在 JPanel 或 JLabel 中调整图像大小并显示，而不会损失质量

我正在开发一个java程序来使用网络摄像头在注册时捕获员工图像。我可以毫无问题地获取图片，并将其保存在我的 C: 驱动器中，但在检索图像时，标签上仅显示图像的一部分。有没有办法在保存之前调整 JPEG 的大小？或者在显示之前？就像在不损失质量的情况下缩小它一样。

好吧，伙计们......这里是：-我已经按照我使用代码的方式对代码进行了评论。

//This method will capture the image from the interface and save it under the unique employee ID
public String captureImage(int picId){

    FrameGrabbingControl ControlFG = (FrameGrabbingControl)

    broadcast.getControl("javax.media.control.FrameGrabbingControl");

    Buffer buffer = ControlFG.grabFrame();

    BufferToImage image = new BufferToImage((VideoFormat)buffer.getFormat());

    img = image.createImage(buffer);

    path="c:\\employee"+picId+".jpg";

    saveJPG(img,path);//method will save the image

    return path;

}

 public void saveJPG(Image img, String s){***//method will save the image***

    System.out.println(s);

    BufferedImage bi = new BufferedImage(img.getWidth(null), img.getHeight(null),

    BufferedImage.TYPE_INT_RGB);

    Graphics2D g2 = bi.createGraphics();

    g2.drawImage(img,null,null);

    FileOutputStream out = null;
    try{

    out = new FileOutputStream(s);

    }
    catch (java.io.FileNotFoundException io){

    System.out.println("File Not Found");
    }

    JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);

    JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bi);

    param.setQuality(0.5f,false);

    encoder.setJPEGEncodeParam(param);

    try
    {
    encoder.encode(bi);
    out.close();
    }

    catch (java.io.IOException io)
    {
    System.out.println("IOException");
    }
    }

也许我可以在保存时缩放图像..以便我可以检索缩放后的图像..

当然，您可以通过多种不同的方式调整图像大小，例如Image#getScaledInstance(int width,int height,int hints) http://docs.oracle.com/javase/7/docs/api/java/awt/Image.html#getScaledInstance%28int,%20int,%20int%29, but 这有其危险 http://today.java.net/pub/a/today/2007/04/03/perils-of-image-getscaledinstance.html.

主要问题是：

Image.getScaledInstance() 不会返回完成的缩放图像。它 当图像像素变大时，将大部分缩放工作留到以后进行 被使用。

我不建议使用它但是here http://www.java2s.com/Code/JavaAPI/java.awt/ImagegetScaledInstanceintwidthintheightinthints.htm是一个很好的例子。

或者，您可以使用此方法：

import javax.swing.ImageIcon;
import java.awt.image.BufferedImage;
import java.awt.Image;
import java.awt.Color;
import java.awt.Graphics2D;
import java.io.File;
import javax.imageio.ImageIO;
import java.awt.RenderingHints;

public class ImgUtils {

public BufferedImage scaleImage(int WIDTH, int HEIGHT, String filename) {
    BufferedImage bi = null;
    try {
        ImageIcon ii = new ImageIcon(filename);//path to image
        bi = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = (Graphics2D) bi.createGraphics();
        g2d.addRenderingHints(new RenderingHints(RenderingHints.KEY_RENDERING,RenderingHints.VALUE_RENDER_QUALITY));
        g2d.drawImage(ii.getImage(), 0, 0, WIDTH, HEIGHT, null);
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
    return bi;
}

}

你会这样使用它：

final BufferedImage img=new ImgUtils().scaleImage(200,200,"c:/test.jpg");
//create label with image as background
JLabel label=new JLabel(new ImageIcon((Image)img));

UPDATE:

这是我做的一个小例子：

import java.awt.BorderLayout;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;

public class JavaApplication117 {

    //change this to your own
    static String filename="c:/test.jpg";

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new JavaApplication117().createAndShowUI();
            }
        });
    }

    private void createAndShowUI() {
        JFrame frame = new JFrame("Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        initComponents(frame);

        frame.setResizable(false);
        frame.pack();
        frame.setVisible(true);
    }

    private void initComponents(JFrame frame) {
        final BufferedImage img = new ImgUtils().scaleImage(200, 200, filename);
        //create label with image as background
        JLabel label = new JLabel(new ImageIcon((Image) img));

        frame.getContentPane().add(label, BorderLayout.CENTER);
    }
}

class ImgUtils {

    public BufferedImage scaleImage(int WIDTH, int HEIGHT, String filename) {
        BufferedImage bi = null;
        try {
            ImageIcon ii = new ImageIcon(filename);//path to image
            bi = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
            Graphics2D g2d = (Graphics2D) bi.createGraphics();
            g2d.addRenderingHints(new RenderingHints(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY));
            g2d.drawImage(ii.getImage(), 0, 0, WIDTH, HEIGHT, null);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
        return bi;
    }
}

参考：

• java getScaledInstance 调整图像大小 https://stackoverflow.com/questions/7252983/resizing-image-java-getscaledinstance