图片压缩和缩略图[JAVA]

最近工作需要对服务器上面的文件进行压缩，并且把原来一些缩略图进行压缩。贴出代码片断供大家交流。
搜略图实现规定大小画布上缩小图片，方便列表显示。
图片压缩提供了2种方法。1、可以自定义压缩比。2、采用ImageIO进行默认压缩（更安全一些，不会出现内存溢出）。

    private void doThumbCompress(File file){
        
        BufferedImage bis=null;
        
        BufferedImage bid=null;
        
        try{

            int nw= 113; // 定义宽为113
            int nh= 84; //  定义高为84
            
            bis = ImageIO.read(file);
            int c_w= bis.getWidth();
            int c_h= bis.getHeight();

            if(c_w<114 && file.length()<MIN_LENGTH){        
                bis = null;
                return;
            }
            if(c_w>WIDTH){
                nw  = WIDTH;
                nh = c_h * (WIDTH)/c_w;
                c_h=nh;
                c_w=nw;
            }    
            
            if(c_h>HEIGHT){
                nh = HEIGHT;
                nw  = c_w * (HEIGHT)/c_h;             
            }
            
            
            
            bid= new BufferedImage(WIDTH, HEIGHT,BufferedImage.TYPE_INT_RGB);                        
            Graphics g = bid.getGraphics();

            g.setColor(Color.white);

            g.fillRect(0,0, WIDTH, HEIGHT);
            
            g.drawImage(bis,(WIDTH-nw)/2,0,nw,nh,null);
            
            
            
            long oldFileSize=file.length();
            
             
            if(isOverlay){
                ImageIO.write(bid, "jpeg", file);
            } else{
                ImageIO.write(ImageIO.read(file), "jpeg", new File(outPath
                                +File.separator+file.getName()));
            }
            long newFileSize=file.length();
            log("ok:"+file+"\t"+oldFileSize+"\t"+newFileSize);
        } catch (Exception e){
            log(file+" error:"+e.getMessage());
             
        }
        
        
        bis=null;
        
        bid=null;
    }
        

     压缩图片代码：

    /** *//**
     * 可以自定义压缩比例
     * @param file
     */
    private void doCompressQuality(File file)  {
        BufferedImage src = null;
        FileOutputStream out =  null;
        JPEGImageEncoder encoder = null;
        JPEGEncodeParam  param   = null;
        
        try{
            src= ImageIO.read(file);//or png.
            if(isOverlay){
                out= new FileOutputStream(file);
            }else{
                out= new FileOutputStream(outPath+File.separator+file.getName());
            }
            encoder= JPEGCodec.createJPEGEncoder(out);
            param= encoder.getDefaultJPEGEncodeParam(src);            
            param.setQuality(imageQuality, false);
            encoder.setJPEGEncodeParam(param);            
            encoder.encode(src);//近JPEG编码
            out.close();
            //ImageIO.write(src, "jpeg", new File(outPath+File.separator+file.getName()));            
            log("over:"+file.getPath());
        } catch (IOException e){
            log("compress error:"+file.getPath()+";error:"+e.getMessage());
        }
        out = null;
        encoder = null;
        param   = null;
        src     = null;
    }

    /** *//**
     * 压缩图片，默认压缩比例75%
     * @param file
     */
    private void doCompress(File file){
        File descFile = null;
        boolean writeOk=false;
        long fileSize=file.length();

        try{
            
            if(isOverlay){                
                descFile = file;
                writeOk = ImageIO.write(ImageIO.read(file), "jpeg", descFile);
            }else{
                descFile = new File(outPath+File.separator+file.getName());
                writeOk = ImageIO.write(ImageIO.read(file), "jpeg", descFile);
            }        
            
            if(writeOk){
                log("ok:"+file.getPath()+"\t"+fileSize+"\t"+descFile.length());
            }else{
                log("fail:"+file.getPath()+"\t"+fileSize+"\t"+descFile.length());
            }            
            
        } catch (Exception e){
            log("compress error:"+file.getPath()+";descFile="+descFile+";error:"+e.getMessage());
        }
        descFile=null;
    }