[英]Component with transparent background to BufferedImage?
我有一個組件擴展了JPanel。 每次調用paintComponent方法時,它將自身保存為bufferedimage。 組件不是完全透明的,只有它的背景。 問題是背景不透明。 我正在使用setOpaque(false);
這是我的相關代碼;
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);
}
-
我也試過了
bufImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
代替
bufImage = (BufferedImage)this.createImage(w, h);
當我這樣做; 背景透明效果很好,但是我只能用白色繪制。 我不知道是什么原因造成的。
注意:我使用該代碼檢查它是否正常工作;
File outputfile = new File("saved.png");
ImageIO.write(bufImage, "png", outputfile);
saved.png具有透明背景,但工程圖只有白色。
這是組件,只允許用鼠標繪制矩形;
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) {}
}
嘗試這個:
bufImage = new BufferedImage(w,h,java.awt.image.BufferedImage.TYPE_INT_ARGB);
Graphics2D graphics = bufImage.createGraphics();
this.print(graphics);
graphics.dispose();
關鍵是要使用print()
編輯:我嘗試了以下和透明的工作就像一個魅力:
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();
}
}
});
}
}
createImage(w, h)
將創建具有指定寬度和高度的“空白”圖像。 話雖這么說,你需要做的是在BufferedImage
實例上調用createGraphics
並直接繪制到返回的Graphics
對象。
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