Task

Write a function to draw a HSV color wheel completely with code.

This is strictly for learning purposes only. It's highly recommended that you use an image in an actual application to actually draw the color wheel   (as procedurally drawing is super slow). This does help you understand how color wheels work and this can easily be used to determine a color value based on a position within a circle.



import java.awt.*;
import javax.swing.*;
 
public class ColorWheel {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                ColorWheelFrame frame = new ColorWheelFrame();
                frame.setVisible(true);
            }
        });
    }
 
    private static class ColorWheelFrame extends JFrame {
        private ColorWheelFrame() {
            super("Color Wheel");
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            getContentPane().add(new ColorWheelPanel());
            pack();
        }
    }
 
    private static class ColorWheelPanel extends JComponent {
        private ColorWheelPanel() {
            setPreferredSize(new Dimension(400, 400));
        }
        public void paint(Graphics g) {
            Graphics2D g2 = (Graphics2D)g;
            int w = getWidth();
            int h = getHeight();
            int margin = 10;
            int radius = (Math.min(w, h) - 2 * margin)/2;
            int cx = w/2;
            int cy = h/2;
            float[] dist = {0.F, 1.0F};
            g2.setColor(Color.BLACK);
            g2.fillRect(0, 0, w, h);
            for (int angle = 0; angle < 360; ++angle) {
                Color color = hsvToRgb(angle, 1.0, 1.0);
                Color[] colors = {Color.WHITE, color};
                RadialGradientPaint paint = new RadialGradientPaint(cx, cy,
                        radius, dist, colors);
                g2.setPaint(paint);
                g2.fillArc(cx - radius, cy - radius, radius*2, radius*2,
                        angle, 1);
            }
        }
    }
 
    private static Color hsvToRgb(int h, double s, double v) {
        double hp = h/60.0;
        double c = s * v;
        double x = c * (1 - Math.abs(hp % 2.0 - 1));
        double m = v - c;
        double r = 0, g = 0, b = 0;
        if (hp <= 1) {
            r = c;
            g = x;
        } else if (hp <= 2) {
            r = x;
            g = c;
        } else if (hp <= 3) {
            g = c;
            b = x;
        } else if (hp <= 4) {
            g = x;
            b = c;
        } else if (hp <= 5) {
            r = x;
            b = c;
        } else {
            r = c;
            b = x;
        }
        r += m;
        g += m;
        b += m;
        return new Color((int)(r * 255), (int)(g * 255), (int)(b * 255));
    }
}