java图片处理，首先上传一个大图然后按照给定比例或大小获取图片

GraphicsMagick + im4java 可以实现 ，而且生成的图片质量很高，已经实践过了。

参考一下这个
http://my.oschina.net/u/1245614/blog/160051

1你是要做上传头像吗？如果是http://download.csdn.net/detail/quadrapop/6552799
(开源的、稍微改改就行）

2如果不是，
上传图片可以用jquery file upload（https://github.com/blueimp/jQuery-File-Upload/wiki）这里有java的例子代码，写好的

图片处理可以用java awt的image api

package com.test;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.awt.image.ConvolveOp;
import java.awt.image.Kernel;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;

import org.apache.commons.fileupload.FileItem;
import org.apache.log4j.Logger;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
/**

• 图片缩放

• @author db2admin
  *
  /
  public class ImageUtil {
  /*

  • Logger for this class */ private static final Logger logger = Logger.getLogger(ImageUtil.class);

  public void imageScale(String srcFilePath, String targetFilePath,
  int width, int height) {
  this.imageScale(new File(srcFilePath), new File(targetFilePath), width,
  height);
  }

  public void imageScale(File srcFile, File targetFile, int width, int height) {
  try {
  Image image = javax.imageio.ImageIO.read(srcFile);

      image = image.getScaledInstance(width, height,
              Image.SCALE_AREA_AVERAGING);
      // Make a BufferedImage from the Image.
      BufferedImage mBufferedImage = new BufferedImage(width, height,
              BufferedImage.TYPE_INT_RGB);
      Graphics2D g2 = mBufferedImage.createGraphics();            
  
      g2.drawImage(image, 0, 0, width, height, Color.white, null);
      g2.dispose();
  
      float[] kernelData2 = { -0.125f, -0.125f, -0.125f, -0.125f, 2,
              -0.125f, -0.125f, -0.125f, -0.125f };
      Kernel kernel = new Kernel(3, 3, kernelData2);
      ConvolveOp cOp = new ConvolveOp(kernel, ConvolveOp.EDGE_NO_OP, null);
      mBufferedImage = cOp.filter(mBufferedImage, null);
  
      File targetDir = targetFile.getParentFile();
      if (!targetDir.exists())
          targetDir.mkdirs();
  
      FileOutputStream out = new FileOutputStream(targetFile);
      JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
      encoder.encode(mBufferedImage);
      out.close();
  } catch (Exception e) {
      logger.error(
              "imageScale(String, String, int, int) - 图片压缩出错 - srcFilePath="
                      + srcFile.getPath() + ", targeFilePath="
                      + targetFile.getPath() + ", width=" + width
                      + ", height=" + height, e);
  }
  

  }

  public void imageScale(FileItem fileItem, String targetFilePath, int width,
  int height) {
  try {
  InputStream input = fileItem.getInputStream();
  Image image = javax.imageio.ImageIO.read(input);

      image = image.getScaledInstance(width, height,
              Image.SCALE_AREA_AVERAGING);
      BufferedImage mBufferedImage = new BufferedImage(width, height,
              BufferedImage.TYPE_INT_RGB);
      Graphics2D g2 = mBufferedImage.createGraphics();
  
      g2.drawImage(image, 0, 0, width, height, Color.white, null);
      g2.dispose();
  
      float[] kernelData2 = { -0.125f, -0.125f, -0.125f, -0.125f, 2,
              -0.125f, -0.125f, -0.125f, -0.125f };
      Kernel kernel = new Kernel(3, 3, kernelData2);
      ConvolveOp cOp = new ConvolveOp(kernel, ConvolveOp.EDGE_NO_OP, null);
      mBufferedImage = cOp.filter(mBufferedImage, null);
  
      File target = new File(targetFilePath);
      File targetDir = target.getParentFile();
      if (!targetDir.exists())
          targetDir.mkdirs();
  
      FileOutputStream out = new FileOutputStream(targetFilePath);
      JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
      encoder.encode(mBufferedImage);
      out.close();
      input.close();
  } catch (Exception e) {
      logger.error(
              "imageScale(String, String, int, int) - 图片压缩出错 - fileItem="
                      + fileItem.getName() + ", targetFilePath="
                      + targetFilePath + ", width=" + width + ", height="
                      + height, e);
  }
  

  }

  public static void main(String[] args) {
  ImageUtil iu=new ImageUtil();
  iu.imageScale("e:/2.jpg", "e:/1.jpg", 270, 220);
  }
  }

看看有没有用