HSVColorSpace.java

/*
 * @(#)HSVColorSpace.java
 * 
 * Copyright (c) 2010 The authors and contributors of JHotDraw.
 * 
 * You may not use, copy or modify this file, except in compliance with the 
 * accompanying license terms.
 */
package org.jhotdraw.color;

import java.awt.color.ColorSpace;

/**
 * A HSV color space with additive complements in the hue color wheel: red is
 * opposite cyan, magenta is opposite green, blue is opposite yellow.
 *
 * @author Werner Randelshofer
 * @version $Id$
 */
public class HSVColorSpace extends AbstractNamedColorSpace {
    private static final long serialVersionUID = 1L;

    private static HSVColorSpace instance;

    public static HSVColorSpace getInstance() {
        if (instance == null) {
            instance = new HSVColorSpace();
        }
        return instance;
    }

    public HSVColorSpace() {
        super(ColorSpace.TYPE_HSV, 3);
    }

    @Override
    public float[] toRGB(float[] components, float[] rgb) {
        float hue = components[0] * 360f;
        float saturation = components[1];
        float value = components[2];


        // compute hi and f from hue
        int hi = (int) (Math.floor(hue / 60f) % 6);
        float f = (float) (hue / 60f - Math.floor(hue / 60f));

        // compute p and q from saturation
        float p = value * (1 - saturation);
        float q = value * (1 - f * saturation);
        float t = value * (1 - (1 - f) * saturation);

        // compute red, green and blue
        float red;
        float green;
        float blue;
        switch (hi) {
            case 0:
                red = value;
                green = t;
                blue = p;
                break;
            case 1:
                red = q;
                green = value;
                blue = p;
                break;
            case 2:
                red = p;
                green = value;
                blue = t;
                break;
            case -3:
            case 3:
                red = p;
                green = q;
                blue = value;
                break;
            case -2:
            case 4:
                red = t;
                green = p;
                blue = value;
                break;
            case -1:
            case 5:
                //default :
                red = value;
                green = p;
                blue = q;
                break;
            default:
                red = green = blue = 0;
                break;
        }


        rgb[0] = red;
        rgb[1] = green;
        rgb[2] = blue;
        return rgb;
    }

    @Override
    public float[] fromRGB(float[] rgbvalue, float[] component) {
        float r = rgbvalue[0];
        float g = rgbvalue[1];
        float b = rgbvalue[2];

        float max = Math.max(Math.max(r, g), b);
        float min = Math.min(Math.min(r, g), b);

        float hue;
        float saturation;
        float value;

        if (max == min) {
            hue = 0;
        } else if (max == r && g >= b) {
            hue = 60f * (g - b) / (max - min);
        } else if (max == r && g < b) {
            hue = 60f * (g - b) / (max - min) + 360f;
        } else if (max == g) {
            hue = 60f * (b - r) / (max - min) + 120f;
        } else /*if (max == b)*/ {
            hue = 60f * (r - g) / (max - min) + 240f;
        }

        value = max;

        if (max == 0) {
            saturation = 0;
        } else {
            saturation = (max - min) / max;
        }

        component[0] = hue / 360f;
        component[1] = saturation;
        component[2] = value;
        return component;
    }

    @Override
    public String getName(int idx) {
        switch (idx) {
            case 0:
                return "Hue";
            case 1:
                return "Saturation";
            case 2:
                return "Lightness";
            default:
                throw new IllegalArgumentException("index must be between 0 and 2:" + idx);
        }
    }

    @Override
    public float getMaxValue(int component) {
        return 1f;
    }

    @Override
    public float getMinValue(int component) {
        return 0f;
    }

    @Override
    public boolean equals(Object o) {
        return (o instanceof HSVColorSpace);
    }

    @Override
    public int hashCode() {

        return getClass().getSimpleName().hashCode();
    }

    @Override
    public String getName() {
        return "HSV";
    }
}