我正在寫一個自定義渲染的程序,並需要渲染帶邊框的矩形。我決定簡單地調用graphics2D.fillRect(),切換到邊框顏色,並調用graphics2D.drawRect()。但是,即使我使用相同的座標和大小背靠背進行調用,但當我繪製的顏色是半透明(具有alpha)時,fillRect()並不總是填充drawRect包含的整個區域。此外,由fillRect()繪製的區域有時在drawRect()所包含的區域之外。爲什麼這兩種方法在不同的地方繪製不同顏色的東西?Java的graphics2D fillRect不能正常工作與半透明的顏色
下面是一個演示問題的例子。點擊窗口中的鼠標將在用alpha和不用繪製填充之間切換。請注意,當使用alpha繪圖時,矩形底部有一行像素爲白色,但在繪製不帶alpha的繪圖時,該行像素不在此處。
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.geom.AffineTransform;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class ColorWithAlpha extends JPanel {
private boolean hasAlpha = true;
private static final long serialVersionUID = 1L;
/**
* @param args
*/
public static void main(String[] args) {
// setup a basic frame with a ColorWithAlpha in it
JFrame frame = new JFrame();
JPanel panel = new ColorWithAlpha();
panel.setPreferredSize(new Dimension(500, 500));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(panel);
frame.pack();
frame.show();
}
public ColorWithAlpha() {
super();
setBackground(Color.WHITE);
this.addMouseListener(new MouseListener() {
@Override
public void mouseClicked(MouseEvent arg0) {
// when the user clicks their mouse, toggle whether we are drawing a color with alhpa or without.
hasAlpha = !hasAlpha;
ColorWithAlpha.this.repaint();
}
@Override
public void mouseEntered(MouseEvent arg0) {}
@Override
public void mouseExited(MouseEvent arg0) {}
@Override
public void mousePressed(MouseEvent arg0) {}
@Override
public void mouseReleased(MouseEvent arg0) {}
});
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Color color = new Color(100, 100, 250);// this color doesnt have an alpha component
// some coordinates that demonstrate the bug. Not all combinations of x,y,width,height will show the bug
int x = -900;
int y = 1557;
int height = 503;
int width = 502;
if (hasAlpha) { // toggle between drawing with alpha and without
color = new Color(200, 100, 250, 100);
}
Graphics2D g2 = (Graphics2D) g;
// this is the transform I was using when I found the bug.
g2.setTransform(new AffineTransform(0.160642570281124, 0.0, 0.0, -0.160642570281124, 250.0, 488.0));
g2.setColor(color);
g2.fillRect(x, y, width, height);
g2.setColor(Color.DARK_GRAY);
g2.setStroke(new BasicStroke(8f));
g2.drawRect(x, y, width, height);
}
}
似乎是Java 2D中的一個bug。 – lbalazscs 2013-05-02 15:31:08