我正在尝试用java将图像绘制到JPanel,并且我把它记下来了,很好。我现在的问题是我试图让它缩放到窗口的整个大小,但它没有这样做。我尝试过一些方法,它们要么使图像消失,要么根本没有图形变化。
我目前正在使用的代码:
class ImagePanel extends JPanel {
private static final long serialVersionUID = 1L;
private Image img;
public ImagePanel(String img) {
this(new ImageIcon(img).getImage());
}
public ImagePanel(Image img) {
this.img = img;
Dimension size = new Dimension(img.getWidth(null), img.getHeight(null));
setPreferredSize(size);
setMinimumSize(size);
setMaximumSize(size);
setSize(size);
setLayout(null);
}
public void paintComponent(Graphics g) {
g.drawImage(img, 0, 0, null);
}
}
全班:http://pastebin.com/CpcBt2j8
我尝试在img = img.getScaledInstance(440, 440, Image.SCALE_SMOOTH)
添加这样的代码,但这没有任何效果。我还尝试制作一个名为scaledImg
的新图像,并将img
的getScaledInstance
值设置为该图像,这将完全从显示中删除图像。
如何使图像缩放到我想要的完整尺寸?
我想"最简单的"方法是做这样的事情......
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Image scaled = img.getScaledInstance(getWidth(), getHeight(), Image.SCALE_SMOOTH);
g.drawImage(scaled, 0, 0, null);
}
这是低效的,昂贵的,并且可能无法产生预期的结果
首先,看看 The Perils of Image.getScaledInstance()
您还可以查看 Java:维护 JPanel 背景图像的纵横比,了解有关维护图像和缩放以适合与缩放以填充的更多详细信息。
我还会缓冲结果,这样您就不会在可能经常被捕获的paintComponent
方法中重复缩放图像......
使用工作示例更新
这对我来说很好用...
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.HeadlessException;
import java.awt.Image;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestImagePane {
public static void main(String[] args) {
new TestImagePane();
}
public TestImagePane() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
try {
Image img = null;
img = ImageIO.read(new File("/path/to/image"));
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new ImagePanel(img));
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
} catch (IOException | HeadlessException exp) {
exp.printStackTrace();
}
}
});
}
class ImagePanel extends JPanel {
private static final long serialVersionUID = 1L;
private Image img;
private Image scaled;
public ImagePanel(String img) {
this(new ImageIcon(img).getImage());
}
public ImagePanel(Image img) {
this.img = img;
}
@Override
public void invalidate() {
super.invalidate();
int width = getWidth();
int height = getHeight();
if (width > 0 && height > 0) {
scaled = img.getScaledInstance(getWidth(), getHeight(), Image.SCALE_SMOOTH);
}
}
@Override
public Dimension getPreferredSize() {
return img == null ? new Dimension(200, 200) : new Dimension(img.getWidth(this), img.getHeight(this));
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(scaled, 0, 0, null);
}
}
}
要动态缩放图像,请使用:
//g.drawImage(img, 0, 0, null);
g.drawImage(image, 0, 0, getWidth(), getHeight(), null);
请参阅背景面板以获取完整的实现以及切片功能。