Re: A few questions about

  To: comp.lang.java.gui
In article
<48f456c3$0$10592$5a62ac22@per-qv1-newsreader-01.iinet.net.au>,
 "Qu0ll" <Qu0llSixFour@gmail.com> wrote:


I am intrigued by the questions you raised up-thread about rendering
errors while scaling. I have seen a few such anomalies on Windows XP.
They tend to be small, off-by-one-pixel errors that are magnified by
scaling: lines that don't meet, circles that aren't circular.

I know that Java2D and Mac OS Quartz (and Linux GDK?) model graphics
devices using "Coordinates [that] are infinitely thin and lie between
the pixels of the output device." I have been told that Windows uses a
slightly different model, but I was using older systems (Java 1.4.2 &
Windows XP).

If you get a chance to run the example on a Mac, use accessibility
magnification or the Pixie tool to see the difference:

/Developer/Applications/Graphics Tools/Pixie.app

I was able to produce some artifact on Mac OS by adding diagonal lines
having CAP_SQUARE ends. Using CAP_ROUND precludes the problem. This
example lines up perfectly on my implementation at all sizes, weights,
aspects and magnifications I tried:

<code>
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.AffineTransform;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class TransTest extends JFrame {

    private class MyPanel extends JPanel {

        @Override
        public void paintComponent(final Graphics g) {
            final Graphics2D g2d = (Graphics2D)g;
            final double scaleX = this.getWidth() / 100.0;
            final double scaleY = this.getHeight() / 100.0;
            final BasicStroke stroke = new BasicStroke(4f,
                BasicStroke.CAP_ROUND , BasicStroke.JOIN_ROUND);
            g2d.setStroke(stroke);
            final AffineTransform at = new AffineTransform(
                AffineTransform.getScaleInstance(scaleX, scaleY));
            at.translate(10, 10);
            g2d.transform(at);
            g2d.setColor(Color.darkGray);
            g2d.drawRect(0, 0, 80, 80);
            fade(g2d);
            g2d.drawLine(0, 40, 80, 40);
            fade(g2d);
            g2d.drawLine(40, 0, 40, 80);
            fade(g2d);
            g2d.drawLine(0, 0, 80, 80);
            fade(g2d);
            g2d.drawLine(80, 0, 0, 80);
        }
    }

    private void fade(Graphics2D g2d) {
        Color color = g2d.getColor();
        g2d.setColor(color.brighter());
    }

    public TransTest() {
        this.setLayout(new BorderLayout());
        final MyPanel panel = new MyPanel();
        this.add(panel, BorderLayout.CENTER);
        panel.setBackground(Color.WHITE);
        this.pack();
        this.setSize(543, 567);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setLocationRelativeTo(null);
    }

    public static void main(final String[] args) {
        EventQueue.invokeLater(new Runnable() {

            public void run() {
                new TransTest().setVisible(true);
            }
        });
    }
}
</code>

--
John B. Matthews
trashgod at gmail dot com
home dot woh dot rr dot com slash jbmatthews

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