如何使用RescaleOp设置图像的大小

我正在写一个testing应用程序。 为图像设置Alpha我使用paintComponent方法。 观看下一个片段…

public class TestImage extends JLabel{ public void paintComponent( Graphics g ) { super.paintComponent( g ); Graphics2D g2d=(Graphics2D)g; g2d.drawImage(this.bImage, rop, 0, 0); } public void setRescaleOp(RescaleOp rop){this.rop=rop;} } 

如你看到的，

g2d.drawImage（this.bImage，rop，0，0）;

不允许设置宽度和高度，就像我使用g.drawImage（bImage，0，0，width，height，null）;

所以问题是…在这种情况下如何设置bImage的宽度和高度？

任何有用的评论表示赞赏

安德鲁

Answer 1

首先filter() ，如下所示，然后使用drawImage()或AffineTransformOp进行缩放，如下所示。

附录：或者，您可以先缩放图像（使用上述任一方法）， 然后在drawImage()使用RescaleOp 。

RescaleOp一下， RescaleOp缩放图像的颜色带; 它不会更改图像的尺寸。 为了避免混淆，尺寸缩放有时称为重采样 。

附录：下面是使用drawImage()重新采样和RescaleOp调整图像的alpha值的RescaleOp 。

 import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.image.BufferedImage; import java.awt.image.RescaleOp; import javax.swing.ImageIcon; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JSlider; import javax.swing.event.ChangeEvent; import javax.swing.event.ChangeListener; /** * @see https://stackoverflow.com/questions/5838842 * @see https://stackoverflow.com/questions/5864490 */ public class AlphaTest { private static void display() { JFrame f = new JFrame("AlphaTest"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ImageIcon icon = new ImageIcon("image.jpg"); final AlphaPanel ip = new AlphaPanel(icon, 0.75); final JSlider slider = new JSlider(); slider.addChangeListener(new ChangeListener() { @Override public void stateChanged(ChangeEvent e) { int v = slider.getValue(); ip.setAlpha((float) v / slider.getMaximum()); ip.repaint(); } }); f.add(ip, BorderLayout.CENTER); f.add(slider, BorderLayout.SOUTH); f.pack(); f.setLocationRelativeTo(null); f.setVisible(true); } public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { display(); } }); } } class AlphaPanel extends JPanel { private BufferedImage bi; private float[] scales = {1f, 1f, 1f, 0.5f}; private float[] offsets = new float[4]; private RescaleOp rop; public AlphaPanel(ImageIcon icon, double scale) { int width = (int) (scale * icon.getIconWidth()); int height = (int) (scale * icon.getIconHeight()); this.setPreferredSize(new Dimension(width, height)); this.bi = new BufferedImage( width, height, BufferedImage.TYPE_INT_ARGB); this.bi.createGraphics().drawImage( icon.getImage(), 0, 0, width, height, null); rop = new RescaleOp(scales, offsets, null); } @Override public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g; g2d.drawImage(bi, rop, 0, 0); } public void setAlpha(float alpha) { this.scales[3] = alpha; this.rop = new RescaleOp(scales, offsets, null); } }