Re: Anti-aliasing in image clipping to non-rectangular sub-images

On 15/08/2008 02:03, Knute Johnson allegedly wrote:


Hmmm. Having played around, and more importantly thought about it a bit,
I'll have to concur with your assessment.

For the record, here's the last state of my experiments. It achieves the
desired effect, but it's cheating (drawing twice and clipping in-between):

<code>
package scratch;

import java.awt.*;
import java.awt.geom.*;
import java.awt.image.*;
import javax.swing.*;
import javax.imageio.*;

/**
 *
 * @author da.futt
 */
public class XORTest
{
    public static void main(String[] ss) {
        EventQueue.invokeLater(
        new Loader() {
            public BufferedImage loadImage() throws Exception {
                return
ImageIO.read(XORTest.class.getResource("animage.png"));
            }
        });
    }

    private static abstract class Loader
    implements Runnable
    {
        public abstract BufferedImage loadImage()
        throws Exception;

        private Image prepareImage()
        throws Exception
        {
            BufferedImage i = loadImage();

            BufferedImage bi = new BufferedImage(i.getWidth(),
i.getHeight(),
            BufferedImage.TYPE_INT_ARGB_PRE);
            Graphics2D g = bi.createGraphics();

            g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);

            int d = Math.min(i.getWidth(), i.getHeight()) >> 1;

            Shape ell = new Ellipse2D.Float((i.getWidth() - d) >> 1,
            (i.getHeight() - d) >> 1, d, d);

            Shape oldclip = g.getClip();

            g.clip(ell);

g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC, .3f));
            g.drawImage(i, 0, 0, null);

            g.setClip(oldclip);

g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OUT));
            g.drawImage(i, 0, 0, null);

            g.dispose();

            return bi;
        }

        public void run() {
            try {
                run0();
            }
            catch (Exception x) {
                x.printStackTrace();
            }
        }

        private void run0()
        throws Exception
        {
            JFrame f = new JFrame("XOR paint test");
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            f.setContentPane(new BackgroundPanel(new BorderLayout()));

            f.getContentPane().setPreferredSize(new Dimension(300, 200));

            f.getContentPane().add(new JLabel(new ImageIcon(
            prepareImage())), BorderLayout.CENTER);

            f.pack();

            f.setLocationRelativeTo(null);
            f.setVisible(true);
        }
    }

    private static class BackgroundPanel
    extends JPanel
    {
        private static final int MARMOR_SIDE_PX = 20;

        public BackgroundPanel() {
            super();
        }

        public BackgroundPanel(LayoutManager layout) {
            super(layout);
        }

        @Override
        public void paintComponent(Graphics g) {
            Color white = new Color(0xf0f0f0),
            black = new Color(0x0f0f0f);

            int x = 0, y = 0, line = 0, col = 0;

            for (final int h = getHeight(), w = getWidth(); y < h;
                    y += MARMOR_SIDE_PX, line++, col = 0, x = 0)
            {
                for (; x < w; x += MARMOR_SIDE_PX, col++) {
                    g.setColor((col + line) % 2 == 0 ? black : white);
                    g.fillRect(x, y, MARMOR_SIDE_PX, MARMOR_SIDE_PX);
                }
            }
        }
    }
}
</code>