第九周作业 实现图片压缩

背景：

     现在的网站为提升与用户的交互，上传文件是难免的，用户上传的图片多种多样，方面有文件大小，尺寸，等等为了处理此类的问题。服务器端必须实现对用户上传的图片进行相应的处理以适应网站的需要。其中最重要的就是压缩图片，将用户上传的图片压缩成宽度等比里大小的图片。

实现方式：

    java实现图片压缩：java有实现图片压缩的jar包，压缩的源文件的格式包括bmp,jig,jpg等等，还有的是压缩动态图片jar，但要购买。价格是好像要几百块人民币。接下里演示的是一个实现简单图片压缩的代码，不包括动态图片，免费的。

代码不是我写的，我在一个论坛看到的。但我测试过可以实现图片的压缩，可以随便看一下。

package cn.hp.utils;

import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.MediaTracker;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.awt.image.ConvolveOp;
import java.awt.image.Kernel;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGEncodeParam;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

/**
 * 图像压缩工具
 * @author lihuoming@sohu.com
 *
 */
public class ImageSizer {
    public static final MediaTracker tracker = new MediaTracker(new Component() {
        private static final long serialVersionUID = 1234162663955668507L;} 
    );
    /**
     * @param originalFile 原图像
     * @param resizedFile 压缩后的图像
     * @param width 图像宽
     * @param format 图片格式 jpg, png, gif(非动画)
     * @throws IOException
     */
    public static void resize(File originalFile, File resizedFile, int width, String format) throws IOException {
        if(format!=null && "gif".equals(format.toLowerCase())){
            resize(originalFile, resizedFile, width, 1);
            return;
        }
        FileInputStream fis = new FileInputStream(originalFile);
        ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
        int readLength = -1;
        int bufferSize = 1024;
        byte bytes[] = new byte[bufferSize];
        while ((readLength = fis.read(bytes, 0, bufferSize)) != -1) {
            byteStream.write(bytes, 0, readLength);
        }
        byte[] in = byteStream.toByteArray();
        fis.close();
        byteStream.close();
        
        Image inputImage = Toolkit.getDefaultToolkit().createImage( in );
        waitForImage( inputImage );
        int imageWidth = inputImage.getWidth( null );
        if ( imageWidth < 1 ) 
           throw new IllegalArgumentException( "image width " + imageWidth + " is out of range" );
        int imageHeight = inputImage.getHeight( null );
        if ( imageHeight < 1 ) 
           throw new IllegalArgumentException( "image height " + imageHeight + " is out of range" );
        
        // Create output image.
        int height = -1;
        double scaleW = (double) imageWidth / (double) width;
        double scaleY = (double) imageHeight / (double) height;
        if (scaleW >= 0 && scaleY >=0) {
            if (scaleW > scaleY) {
                height = -1;
            } else {
                width = -1;
            }
        }
        Image outputImage = inputImage.getScaledInstance( width, height, java.awt.Image.SCALE_DEFAULT);
        checkImage( outputImage );        
        encode(new FileOutputStream(resizedFile), outputImage, format);        
    }    

    /** Checks the given image for valid width and height. */
    private static void checkImage( Image image ) {
       waitForImage( image );
       int imageWidth = image.getWidth( null );
       if ( imageWidth < 1 ) 
          throw new IllegalArgumentException( "image width " + imageWidth + " is out of range" );
       int imageHeight = image.getHeight( null );
       if ( imageHeight < 1 ) 
          throw new IllegalArgumentException( "image height " + imageHeight + " is out of range" );
    }

    /** Waits for given image to load. Use before querying image height/width/colors. */
    private static void waitForImage( Image image ) {
       try {
          tracker.addImage( image, 0 );
          tracker.waitForID( 0 );
          tracker.removeImage(image, 0);
       } catch( InterruptedException e ) { e.printStackTrace(); }
    } 

    /** Encodes the given image at the given quality to the output stream. */
    private static void encode( OutputStream outputStream, Image outputImage, String format ) 
       throws java.io.IOException {
       int outputWidth  = outputImage.getWidth( null );
       if ( outputWidth < 1 ) 
          throw new IllegalArgumentException( "output image width " + outputWidth + " is out of range" );
       int outputHeight = outputImage.getHeight( null );
       if ( outputHeight < 1 ) 
          throw new IllegalArgumentException( "output image height " + outputHeight + " is out of range" );

       // Get a buffered image from the image.
       BufferedImage bi = new BufferedImage( outputWidth, outputHeight,
          BufferedImage.TYPE_INT_RGB );                                                   
       Graphics2D biContext = bi.createGraphics();
       biContext.drawImage( outputImage, 0, 0, null );
       ImageIO.write(bi, format, outputStream);
       outputStream.flush();      
    } 
    
    /**
     * 缩放gif图片
     * @param originalFile 原图片
     * @param resizedFile 缩放后的图片
     * @param newWidth 宽度
     * @param quality 缩放比例 (等比例)
     * @throws IOException
     */
    private static void resize(File originalFile, File resizedFile, int newWidth, float quality) throws IOException {
        if (quality < 0 || quality > 1) {
            throw new IllegalArgumentException("Quality has to be between 0 and 1");
        } 
        ImageIcon ii = new ImageIcon(originalFile.getCanonicalPath());
        Image i = ii.getImage();
        Image resizedImage = null; 
        int iWidth = i.getWidth(null);
        int iHeight = i.getHeight(null); 
        if (iWidth > iHeight) {
            resizedImage = i.getScaledInstance(newWidth, (newWidth * iHeight) / iWidth, Image.SCALE_SMOOTH);
        } else {
            resizedImage = i.getScaledInstance((newWidth * iWidth) / iHeight, newWidth, Image.SCALE_SMOOTH);
        } 
        // This code ensures that all the pixels in the image are loaded.
        Image temp = new ImageIcon(resizedImage).getImage(); 
        // Create the buffered image.
        BufferedImage bufferedImage = new BufferedImage(temp.getWidth(null), temp.getHeight(null),
                                                        BufferedImage.TYPE_INT_RGB); 
        // Copy image to buffered image.
        Graphics g = bufferedImage.createGraphics(); 
        // Clear background and paint the image.
        g.setColor(Color.white);
        g.fillRect(0, 0, temp.getWidth(null), temp.getHeight(null));
        g.drawImage(temp, 0, 0, null);
        g.dispose(); 
        // Soften.
        float softenFactor = 0.05f;
        float[] softenArray = {0, softenFactor, 0, softenFactor, 1-(softenFactor*4), softenFactor, 0, softenFactor, 0};
        Kernel kernel = new Kernel(3, 3, softenArray);
        ConvolveOp cOp = new ConvolveOp(kernel, ConvolveOp.EDGE_NO_OP, null);
        bufferedImage = cOp.filter(bufferedImage, null); 
        // Write the jpeg to a file.
        FileOutputStream out = new FileOutputStream(resizedFile);        
        // Encodes image as a JPEG data stream
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); 
        JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bufferedImage); 
        param.setQuality(quality, true); 
        encoder.setJPEGEncodeParam(param);
        encoder.encode(bufferedImage);
    }
}

简单的单元测试类。

package junit.test;

import java.io.File;
import java.io.IOException;

import org.junit.Test;

import cn.hp.utils.ImageSizer;


public class ImageTest {
    @Test
    public void createImage(){
        try {
            ImageSizer.resize(new File("d:\12.jpg"), new File("d:\testabc.jpg"), 200, "jpg");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

发现经过压缩后的图片大小变化了。

压缩前的图片大小

压缩后的图片大小