How can I use the HSL colorspace in Java?

Question

I've had a look at the ColorSpace class, and found the constant TYPE_HLS (which presumably is just HSL in a different order).

Can I use this constant to create a Color from hue, saturation, and luminosity? If not, are there any Java classes for this, or do I need to write my own?

Answer 1

Most of the given answers here seem to assume that HSL == HSB, which is false. The HSB colorspace is useful (and used) in many cases, but there is one notable exception: CSS. The non-RGB css color functions, hsl() and hsla() are HSL, not HSB. As such, it is very useful to be able to convert to and from HSL in java.

There is a good writeup about the problem here: http://tips4java.wordpress.com/2009/07/05/hsl-color/ TL;DR: the code is here: http://www.camick.com/java/source/HSLColor.java

The methods therein are pretty easy to extract if you don't want to use the whole class.

It doesn't appear that the author of the class included a license, though the context of the blog post seems to imply public domain. Use your own judgement.

Answer 2

Here is a simple implementation that will return a Color based on hue, saturation, and lightness values from 0.0 to 1.0...

static public Color hslColor(float h, float s, float l) {
    float q, p, r, g, b;

    if (s == 0) {
        r = g = b = l; // achromatic
    } else {
        q = l < 0.5 ? (l * (1 + s)) : (l + s - l * s);
        p = 2 * l - q;
        r = hue2rgb(p, q, h + 1.0f / 3);
        g = hue2rgb(p, q, h);
        b = hue2rgb(p, q, h - 1.0f / 3);
    }
    return new Color(Math.round(r * 255), Math.round(g * 255), Math.round(b * 255));
}

EDIT by Yona-Appletree:

I found what I think is the correct hue2rgb function and tested it as working:

private static float hue2rgb(float p, float q, float h) {
    if (h < 0) {
        h += 1;
    }

    if (h > 1) {
        h -= 1;
    }

    if (6 * h < 1) {
        return p + ((q - p) * 6 * h);
    }

    if (2 * h < 1) {
        return q;
    }

    if (3 * h < 2) {
        return p + ((q - p) * 6 * ((2.0f / 3.0f) - h));
    }

    return p;
}

Answer 3

Maybe this will help. The JDK doesn't seem to be very helpful when wanting to use colors in another color space.

Edit: In ColorSpace.getName(idx) there's this little snippet:

 case ColorSpace.TYPE_HLS:
                    compName = new String[] {"Hue", "Lightness", 
                                             "Saturation"};

so it was what you thought, but looking at the type hierarchy of ColorSpace it doesn't seem to be used or implemented in any way anywhere. ColorSpace is extended by only two other classes BogusColorSpace and ICC_ColorSpace, so I'm guessing they're expecting developers to create their own implementations for different color spaces.

Answer 4

EDIT: I realize HSB != HSL, the answer below is for HSB.

I don't think there is any need to use ColorSpaces here. Try something like the following:

float hue = 0.9f; //hue
float saturation = 1.0f; //saturation
float brightness = 0.8f; //brightness

Color myRGBColor = Color.getHSBColor(hue, saturation, brightness);

Answer 5

If your input is swing/awt widgets, then with Java 7 JColorChooser you can get Color by HSV and HSL spaces. http://java.dzone.com/articles/new-color-chooser-jdk-7

Answer 6

Found it:

Color.getHSBColor(float h, float s, float b)