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
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;
}
}
}