batman

main.c

@@ -0,0 +1,127 @@
+#include <math.h>
+#include <png.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/random.h>
+
+float noise(float x, float y);
+float linear_interpolation(float a, float b, float t);
+float quintic_curve(float t);
+float dot_product(float a[], float b[]);
+float *pseudo_random_gradient_vector_get(float x, float y);
+
+static unsigned char random_bytes[1024];
+
+int main() {
+  int n = getrandom(random_bytes, 1024, 0);
+  if (n != 1024) {
+    fprintf(stderr, "err: getrandom didn't work out as planned\n");
+    return 1;
+  }
+
+  int width = 1024, height = 1024;
+
+  png_image img;
+  memset(&img, 0, sizeof(img));
+  img.format = PNG_FORMAT_GRAY;
+  img.width = width;
+  img.height = height;
+  img.version = PNG_IMAGE_VERSION;
+
+  unsigned char *buffer;
+  printf("PNG IMAGE SIZE: %u\n", PNG_IMAGE_SIZE(img));
+  buffer = malloc(PNG_IMAGE_SIZE(img));
+
+  for (int x = 0; x < height; ++x) {
+    for (int y = 0; y < width; ++y) {
+      float noise_val = noise(x * 0.05, y * 0.05);
+      unsigned char pixel = (unsigned char)((noise_val + 1.0f) * 127.5f);
+
+      buffer[y + x * width] = pixel;
+    }
+  }
+
+  png_image_write_to_file(&img, "noise.png", 0, buffer, 0, NULL);
+
+  free(buffer);
+}
+
+float noise(float x, float y) {
+  int left = floorf(x);
+  int top = floorf(y);
+
+  float point_in_quad_x = x - left;
+  float point_in_quad_y = y - top;
+
+  float *top_left_gradient = pseudo_random_gradient_vector_get(left, top);
+  float *top_right_gradient = pseudo_random_gradient_vector_get(left + 1, top);
+  float *bottom_left_gradient =
+      pseudo_random_gradient_vector_get(left, top + 1);
+  float *bottom_right_gradient =
+      pseudo_random_gradient_vector_get(left + 1, top + 1);
+
+  float distance_to_top_left[] = {point_in_quad_x, point_in_quad_y};
+  float distance_to_top_right[] = {point_in_quad_x - 1, point_in_quad_y};
+  float distance_to_bottom_left[] = {point_in_quad_x, point_in_quad_y - 1};
+  float distance_to_bottom_right[] = {point_in_quad_x - 1, point_in_quad_y - 1};
+
+  float tx1 = dot_product(distance_to_top_left, top_left_gradient);
+  float tx2 = dot_product(distance_to_top_right, top_right_gradient);
+  float bx1 = dot_product(distance_to_bottom_left, bottom_left_gradient);
+  float bx2 = dot_product(distance_to_bottom_right, bottom_right_gradient);
+
+  point_in_quad_x = quintic_curve(point_in_quad_x);
+  point_in_quad_y = quintic_curve(point_in_quad_y);
+
+  float tx = linear_interpolation(tx1, tx2, point_in_quad_x);
+  float bx = linear_interpolation(bx1, bx2, point_in_quad_x);
+  float tb = linear_interpolation(tx, bx, point_in_quad_y);
+
+  free(top_left_gradient);
+  free(top_right_gradient);
+  free(bottom_left_gradient);
+  free(bottom_right_gradient);
+
+  return tb;
+}
+
+float linear_interpolation(float a, float b, float t) {
+  return a + (b - a) * t;
+}
+
+float quintic_curve(float t) { return t * t * t * (t * (t * 6 - 15) + 10); }
+
+float dot_product(float a[2], float b[2]) { return a[0] * b[0] + a[1] * b[1]; }
+
+float *pseudo_random_gradient_vector_get(float x, float y) {
+  float *a;
+  a = malloc(sizeof *a * 2);
+
+  int xi = (int)x & 1023;
+  int yi = (int)y & 1023;
+
+  int hash = random_bytes[(random_bytes[xi] + yi) & 1023];
+  int v = hash & 3;
+
+  switch (v) {
+  case 0:
+    a[0] = 1;
+    a[1] = 0;
+    break;
+  case 1:
+    a[0] = -1;
+    a[1] = 0;
+    break;
+  case 2:
+    a[0] = 0;
+    a[1] = 1;
+    break;
+  case 3:
+    a[0] = 0;
+    a[1] = -1;
+    break;
+  }
+
+  return a;
+}