/// <summary>
/// Convert from RGB to HSL color space.
/// </summary>
///
/// <param name="rgb">Source color in <b>RGB</b> color space.</param>
/// <param name="hsl">Destination color in <b>HSL</b> color space.</param>
///
/// <remarks><para>See <a href="http://en.wikipedia.org/wiki/HSI_color_space#Conversion_from_RGB_to_HSL_or_HSV">HSL and HSV Wiki</a>
/// for information about the algorithm to convert from RGB to HSL.</para></remarks>
///
public static void FromRGB(RGB rgb, HSL hsl)
{
float r = (rgb.Red / 255.0f);
float g = (rgb.Green / 255.0f);
float b = (rgb.Blue / 255.0f);
float min = Math.Min(Math.Min(r, g), b);
float max = Math.Max(Math.Max(r, g), b);
float delta = max - min;
// get luminance value
hsl.Luminance = (max + min) / 2;
if (delta == 0)
{
// gray color
hsl.Hue = 0;
hsl.Saturation = 0.0f;
}
else
{
// get saturation value
hsl.Saturation = (hsl.Luminance <= 0.5) ? (delta / (max + min)) : (delta / (2 - max - min));
// get hue value
float hue;
if (r == max)
{
hue = ((g - b) / 6) / delta;
}
else if (g == max)
{
hue = (1.0f / 3) + ((b - r) / 6) / delta;
}
else
{
hue = (2.0f / 3) + ((r - g) / 6) / delta;
}
// correct hue if needed
if (hue < 0)
hue += 1;
if (hue > 1)
hue -= 1;
hsl.Hue = (int)(hue * 360);
}
}
/// <summary>
/// Convert from HSL to RGB color space.
/// </summary>
///
/// <param name="hsl">Source color in <b>HSL</b> color space.</param>
/// <param name="rgb">Destination color in <b>RGB</b> color space.</param>
///
public static void ToRGB(HSL hsl, RGB rgb)
{
if (hsl.Saturation == 0)
{
// gray values
rgb.Red = rgb.Green = rgb.Blue = (byte)(hsl.Luminance * 255);
}
else
{
float v1, v2;
float hue = (float)hsl.Hue / 360;
v2 = (hsl.Luminance < 0.5) ?
(hsl.Luminance * (1 + hsl.Saturation)) :
((hsl.Luminance + hsl.Saturation) - (hsl.Luminance * hsl.Saturation));
v1 = 2 * hsl.Luminance - v2;
rgb.Red = (byte)(255 * Hue_2_RGB(v1, v2, hue + (1.0f / 3)));
rgb.Green = (byte)(255 * Hue_2_RGB(v1, v2, hue));
rgb.Blue = (byte)(255 * Hue_2_RGB(v1, v2, hue - (1.0f / 3)));
}
}
/// <summary>
/// Convert from HSL to RGB color space.
/// </summary>
///
/// <param name="hsl">Source color in <b>HSL</b> color space.</param>
/// <param name="rgb">Destination color in <b>RGB</b> color space.</param>
///
public static void ToRGB(HSL hsl, RGB rgb)
{
if (hsl.Saturation == 0)
{
// gray values
rgb.Red = rgb.Green = rgb.Blue = (byte)(hsl.Luminance * 255);
}
else
{
float v1, v2;
float hue = (float)hsl.Hue / 360;
v2 = (hsl.Luminance < 0.5) ?
(hsl.Luminance * (1 + hsl.Saturation)) :
((hsl.Luminance + hsl.Saturation) - (hsl.Luminance * hsl.Saturation));
v1 = 2 * hsl.Luminance - v2;
rgb.Red = (byte)(255 * Hue_2_RGB(v1, v2, hue + (1.0f / 3)));
rgb.Green = (byte)(255 * Hue_2_RGB(v1, v2, hue));
rgb.Blue = (byte)(255 * Hue_2_RGB(v1, v2, hue - (1.0f / 3)));
}
}
/// <summary>
/// Convert from RGB to HSL color space.
/// </summary>
///
/// <param name="rgb">Source color in <b>RGB</b> color space.</param>
///
/// <returns>Returns <see cref="HSL"/> instance, which represents converted color value.</returns>
///
public static HSL FromRGB(RGB rgb)
{
HSL hsl = new HSL();
FromRGB(rgb, hsl);
return hsl;
}
