Java 覆盖图片

我在学校学AP计算机科学已经三个半月了。我的老师要我们拍一张照片，在上面做一个法国国旗滤镜，我做到了

private void france(int w, int h, int x, int y, int pixel, int alpha, int red, int green, int blue){
    int ft = w/3;
    int lt = w-ft;
    if(x >= lt){
        red = red + 50;
        if(red >= 255){
            red = 255;
        }
    }
    if(x <= ft){
        blue = blue + 50;
        if(blue >= 255){
            blue = 255;
    }
}
    if(x > ft && x < lt){
        blue = blue + 50;
        if(blue >= 255){
            blue = 255;
        }
        red = red + 50;
        if(red >= 255){
            red = 255;
        }
        green = green + 50;
        if(green >= 255){
            green = 255;
        }
    }

    pixel = (alpha<<24) | (red<<16) | (green<<8) | blue;
    img.setRGB(x, y, pixel);
}

private void france（整数w、整数h、整数x、整数y、整数像素、整数alpha、整数红色、整数绿色、整数蓝色）{
int ft=w/3；
int lt=w-ft；
如果（x>=lt）{
红色=红色+50；
如果（红色>=255）{
红色=255；
}
}
如果（x=255）{
蓝色=255；
}
}
如果（x>ft&&x=255）{
蓝色=255；
}
红色=红色+50；
如果（红色>=255）{
红色=255；
}
绿色=绿色+50；
如果（绿色>=255）{
绿色=255；
}
}
像素=（alpha有一种方法可以在任何东西上添加（图像的）过滤器，同时可以设置其透明度

因此，您已经了解了如何加载图像，因此我将在这里举一个示例，展示一个swing小程序，它将放置一个带有滑块的覆盖层来调整透明度。此外，如果您想实际试用此代码以了解其工作原理，您将需要一个图像文件

/*
 * Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle or the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.imageio.*;
import javax.swing.*;
import javax.swing.event.*;

class SeeThroughComponent extends Component {

    private BufferedImage bi;
    float[] scales = { 1f, 1f, 1f, 0.5f };
    float[] offsets = new float[4];
    RescaleOp rop;

    public SeeThroughComponent(URL imageSrc) {
        try {
            BufferedImage img = ImageIO.read(imageSrc);
            int w = img.getWidth(null);
            int h = img.getHeight(null);
            bi = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
            Graphics g = bi.getGraphics();
            g.drawImage(img, 0, 0, null);

        } catch (IOException e) {
            System.out.println("Image could not be read");
//            System.exit(1);
        }
        setOpacity(0.5f);
    }

    public Dimension getPreferredSize() {
        return new Dimension(bi.getWidth(null), bi.getHeight(null));
    }

    public void setOpacity(float opacity) {
        scales[3] = opacity;
        rop = new RescaleOp(scales, offsets, null);
    }

    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D)g;
        g2d.setColor(Color.white);
        g2d.fillRect(0,0, getWidth(), getHeight());
        g2d.setColor(Color.black);
        g2d.setFont(new Font("Dialog", Font.BOLD, 24));
        g2d.drawString("Java 2D is great!", 10, 80);
        g2d.drawImage(bi, rop, 0, 0);
    }
}

public class SeeThroughImageApplet extends JApplet {

    static String imageFileName = "examples/duke_skateboard.jpg";
    private URL imageSrc;

    public SeeThroughImageApplet () {
    }

    public SeeThroughImageApplet (URL imageSrc) {
        this.imageSrc = imageSrc;
    }

    public void init() {
        try {
            imageSrc = new URL(getCodeBase(), imageFileName);
        } catch (MalformedURLException e) {
        }
        buildUI();
    }

    public void buildUI() {
        final SeeThroughComponent st = new SeeThroughComponent(imageSrc);
        add("Center", st);
        JSlider opacitySlider = new JSlider(0, 100);
        opacitySlider.addChangeListener(new ChangeListener() {
                public void stateChanged(ChangeEvent e) {
                    JSlider slider = (JSlider)e.getSource();
                    st.setOpacity(slider.getValue()/100f);
                    st.repaint();
                };
            });
        Dimension size = st.getPreferredSize();
        Dimension sliderSize = opacitySlider.getPreferredSize();
        resize(size.width, size.height+sliderSize.height);
        add("South", opacitySlider);
    }

    public static void main(String s[]) {
        JFrame f = new JFrame("See Through Image");
        f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {System.exit(0);}
        });
        URL imageSrc = null;
        try {
             imageSrc = ((new File(imageFileName)).toURI()).toURL();
        } catch (MalformedURLException e) {
        }
        SeeThroughImageApplet sta = new SeeThroughImageApplet(imageSrc);
        sta.buildUI();
        f.add("Center", sta);
        f.pack();
        f.setVisible(true);
    }
}