我正在写一个自定义渲染的程序，并需要渲染带边框的矩形。我决定简单地调用graphics2D.fillRect()，切换到边框颜色，并调用graphics2D.drawRect()。但是，即使我使用相同的坐标和大小背靠背进行调用，但当我绘制的颜色是半透明(具有alpha)时，fillRect()并不总是填充drawRect包含的整个区域。此外，由fillRect()绘制的区域有时在drawRect()所包含的区域之外。为什么这两种方法在不同的地方绘制不同颜色的东西？Java的graphics2D fillRect不能正常工作与半透明的颜色

下面是一个演示问题的例子。点击窗口中的鼠标将在用alpha和不用绘制填充之间切换。请注意，当使用alpha绘图时，矩形底部有一行像素为白色，但在绘制不带alpha的绘图时，该行像素不在此处。

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);

}

}

+0

似乎是Java 2D中的一个bug。 –

2013-05-02 15:31:08