为图片文件生成缩略图

package ImageTest;

import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.WritableRaster;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

public class Test {

	/**
	 * 为图片文件生成缩略图
	 * @param args
	 */
	public static void main(String[] args) {
		try {
			//参数1（源图片路径），参数2 （缩略图路径），参数3（缩略图宽）参数4（缩略图高）
			Test.saveImageAsJpg("E:\\QQ20120612154244.gif", "E:\\test.jpg", 400, 400);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 生成缩略图
	 * @param fromFileStr 源图片路径
	 * @param saveToFileStr 缩略图路径
	 * @param width 缩略图的宽
	 * @param hight 缩略图的高
	 * @throws IOException
	 */
	public static void saveImageAsJpg(String fromFileStr,String saveToFileStr,int width,int hight) throws IOException
	{
		BufferedImage srcImage;
		String imgType="JPEG";
		if(fromFileStr.toLowerCase().endsWith(".png")){
			imgType="PNG";
		}
		File saveFile=new File(saveToFileStr);
		File fromFile=new File(fromFileStr);
		srcImage=ImageIO.read(fromFile);
		if(width>0||hight>0){
			srcImage=resize(srcImage,width,hight);
		}
		ImageIO.write(srcImage, imgType, saveFile);
	}

	/**
	 * 将源图片的BufferedImage对象生成缩略图
	 * @param source 源图片的BufferedImage对象
	 * @param targetW 缩略图的宽
	 * @param targetH 缩略图的高
	 * @return
	 */
	private static BufferedImage resize(BufferedImage source, int targetW,
			int targetH) {
		int type=source.getType();
		BufferedImage target=null;
		double sx=(double)targetW/source.getWidth();
		double sy=(double)targetH/source.getHeight();
		if(sx>sy)
		{
			sx=sy;
			targetW=(int)(sx*source.getWidth());
		}else{
			sy=sx;
			targetH=(int)(sy*source.getHeight());
		}
		
		if(type==BufferedImage.TYPE_CUSTOM){
			ColorModel cm=source.getColorModel();
				WritableRaster raster=cm.createCompatibleWritableRaster(targetW, targetH);
				boolean alphaPremultiplied=cm.isAlphaPremultiplied();
				target=new BufferedImage(cm,raster,alphaPremultiplied,null);
		}else{
			target=new BufferedImage(targetW, targetH,type);
		}
		Graphics2D g=target.createGraphics();
		g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
		g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));
		g.dispose();
		return target;
	}
	
	
	
}