JavaScript 图片上传预览效果(支持ie7/ie8,firefox 3.55)

package com.fel.util; import java.awt.Color; import java.awt.Graphics2D; import java.awt.Image; import java.awt.geom.AffineTransform; import java.awt.image.AffineTransformOp; import java.awt.image.BufferedImage; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.util.Iterator; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import sun.misc.BASE64Encoder; import javax.imageio.*; import org.apache.commons.fileupload.FileItem; import org.apache.commons.fileupload.FileUploadException; import org.apache.commons.fileupload.disk.DiskFileItemFactory; import org.apache.commons.fileupload.servlet.ServletFileUpload; import org.apache.commons.io.output.DeferredFileOutputStream; import org.apache.log4j.Logger; import com.sun.image.codec.jpeg.JPEGCodec; import com.sun.image.codec.jpeg.JPEGImageEncoder; public class ImagePreview { private final static Logger LOGGER = Logger.getLogger(ImagePreview.class); public ImagePreview(){ } public String ProcessRequest(HttpServletRequest request) throws ServletException, IOException{ BASE64Encoder encoder = new BASE64Encoder(); byte[] bs = null; long filesize = 0; DiskFileItemFactory factory = new DiskFileItemFactory(); int width = 0; int height = 0; InputStream inputStream = null; ByteArrayOutputStream op = null; DeferredFileOutputStream dfo = null; try{ factory.setSizeThreshold(4096);// 设置缓冲,这个值决定了是fileinputstream还是bytearrayinputstream //factory.setRepository(new File("d:\\temp"));//设置临时存放目录,默认是new File(System.getProperty("java.io.tmpdir")) ServletFileUpload sfileUpLoad = new ServletFileUpload(factory); sfileUpLoad.setSizeMax(10*1024*1024);//10M List items = sfileUpLoad.parseRequest(request); Iterator it = items.iterator(); //暂时只考虑单文件 while(it.hasNext()){ FileItem fileItem = (FileItem)it.next(); if(!fileItem.isFormField()){ inputStream = fileItem.getInputStream(); filesize = fileItem.getSize(); bs = new byte[(int)filesize]; }else{ if (fileItem.getFieldName().equals("width")) { dfo = (DeferredFileOutputStream) fileItem.getOutputStream(); width = Integer.parseInt(new String(dfo.getData())); } if (fileItem.getFieldName().equals("height")) { dfo = (DeferredFileOutputStream) fileItem.getOutputStream(); height = Integer.parseInt(new String(dfo.getData())); } } } op = ResizeImg(inputStream, width, height); bs = op.toByteArray(); String imgpath = "data:image/jpeg;base64," ; String img = encoder.encode(bs); imgpath += img; return imgpath; }catch (FileUploadException e) { e.printStackTrace(); LOGGER.error(e); } catch (IOException e) { e.printStackTrace(); LOGGER.error(e); }finally{ if(dfo != null){ dfo.close(); } if(inputStream != null){ inputStream.close(); } if(op!= null){ op.close(); } } //blankimage return "data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw=="; } //只对jpg缩放 public ByteArrayOutputStream ResizeImg(InputStream inputStream,int maxWidth,int maxHeight) throws IOException{ BufferedImage bufferimage = ImageIO.read(inputStream); int curWidth = bufferimage.getWidth(); int curHeight = bufferimage.getHeight(); // double desiredRatio = Math.min((double)(maxWidth)/(double)curWidth,(double)maxHeight/(double)curHeight); // curWidth = (int) (curWidth*desiredRatio); // curHeight = (int)(curHeight*desiredRatio); double ratio = 0; Image itemp = bufferimage.getScaledInstance(maxWidth, maxHeight, bufferimage.SCALE_SMOOTH); // 计算比例 if ((bufferimage.getHeight() > maxHeight) || (bufferimage.getWidth() > maxWidth)) { if (bufferimage.getHeight() > bufferimage.getWidth()) { ratio = (new Integer(maxHeight)).doubleValue() / bufferimage.getHeight(); } else { ratio = (new Integer(maxWidth)).doubleValue() / bufferimage.getWidth(); } AffineTransformOp op = new AffineTransformOp(AffineTransform.getScaleInstance(ratio, ratio), null); itemp = op.filter(bufferimage, null); } BufferedImage bufftmp = new BufferedImage(curWidth,curHeight,BufferedImage.TYPE_INT_RGB); Graphics2D g2D = bufftmp.createGraphics(); g2D.setColor(Color.white); g2D.fillRect(0, 0, curWidth, curHeight); // g2D.drawImage(bufferimage, null, 0, 0); if (maxWidth == itemp.getWidth(null)) g2D.drawImage(itemp, 0, (maxHeight - itemp.getHeight(null)) / 2, itemp.getWidth(null), itemp.getHeight(null), Color.white, null); else g2D.drawImage(itemp, (maxWidth - itemp.getWidth(null)) / 2, 0, itemp.getWidth(null), itemp.getHeight(null), Color.white, null); g2D.dispose(); // itemp = bufftmp; ByteArrayOutputStream op = new ByteArrayOutputStream(); JPEGImageEncoder imageEncoder = JPEGCodec.createJPEGEncoder(op); imageEncoder.encode((BufferedImage)itemp); return op; } }