图片缩略图

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package com.mingoe.util;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.WritableRaster;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.io.File;
/**
* 图片缩略图
* @author QuXiuNa
* 2009.3.2
*/
public class ImageSmaller {

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 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);
}
}