java 实现对图片进行指定的缩小或放大

import java.awt.Graphics2D;    
import java.awt.Rectangle;    
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.FileInputStream;    
import java.io.IOException;    
import java.io.InputStream;    
import javax.imageio.ImageIO;    

/**   
 * 图片工具类，完成图片的截取   
 *    
 * @author inc062977   
 *    
 */   
public class AlterUploadImage {    
 /**   
  * 实现图像的等比缩放   
  * @param source   
  * @param targetW   
  * @param targetH   
  * @return   
  */   
 private 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_INTERPOLATION,    
    RenderingHints.VALUE_INTERPOLATION_BICUBIC);    
  g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));    
  g.dispose();    
  return target;    
 }    

 /**   
  * 实现图像的等比缩放和缩放后的截取   
  * @param inFilePath 要截取文件的路径   
  * @param outFilePath 截取后输出的路径   
  * @param width 要截取宽度   
  * @param hight 要截取的高度   
  * @param proportion   
  * @throws Exception   
  */   

 public static void saveImageAsJpg(String inFilePath, String outFilePath,    
   int width, int hight, boolean proportion)throws Exception {    
  File file = new File(inFilePath);    
  InputStream in = new FileInputStream(file);    
  File saveFile = new File(outFilePath);    

  BufferedImage srcImage = ImageIO.read(in);    
  if (width > 0 || hight > 0) {    
   // 原图的大小    
   int sw = srcImage.getWidth();    
   int sh = srcImage.getHeight();    
   // 如果原图像的大小小于要缩放的图像大小，直接将要缩放的图像复制过去    
   if (sw > width && sh > hight) {    
    srcImage = resize(srcImage, width, hight);    
   } else {    
    String fileName = saveFile.getName();    
    String formatName = fileName.substring(fileName    
      .lastIndexOf('.') + 1);    
    ImageIO.write(srcImage, formatName, saveFile);    
    return;    
   }    
  }    
  // 缩放后的图像的宽和高    
  int w = srcImage.getWidth();    
  int h = srcImage.getHeight();    
  // 如果缩放后的图像和要求的图像宽度一样，就对缩放的图像的高度进行截取    
  if (w == width) {    
   // 计算X轴坐标    
   int x = 0;    
   int y = h / 2 - hight / 2;    
   saveSubImage(srcImage, new Rectangle(x, y, width, hight), saveFile);    
  }    
  // 否则如果是缩放后的图像的高度和要求的图像高度一样，就对缩放后的图像的宽度进行截取    
  else if (h == hight) {    
   // 计算X轴坐标    
   int x = w / 2 - width / 2;    
   int y = 0;    
   saveSubImage(srcImage, new Rectangle(x, y, width, hight), saveFile);    
  }    
  in.close();    
 }    
 /**   
  * 实现缩放后的截图   
  * @param image 缩放后的图像   
  * @param subImageBounds 要截取的子图的范围   
  * @param subImageFile 要保存的文件   
  * @throws IOException   
  */   
 private static void saveSubImage(BufferedImage image,    
   Rectangle subImageBounds, File subImageFile) throws IOException {    
  if (subImageBounds.x < 0 || subImageBounds.y < 0   
    || subImageBounds.width - subImageBounds.x > image.getWidth()    
    || subImageBounds.height - subImageBounds.y > image.getHeight()) {    
   System.out.println("Bad   subimage   bounds");    
   return;    
  }    
  BufferedImage subImage = image.getSubimage(subImageBounds.x,subImageBounds.y, subImageBounds.width, subImageBounds.height);    
  String fileName = subImageFile.getName();    
  String formatName = fileName.substring(fileName.lastIndexOf('.') + 1);    
  ImageIO.write(subImage, formatName, subImageFile);    
 }    

 public static void main(String[] args)
 {
  AlterUploadImage au = new AlterUploadImage();
  try {
   au.saveImageAsJpg("d://psu[3].jpg", "d://new.jpg", 900, 800, true);
   System.out.println("Done");
  } catch (Exception e) {
   e.printStackTrace();
  }
 }


}