I am looking for a JavaScript / PHP algorithm to convert between HSL color to RGB.
It seems to me that HSL is not very widely used so I am not having much luck search
I needed a really light weight one, Its not 100%, but it gets close enough for some usecases.
float3 Hue(float h, float s, float l)
{
float r = max(cos(h * 2 * UNITY_PI) * 0.5 + 0.5, 0);
float g = max(cos((h + 0.666666) * 2 * UNITY_PI) * 0.5 + 0.5, 0);
float b = max(cos((h + 0.333333) * 2 * UNITY_PI) * 0.5 + 0.5, 0);
float gray = 0.2989 * r + 0.5870 * g + 0.1140 * b;
return lerp(gray, float3(r, g, b), s) * smoothstep(0, 0.5, l) + 1 * smoothstep(0.5, 1, l);
}
Here is the modified javascript function, it outputs Hue in set 0-360 degrees.
function rgbToHsl(r, g, b) {
r /= 255, g /= 255, b /= 255;
var max = Math.max(r, g, b), min = Math.min(r, g, b);
var h, s, l = (max + min) / 2;
if(max == min){
h = s = 0; // achromatic
} else {
var d = max - min;
s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
switch(max){
case r: h = (g - b) / d ; break;
case g: h = 2 + ( (b - r) / d); break;
case b: h = 4 + ( (r - g) / d); break;
}
h*=60;
if (h < 0) h +=360;
}
return([h, s, l]);
}
alert(rgbToHsl(125,115,145));
Found the easiest way, python to the rescue :D
colorsys.hls_to_rgb(h, l, s)
Convert the color from HLS coordinates to RGB coordinates.
For when you need RGB to HSV and vice versa instead:
function rgbToHsv(r, g, b)
{
r /= 255, g /= 255, b /= 255;
var min = Math.min(r, g, b),
max = Math.max(r, g, b),
delta = max - min,
h = 0, s = 0, v = max;
if (min != max)
{
s = (delta / max);
switch (max)
{
case r: h = (g - b) / delta + (g < b ? 6 : 0); break;
case g: h = (b - r) / delta + 2; break;
case b: h = (r - g) / delta + 4; break;
}
h /= 6;
}
return [h, s, v];
}
function hsvToRgb(h, s, v)
{
var step = h / (1 / 6),
pos = step - Math.floor(step), // the hue position within the current step
m = (Math.floor(step) % 2) ? (1 - pos) * v : pos * v, // mix color value adjusted to the brightness(v)
max = 1 * v,
min = (1 - s) * v,
med = m + ((1 - s) * (v - m)),
r, g, b;
switch (Math.floor(step))
{
case 0:
r = max;
g = med;
b = min;
break;
case 1:
r = med;
g = max;
b = min;
break;
case 2:
r = min;
g = max;
b = med;
break;
case 3:
r = min;
g = med;
b = max;
break;
case 4:
r = med;
g = min;
b = max;
break;
case 5:
r = max;
g = min;
b = med;
break;
}
return [Math.round(r * 255), Math.round(g * 255), Math.round(b * 255)];
}
C++ implementation with probably better performance than @Mohsen code. It uses a [0-6] range for the hue, avoiding the division and multiplication by 6. S and L range is [0,1]
void fromRGBtoHSL(float rgb[], float hsl[])
{
const float maxRGB = max(rgb[0], max(rgb[1], rgb[2]));
const float minRGB = min(rgb[0], min(rgb[1], rgb[2]));
const float delta2 = maxRGB + minRGB;
hsl[2] = delta2 * 0.5f;
const float delta = maxRGB - minRGB;
if (delta < FLT_MIN)
hsl[0] = hsl[1] = 0.0f;
else
{
hsl[1] = delta / (hsl[2] > 0.5f ? 2.0f - delta2 : delta2);
if (rgb[0] >= maxRGB)
{
hsl[0] = (rgb[1] - rgb[2]) / delta;
if (hsl[0] < 0.0f)
hsl[0] += 6.0f;
}
else if (rgb[1] >= maxRGB)
hsl[0] = 2.0f + (rgb[2] - rgb[0]) / delta;
else
hsl[0] = 4.0f + (rgb[0] - rgb[1]) / delta;
}
}
void fromHSLtoRGB(const float hsl[], float rgb[])
{
if(hsl[1] < FLT_MIN)
rgb[0] = rgb[1] = rgb[2] = hsl[2];
else if(hsl[2] < FLT_MIN)
rgb[0] = rgb[1] = rgb[2] = 0.0f;
else
{
const float q = hsl[2] < 0.5f ? hsl[2] * (1.0f + hsl[1]) : hsl[2] + hsl[1] - hsl[2] * hsl[1];
const float p = 2.0f * hsl[2] - q;
float t[] = {hsl[0] + 2.0f, hsl[0], hsl[0] - 2.0f};
for(int i=0; i<3; ++i)
{
if(t[i] < 0.0f)
t[i] += 6.0f;
else if(t[i] > 6.0f)
t[i] -= 6.0f;
if(t[i] < 1.0f)
rgb[i] = p + (q - p) * t[i];
else if(t[i] < 3.0f)
rgb[i] = q;
else if(t[i] < 4.0f)
rgb[i] = p + (q - p) * (4.0f - t[i]);
else
rgb[i] = p;
}
}
}
With H, S,and L in [0,1] range:
ConvertHslToRgb: function (iHsl)
{
var min, sv, sextant, fract, vsf;
var v = (iHsl.l <= 0.5) ? (iHsl.l * (1 + iHsl.s)) : (iHsl.l + iHsl.s - iHsl.l * iHsl.s);
if (v === 0)
return { Red: 0, Green: 0, Blue: 0 };
min = 2 * iHsl.l - v;
sv = (v - min) / v;
var h = (6 * iHsl.h) % 6;
sextant = Math.floor(h);
fract = h - sextant;
vsf = v * sv * fract;
switch (sextant)
{
case 0: return { r: v, g: min + vsf, b: min };
case 1: return { r: v - vsf, g: v, b: min };
case 2: return { r: min, g: v, b: min + vsf };
case 3: return { r: min, g: v - vsf, b: v };
case 4: return { r: min + vsf, g: min, b: v };
case 5: return { r: v, g: min, b: v - vsf };
}
}