Uint32 color;
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if (diverges) {
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color = outcolor(it);
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} else {
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color = incolor();
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}
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pixels[i] = color;
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/* Update the screen every 10 lines. */
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if (y % 10 == 0 && x == 0) {
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SDL_Flip(surface);
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}
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}
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/* Update the screen a final time. */
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SDL_Flip(surface);
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if (SDL_MUSTLOCK(surface)) {
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SDL_UnlockSurface(surface);
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}
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}
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int main(void) {
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/* Set up SDL. */
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if (SDL_Init(SDL_INIT_EVERYTHING) < 0) {
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fprintf(stderr, "Error: Could not initialize SDL: %s.\n",
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SDL_GetError());
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exit(1);
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}
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SDL_Surface *screen = SDL_SetVideoMode(320, 240, 32, SDL_SWSURFACE);
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/* Do the mandelbrot. */
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drawmandelbrot(screen);
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/* Save BMP */
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char *file = "mandelbrot.bmp";
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if (SDL_SaveBMP(screen, file) != 0) {
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fprintf(stderr, "Could not write %s!\n", file);
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}
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/* Quit. */
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SDL_Delay(20000);
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SDL_Quit();
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}
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