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java PC端如何对用户头像处理成圆形头像啊?
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看看这个,你把图片修改成圆角的就行.

主要原理是这个:可以看看这本书:  Filthy Rich Clients (Java极富客户端效果)

 Composite oldComposite = g2.getComposite();
   g2.setComposite(AlphaComposite.SrcIn);

   SrcOver: 其运算公式为Ar = As + Ad * (1 - As), Cr = Cs + Cd * (1 - As), 其中Ar为结果Alpha,As表示源图像的Alpha,As为目的图像的Alpha,Cr表示(RGB)中每个通道的结果值,Cs为源图像中(RGB)单个通道的值,Cd为目的图像的单个通道值。
一般的用法为在目的图像上绘制半透明的源图像。
SrcIn:位于目的地内部的那部分源代替目的地,位于目的地之外的那部分源丢弃掉。

 

 

/*
 * Copyright (c) 2007, Romain Guy
 * All rights reserved.
 *
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 * modification, are permitted provided that the following conditions
 * are met:
 *
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 *     from this software without specific prior written permission.
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 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 * (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.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Composite;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JCheckBox;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

/**
 *
 * @author Romain Guy
 */
public class SourceInDemo extends JFrame {
    private JCheckBox shadow;
    
    public SourceInDemo() {
        super("Source In");
        
        add(new ImageViewer(), BorderLayout.CENTER);
        JPanel panel = new JPanel(new FlowLayout(FlowLayout.LEADING));
        panel.add(shadow = new JCheckBox("Drop Shadow"));
        shadow.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent changeEvent) {
                repaint();
            }
        });
        add(panel, BorderLayout.SOUTH);
        
        setSize(350, 250);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    
    private class ImageViewer extends JComponent {
        private BufferedImage image, landscape;

        private ImageViewer() {
            try {
                image = ImageIO.read(getClass().getResource("picture.png"));
                landscape = ImageIO.read(getClass().getResource("landscape.jpg"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        
        @Override
        protected void paintComponent(Graphics g) {
            BufferedImage temp = new BufferedImage(getWidth(), getHeight(),
                BufferedImage.TYPE_INT_ARGB);
            Graphics2D g2 = temp.createGraphics();
            
            if (shadow.isSelected()) {
                int x = (getWidth() - image.getWidth()) / 2;
                int y = (getHeight() - image.getHeight()) / 2;
                g2.drawImage(image, x + 4, y + 10, null);

                Composite oldComposite = g2.getComposite();
                g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_IN, 0.75f));
                g2.setColor(Color.BLACK);
                g2.fillRect(0, 0, getWidth(), getHeight());
                g2.setComposite(oldComposite);
                g2.drawImage(image, x, y, null);
            } else {
                int x = (getWidth() - image.getWidth()) / 2;
                int y = (getHeight() - image.getHeight()) / 2;
                g2.drawImage(image, x, y, null);

                Composite oldComposite = g2.getComposite();
                g2.setComposite(AlphaComposite.SrcIn);
                x = (getWidth() - landscape.getWidth()) / 2;
                y = (getHeight() - landscape.getHeight()) / 2;
                g2.drawImage(landscape, x, y, null);
                g2.setComposite(oldComposite);
            }
            
            g2.dispose();
            g.drawImage(temp, 0, 0, null);
        }
    }
    
    public static void main(String... args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new SourceInDemo().setVisible(true);
            }
        });
    }
}

 

肯定是显示在前端页面上,前端写页面的时候只用写个css

.div{ width: 100px; height: 100px; border-radius: 100px; overflow: hidden;}
.div img{width: 100%; height: 100%;}

 应该就可以了  后台只用切换img路径;

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