Java Graphics2D浮点准确的drawOval替代方案？ [英] Java Graphics2D floating point accurate drawOval alternative?
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问题描述
有没有办法使用浮点和反走样来消除这个舍入错误？ b
$ b
您可以运行此代码来查看问题。为了清楚起见，我绘制了0长度的弧（显示为大点）而不是全弧。
import java.awt。* ;
import javax.swing。*;
public class范例扩展JFrame {
private int CENTER = 200;
private static int WINDOW = 400;
private int LEFT = 50;
private int TOP = 50;
private int DIM = 300;
private int DIAMETER = 26;
public示例（）{
super（）;
}
public void paint（Graphics g）{
Graphics2D g2 =（Graphics2D）g;
g2.setRenderingHint（RenderingHints.KEY_ANTIALIASING，RenderingHints.VALUE_ANTIALIAS_ON）;
g2.setStroke（new BasicStroke（16，BasicStroke.CAP_ROUND，BasicStroke.JOIN_MITER））;
g2.setColor（new Color（0，0，255））;
g2.drawArc（LEFT，TOP，DIM，DIM，0，0）;
g2.drawArc（LEFT，TOP，DIM，DIM，32，0）;
g2.drawArc（LEFT，TOP，DIM，DIM，115，0）;
g2.drawArc（LEFT，TOP，DIM，DIM，200，0）;
g2.drawArc（LEFT，TOP，DIM，DIM，331，0）;
this.drawCircle（g2，0）;
this.drawCircle（g2，32）;
this.drawCircle（g2，115）;
this.drawCircle（g2，200）;
this.drawCircle（g2，331）;
g2.setStroke（new BasicStroke（1））;
g2.setColor（new Color（0，0，0））;
g2.drawLine（0，CENTER，DIM * 2，CENTER）;
g2.drawLine（CENTER，0，CENTER，DIM * 2）;
private void drawCircle（Graphics2D g，int angle）{
g.setStroke（new BasicStroke（3））;
g.setColor（new Color（0，0，255））;
g.drawOval（
Math.round（CENTER +（float）（Math.cos（Math.toRadians（angle））*（DIM / 2）） - DIAMETER / 2），
Math.round（Center - （float）（Math.sin（Math.toRadians（angle））*（DIM / 2）） - DIAMETER / 2），
DIAMETER，
DIAMETER
） ;
public static void main（String args []）{
示例e = new示例（）;
e.setSize（WINDOW，WINDOW）;
e.setVisible（true）;
e.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;
解决方案
另一种方法是，考虑
import java.awt.BasicStroke;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.Ellipse2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
/ **
* @see https://stackoverflow.com/a/38669048/230513
* /
public class Test {
private void display（）{
JFrame f = new JFrame（Test）;
f.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;
f.add（new JPanel（）{
private static final int N = 8;
private final Ellipse2D ellipse = new Ellipse2D.Float（）;
@覆盖
protected void paintComponent（Graphics g）{
super.paintComponent（g）;
Graphics2D g2d =（Graphics2D）g;
g2d.setRenderingHint（RenderingHints.KEY_ANTIALIASING，
RenderingHints.VALUE_ANTIALIAS_ON）;
g2d.setRenderingHint（RenderingHints.KEY_STROKE_CONTROL，
RenderingHints.VALUE_STROKE_PURE）;
g2d.setStroke（new BasicStroke（N））;
ellipse.setFrame （N，N，getWidth（） - 2 * N，getHeight（） - 2 * N）;
g2d.draw（ellipse）;
}
@Override
public Dimension getPreferredSize（）{
return new Dimension（320，240）;
}
}） ;
f.pack（）;
f.setLocationRelativeTo（null）;
f.setVisible（true）;
public static void main（String [] args）{
EventQueue.invokeLater（new Test（）:: display）;
}
}
So I am trying to draw an arc and put a circle around its round endpoint, but I am having issues due to rounding to the nearest pixel. This is visible in some but not all cases.
Is there a way to draw circles using floating points and anti-aliasing to eliminate this rounding error?
You can run this code to see the problem. I have drawn arcs of 0 length (appearing as large dots) instead of full arcs for clarity.
import java.awt.*;
import javax.swing.*;
public class Example extends JFrame {
private int CENTER = 200;
private static int WINDOW = 400;
private int LEFT = 50;
private int TOP = 50;
private int DIM = 300;
private int DIAMETER = 26;
public Example () {
super();
}
public void paint (Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(new BasicStroke(16, BasicStroke.CAP_ROUND, BasicStroke.JOIN_MITER));
g2.setColor(new Color(0, 0, 255));
g2.drawArc(LEFT, TOP, DIM, DIM, 0, 0);
g2.drawArc(LEFT, TOP, DIM, DIM, 32, 0);
g2.drawArc(LEFT, TOP, DIM, DIM, 115, 0);
g2.drawArc(LEFT, TOP, DIM, DIM, 200, 0);
g2.drawArc(LEFT, TOP, DIM, DIM, 331, 0);
this.drawCircle(g2, 0);
this.drawCircle(g2, 32);
this.drawCircle(g2, 115);
this.drawCircle(g2, 200);
this.drawCircle(g2, 331);
g2.setStroke(new BasicStroke(1));
g2.setColor(new Color(0, 0, 0));
g2.drawLine(0, CENTER, DIM * 2, CENTER);
g2.drawLine(CENTER, 0, CENTER, DIM * 2);
}
private void drawCircle(Graphics2D g, int angle) {
g.setStroke(new BasicStroke(3));
g.setColor(new Color(0, 0, 255));
g.drawOval(
Math.round(CENTER + (float)(Math.cos(Math.toRadians(angle)) * (DIM/2)) - DIAMETER/2),
Math.round(CENTER - (float)(Math.sin(Math.toRadians(angle)) * (DIM/2)) - DIAMETER/2),
DIAMETER,
DIAMETER
);
}
public static void main (String args[]) {
Example e = new Example();
e.setSize(WINDOW, WINDOW);
e.setVisible(true);
e.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
解决方案
As an alternative, consider Ellipse2D with suitable RenderingHints. Typical usage is shown here.
Ellipse2D circle = new Ellipse2D.Float(…);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHints(…);
g2d.fill(circle);
Because various RenderingHints are implementation dependent, the example below will let you evaluate the effects individually.
import java.awt.BasicStroke;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.Ellipse2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
* @see https://stackoverflow.com/a/38669048/230513
*/
public class Test {
private void display() {
JFrame f = new JFrame("Test");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(new JPanel() {
private static final int N = 8;
private final Ellipse2D ellipse = new Ellipse2D.Float();
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL,
RenderingHints.VALUE_STROKE_PURE);
g2d.setStroke(new BasicStroke(N));
ellipse.setFrame(N, N, getWidth() - 2 * N, getHeight() - 2 * N);
g2d.draw(ellipse);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(320, 240);
}
});
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Test()::display);
}
}
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