Convert a HSV color value to RGB colorspace. - Java 2D Graphics

Java examples for 2D Graphics:Color RGB

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Description

Convert a HSV color value to RGB colorspace.

Demo Code

/**//www  . ja v a 2s  .  co  m
 * This file is part of Sonar.
 *
 * Sonar is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 2 of the License.
 *
 * Sonar is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Sonar.  If not, see <http://www.gnu.org/licenses/>.
 */

public class Main{
    public static void main(String[] argv) throws Exception{
        int hue = 2;
        float sat = 2.45678f;
        float val = 2.45678f;
        System.out.println(transformHSVtoRGB(hue,sat,val));
    }
    /** first 60 degrees hue are red to yellow in HSV. */
    private static final int RED_YELLOW = 1;
    /** second 60 degrees hue are yellow to green in HSV. */
    private static final int YELLOW_GREEN = 2;
    /** third 60 degrees hue are green to cyan in HSV. */
    private static final int GREEN_CYAN = 3;
    /** fourth 60 degrees hue are cyan to blue in HSV. */
    private static final int CYAN_BLUE = 4;
    /** fifth 60 degrees hue are blue to magenta in HSV. */
    private static final int BLUE_MAGENTA = 5;
    /** last 60 degrees hue are magenta to red in HSV. */
    private static final int MAGENTA_RED = 6;
    /**
     * Splits the 360 degree hue into 6 parts.
     */
    private static final float HUE_SPLIT = 60.f;
    /**
     * Maximum amount of the hue value.
     */
    private static final int HUE_MAX = 360;
    /**
     * Convert a HSV color value to RGB colorspace.
     *
     * The method provides a convertion calculation to map a HSV 3-tupel to
     * back to the RGB colorspace.
     * <p/>
     * The HSV colorspace is a 3-tupel of a hue, expressed in 0-360 degree
     * angle a saturation value between 0.0 and 1.0 and a lightness value
     * between 0.0 and 1.0.
     * <p/>
     * HSV colorspaces are good to variate saturation and lightness
     * while the color stays the same. We primarly use this to display
     * different node weights as different saturation values of the same color.
     *
     * @param hue The hue as defined in HSV
     * @param sat The saturation to be used. Can be ranged from 0.0 to 1.0
     * @param val The value
     *
     * @return An RGB color
     */
    public static Color transformHSVtoRGB(final int hue, final float sat,
            final float val) {
        if (hue < 0 || hue > HUE_MAX) {
            throw new IllegalArgumentException("hue needs to be between"
                    + " 0 and 360");
        }

        if (sat < 0.0 || sat > 1.0) {
            throw new IllegalArgumentException(
                    "saturation needs to be between" + " 0.0 and 1.0");
        }

        if (val < 0.0 || val > 1.0) {
            throw new IllegalArgumentException("value needs to be between"
                    + " 0.0 and 1.0");
        }

        /* check wikipedia or something similar for the actual algorithm,
           it's standard. */
        int h = (int) (hue / HUE_SPLIT);
        float f = (hue / HUE_SPLIT) - h;
        float p = val * (1 - sat);
        float q = val * (1 - sat * f);
        float t = val * (1 - sat * (1 - f));

        switch (h) {
        case RED_YELLOW:
            return new Color(q, val, p);
        case YELLOW_GREEN:
            return new Color(p, val, t);
        case GREEN_CYAN:
            return new Color(p, q, val);
        case CYAN_BLUE:
            return new Color(t, p, val);
        case BLUE_MAGENTA:
            return new Color(val, p, q);
        case MAGENTA_RED:
        default: //<- default value to ensure 360 != 0?
            return new Color(val, t, p);
        }
    }
}

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