[iOS开发] RGB、YUV、HSV和HSL区别和关联

• RGB_1：110,0,110
  
• RGB_2：60,0,100
  
• RGB_3：160,0,110
  

• 色调 Hue
  
• 饱和度 Saturation
  
• 明度（亮度）Value
  

• 增加黑色可以减小V而S不变
  
• 同样增加白色可以减少S而V不变
  

• H 指的是色相（Hue），就是颜色名称，例如“红色”、“蓝色”；
  
• S 指的是饱和度（Saturation），即颜色的纯度；
  
• L（Lightness） 和 V（Value）是明度，颜色的明亮程度
  

• HSV 中的 S 控制纯色中混入白色的量，值越大，白色越少，颜色越纯；
  
• HSV 中的 V 控制纯色中混入黑色的量，值越大，黑色越少，明度越高
  
• HSL 中的 S 和黑白没有关系，饱和度不控制颜色中混入黑白的多寡；
  
• HSL 中的 L 控制纯色中的混入的黑白两种颜色。
  

typedef struct {
  NSUInteger r;
  NSUInteger g;
  NSUInteger b;
  CGFloat a;
} RGB;
typedef struct {
  NSUInteger h;
  CGFloat s;
  CGFloat l;
  CGFloat a;
} HSL;
typedef struct {
  NSUInteger h;
  CGFloat s;
  CGFloat v;
  CGFloat a;
} HSV;
/**
 * Converts an RGB color value to HSL. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
 * Assumes r, g, and b are contained in the set [0, 255] and
 * returns h, s, and l in the set [0, 1].
 *
 * @param   Number  r     The red color value
 * @param   Number  g     The green color value
 * @param   Number  b     The blue color value
 * @return  Array       The HSL representation
 */
HSL RGBToHSL(RGB rgb) {
  CGFloat r = rgb.r / 255.0, g = rgb.g / 255.0, b = rgb.b / 255.0;
  CGFloat max = MAX(MAX(r, g), b), min = MIN(MIN(r, g), b);
  CGFloat h = 0, s = 0, l = (max + min) / 2;
  if (max == min) {
    h = s = 0; // achromatic
  } else {
    CGFloat d = max - min;
    s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
    if (max == r) {
      h = (g - b) / d + (g < b ? 6 : 0);
    } else if (max == g) {
      h = (b - r) / d + 2;
    } else {
      h = (r - g) / d + 4;
    }
    h /= 6;
  }
  return (HSL){ .h = static_cast<NSUInteger>(round(h * 360.0)), .s = s, .l = l, .a = rgb.a };
}
/**
 * Converts an HSL color value to RGB. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
 * Assumes h, s, and l are contained in the set [0, 1] and
 * returns r, g, and b in the set [0, 255].
 *
 * @param   Number  h     The hue
 * @param   Number  s     The saturation
 * @param   Number  l     The lightness
 * @return  Array       The RGB representation
 */
RGB HSLToRGB(HSL hsl) {
  CGFloat h = hsl.h / 360.0, s = hsl.s, l = hsl.l;
  CGFloat r = 0, g = 0, b = 0;
  if (s == 0) {
    r = g = b = l; // achromatic
  } else {
    CGFloat (^hue2rgb)(CGFloat, CGFloat, CGFloat) = ^CGFloat(CGFloat p, CGFloat q, CGFloat t) {
      if (t < 0.0)
        t += 1;
      if (t > 1.0)
        t -= 1;
      if (t < 1 / 6.0)
        return p + (q - p) * 6 * t;
      if (t < 1 / 2.0)
        return q;
      if (t < 2 / 3.0)
        return p + (q - p) * (2 / 3.0 - t) * 6;
      return p;
    };
    CGFloat q = l < 0.5 ? l * (1 + s) : l + s - l * s;
    CGFloat p = 2 * l - q;
    r = hue2rgb(p, q, h + 1 / 3.0);
    g = hue2rgb(p, q, h);
    b = hue2rgb(p, q, h - 1 / 3.0);
  }
  NSUInteger red = round(r * 255);
  NSUInteger green = round(g * 255);
  NSUInteger blue = round(b * 255);
  return (RGB){ .r = red, .g = green, .b = blue, .a = hsl.a };
}
/**
 * Converts an RGB color value to HSV. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSV_color_space.
 * Assumes r, g, and b are contained in the set [0, 255] and
 * returns h, s, and v in the set [0, 1].
 *
 * @param   Number  r     The red color value
 * @param   Number  g     The green color value
 * @param   Number  b     The blue color value
 * @return  Array       The HSV representation
 */
HSV RGBToHSV(RGB rgb) {
  CGFloat r = rgb.r / 255.0, g = rgb.g / 255.0, b = rgb.b / 255.0;
  CGFloat max = MAX(MAX(r, g), b), min = MIN(MIN(r, g), b);
  CGFloat h = 0, s = 0, v = max;
  CGFloat d = max - min;
  s = max == 0 ? 0 : d / max;
  if (max == min) {
    h = 0; // achromatic
  } else {
    if (max == r) {
      h = (g - b) / d + (g < b ? 6 : 0);
    } else if (max == g) {
      h = (b - r) / d + 2;
    } else {
      h = (r - g) / d + 4;
    }
    h /= 6;
  }
  return (HSV){ .h = static_cast<NSUInteger>(round(h * 360)), .s = s, .v = v, .a = rgb.a };
}
/**
 * Converts an HSV color value to RGB. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSV_color_space.
 * Assumes h, s, and v are contained in the set [0, 1] and
 * returns r, g, and b in the set [0, 255].
 *
 * @param   Number  h     The hue
 * @param   Number  s     The saturation
 * @param   Number  v     The value
 * @return  Array       The RGB representation
 */
RGB HSVToRGB(HSV hsv) {
  CGFloat r = 0, g = 0, b = 0, h = hsv.h / 360.0, s = hsv.s, v = hsv.v;
  NSUInteger i = floor(h * 6);
  CGFloat f = h * 6 - i;
  CGFloat p = v * (1 - s);
  CGFloat q = v * (1 - f * s);
  CGFloat t = v * (1 - (1 - f) * s);
  switch (i % 6) {
    case 0: {
      r = v;
      g = t;
      b = p;
      break;
    }
    case 1: {
      r = q;
      g = v;
      b = p;
      break;
    }
    case 2: {
      r = p;
      g = v;
      b = t;
      break;
    }
    case 3: {
      r = p;
      g = q;
      b = v;
      break;
    }
    case 4: {
      r = t;
      g = p;
      b = v;
      break;
    }
    case 5: {
      r = v;
      g = p;
      b = q;
      break;
    }
  }
  NSUInteger red = round(r * 255);
  NSUInteger green = round(g * 255);
  NSUInteger blue = round(b * 255);
  return (RGB){ .r = red, .g = green, .b = blue, .a = hsv.a };
}