131 lines
3.1 KiB
C
131 lines
3.1 KiB
C
#include "buddhabrot.h"
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#include <err.h>
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#include <float.h>
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#include <limits.h>
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#include <math.h>
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <string.h>
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#include "image.h"
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struct data {
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float min_x;
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float max_x;
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float min_y;
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float max_y;
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size_t max_iter;
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size_t h;
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size_t w;
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size_t buf[];
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};
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struct orbit {
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size_t len;
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struct my_complex {
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float r;
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float i;
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} values[];
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};
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static size_t data_index(size_t h, size_t w, const struct data *d) {
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return h * d->w + w;
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}
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static float scale(float min, float max, size_t x, size_t width) {
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return min + x * (max - min) / (width - 1);
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}
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static size_t inv_scale(float min, float max, float x, size_t width) {
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return (x - min) / (max - min) * (width - 1);
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}
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static bool compute_orbit(struct my_complex z,
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struct orbit *o, size_t max_iter) {
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float r = 0.0;
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float i = 0.0;
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for (o->len = 0; o->len < max_iter; ++o->len) {
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float xtemp = r * r - i * i + z.r;
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i = 2 * r * i + z.i;
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r = xtemp;
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if (r * r + i * i >= 4)
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return true; // Diverges
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o->values[o->len].r = r;
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o->values[o->len].i = i;
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}
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return false;
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}
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static void compute_buddahbrot(struct data *d) {
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// FIXME: does not check overflow
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struct orbit *o = calloc(1, d->max_iter * sizeof(*o->values) + sizeof(*o));
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if (!o)
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err(EXIT_FAILURE, "could not allocate orbit data");
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for (size_t i = 0; i < d->h; ++i) {
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for (size_t j = 0; j < d->w; ++j) {
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struct my_complex z = {
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scale(d->min_x, d->max_x, j, d->w),
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scale(d->min_y, d->max_y, i, d->h),
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};
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// Only keep if it diverges
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if (!compute_orbit(z, o, d->max_iter))
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continue;
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for (size_t i = 0; i < o->len; ++i) {
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size_t w = inv_scale(d->min_x, d->max_x,
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o->values[i].r, d->w);
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size_t h = inv_scale(d->min_y, d->max_y,
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o->values[i].i, d->h);
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if (w >= d->w || h >= d->h)
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continue; // We've diverged, keep going just in case
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d->buf[data_index(h, w, d)] += 1;
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}
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}
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}
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free(o);
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}
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static void fillout_image(const struct data *d, struct image *i) {
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size_t max = 0;
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for (size_t ind = 0; ind < i->h * i->w; ++ind)
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if (max < d->buf[ind])
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max = d->buf[ind];
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for (size_t ind = 0; ind < i->h * i->w; ++ind) {
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unsigned char v = d->buf[ind] * 255 / max;
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i->buf[ind] = (struct pixel){ v, v, v };
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}
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}
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void buddhabrot(struct image *i, size_t max_iter) {
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struct data *d = calloc(1, sizeof(*d->buf) * i->w * i->h + sizeof(*d));
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if (!d)
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err(EXIT_FAILURE, "could not allocate buddhabrot data");
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d->h = i->h;
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d->w = i->w;
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d->max_iter = max_iter;
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// FIXME" make it user-definable
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d->min_x = -2.5;
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d->max_x = 1.0;
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d->min_y = -1.0;
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d->max_y = 1.0;
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compute_buddahbrot(d);
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fillout_image(d, i);
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free(d);
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}
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