Application: gvSIG desktop

package org.gvsig.raster.lib.legend.impl;

import java.awt.Color;

/**

 * Utility class to color conversions

 * @author dmartinezizquierdo

 *

 */

public class ColorUtils {

    /**

     *

     * @param y

     * @param cb

     * @param cr

     * @return the RGB values

     */

    public static Number[] fromYCBCRtoRGB(float y, float cb, float cr){

        Number[] rgbValues = new Number[3];

        int r = (int) (y + 1.40200 * (cr - 0x80));

        int g = (int) (y - 0.34414 * (cb - 0x80) - 0.71414 * (cr - 0x80));

        int b = (int) (y + 1.77200 * (cb - 0x80));

        rgbValues[0] = Math.max(0, Math.min(255, r));

        rgbValues[1] = Math.max(0, Math.min(255, g));

        rgbValues[2] = Math.max(0, Math.min(255, b));

        return rgbValues;

    }

    /**

     * Convert CMYK values to RGB values

     * NOTE: Conversion maybe very inaccurate

     *

     * @param cyan

     * @param magenta

     * @param yellow

     * @param black

     * @return the RGB values

     */

    public static Number[] fromCMYKtoRGB(float cyan, float magenta, float yellow, float black){

        //TODO: ICC profiles should be used to more precise conversion, as shown here:

        //http://stackoverflow.com/questions/3123574/how-to-convert-from-cmyk-to-rgb-in-java-correctly

        Number[] rgbValues = new Number[3];

        float colors = 255 - black;

        rgbValues[0] = colors * (255 - cyan) / 255;

        rgbValues[1] = colors * (255 - magenta) / 255;

        rgbValues[2] = colors * (255 - yellow) / 255;

        return rgbValues;

    }

    /**

     *  Convert HSL values to RGBA values with a default alpha value of 1.

     *

     *  @param h Hue is specified as degrees in the range 0 - 360.

     *  @param s Saturation is specified as a percentage in the range 1 - 100.

     *  @param l Lumanance is specified as a percentage in the range 1 - 100.

     *

     *  @returns the RGBA values

     */

    public static Number[] fromHSLtoRGBA(float h, float s, float l)

    {

        return fromHSLtoRGBA(h, s, l, 1.0f);

    }

    /**

     *  Convert HSL values to RGBA values

     *

     *  @param h Hue is specified as degrees in the range 0 - 360.

     *  @param s Saturation is specified as a percentage in the range 1 - 100.

     *  @param l Lumanance is specified as a percentage in the range 1 - 100.

     *  @param alpha  the alpha value between 0 - 1

     *

     *  @returns the RGBA values

     */

    public static Number[] fromHSLtoRGBA(float h, float s, float l, float alpha)

    {

        if (s <0.0f || s > 100.0f)

        {

            String message = "Color parameter outside of expected range - Saturation";

            throw new IllegalArgumentException( message );

        }

        if (l <0.0f || l > 100.0f)

        {

            String message = "Color parameter outside of expected range - Luminance";

            throw new IllegalArgumentException( message );

        }

        if (alpha <0.0f || alpha > 1.0f)

        {

            String message = "Color parameter outside of expected range - Alpha";

            throw new IllegalArgumentException( message );

        }

        //  Formula needs all values between 0 - 1.

        h = h % 360.0f;

        h /= 360f;

        s /= 100f;

        l /= 100f;

        float q = 0;

        if (l < 0.5)

            q = l * (1 + s);

        else

            q = (l + s) - (s * l);

        float p = 2 * l - q;

        float r = Math.max(0, HueToRGB(p, q, h + (1.0f / 3.0f)));

        float g = Math.max(0, HueToRGB(p, q, h));

        float b = Math.max(0, HueToRGB(p, q, h - (1.0f / 3.0f)));

        r = Math.min(r, 1.0f);

        g = Math.min(g, 1.0f);

        b = Math.min(b, 1.0f);

        Number[] rgbValues=new Number[4];

        rgbValues[0]=r;

        rgbValues[1]=g;

        rgbValues[2]=b;

        rgbValues[3]=alpha;

        return rgbValues;

    }

    private static float HueToRGB(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;

    }

}