图片压缩

package com.u.image;

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 javax.imageio.ImageIO;

public class Lessen {

	public Lessen() {

	}

	public static BufferedImage resize(BufferedImage source, int targetw,
			int targeth) {
		// targetw，targeth分别表示目标长和宽
		int type = source.getType();
		BufferedImage target = null;
		double sx = (double) targetw / source.getWidth();
		double sy = (double) targeth / source.getHeight();
		// 这里想实现在targetw，targeth范围内实现等比缩放。如果不需要等比缩放
		// 则将下面的if else语句注释即可
		if (sx > sy) {
			sx = sy;
			targetw = (int) (sx * source.getWidth());
		} else {
			sy = sx;
			targeth = (int) (sy * source.getHeight());
		}
		if (type == BufferedImage.TYPE_CUSTOM) {
			// handmade
			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();
		// smoother than exlax:
		g.setRenderingHint(RenderingHints.KEY_RENDERING,
				RenderingHints.VALUE_RENDER_QUALITY);
		g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));
		g.dispose();
		return target;
	}

	public static void saveimageasjpg(String fromfilestr, String savetofilestr,
			int width, int hight) throws Exception {
		BufferedImage srcimage;
		// string ex =
		// fromfilestr.substring(fromfilestr.indexof("."),fromfilestr.length());
		String imgtype = "jpeg";
		if (fromfilestr.toLowerCase().endsWith(".png")) {
			imgtype = "png";
		}
		// system.out.println(ex);
		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);
	}

	public static void main(String argv[]) {

		
		/*
		 * try { // 参数1(from),参数2(to),参数3(宽),参数4(高)
		 * saveimageasjpg("F:\\DSC_0272.JPG", "F:\\2.jpg", 800, 600); } catch
		 * (Exception e) { e.printStackTrace(); }
		 */
		// http://www.111cn.net/jsp/Java/34831.htm
		System.out.println(800 / 600.0);
		System.out.println(800 / 1.5);
		System.out.println(4608 / 3072.0);
	}

}