98 lines
3.3 KiB
C
98 lines
3.3 KiB
C
#include "colors.h"
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#include <math.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdbool.h>
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int main() {
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long double eps = 1e-17;
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long double Q1LOG2 = 1.44269504088896340735992468100189213742664595415299;
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long double LOG2 = 0.69314718055994530941723212145817656807550013436026;
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int width = 640;
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int height = 480;
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char* image = malloc(width*height*3);
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int x, y;
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long double centerx = -0.743643887037158704752191506114774;
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long double centery = 0.131825904205311970493132056385139;
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long double bailout = 128;
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long double logLogBailout = log(log(bailout));
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int foundperiods = 0;
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long double magn = 1e18;
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long maxiter = width * sqrt(magn);
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long double x0d = 4 / magn / width;
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long double x2 = -2 / magn + centerx;
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long double y1d = -4 / magn / width;
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long double y2 = 2 / magn * height / width + centery;
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int imgidx = 0;
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for (y = 0; y < height; y++) {
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fprintf(stderr, "\r%f %%", (float)imgidx/(width*height*3)*100);
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for (x = 0; x < width; x++) {
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long double px = x*x0d + x2;
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long double py = y*y1d + y2;
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// no Main bulb or Cardoid check to be faster
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long double zx = px;
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long double zy = py;
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long i;
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// Initial maximum period to detect.
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int check = 3;
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// Maximum period doubles every iterations:
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int whenupdate = 10;
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// Period history registers.
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long double hx = 0;
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long double hy = 0;
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long double xx, yy;
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bool inside = true;
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for (i = 1; i <= maxiter; i++) {
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xx = zx * zx;
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yy = zy * zy;
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if (xx + yy > bailout) {
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inside = false;
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break;
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}
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// iterate
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zy = 2 * zx * zy + py;
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zx = xx - yy + px;
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// periodicity check
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long double d = zx - hx;
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if (d > 0.0 ? d < eps : d > -eps) {
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d = zy - hy;
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if (d > 0.0 ? d < eps : d > -eps) {
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// Period found.
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foundperiods++;
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break;
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}
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}
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if ((i & check) == 0) {
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if (--whenupdate == 0) {
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whenupdate = 10;
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check <<= 1;
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check++;
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}
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// period = 0;
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hx = zx;
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hy = zy;
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}
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}
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if (inside) {
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image[imgidx++] = 0;
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image[imgidx++] = 0;
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image[imgidx++] = 0;
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} else {
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long double r = sqrtl(zx*zx + zy*zy);
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long double c = i - 1.28 + (logLogBailout - logl(logl(r))) * Q1LOG2;
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int idx = fmodl((logl(c/64+1)/LOG2+0.45), 1)*GRADIENTLENGTH + 0.5;
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image[imgidx++] = colors[idx][0];
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image[imgidx++] = colors[idx][1];
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image[imgidx++] = colors[idx][2];
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}
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}
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}
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// write out image
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printf("P6 %d %d 255\n", width, height);
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fwrite(image, 1, width*height*3, stdout);
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fprintf(stderr, "%d periods found\n", foundperiods);
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return 0;
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}
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