node-canvas/src/color.h

//
// color.h
//
// Copyright (c) 2010 LearnBoost <tj@learnboost.com>
//

#include <stdio.h>
#include <stdint.h>
#include <string.h>

/*
 * Consume whitespace.
 */

#define WHITESPACE \
  while (' ' == *str) ++str;

/*
 * Parse color channel value
 */

#define CHANNEL(NAME) \
   if (*str >= '0' && *str <= '9') { \
     do { \
       NAME *= 10; \
       NAME += *str++ - '0'; \
     } while (*str >= '0' && *str <= '9'); \
   } else { \
     return -1; \
   } \
   while (' ' == *str || ',' == *str) str++;

/*
 * Named colors.
 */

static struct named_color {
  char *name;
  uint32_t val;
} named_colors[] = {
    "transparent", 0xffffff00
  , "aliceblue", 0xf0f8ffff
  , "antiquewhite", 0xfaebd7ff
  , "aqua", 0x00ffffff
  , "aquamarine", 0x7fffd4ff
  , "azure", 0xf0ffffff
  , "beige", 0xf5f5dcff
  , "bisque", 0xffe4c4ff
  , "black", 0x000000ff
  , "blanchedalmond", 0xffebcdff
  , "blue", 0x0000ffff
  , "blueviolet", 0x8a2be2ff
  , "brown", 0xa52a2aff
  , "burlywood", 0xdeb887ff
  , "cadetblue", 0x5f9ea0ff
  , "chartreuse", 0x7fff00ff
  , "chocolate", 0xd2691eff
  , "coral", 0xff7f50ff
  , "cornflowerblue", 0x6495edff
  , "cornsilk", 0xfff8dcff
  , "crimson", 0xdc143cff
  , "cyan", 0x00ffffff
  , "darkblue", 0x00008bff
  , "darkcyan", 0x008b8bff
  , "darkgoldenrod", 0xb8860bff
  , "darkgray", 0xa9a9a9ff
  , "darkgreen", 0x006400ff
  , "darkkhaki", 0xbdb76bff
  , "darkmagenta", 0x8b008bff
  , "darkolivegreen", 0x556b2fff
  , "darkorange", 0xff8c00ff
  , "darkorchid", 0x9932ccff
  , "darkred", 0x8b0000ff
  , "darksalmon", 0xe9967aff
  , "darkseagreen", 0x8fbc8fff
  , "darkslateblue", 0x483d8bff
  , "darkslategray", 0x2f4f4fff
  , "darkturquoise", 0x00ced1ff
  , "darkviolet", 0x9400d3ff
  , "deeppink", 0xff1493ff
  , "deepskyblue", 0x00bfffff
  , "dimgray", 0x696969ff
  , "dodgerblue", 0x1e90ffff
  , "feldspar", 0xd19275ff
  , "firebrick", 0xb22222ff
  , "floralwhite", 0xfffaf0ff
  , "forestgreen", 0x228b22ff
  , "fuchsia", 0xff00ffff
  , "gainsboro", 0xdcdcdcff
  , "ghostwhite", 0xf8f8ffff
  , "gold", 0xffd700ff
  , "goldenrod", 0xdaa520ff
  , "gray", 0x808080ff
  , "green", 0x008000ff
  , "greenyellow", 0xadff2fff
  , "honeydew", 0xf0fff0ff
  , "hotpink", 0xff69b4ff
  , "indianred ", 0xcd5c5cff
  , "indigo ", 0x4b0082ff
  , "ivory", 0xfffff0ff
  , "khaki", 0xf0e68cff
  , "lavender", 0xe6e6faff
  , "lavenderblush", 0xfff0f5ff
  , "lawngreen", 0x7cfc00ff
  , "lemonchiffon", 0xfffacdff
  , "lightblue", 0xadd8e6ff
  , "lightcoral", 0xf08080ff
  , "lightcyan", 0xe0ffffff
  , "lightgoldenrodyellow", 0xfafad2ff
  , "lightgrey", 0xd3d3d3ff
  , "lightgreen", 0x90ee90ff
  , "lightpink", 0xffb6c1ff
  , "lightsalmon", 0xffa07aff
  , "lightseagreen", 0x20b2aaff
  , "lightskyblue", 0x87cefaff
  , "lightslateblue", 0x8470ffff
  , "lightslategray", 0x778899ff
  , "lightsteelblue", 0xb0c4deff
  , "lightyellow", 0xffffe0ff
  , "lime", 0x00ff00ff
  , "limegreen", 0x32cd32ff
  , "linen", 0xfaf0e6ff
  , "magenta", 0xff00ffff
  , "maroon", 0x800000ff
  , "mediumaquamarine", 0x66cdaaff
  , "mediumblue", 0x0000cdff
  , "mediumorchid", 0xba55d3ff
  , "mediumpurple", 0x9370d8ff
  , "mediumseagreen", 0x3cb371ff
  , "mediumslateblue", 0x7b68eeff
  , "mediumspringgreen", 0x00fa9aff
  , "mediumturquoise", 0x48d1ccff
  , "mediumvioletred", 0xc71585ff
  , "midnightblue", 0x191970ff
  , "mintcream", 0xf5fffaff
  , "mistyrose", 0xffe4e1ff
  , "moccasin", 0xffe4b5ff
  , "navajowhite", 0xffdeadff
  , "navy", 0x000080ff
  , "oldlace", 0xfdf5e6ff
  , "olive", 0x808000ff
  , "olivedrab", 0x6b8e23ff
  , "orange", 0xffa500ff
  , "orangered", 0xff4500ff
  , "orchid", 0xda70d6ff
  , "palegoldenrod", 0xeee8aaff
  , "palegreen", 0x98fb98ff
  , "paleturquoise", 0xafeeeeff
  , "palevioletred", 0xd87093ff
  , "papayawhip", 0xffefd5ff
  , "peachpuff", 0xffdab9ff
  , "peru", 0xcd853fff
  , "pink", 0xffc0cbff
  , "plum", 0xdda0ddff
  , "powderblue", 0xb0e0e6ff
  , "purple", 0x800080ff
  , "red", 0xff0000ff
  , "rosybrown", 0xbc8f8fff
  , "royalblue", 0x4169e1ff
  , "saddlebrown", 0x8b4513ff
  , "salmon", 0xfa8072ff
  , "sandybrown", 0xf4a460ff
  , "seagreen", 0x2e8b57ff
  , "seashell", 0xfff5eeff
  , "sienna", 0xa0522dff
  , "silver", 0xc0c0c0ff
  , "skyblue", 0x87ceebff
  , "slateblue", 0x6a5acdff
  , "slategray", 0x708090ff
  , "snow", 0xfffafaff
  , "springgreen", 0x00ff7fff
  , "steelblue", 0x4682b4ff
  , "tan", 0xd2b48cff
  , "teal", 0x008080ff
  , "thistle", 0xd8bfd8ff
  , "tomato", 0xff6347ff
  , "turquoise", 0x40e0d0ff
  , "violet", 0xee82eeff
  , "violetred", 0xd02090ff
  , "wheat", 0xf5deb3ff
  , "white", 0xffffffff
  , "whitesmoke", 0xf5f5f5ff
  , "yellow", 0xffff00ff
  , "yellowgreen", 0x9acd32ff
  , NULL, NULL
};

/*
 * Hex digit int val.
 */

static int
h(char c) {
  switch (c) {
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
      return c - '0';
    case 'a':
    case 'b':
    case 'c':
    case 'd':
    case 'e':
    case 'f':
      return (c - 'a') + 10;
    case 'A':
    case 'B':
    case 'C':
    case 'D':
    case 'E':
    case 'F':
      return (c - 'A') + 10;
  }
  return 0;
}

/*
 * Return rgba from (r,g,b,a).
 */

int32_t
rgba_from_rgba(uint8_t r, uint8_t g, uint8_t b, uint8_t a) {
  return
      r << 24
    | g << 16
    | b << 8
    | a;
}

/*
 * Return rgba from (r,g,b).
 */

int32_t
rgba_from_rgb(uint8_t r, uint8_t g, uint8_t b) {
  return rgba_from_rgba(r, g, b, 0);
}

/*
 * Return rgb from "#RRGGBB".
 */

int32_t
rgba_from_hex6_string(const char *str) {
  return rgba_from_rgb(
      (h(str[0]) << 4) + h(str[1])
    , (h(str[2]) << 4) + h(str[3])
    , (h(str[4]) << 4) + h(str[5])
    );
}

/*
 * Return rgb from "#RGB"
 */

int32_t
rgba_from_hex3_string(const char *str) {
  return rgba_from_rgb(
      (h(str[0]) << 4) + h(str[0])
    , (h(str[1]) << 4) + h(str[1])
    , (h(str[2]) << 4) + h(str[2])
    );
}

/*
 * Return rgb from "rgb()"
 */

int32_t
rgba_from_rgb_string(const char *str) {
  if (str == strnstr(str, "rgb(", 4)) {
    str += 4;
    WHITESPACE;
    uint8_t r = 0, g = 0, b = 0;
    CHANNEL(r);
    CHANNEL(g);
    CHANNEL(b);
    return rgba_from_rgb(r, g, b);
  }
  return -1;
}

/*
 * Return rgb from "rgba()"
 */

int32_t
rgba_from_rgba_string(const char *str) {
  if (str == strnstr(str, "rgba(", 5)) {
    str += 5;
    WHITESPACE;
    uint8_t r = 0, g = 0, b = 0;
    float a = 0;
    CHANNEL(r);
    CHANNEL(g);
    CHANNEL(b);
    // TODO: less strict
    if ('1' == *str) {
      a = 1;
    } else {
      if ('0' == *str) a = 0, ++str;
      if ('.' == *str) {
        ++str;
        float n = .1;
        while (*str >= '0' && *str <= '9') {
          a += (*str++ - '0') * n;
          n *= .1;
        }
      }
    }
    return rgba_from_rgba(r, g, b, a * 255);
  }
  return -1;
}

/*
 * Return rgb from:
 *  
 *  - "#RGB"
 *  - "#RRGGBB"
 *
 */

int32_t
rgba_from_hex_string(const char *str) {
  size_t len = strlen(str);
  if (6 == len) return rgba_from_hex6_string(str);
  if (3 == len) return rgba_from_hex3_string(str);
  return -1;
}

/*
 * Return named color value.
 */

int32_t
rgba_from_name_string(const char *str) {
  int i = 0;
  struct named_color color;
  while ((color = named_colors[i++]).name) {
    if (*str == *color.name && 0 == strcmp(str, color.name))
      return color.val;
  }
  return -1;
}

/*
 * Return rgb from:
 *  
 *  - #RGB
 *  - #RRGGBB
 *  - rgb(r,g,b)
 *  - rgba(r,g,b,a)
 *  - name
 *
 */

int32_t
rgba_from_string(const char *str) {
  if ('#' == str[0]) 
    return rgba_from_hex_string(++str);
  if (str == strnstr(str, "rgba", 4))
    return rgba_from_rgba_string(str);
  if (str == strnstr(str, "rgb", 3))
    return rgba_from_rgb_string(str);
  return rgba_from_name_string(str);
}

/*
 * Inspect the given rgba color.
 */

void
rgba_inspect(int32_t rgba) {
  printf("rgba(%d,%d,%d,%d)\n"
    , rgba >> 24 & 0xFF
    , rgba >> 16 & 0xFF
    , rgba >> 8 & 0xFF
    , rgba & 0xFF
    );
}