我有一个扩展JPanel的组件。它在paintComponent方法的每次调用中都将自己保存为bufferedimage。组件不是完全透明的,只有它的背景。问题是背景不透明。我正在使用setOpaque(false);
这是我的相关代码;
private BufferedImage bufImage = null;
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
// if first time call
if (bufImage == null) {
int w = this.getWidth();
int h = this.getHeight();
bufImage = (BufferedImage)this.createImage(w, h);
}
g2.drawImage(bufImage, null, 0, 0);
// draw sth
g2.draw(sth);
}
-
我也试过
bufImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
而不是
bufImage = (BufferedImage)this.createImage(w, h);
当我这样做时;背景transperancy工作,但我只能画白色。我不知道是什么原因造成的。
注意: 我使用该代码检查它是否正常工作;
File outputfile = new File("saved.png");
ImageIO.write(bufImage, "png", outputfile);
saved.png有透明背景,但图纸只有白色。
这是组件,只允许用鼠标绘制矩形;
class PaintPanel extends JPanel implements MouseListener, MouseMotionListener {
private BufferedImage _bufImage = null;
private boolean dragging = false;
private Point _start = null, _end = null;
public PaintPanel() {
setOpaque(false);
this.addMouseListener(this);
this.addMouseMotionListener(this);
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
if (_bufImage == null) {
int w = this.getWidth();
int h = this.getHeight();
_bufImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
//_bufImage = (BufferedImage)this.createImage(w, h);
}
g2.drawImage(_bufImage, null, 0, 0);
if (dragging) {
drawCurrentShape(g2);
}
}
private void drawCurrentShape(Graphics2D g2) {
int startx = (int) _start.getX();
int starty = (int) _start.getY();
int stopx = (int) _end.getX();
int stopy = (int) _end.getY();
int width = Math.abs(startx - stopx);
int height = Math.abs(starty - stopy);
int x = startx, y = starty;
if(x > stopx)
x = stopx;
if(y > stopy)
y = stopy;
Rectangle r = new Rectangle(x, y, width, height);
g2.draw(r);
}
public void mousePressed(MouseEvent e) {
dragging = true;
_start = e.getPoint();
_end = _start;
}
public void mouseDragged(MouseEvent e) {
_end = e.getPoint();
this.repaint();
}
public void mouseReleased(MouseEvent e) {
_end = e.getPoint();
if (dragging) {
dragging = false;
drawCurrentShape(_bufImage.createGraphics());
this.repaint();
}
}
public void mouseMoved (MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited (MouseEvent e) {}
public void mouseClicked(MouseEvent e) {}
}
答案 0 :(得分:2)
试试这个:
bufImage = new BufferedImage(w,h,java.awt.image.BufferedImage.TYPE_INT_ARGB);
Graphics2D graphics = bufImage.createGraphics();
this.print(graphics);
graphics.dispose();
关键是使用print()
编辑:我尝试了以下内容,透明度就像一个魅力:
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Test2 {
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JPanel p = new JPanel();
p.setPreferredSize(new Dimension(400, 400));
p.setOpaque(false);
JButton button = new JButton("Hello world");
p.add(button);
frame.add(p);
frame.pack();
frame.setVisible(true);
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
BufferedImage bufImage = new BufferedImage(p.getWidth(), p.getHeight(), java.awt.image.BufferedImage.TYPE_INT_ARGB);
Graphics2D graphics = bufImage.createGraphics();
p.print(graphics);
graphics.dispose();
try {
ImageIO.write(bufImage, "png", new File("d:/tmp/tmp.png"));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
}
答案 1 :(得分:1)
createImage(w, h)
将创建具有指定宽度和高度的“空白”图像。话虽这么说,您需要做的是在createGraphics
实例上调用BufferedImage
并直接绘制到返回的Graphics
对象。