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| 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 };
}
|
