color.c

/* Addon which allows converting between different color
 * representations. Included are:
 * - HSV (like A4)
 * - names (mostly X11 color names, except where CSS redefines them)
 * - HSL (the "better" HSV)
 * - CMYK (a bit like the opposite of RGB)
 * - YUV (the Y channel is quite useful for creating grayscale pictures)
 */
#include "allegro5/allegro.h"
#include "allegro5/allegro_color.h"
#include "allegro5/internal/aintern.h"
#include <math.h>
#include <stdio.h>

typedef struct {
   char const *name;
   int r, g, b;
} ColorName;

/* Taken from http://www.w3.org/TR/2010/PR-css3-color-20101028/#svg-color
 * This must be sorted correctly for binary search.
 */
static ColorName _al_color_names[] = {
   {"aliceblue", 0xf0, 0xf8, 0xff},
   {"antiquewhite", 0xfa, 0xeb, 0xd7},
   {"aqua", 0x00, 0xff, 0xff},
   {"aquamarine", 0x7f, 0xff, 0xd4},
   {"azure", 0xf0, 0xff, 0xff},
   {"beige", 0xf5, 0xf5, 0xdc},
   {"bisque", 0xff, 0xe4, 0xc4},
   {"black", 0x00, 0x00, 0x00},
   {"blanchedalmond", 0xff, 0xeb, 0xcd},
   {"blue", 0x00, 0x00, 0xff},
   {"blueviolet", 0x8a, 0x2b, 0xe2},
   {"brown", 0xa5, 0x2a, 0x2a},
   {"burlywood", 0xde, 0xb8, 0x87},
   {"cadetblue", 0x5f, 0x9e, 0xa0},
   {"chartreuse", 0x7f, 0xff, 0x00},
   {"chocolate", 0xd2, 0x69, 0x1e},
   {"coral", 0xff, 0x7f, 0x50},
   {"cornflowerblue", 0x64, 0x95, 0xed},
   {"cornsilk", 0xff, 0xf8, 0xdc},
   {"crimson", 0xdc, 0x14, 0x3c},
   {"cyan", 0x00, 0xff, 0xff},
   {"darkblue", 0x00, 0x00, 0x8b},
   {"darkcyan", 0x00, 0x8b, 0x8b},
   {"darkgoldenrod", 0xb8, 0x86, 0x0b},
   {"darkgray", 0xa9, 0xa9, 0xa9},
   {"darkgreen", 0x00, 0x64, 0x00},
   {"darkgrey", 0xa9, 0xa9, 0xa9},
   {"darkkhaki", 0xbd, 0xb7, 0x6b},
   {"darkmagenta", 0x8b, 0x00, 0x8b},
   {"darkolivegreen", 0x55, 0x6b, 0x2f},
   {"darkorange", 0xff, 0x8c, 0x00},
   {"darkorchid", 0x99, 0x32, 0xcc},
   {"darkred", 0x8b, 0x00, 0x00},
   {"darksalmon", 0xe9, 0x96, 0x7a},
   {"darkseagreen", 0x8f, 0xbc, 0x8f},
   {"darkslateblue", 0x48, 0x3d, 0x8b},
   {"darkslategray", 0x2f, 0x4f, 0x4f},
   {"darkslategrey", 0x2f, 0x4f, 0x4f},
   {"darkturquoise", 0x00, 0xce, 0xd1},
   {"darkviolet", 0x94, 0x00, 0xd3},
   {"deeppink", 0xff, 0x14, 0x93},
   {"deepskyblue", 0x00, 0xbf, 0xff},
   {"dimgray", 0x69, 0x69, 0x69},
   {"dimgrey", 0x69, 0x69, 0x69},
   {"dodgerblue", 0x1e, 0x90, 0xff},
   {"firebrick", 0xb2, 0x22, 0x22},
   {"floralwhite", 0xff, 0xfa, 0xf0},
   {"forestgreen", 0x22, 0x8b, 0x22},
   {"fuchsia", 0xff, 0x00, 0xff},
   {"gainsboro", 0xdc, 0xdc, 0xdc},
   {"ghostwhite", 0xf8, 0xf8, 0xff},
   {"gold", 0xff, 0xd7, 0x00},
   {"goldenrod", 0xda, 0xa5, 0x20},
   {"gray", 0x80, 0x80, 0x80},
   {"green", 0x00, 0x80, 0x00},
   {"greenyellow", 0xad, 0xff, 0x2f},
   {"grey", 0x80, 0x80, 0x80},
   {"honeydew", 0xf0, 0xff, 0xf0},
   {"hotpink", 0xff, 0x69, 0xb4},
   {"indianred", 0xcd, 0x5c, 0x5c},
   {"indigo", 0x4b, 0x00, 0x82},
   {"ivory", 0xff, 0xff, 0xf0},
   {"khaki", 0xf0, 0xe6, 0x8c},
   {"lavender", 0xe6, 0xe6, 0xfa},
   {"lavenderblush", 0xff, 0xf0, 0xf5},
   {"lawngreen", 0x7c, 0xfc, 0x00},
   {"lemonchiffon", 0xff, 0xfa, 0xcd},
   {"lightblue", 0xad, 0xd8, 0xe6},
   {"lightcoral", 0xf0, 0x80, 0x80},
   {"lightcyan", 0xe0, 0xff, 0xff},
   {"lightgoldenrodyellow", 0xfa, 0xfa, 0xd2},
   {"lightgray", 0xd3, 0xd3, 0xd3},
   {"lightgreen", 0x90, 0xee, 0x90},
   {"lightgrey", 0xd3, 0xd3, 0xd3},
   {"lightpink", 0xff, 0xb6, 0xc1},
   {"lightsalmon", 0xff, 0xa0, 0x7a},
   {"lightseagreen", 0x20, 0xb2, 0xaa},
   {"lightskyblue", 0x87, 0xce, 0xfa},
   {"lightslategray", 0x77, 0x88, 0x99},
   {"lightslategrey", 0x77, 0x88, 0x99},
   {"lightsteelblue", 0xb0, 0xc4, 0xde},
   {"lightyellow", 0xff, 0xff, 0xe0},
   {"lime", 0x00, 0xff, 0x00},
   {"limegreen", 0x32, 0xcd, 0x32},
   {"linen", 0xfa, 0xf0, 0xe6},
   {"magenta", 0xff, 0x00, 0xff},
   {"maroon", 0x80, 0x00, 0x00},
   {"mediumaquamarine", 0x66, 0xcd, 0xaa},
   {"mediumblue", 0x00, 0x00, 0xcd},
   {"mediumorchid", 0xba, 0x55, 0xd3},
   {"mediumpurple", 0x93, 0x70, 0xdb},
   {"mediumseagreen", 0x3c, 0xb3, 0x71},
   {"mediumslateblue", 0x7b, 0x68, 0xee},
   {"mediumspringgreen", 0x00, 0xfa, 0x9a},
   {"mediumturquoise", 0x48, 0xd1, 0xcc},
   {"mediumvioletred", 0xc7, 0x15, 0x85},
   {"midnightblue", 0x19, 0x19, 0x70},
   {"mintcream", 0xf5, 0xff, 0xfa},
   {"mistyrose", 0xff, 0xe4, 0xe1},
   {"moccasin", 0xff, 0xe4, 0xb5},
   {"navajowhite", 0xff, 0xde, 0xad},
   {"navy", 0x00, 0x00, 0x80},
   {"oldlace", 0xfd, 0xf5, 0xe6},
   {"olive", 0x80, 0x80, 0x00},
   {"olivedrab", 0x6b, 0x8e, 0x23},
   {"orange", 0xff, 0xa5, 0x00},
   {"orangered", 0xff, 0x45, 0x00},
   {"orchid", 0xda, 0x70, 0xd6},
   {"palegoldenrod", 0xee, 0xe8, 0xaa},
   {"palegreen", 0x98, 0xfb, 0x98},
   {"paleturquoise", 0xaf, 0xee, 0xee},
   {"palevioletred", 0xdb, 0x70, 0x93},
   {"papayawhip", 0xff, 0xef, 0xd5},
   {"peachpuff", 0xff, 0xda, 0xb9},
   {"peru", 0xcd, 0x85, 0x3f},
   {"pink", 0xff, 0xc0, 0xcb},
   {"plum", 0xdd, 0xa0, 0xdd},
   {"powderblue", 0xb0, 0xe0, 0xe6},
   {"purple", 0x80, 0x00, 0x80},
   {"rebeccapurple", 0x66, 0x33, 0x99},
   {"red", 0xff, 0x00, 0x00},
   {"rosybrown", 0xbc, 0x8f, 0x8f},
   {"royalblue", 0x41, 0x69, 0xe1},
   {"saddlebrown", 0x8b, 0x45, 0x13},
   {"salmon", 0xfa, 0x80, 0x72},
   {"sandybrown", 0xf4, 0xa4, 0x60},
   {"seagreen", 0x2e, 0x8b, 0x57},
   {"seashell", 0xff, 0xf5, 0xee},
   {"sienna", 0xa0, 0x52, 0x2d},
   {"silver", 0xc0, 0xc0, 0xc0},
   {"skyblue", 0x87, 0xce, 0xeb},
   {"slateblue", 0x6a, 0x5a, 0xcd},
   {"slategray", 0x70, 0x80, 0x90},
   {"slategrey", 0x70, 0x80, 0x90},
   {"snow", 0xff, 0xfa, 0xfa},
   {"springgreen", 0x00, 0xff, 0x7f},
   {"steelblue", 0x46, 0x82, 0xb4},
   {"tan", 0xd2, 0xb4, 0x8c},
   {"teal", 0x00, 0x80, 0x80},
   {"thistle", 0xd8, 0xbf, 0xd8},
   {"tomato", 0xff, 0x63, 0x47},
   {"turquoise", 0x40, 0xe0, 0xd0},
   {"violet", 0xee, 0x82, 0xee},
   {"wheat", 0xf5, 0xde, 0xb3},
   {"white", 0xff, 0xff, 0xff},
   {"whitesmoke", 0xf5, 0xf5, 0xf5},
   {"yellow", 0xff, 0xff, 0x00},
   {"yellowgreen", 0x9a, 0xcd, 0x32},
};

#define NUM_COLORS (sizeof(_al_color_names) / sizeof(ColorName))

static double const Xn = 0.95047;
static double const Yn = 1.00000;
static double const Zn = 1.08883;
static double const delta = 6.0 / 29;
static double const delta2 = 6.0 / 29 * 6.0 / 29;
static double const delta3 = 6.0 / 29 * 6.0 / 29 * 6.0 / 29;
static double const tf7 = 1.0 / 4 / 4 / 4 / 4 / 4 / 4 / 4;

static void assert_sorted_names(void)
{
   /* In debug mode, check once that the array is sorted. */
#ifdef DEBUGMODE
   static bool done = false;
   unsigned i;

   if (!done) {
      for (i = 1; i < NUM_COLORS; i++) {
         ASSERT(strcmp(_al_color_names[i-1].name, _al_color_names[i].name) < 0);
      }
      done = true;
   }
#endif
}

static int compare(const void *va, const void *vb)
{
   char const *ca = va;
   ColorName const *cb = vb;
   return strcmp(ca, cb->name);
}


/* Function: al_color_name_to_rgb
 */
bool al_color_name_to_rgb(char const *name, float *r, float *g, float *b)
{
   void *result;
   assert_sorted_names();
   result = bsearch(name, _al_color_names, NUM_COLORS, sizeof(ColorName),
      compare);
   if (result) {
      ColorName *c = result;
      *r = c->r / 255.0;
      *g = c->g / 255.0;
      *b = c->b / 255.0;
      return true;
   }
   return false;
}


/* Function: al_color_rgb_to_name
 */
char const *al_color_rgb_to_name(float r, float g, float b)
{
   int i;
   int ir = r * 255;
   int ig = g * 255;
   int ib = b * 255;
   int n = NUM_COLORS;
   int min = n, mind = 0;
   /* Could optimize this, right now it does linear search. */
   for (i = 0; i < n; i++) {
      int dr = _al_color_names[i].r - ir;
      int dg = _al_color_names[i].g - ig;
      int db = _al_color_names[i].b - ib;
      int d = dr * dr + dg * dg + db * db;
      if (min == n || d < mind) {
         min = i;
         mind = d;
      }
   }
   return _al_color_names[min].name;
}


/* Function: al_color_name
 */
ALLEGRO_COLOR al_color_name(char const *name)
{
   float r, g, b;
   if (al_color_name_to_rgb(name, &r, &g, &b))
      return al_map_rgb_f(r, g, b);
   else
      return al_map_rgb_f(0, 0, 0);
}


/* Function: al_color_hsv_to_rgb
 */
void al_color_hsv_to_rgb(float hue, float saturation, float value,
   float *red, float *green, float *blue)
{
   int d;
   float e, a, b, c;

   hue = fmodf(hue, 360);
   if (hue < 0)
      hue += 360;
   d = hue / 60;
   e = hue / 60 - d;
   a = value * (1 - saturation);
   b = value * (1 - e * saturation);
   c = value * (1 - (1 - e) * saturation);
   switch (d) {
      default:
      case 0: *red = value, *green = c,     *blue = a;     return;
      case 1: *red = b,     *green = value, *blue = a;     return;
      case 2: *red = a,     *green = value, *blue = c;     return;
      case 3: *red = a,     *green = b,     *blue = value; return;
      case 4: *red = c,     *green = a,     *blue = value; return;
      case 5: *red = value, *green = a,     *blue = b;     return;
   }
}


/* Function: al_color_rgb_to_hsv
 */
void al_color_rgb_to_hsv(float red, float green, float blue,
   float *hue, float *saturation, float *value)
{
   float a, b, c, d;
   if (red > green) {
      if (red > blue) {
         if (green > blue)
            a = red, b = green - blue, c = blue, d = 0;
         else
            a = red, b = green - blue, c = green, d = 0;
      }
      else {
         a = blue, b = red - green, c = green, d = 4;
      }
   }
   else {
      if (red > blue)
          a = green, b = blue - red, c = blue, d = 2;
      else if (green > blue)
         a = green, b = blue - red, c = red, d = 2;
      else
         a = blue, b = red - green, c = red, d = 4;
   }

   if (a == c) {
      *hue = 0;
   }
   else {
      *hue = 60 * (d + b / (a - c));
      if (*hue < 0)
         *hue += 360;
      if (*hue > 360)
         *hue -= 360;
   }

   if (a == 0)
      *saturation = 0;
   else
      *saturation = (a - c) / a;
   *value = a;
}


/* Function: al_color_hsv
 */
ALLEGRO_COLOR al_color_hsv(float h, float s, float v)
{
   float r, g, b;

   al_color_hsv_to_rgb(h, s, v, &r, &g, &b);
   return al_map_rgb_f(r, g, b);
}


static float hsl_to_rgb_helper(float x, float a, float b)
{
   if (x < 0)
      x += 1;
   if (x > 1)
      x -= 1;

   if (x * 6 < 1)
      return b + (a - b) * 6 * x;
   if (x * 6 < 3)
      return a;
   if (x * 6 < 4)
      return b + (a - b) * (4.0 - 6.0 * x);
   return b;
}


/* Function: al_color_hsl_to_rgb
 */
void al_color_hsl_to_rgb(float hue, float saturation, float lightness,
   float *red, float *green, float *blue)
{
   float a, b, h;

   hue = fmodf(hue, 360);
   if (hue < 0)
      hue += 360;
   h = hue / 360;
   if (lightness < 0.5)
      a = lightness + lightness * saturation;
   else
      a = lightness + saturation - lightness * saturation;
   b = lightness * 2 - a;
   *red = hsl_to_rgb_helper(h + 1.0 / 3.0, a, b);
   *green = hsl_to_rgb_helper(h, a, b);
   *blue = hsl_to_rgb_helper(h - 1.0 / 3.0, a, b);
}


/* Function: al_color_rgb_to_hsl
 */
void al_color_rgb_to_hsl(float red, float green, float blue,
   float *hue, float *saturation, float *lightness)
{
   float a, b, c, d;

   if (red > green) {
      if (red > blue) {
         if (green > blue)
            a = red, b = green - blue, c = blue, d = 0;
         else
            a = red, b = green - blue, c = green, d = 0;
      }
      else {
         a = blue, b = red - green, c = green, d = 4;
      }
   }
   else {
      if (red > blue)
         a = green, b = blue - red, c = blue, d = 2;
      else if (green > blue)
         a = green, b = blue - red, c = red, d = 2;
      else
         a = blue, b = red - green, c = red, d = 4;
   }

   if (a == c) {
      *hue = 0;
   }
   else {
      *hue = 60 * (d + b / (a - c));
      if (*hue < 0)
         *hue += 360;
   }

   if (a == c)
      *saturation = 0;
   else if (a + c < 1)
      *saturation = (a - c) / (a + c);
   else
      *saturation = (a - c) / (2 - a - c);

   *lightness = (a + c) / 2;
}


/* Function: al_color_hsl
 */
ALLEGRO_COLOR al_color_hsl(float h, float s, float l)
{
   float r, g, b;
   al_color_hsl_to_rgb(h, s, l, &r, &g, &b);
   return al_map_rgb_f(r, g, b);
}


/* Function: al_color_cmyk_to_rgb
 */
void al_color_cmyk_to_rgb(float cyan, float magenta, float yellow,
    float key, float *red, float *green, float *blue)
{
   float max = 1 - key;
   *red = max - cyan * max;
   *green = max - magenta * max;
   *blue = max - yellow * max;
}


/* Function: al_color_rgb_to_cmyk
 */
void al_color_rgb_to_cmyk(float red, float green, float blue,
   float *cyan, float *magenta, float *yellow, float *key)
{
   float max = red;
   if (green > max)
      max = green;
   if (blue > max)
      max = blue;
   *key = 1 - max;
   if (max > 0) {
      *cyan = (max - red) / max;
      *magenta = (max - green) / max;
      *yellow = (max - blue) / max;
   }
   else {
      *cyan = *magenta = *yellow = 0;
   }
}


/* Function: al_color_cmyk
 */
ALLEGRO_COLOR al_color_cmyk(float c, float m, float y, float k)
{
   float r, g, b;
   al_color_cmyk_to_rgb(c, m, y, k, &r, &g, &b);
   return al_map_rgb_f(r, g, b);
}


/* Function: al_color_yuv_to_rgb
 */
void al_color_yuv_to_rgb(float y, float u, float v,
    float *red, float *green, float *blue)
{
   /* Translate range 0..1 to actual range. */
   u = 0.436 * (u * 2 - 1);
   v = 0.615 * (v * 2 - 1);
   *red = _ALLEGRO_CLAMP(0, 1, y + v * 1.13983);
   *green = _ALLEGRO_CLAMP(0, 1, y + u * -0.39465 + v * -0.58060);
   *blue = _ALLEGRO_CLAMP(0, 1, y + u * 2.03211);
}


/* Function: al_color_rgb_to_yuv
 */
void al_color_rgb_to_yuv(float red, float green, float blue,
   float *y, float *u, float *v)
{
   *y = red * 0.299 + green * 0.587 + blue * 0.114;
   *u = red * -0.14713 + green * -0.28886 + blue * 0.436;
   *v = red * 0.615 + green * -0.51499 + blue * -0.10001;
   /* Normalize chroma components into 0..1 range. */
   *u = (*u / 0.436 + 1) * 0.5;
   *v = (*v / 0.615 + 1) * 0.5;
}


/* Function: al_color_yuv
 */
ALLEGRO_COLOR al_color_yuv(float y, float u, float v)
{
   float r, g, b;
   al_color_yuv_to_rgb(y, u, v, &r, &g, &b);
   return al_map_rgb_f(r, g, b);
}


/* Function: al_color_rgb_to_html
 */
void al_color_rgb_to_html(float red, float green, float blue,
    char *string)
{
   sprintf(string, "#%02x%02x%02x", (int)(red * 255),
      (int)(green * 255), (int)(blue * 255));
}


/* Function: al_color_html_to_rgb
 */
bool al_color_html_to_rgb(char const *string,
   float *red, float *green, float *blue)
{
   char const *ptr = string;
   int ir, ig, ib;
   ASSERT(ptr);
   ASSERT(red);
   ASSERT(green);
   ASSERT(blue);

   *red = *green = *blue = 0.0f;

   if (*ptr == '#')
      ptr++;

   if (strlen(ptr) != 6)
      return false;

   if (sscanf(ptr, "%02x%02x%02x", &ir, &ig, &ib) != 3)
      return false;

   *red = ir / 255.0;
   *green = ig / 255.0;
   *blue = ib / 255.0;
   return true;
}


/* Function: al_color_html
 */
ALLEGRO_COLOR al_color_html(char const *string)
{
   float r, g, b;

   if (al_color_html_to_rgb(string, &r, &g, &b))
      return al_map_rgb_f(r, g, b);
   else
      return al_map_rgba(0, 0, 0, 0);
}


/* Function: al_get_allegro_color_version
 */
uint32_t al_get_allegro_color_version(void)
{
   return ALLEGRO_VERSION_INT;
}


/* Converts from an sRGB color component to the linear value.
 */
static double srgba_gamma_to_linear(double x) {
   double const a = 0.055;
   if (x < 0.04045) return x / 12.92;
   return pow((x + a) / (1 + a), 2.4);
}


/* Converts a linear color component back into sRGB.
 */
static double srgba_linear_to_gamma(double x) {
   double const a = 0.055;
   if (x < 0.0031308) return x * 12.92;
   return pow(x, 1 / 2.4) * (1 + a) - a;
}


/* Function: al_color_linear_to_rgb
 */
void al_color_linear_to_rgb(float r, float g, float b,
    float *red, float *green, float *blue)
{
   *red = srgba_linear_to_gamma(r);
   *green = srgba_linear_to_gamma(g);
   *blue = srgba_linear_to_gamma(b);
}


/* Function: al_color_rgb_to_linear
 */
void al_color_rgb_to_linear(float red, float green, float blue,
   float *r, float *g, float *b)
{
   *r = srgba_gamma_to_linear(red);
   *g = srgba_gamma_to_linear(green);
   *b = srgba_gamma_to_linear(blue);
}


/* Function: al_color_linear
 */
ALLEGRO_COLOR al_color_linear(float r, float g, float b)
{
   float r2, g2, b2;
   al_color_linear_to_rgb(r, g, b, &r2, &g2, &b2);
   return al_map_rgb_f(r2, g2, b2);
}


/* Function: al_color_xyz_to_rgb
 */
void al_color_xyz_to_rgb(float x, float y, float z,
    float *red, float *green, float *blue)
{
   double r = 3.2406 * x + (-1.5372 * y) + (-0.4986 * z);
   double g = -0.9689 * x + 1.8758 * y + 0.0415 * z;
   double b = 0.0557 * x + (-0.2040 * y) + 1.0570 * z;
   *red = srgba_linear_to_gamma(r);
   *green = srgba_linear_to_gamma(g);
   *blue = srgba_linear_to_gamma(b);
}


/* Function: al_color_rgb_to_xyz
 */
void al_color_rgb_to_xyz(float red, float green, float blue,
   float *x, float *y, float *z)
{
   double r = srgba_gamma_to_linear(red);
   double g = srgba_gamma_to_linear(green);
   double b = srgba_gamma_to_linear(blue);
   *x = r * 0.4124 + g * 0.3576 + b * 0.1805;
   *y = r * 0.2126 + g * 0.7152 + b * 0.0722;
   *z = r * 0.0193 + g * 0.1192 + b * 0.9505;
}


/* Function: al_color_xyz
 */
ALLEGRO_COLOR al_color_xyz(float x, float y, float z)
{
   float r, g, b;
   al_color_xyz_to_rgb(x, y, z, &r, &g, &b);
   return al_map_rgb_f(r, g, b);
}


static double cielab_f(double x) {
   if (x > delta3) return pow(x, 1.0 / 3);
   return 4.0 / 29 + x / delta2 / 3;
}


static double cielab_f_inv(double x) {
   if (x > delta) return pow(x, 3);
   return (x - 4.0 / 29) * 3 * delta2;
}


/* Function: al_color_lab_to_rgb
 */
void al_color_lab_to_rgb(float l, float a, float b,
    float *red, float *green, float *blue)
{
   float x = Xn * cielab_f_inv((l + 0.16) / 1.16 + a / 5.00);
   float y = Yn * cielab_f_inv((l + 0.16) / 1.16);
   float z = Zn * cielab_f_inv((l + 0.16) / 1.16 - b / 2.00);
   al_color_xyz_to_rgb(x, y, z, red, green, blue);
}


/* Function: al_color_rgb_to_lab
 */
void al_color_rgb_to_lab(float red, float green, float blue,
   float *l, float *a, float *b)
{
   float x, y, z;
   al_color_rgb_to_xyz(red, green, blue, &x, &y, &z);
   x /= Xn;
   y /= Yn;
   z /= Zn;
   *l = 1.16 * cielab_f(y) - 0.16;
   *a = 5.00 * (cielab_f(x) - cielab_f(y));
   *b = 2.00 * (cielab_f(y) - cielab_f(z));
}


/* Function: al_color_lab
 */
ALLEGRO_COLOR al_color_lab(float l, float a, float b)
{
   float r2, g2, b2;
   al_color_lab_to_rgb(l, a, b, &r2, &g2, &b2);
   return al_map_rgb_f(r2, g2, b2);
}


/* Function: al_color_lch_to_rgb
 */
void al_color_lch_to_rgb(float l, float c, float h,
    float *red, float *green, float *blue)
{
   double a = c * cos(h);
   double b = c * sin(h);
   al_color_lab_to_rgb(l, a, b, red, green, blue);
}


/* Function: al_color_rgb_to_lch
 */
void al_color_rgb_to_lch(float red, float green, float blue,
   float *l, float *c, float *h)
{
   float a, b;
   al_color_rgb_to_lab(red, green, blue, l, &a, &b);
   *c = sqrt(a * a + b * b);
   *h = fmod(ALLEGRO_PI * 2 + atan2(b, a), ALLEGRO_PI * 2);
}


/* Function: al_color_lch
 */
ALLEGRO_COLOR al_color_lch(float l, float c, float h)
{
   float r, g, b;
   al_color_lch_to_rgb(l, c, h, &r, &g, &b);
   return al_map_rgb_f(r, g, b);
}


/* Function: al_color_xyy_to_rgb
 */
void al_color_xyy_to_rgb(float x, float y, float y2,
    float *red, float *green, float *blue)
{
   double x2 = x * y / y2;
   double z2 = (1 - y2 - x) * y / y2;
   al_color_xyz_to_rgb(x2, y2, z2, red, green, blue);
}


/* Function: al_color_rgb_to_xyy
 */
void al_color_rgb_to_xyy(float red, float green, float blue,
   float *x, float *y, float *y2)
{
   float x2, z2;
   al_color_rgb_to_xyz(red, green, blue, &x2, y2, &z2);
   *x = x2 / (x2 + *y2 + z2);
   *y = *y2 / (x2 + *y2 + z2);
}


/* Function: al_color_xyy
 */
ALLEGRO_COLOR al_color_xyy(float x, float y, float y2)
{
   float r, g, b;
   al_color_xyy_to_rgb(x, y, y2, &r, &g, &b);
   return al_map_rgb_f(r, g, b);
}


/* Function: al_color_distance_ciede2000
 */
double al_color_distance_ciede2000(ALLEGRO_COLOR color1,
      ALLEGRO_COLOR color2) {
   /* For implementation details refer to e.g.
    * http://www.ece.rochester.edu/~gsharma/ciede2000/ciede2000noteCRNA.pdf
    */
   float l1, a1, b1, l2, a2, b2;
   al_color_rgb_to_lab(color1.r, color1.g, color1.b, &l1, &a1, &b1);
   al_color_rgb_to_lab(color2.r, color2.g, color2.b, &l2, &a2, &b2);
   double pi = ALLEGRO_PI;
   double dl = l1 - l2;
   double ml = (l1 + l2) / 2;
   double c1 = sqrt(a1 * a1 + b1 * b1);
   double c2 = sqrt(a2 * a2 + b2 * b2);
   double mc = (c1 + c2) / 2;
   double fac = sqrt(pow(mc, 7) / (pow(mc, 7) + tf7));
   double g = 0.5 * (1 - fac);
   a1 *= 1 + g;
   a2 *= 1 + g;
   c1 = sqrt(a1 * a1 + b1 * b1);
   c2 = sqrt(a2 * a2 + b2 * b2);
   double dc = c2 - c1;
   mc = (c1 + c2) / 2;
   fac = sqrt(pow(mc, 7) / (pow(mc, 7) + tf7));
   double h1 = fmod(2 * pi + atan2(b1, a1), 2 * pi);
   double h2 = fmod(2 * pi + atan2(b2, a2), 2 * pi);
   double dh = 0;
   double mh = h1 + h2;
   if (c1 * c2 != 0) {
      dh = h2 - h1;
      if (dh > pi) dh -= 2 * pi;
      if (dh < -pi) dh += 2 * pi;
      if (fabs(h1 - h2) <= pi) mh = (h1 + h2) / 2;
      else if (h1 + h2 < 2 * pi) mh = (h1 + h2 + 2 * pi) / 2;
      else mh = (h1 + h2 - 2 * pi) / 2;
   }
   dh = 2 * sqrt(c1 * c2) * sin(dh / 2);
   double t = 1 - 0.17 * cos(mh - pi / 6) + 0.24 * cos(2 * mh) +
         0.32 * cos(3 * mh + pi / 30) - 0.2 * cos(4 * mh - pi * 7 / 20);
   double mls = pow(ml - 0.5, 2);
   double sl = 1 + 1.5 * mls / sqrt(0.002 + mls);
   double sc = 1 + 4.5 * mc;
   double sh = 1 + 1.5 * mc * t;
   double rt = -2 * fac * sin(pi / 3 *
         exp(-pow(mh / pi * 36 / 5 - 11, 2)));
   return sqrt(pow(dl / sl, 2) + pow(dc / sc, 2) +
         pow(dh / sh, 2) + rt * dc / sc * dh / sh);
}

/* Function al_color_is_valid
 */
bool al_is_color_valid(ALLEGRO_COLOR color)
{
   return color.r >= 0 && color.g >= 0 && color.b >= 0 &&
      color.r <= 1 && color.g <= 1 && color.b <= 1;
}


/* Function: al_color_oklab_to_rgb
 * Note: Oklab code from https://bottosson.github.io/posts/oklab/
 */
void al_color_oklab_to_rgb(float ol, float oa, float ob,
    float *red, float *green, float *blue)
{
   float l_ = ol + 0.3963377774f * oa + 0.2158037573f * ob;
   float m_ = ol - 0.1055613458f * oa - 0.0638541728f * ob;
   float s_ = ol - 0.0894841775f * oa - 1.2914855480f * ob;
   float l = l_*l_*l_;
   float m = m_*m_*m_;
   float s = s_*s_*s_;
   float r = +4.0767416621f * l - 3.3077115913f * m + 0.2309699292f * s;
   float g = -1.2684380046f * l + 2.6097574011f * m - 0.3413193965f * s;
   float b = -0.0041960863f * l - 0.7034186147f * m + 1.7076147010f * s;
   *red = srgba_linear_to_gamma(r);
   *green = srgba_linear_to_gamma(g);
   *blue = srgba_linear_to_gamma(b);
}


/* Function: al_color_rgb_to_oklab
 * Note: Oklab code from https://bottosson.github.io/posts/oklab/
 */
void al_color_rgb_to_oklab(float red, float green, float blue,
   float *ol, float *oa, float *ob)
{
   double r = srgba_gamma_to_linear(red);
   double g = srgba_gamma_to_linear(green);
   double b = srgba_gamma_to_linear(blue);
   float l = 0.4122214708f * r + 0.5363325363f * g + 0.0514459929f * b;
   float m = 0.2119034982f * r + 0.6806995451f * g + 0.1073969566f * b;
   float s = 0.0883024619f * r + 0.2817188376f * g + 0.6299787005f * b;
   float l_ = cbrtf(l);
   float m_ = cbrtf(m);
   float s_ = cbrtf(s);
   *ol = 0.2104542553f*l_ + 0.7936177850f*m_ - 0.0040720468f*s_;
   *oa = 1.9779984951f*l_ - 2.4285922050f*m_ + 0.4505937099f*s_;
   *ob = 0.0259040371f*l_ + 0.7827717662f*m_ - 0.8086757660f*s_;
}


/* Function: al_color_oklab
 */
ALLEGRO_COLOR al_color_oklab(float l, float a, float b)
{
   float r2, g2, b2;
   al_color_oklab_to_rgb(l, a, b, &r2, &g2, &b2);
   return al_map_rgb_f(r2, g2, b2);
}



/* vim: set sts=3 sw=3 et: */