Conversion between RGB and HSV

ColorSpace.java

import java.awt.Color;
import java.util.Arrays;

/**
 * Created by wanghong on 10/8/16.
 */

public class ColorSpace {

    public static void main(String[] args) {
        System.out.println("Our implementation");
        System.out.println(rgb2hsv(new Rgb(0.5, 0.6, 0.3)));
        System.out.println(hsv2rgb(new Hsv(80, 0.5, 0.6)));

        System.out.println();
        System.out.println("AWT implementation");
        float[] hsb = new float[3];
        Color.RGBtoHSB((int) (0.5 * 255), (int) (0.6 * 255), (int) (0.3 * 255), hsb);
        hsb[0] *= 360;
        System.out.println(Arrays.toString(hsb));

        int color = Color.HSBtoRGB(80.0f / 360.0f, 0.5f, 0.6f);
        System.out.println("[r = " + (color >> 16 & 0xff) / 255.0 +
                ", g = " + (color >> 8 & 0xff) / 255.0 +
                ", b = " + (color & 0xff) / 255.0 + "]");
    }

    public static Rgb hsv2rgb(Hsv hsv) {
        Rgb rgb = new Rgb();

        double hh = hsv.h / 60;
        int i = ((int) hh) % 6;

        double f = hh - i;
        double p = hsv.v * (1 - hsv.s);
        double q = hsv.v * (1 - f * hsv.s);
        double t = hsv.v * (1 - (1 - f) * hsv.s);

        switch (i) {
            case 0:
                rgb.r = hsv.v; rgb.g = t; rgb.b = q; break;
            case 1:
                rgb.r = q; rgb.g = hsv.v; rgb.b = p; break;
            case 2:
                rgb.r = p; rgb.g = hsv.v; rgb.b = t; break;
            case 3:
                rgb.r = p; rgb.g = q; rgb.b = hsv.v; break;
            case 4:
                rgb.r = t; rgb.g = p; rgb.b = hsv.v; break;
            case 5:
                rgb.r = hsv.v; rgb.g = p; rgb.b = q; break;
                default:
        }

        return rgb;
    }

    public static Hsv rgb2hsv(Rgb rgb) {
        Hsv hsv = new Hsv();

        double max = Math.max(Math.max(rgb.r, rgb.g), rgb.b);
        double min = Math.min(Math.min(rgb.r, rgb.g), rgb.b);
        double delta = max - min;

        if (delta == 0) {
            hsv.h = 360;
            hsv.s = 0;
            hsv.v = max;
            return hsv;
        }

        if (max == rgb.r) {
            hsv.h = (rgb.g - rgb.b) / delta % 6;
        } else if (max == rgb.g) {
            hsv.h = (rgb.b - rgb.r) / delta + 2;
        } else {
            hsv.h = (rgb.r - rgb.g) / delta + 4;
        }
        hsv.h *= 60;

        if (max == 0) {
            hsv.s = 0;
        } else {
            hsv.s = delta / max;
        }

        hsv.v = max;

        return hsv;
    }

    private static class Hsv {
        double h; /* 0 ~ 360 degree */
        double s; /* 0.0 ~ 1.0 */
        double v; /* 0.0 ~ 1.0 */

        public Hsv() {
        }

        public Hsv(double h, double s, double v) {
            this.h = h;
            this.s = s;
            this.v = v;
        }

        @Override
        public String toString() {
            return "[h = " + h + ", s = " + s + ", v = " + v + "]";
        }
    }

    private static class Rgb {
        double r; /* 0.0 ~ 1.0 */
        double g; /* 0.0 ~ 1.0 */
        double b; /* 0.0 ~ 1.0 */

        public Rgb() {
        }

        public Rgb(double r, double g, double b) {
            this.r = r;
            this.g = g;
            this.b = b;
        }

        @Override
        public String toString() {
            return "[r = " + r + ", g = " + g + ", b = " + b + "]";
        }
    }

}