Created
November 7, 2019 03:31
-
-
Save higuoxing/db4d27e387f9099516391dd99bd4261c to your computer and use it in GitHub Desktop.
C code for generating mandelbrot set.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| #include <stdio.h> | |
| #include <math.h> | |
| #define PPM_FILE_NAME "mandelbrot.ppm" | |
| #define COMMENT "# This is an image on mandelbrot set" | |
| #define IMAGE_WIDTH 800 | |
| #define IMAGE_HEIGHT 800 | |
| #define MAX_COLOR_VALUE 255 | |
| #define CX_MIN (-2.5 - 0.5) / 1.9 | |
| #define CX_MAX (1.5 - 0.5) / 1.9 | |
| #define CY_MIN -2.0 / 1.9 | |
| #define CY_MAX 2.0 / 1.9 | |
| #define PIXEL_WIDTH (CX_MAX - CX_MIN) / IMAGE_WIDTH | |
| #define PIXEL_HEIGHT (CY_MAX - CY_MIN) / IMAGE_HEIGHT | |
| #define ITERATION_TIMES 200 | |
| #define ESCAPE_CIRCLE 2 * 2 | |
| FILE *file; | |
| static unsigned char pixel[3]; | |
| void init_ppm_image() { | |
| file = fopen(PPM_FILE_NAME, "wb" /* Binary Mode */); | |
| // Write file headers. | |
| fprintf(file, | |
| "P6\n" | |
| " %s\n" /* Comments */ | |
| " %d\n %d\n" /* File Size */ | |
| " %d\n" /* 0-255 */, | |
| COMMENT, IMAGE_WIDTH, IMAGE_HEIGHT, MAX_COLOR_VALUE); | |
| } | |
| int main() { | |
| init_ppm_image(); | |
| // Z = Zx + i * Zy | |
| double Zx, Zy; | |
| double Cx, Cy; | |
| // Iterate over every pixel. | |
| for (int y = 0; y < IMAGE_HEIGHT; ++ y) { | |
| Cy = CY_MIN + y * PIXEL_HEIGHT; | |
| if (fabs(Cy) < PIXEL_HEIGHT / 2) { | |
| Cy = 0.0; | |
| } | |
| for (int x = 0; x < IMAGE_WIDTH; ++ x) { | |
| Cx = CX_MIN + x * PIXEL_WIDTH; | |
| Zx = 0.0; | |
| Zy = 0.0; | |
| int iter; | |
| for (iter = 0; iter < ITERATION_TIMES && | |
| Zx * Zx + Zy * Zy < ESCAPE_CIRCLE; ++ iter) { | |
| double Zxx = Zx; | |
| double Zyy = Zy; | |
| // Z(n) = Z(n - 1) ^ 2 + C | |
| // Z_x(n) = Z_x(n - 1) ^ 2 - Z_y(n - 1) ^ 2 + C_x | |
| Zx = Zxx * Zxx - Zyy * Zyy + Cx; | |
| // Z_y(n) = 2 * Z_x(n - 1) * Z_y(n - 1) + C_y | |
| Zy = 2 * Zxx * Zyy + Cy; | |
| } | |
| if (iter == ITERATION_TIMES) { | |
| pixel[0] = 0; | |
| pixel[1] = 0; | |
| pixel[2] = 0; | |
| } else { | |
| pixel[0] = 255; | |
| pixel[1] = 255; | |
| pixel[2] = 255; | |
| } | |
| fwrite(pixel, 1, 3, file); | |
| } | |
| } | |
| fclose(file); | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment