图片压缩，只压缩大小，不压缩宽高

图片压缩，这里我把图片压缩在64kb以内来满足业务需求，利用了while循环！

package test;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.io.File;
import java.io.FileOutputStream;

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;

import org.apache.commons.lang.StringUtils;
public class ImageTest {
	public static void main(String[] s)
    {	File file = new File("C:/Users/Administrator.USER-20140717GA/Desktop/2.jpg");
    	double b = file.length()/(double)1024;
    	double a = 64/b;
    	System.out.println(b+"KB");
    	System.out.println(a);
    	System.out.println("============================================================="); 
    	double image = compressPic("C:/Users/Administrator.USER-20140717GA/Desktop/2.jpg", "C:/Users/Administrator.USER-20140717GA/Desktop/2.jpg",a);
        while(image>64){
        	image = compressPic("C:/Users/Administrator.USER-20140717GA/Desktop/2.jpg", "C:/Users/Administrator.USER-20140717GA/Desktop/2.jpg",a-0.1);
        }
        File file1 = new File("C:/Users/Administrator.USER-20140717GA/Desktop/2.jpg");
    	double b1 = file1.length()/(double)1024;
    	System.out.println(b1+"KB");
    }
    

    public static double compressPic(String srcFilePath, String descFilePath,double a)
    {
        File file = null;
        BufferedImage src = null;
        FileOutputStream out = null;
        ImageWriter imgWrier;
        ImageWriteParam imgWriteParams;

        // 指定写图片的方式为 jpg
        imgWrier = ImageIO.getImageWritersByFormatName("jpg").next();
        imgWriteParams = new javax.imageio.plugins.jpeg.JPEGImageWriteParam(null);
        // 要使用压缩，必须指定压缩方式为MODE_EXPLICIT
        imgWriteParams.setCompressionMode(imgWriteParams.MODE_EXPLICIT);
        // 这里指定压缩的程度，参数qality是取值0~1范围内，
        imgWriteParams.setCompressionQuality((float)a);
        imgWriteParams.setProgressiveMode(imgWriteParams.MODE_DISABLED);
        ColorModel colorModel = ColorModel.getRGBdefault();
        // 指定压缩时使用的色彩模式
        imgWriteParams.setDestinationType(new javax.imageio.ImageTypeSpecifier(colorModel, colorModel
                .createCompatibleSampleModel(16, 16)));

        try
        {
            if(StringUtils.isBlank(srcFilePath))
            {
                System.out.println("压缩失败");
                
            }
            else
            {
                file = new File(srcFilePath);
                src = ImageIO.read(file);
                out = new FileOutputStream(descFilePath);

                imgWrier.reset();
                // 必须先指定 out值，才能调用write方法, ImageOutputStream可以通过任何 OutputStream构造
                imgWrier.setOutput(ImageIO.createImageOutputStream(out));
                // 调用write方法，就可以向输入流写图片
                imgWrier.write(null, new IIOImage(src, null, null), imgWriteParams);
                out.flush();
                out.close();
            }
        }
        catch(Exception e)
        {
            e.printStackTrace();
            //return false;
        }
        File file1 = new File(descFilePath);
    	double b1 = file1.length()/(double)1024;
    	return b1;
    }
}