如何使用 RescaleOp 设置图像的大小 [英] How to setSize of image using RescaleOp

问题描述

我正在编写一个测试应用程序.要为图像设置 Alpha，我使用了paintComponent 方法.观看下一个片段...

I am writing a test app. To set Alpha for image I use paintComponent method. Watch next snippet...

    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;}
}

如你所见，

g2d.drawImage(this.bImage, rop, 0, 0);

g2d.drawImage(this.bImage, rop, 0, 0);

不允许像使用 g.drawImage(bImage, 0, 0,width,height, null) 一样设置宽度和高度；

does not allow to set width and height as if I use g.drawImage(bImage, 0, 0,width,height, null);

那么问题是...在这种情况下如何为 bImage 设置宽度和高度?

So the question is... How to set width and height for bImage in this case?

感谢任何有用的评论

安德鲁

推荐答案

先filter()，如图此处，然后使用 drawImage() 或 AffineTransformOp 缩放，如此处所示.

First filter(), as shown here, and then scale using drawImage() or AffineTransformOp, as shown here.

附录:或者，您可以先缩放图像(使用上述任一方法)，然后然后使用您的RescaleOp 在 drawImage().

Addendum: Alternatively, you can scale the image first (using either approach above) and then use your RescaleOp in drawImage().

顺便说一句，RescaleOp 缩放图像的色带；它不会改变图像的尺寸.为避免混淆，维度缩放有时称为重新采样.

As an aside, RescaleOp scales the image's color bands; it does not change the image's dimensions. To avoid confusion, dimensional scaling is sometimes called resampling.

附录:这是使用 drawImage() 重新采样和 RescaleOp 调整图像的 alpha.

Addendum: Here's an example of using drawImage() to resample and RescaleOp to adjust the alpha of an image.

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);
    }
}

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