Created
February 18, 2016 10:25
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// Changes the RGB/HEX temporarily to a HSL-Value, modifies that value | |
// and changes it back to RGB/HEX. | |
function changeHue(rgb, degree) { | |
var hsl = rgbToHSL(rgb); | |
hsl.h += degree; | |
if (hsl.h > 360) { | |
hsl.h -= 360; | |
} | |
else if (hsl.h < 0) { | |
hsl.h += 360; | |
} | |
return hslToRGB(hsl); | |
} | |
// exepcts a string and returns an object | |
function rgbToHSL(rgb) { | |
// strip the leading # if it's there | |
rgb = rgb.replace(/^\s*#|\s*$/g, ''); | |
// convert 3 char codes --> 6, e.g. `E0F` --> `EE00FF` | |
if(rgb.length == 3){ | |
rgb = rgb.replace(/(.)/g, '$1$1'); | |
} | |
var r = parseInt(rgb.substr(0, 2), 16) / 255, | |
g = parseInt(rgb.substr(2, 2), 16) / 255, | |
b = parseInt(rgb.substr(4, 2), 16) / 255, | |
cMax = Math.max(r, g, b), | |
cMin = Math.min(r, g, b), | |
delta = cMax - cMin, | |
l = (cMax + cMin) / 2, | |
h = 0, | |
s = 0; | |
if (delta == 0) { | |
h = 0; | |
} | |
else if (cMax == r) { | |
h = 60 * (((g - b) / delta) % 6); | |
} | |
else if (cMax == g) { | |
h = 60 * (((b - r) / delta) + 2); | |
} | |
else { | |
h = 60 * (((r - g) / delta) + 4); | |
} | |
if (delta == 0) { | |
s = 0; | |
} | |
else { | |
s = (delta/(1-Math.abs(2*l - 1))) | |
} | |
return { | |
h: h, | |
s: s, | |
l: l | |
} | |
} | |
// expects an object and returns a string | |
function hslToRGB(hsl) { | |
var h = hsl.h, | |
s = hsl.s, | |
l = hsl.l, | |
c = (1 - Math.abs(2*l - 1)) * s, | |
x = c * ( 1 - Math.abs((h / 60 ) % 2 - 1 )), | |
m = l - c/ 2, | |
r, g, b; | |
if (h < 60) { | |
r = c; | |
g = x; | |
b = 0; | |
} | |
else if (h < 120) { | |
r = x; | |
g = c; | |
b = 0; | |
} | |
else if (h < 180) { | |
r = 0; | |
g = c; | |
b = x; | |
} | |
else if (h < 240) { | |
r = 0; | |
g = x; | |
b = c; | |
} | |
else if (h < 300) { | |
r = x; | |
g = 0; | |
b = c; | |
} | |
else { | |
r = c; | |
g = 0; | |
b = x; | |
} | |
r = normalize_rgb_value(r, m); | |
g = normalize_rgb_value(g, m); | |
b = normalize_rgb_value(b, m); | |
return rgbToHex(r,g,b); | |
} | |
function normalize_rgb_value(color, m) { | |
color = Math.floor((color + m) * 255); | |
if (color < 0) { | |
color = 0; | |
} | |
return color; | |
} | |
function rgbToHex(r, g, b) { | |
return "#" + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1); | |
} |
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