1.如何从BufferedImage对象中获取InputStream对象  
public InputStream getImageStream(String layerName,List<Color> colors,String[] pixels){  
        InputStream is = null;  
          
        BufferedImage bi = createImage(layerName, colors, pixels);  
          
        bi.flush();  
          
        ByteArrayOutputStream bs = new ByteArrayOutputStream();   
          
        ImageOutputStream imOut;  
        try {  
            imOut = ImageIO.createImageOutputStream(bs);  
              
            ImageIO.write(bi, "png",imOut);  
              
            is= new ByteArrayInputStream(bs.toByteArray());  
              
        } catch (IOException e) {  
            e.printStackTrace();  
        }   
        return is;  
    }