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render.c
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render.c
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#include <stdint.h>
extern unsigned char __heap_base;
#define EXPORT __attribute__((visibility("default")))
#define PI 3.1415926
double floor(double);
double fabs(double);
struct Point
{
double a, b;
};
struct Pixel
{
unsigned long r, g, b;
};
double transformMatrix[8] = {0, 1, 0, 0, 1, 0, 0, 0};
EXPORT
unsigned int get_required_memory_size(int iters, int w, int h)
{
return (unsigned int)&__heap_base + (w * h) * sizeof(struct Pixel) + sizeof(struct Point) * iters;
}
EXPORT
void *get_color_buf_ptr()
{
return (void *)&__heap_base;
}
EXPORT
void *get_transform_matrix_ptr()
{
return (void *)&transformMatrix;
}
double hue2rgb(double p, double q, double t)
{
if (t < 0)
t += 1;
if (t > 1)
t -= 1;
if (t < 1. / 6)
return p + (q - p) * 6 * t;
if (t < 1. / 2)
return q;
if (t < 2. / 3)
return p + (q - p) * (2. / 3 - t) * 6;
return p;
}
struct Pixel hslToRgb(double h, double s, double l)
{
double r, g, b;
if (s == 0)
{
r = g = b = l; // achromatic
}
else
{
double q = l < 0.5 ? l * (1 + s) : l + s - l * s;
double p = 2 * l - q;
r = hue2rgb(p, q, h + 1. / 3);
g = hue2rgb(p, q, h);
b = hue2rgb(p, q, h - 1. / 3);
}
struct Pixel pix = {floor(r * 255.999), floor(g * 255.999), floor(b * 255.999)};
return pix;
}
double atan2(double y, double x)
{
//http://pubs.opengroup.org/onlinepubs/009695399/functions/atan2.html
//Volkan SALMA
const double ONEQTR_PI = PI / 4.0;
const double THRQTR_PI = 3.0 * PI / 4.0;
double r, angle;
double abs_y = fabs(y) + 1e-10; // kludge to prevent 0/0 condition
if (x < 0.0)
{
r = (x + abs_y) / (abs_y - x);
angle = THRQTR_PI;
}
else
{
r = (x - abs_y) / (x + abs_y);
angle = ONEQTR_PI;
}
angle += (0.1963 * r * r - 0.9817) * r;
if (y < 0.0)
return -angle; // negate if in quad III or IV
else
return angle;
}
// https://www.pcg-random.org/download.html
// *Really* minimal PCG32 code / (c) 2014 M.E. O'Neill / pcg-random.org
// Licensed under Apache License 2.0 (NO WARRANTY, etc. see website)
typedef struct
{
uint64_t state;
uint64_t inc;
} pcg32_random_t;
static pcg32_random_t pcg32_global = {0x853c49e6748fea9bULL, 0xda3e39cb94b95bdbULL};
uint32_t pcg32_random_r(pcg32_random_t *rng)
{
uint64_t oldstate = rng->state;
// Advance internal state
rng->state = oldstate * 6364136223846793005ULL + (rng->inc | 1);
// Calculate output function (XSH RR), uses old state for max ILP
uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
uint32_t rot = oldstate >> 59u;
return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
}
uint32_t pcg32_random()
{
return pcg32_random_r(&pcg32_global);
}
void pcg32_srandom_r(pcg32_random_t *rng, uint64_t initstate, uint64_t initseq)
{
rng->state = 0U;
rng->inc = (initseq << 1u) | 1u;
pcg32_random_r(rng);
rng->state += initstate;
pcg32_random_r(rng);
}
void pcg32_srandom(uint64_t seed, uint64_t seq)
{
pcg32_srandom_r(&pcg32_global, seed, seq);
}
EXPORT
void srand(unsigned long seed)
{
pcg32_srandom(0, seed);
}
EXPORT const int PM_inner = 0;
EXPORT const int PM_outer = 1;
EXPORT const int CM_white_black = 0;
EXPORT const int CM_hue_atan_red = 1;
EXPORT const int CM_hue_atan_blue = 2;
EXPORT const int CM_hue_atan_green = 3;
EXPORT const int CM_hue_atan_asymm = 4;
EXPORT const int CM_hue_iters = 5;
EXPORT const int CM_rgb_layers = 6;
inline void override_cxy(double *cx, double *cy, struct Point *points, int c_offset, int iters, int iter, int k)
{
int i = k - c_offset;
if (c_offset != 0 && i < iters && i >= iter)
{
struct Point point = points[i];
*cx = point.a;
*cy = point.b;
}
}
EXPORT
void clear_color_buf(int w, int h)
{
struct Pixel *buf = (struct Pixel *)(&__heap_base);
struct Pixel zero = {0, 0, 0};
for (int i = 0; i < w * h; i++)
buf[i] = zero;
}
EXPORT
void render(int w, int h, int iters, int samples, int c_offset, int points_mode, int color_mode)
{
struct Pixel *buf = (struct Pixel *)(&__heap_base);
struct Point *points = (struct Point *)(&__heap_base + (w * h) * sizeof(struct Pixel));
double m0 = transformMatrix[0];
double m1 = transformMatrix[1];
double m2 = transformMatrix[2];
double m3 = transformMatrix[3];
double m4 = transformMatrix[4];
double m5 = transformMatrix[5];
double m6 = transformMatrix[6];
double m7 = transformMatrix[7];
for (int i = 0; i < samples; i++)
{
double cx = ((double)pcg32_random()) / UINT32_MAX * 4 - 2;
double cy = ((double)pcg32_random()) / UINT32_MAX * 4 - 2;
double a = cx;
double b = cy;
int iter = iters;
while (iter > 0)
{
iter--;
double aa = a * a;
double bb = b * b;
if (aa + bb > 4)
break;
b = 2 * a * b + cy;
a = aa - bb + cx;
struct Point point = {
.a = a,
.b = b,
};
points[iter] = point;
}
if ((points_mode == PM_inner && iter == 0) || (points_mode == PM_outer && iter != 0))
{
switch (color_mode)
{
case CM_white_black:
for (int k = iter; k < iters; k++)
{
override_cxy(&cx, &cy, points, c_offset, iters, iter, k);
struct Point point = points[k];
double a = point.a;
double b = point.b;
int x = floor(((a * m0 + b * m1 + cx * m2 + cy * m3 + 2) / 4) * w);
int y = floor(((a * m4 + b * m5 + cx * m6 + cy * m7 + 2) / 4) * h);
if (x >= 0 && y >= 0 && x < w && y < h)
{
struct Pixel *pix = &buf[x + y * w];
pix->r += 1;
pix->g += 1;
pix->b += 1;
}
}
break;
case CM_hue_atan_red:
for (int k = iter + 1; k < iters - 1; k++)
{
override_cxy(&cx, &cy, points, c_offset, iters, iter, k);
struct Point point = points[k];
double a = point.a;
double b = point.b;
int x = floor(((a * m0 + b * m1 + cx * m2 + cy * m3 + 2) / 4) * w);
int y = floor(((a * m4 + b * m5 + cx * m6 + cy * m7 + 2) / 4) * h);
if (x >= 0 && y >= 0 && x < w && y < h)
{
double angle0 = atan2(b - points[k - 1].b, a - points[k - 1].a);
double angle1 = atan2(points[k + 1].b - b, points[k + 1].a - a);
double hue = fabs(angle1 - angle0) / PI;
if (hue > 1)
hue = 2 - hue;
struct Pixel inc = hslToRgb(hue, 1, 0.5);
struct Pixel *pix = &buf[x + y * w];
pix->r += inc.r;
pix->g += inc.g;
pix->b += inc.b;
}
}
break;
case CM_hue_atan_blue:
for (int k = iter + 1; k < iters - 1; k++)
{
override_cxy(&cx, &cy, points, c_offset, iters, iter, k);
struct Point point = points[k];
double a = point.a;
double b = point.b;
int x = floor(((a * m0 + b * m1 + cx * m2 + cy * m3 + 2) / 4) * w);
int y = floor(((a * m4 + b * m5 + cx * m6 + cy * m7 + 2) / 4) * h);
if (x >= 0 && y >= 0 && x < w && y < h)
{
double angle0 = atan2(b - points[k - 1].b, a - points[k - 1].a);
double angle1 = atan2(-points[k + 1].b + points[k - 1].b, -points[k + 1].a + points[k - 1].a);
double hue = fabs(angle1 - angle0) / PI;
if (hue > 1)
hue = hue - 1;
struct Pixel inc = hslToRgb(hue, 1, 0.5);
struct Pixel *pix = &buf[x + y * w];
pix->r += inc.r;
pix->g += inc.g;
pix->b += inc.b;
}
}
break;
case CM_hue_atan_green:
for (int k = iter + 1; k < iters - 1; k++)
{
override_cxy(&cx, &cy, points, c_offset, iters, iter, k);
struct Point point = points[k];
double a = point.a;
double b = point.b;
int x = floor(((a * m0 + b * m1 + cx * m2 + cy * m3 + 2) / 4) * w);
int y = floor(((a * m4 + b * m5 + cx * m6 + cy * m7 + 2) / 4) * h);
if (x >= 0 && y >= 0 && x < w && y < h)
{
double angle0 = atan2(b - points[k - 1].b, a - points[k - 1].a);
double angle1 = atan2(-points[k + 1].b + b, -points[k + 1].a + a);
double hue = fabs(angle1 - angle0) / PI;
if (hue > 1)
hue = 2 - hue;
struct Pixel inc = hslToRgb(hue, 1, 0.5);
struct Pixel *pix = &buf[x + y * w];
pix->r += inc.r;
pix->g += inc.g;
pix->b += inc.b;
}
}
break;
case CM_hue_atan_asymm:
for (int k = iter + 1; k < iters - 1; k++)
{
override_cxy(&cx, &cy, points, c_offset, iters, iter, k);
struct Point point = points[k];
double a = point.a;
double b = point.b;
int x = floor(((a * m0 + b * m1 + cx * m2 + cy * m3 + 2) / 4) * w);
int y = floor(((a * m4 + b * m5 + cx * m6 + cy * m7 + 2) / 4) * h);
if (x >= 0 && y >= 0 && x < w && y < h)
{
double angle0 = atan2(b - points[k - 1].b, a - points[k - 1].a);
double angle1 = atan2(points[k + 1].b - a, points[k + 1].a - b);
double hue = fabs(angle1 - angle0) / PI;
if (hue > 1)
hue = 2 - hue;
struct Pixel inc = hslToRgb(hue, 1, 0.5);
struct Pixel *pix = &buf[x + y * w];
pix->r += inc.r;
pix->g += inc.g;
pix->b += inc.b;
}
}
break;
case CM_hue_iters:
if (iter == 0)
{
double hue = 0;
for (int k = iter + 1; k < iters; k++)
if (fabs(points[k].a - points[iter].a) < 0.01f && fabs(points[k].b - points[iter].b) < 0.01f)
{
hue = (double)(k - iter - 1) / 16;
hue = hue - (int)hue; //TODO
break;
}
struct Pixel inc = hslToRgb(hue, 1, hue / 2);
if (inc.r == 0 && inc.g == 0 && inc.b == 0)
inc.r += 2;
for (int k = iter; k < iters; k++)
{
override_cxy(&cx, &cy, points, c_offset, iters, iter, k);
struct Point point = points[k];
double a = point.a;
double b = point.b;
int x = floor(((a * m0 + b * m1 + cx * m2 + cy * m3 + 2) / 4) * w);
int y = floor(((a * m4 + b * m5 + cx * m6 + cy * m7 + 2) / 4) * h);
if (x >= 0 && y >= 0 && x < w && y < h)
{
struct Pixel *pix = &buf[x + y * w];
pix->r += inc.r;
pix->g += inc.g;
pix->b += inc.b;
}
}
}
else
{
for (int k = iter; k < iters; k++)
{
override_cxy(&cx, &cy, points, c_offset, iters, iter, k);
struct Point point = points[k];
double a = point.a;
double b = point.b;
int x = floor(((a * m0 + b * m1 + cx * m2 + cy * m3 + 2) / 4) * w);
int y = floor(((a * m4 + b * m5 + cx * m6 + cy * m7 + 2) / 4) * h);
if (x >= 0 && y >= 0 && x < w && y < h)
{
double hue = (double)(iters - iter) / iters;
struct Pixel inc = hslToRgb(hue, 1, 0.5);
struct Pixel *pix = &buf[x + y * w];
if (inc.r == 0 && inc.g == 0 && inc.b == 0)
inc.r += 2;
pix->r += inc.r;
pix->g += inc.g;
pix->b += inc.b;
}
}
}
break;
case CM_rgb_layers:
{
int n = iters - iter;
int thresh_b = iters * 99 / 100;
int thresh_g = iters * 9 / 10;
// skipping first iter to remove bright lines near center (they darken whole image and make it less contrast)
for (int k = iter + 1; k < iters; k++)
{
override_cxy(&cx, &cy, points, c_offset, iters, iter, k);
struct Point point = points[k];
double a = point.a;
double b = point.b;
int x = floor(((a * m0 + b * m1 + cx * m2 + cy * m3 + 2) / 4) * w);
int y = floor(((a * m4 + b * m5 + cx * m6 + cy * m7 + 2) / 4) * h);
if (x >= 0 && y >= 0 && x < w && y < h)
{
struct Pixel *pix = &buf[x + y * w];
if (k >= thresh_b)
pix->b += 4;
else if (k >= thresh_g)
pix->g += 3; //a bit less green
else
pix->r += 4;
}
}
break;
}
default:
break;
}
}
}
}