压缩图片 解决图片背景透明压缩后变黑色问题

public class Picture {  
  
        // TODO Auto-generated constructor stub  
    	public static void resizePNG(String fromFile, String toFile, int outputWidth, int outputHeight,boolean proportion) {  
    		
    		        try {  
    		        	File f2 = new File(fromFile);  
     		       		
        		        BufferedImage bi2 = ImageIO.read(f2);  
    		        	int newWidth;
      				    int newHeight;
      					// 判断是否是等比缩放
      					if (proportion == true) {
      						// 为等比缩放计算输出的图片宽度及高度
      						double rate1 = ((double) bi2.getWidth(null)) / (double) outputWidth + 0.1;
      						double rate2 = ((double) bi2.getHeight(null)) / (double) outputHeight + 0.1;
      						// 根据缩放比率大的进行缩放控制
      						double rate = rate1 < rate2 ? rate1 : rate2;
      						newWidth = (int) (((double) bi2.getWidth(null)) / rate);
      						newHeight = (int) (((double) bi2.getHeight(null)) / rate);
      					} else {
      						newWidth = outputWidth; // 输出的图片宽度
      						newHeight = outputHeight; // 输出的图片高度
      					}
    		            BufferedImage to = new BufferedImage(newWidth, newHeight,  
    		
    		                    BufferedImage.TYPE_INT_RGB);  
    		
    		            Graphics2D g2d = to.createGraphics();  
    		
    		            to = g2d.getDeviceConfiguration().createCompatibleImage(newWidth,newHeight,  
    		
    		                    Transparency.TRANSLUCENT);  
    		
    		            g2d.dispose();  
    		
    		            g2d = to.createGraphics();  
    		
    		            Image from = bi2.getScaledInstance(newWidth, newHeight, bi2.SCALE_AREA_AVERAGING);  
    		            g2d.drawImage(from, 0, 0, null);
    		            g2d.dispose();  
    		
    		            ImageIO.write(to, "png", new File(toFile));  
    		
    		        } catch (IOException e) {  
    		
    		            e.printStackTrace();  
    		
    		        }  
    		
    		    }  
    		
    		    public static void main(String[] args) throws IOException {  
    	
    		        System.out.println("Start");  
    		
    		        resizePNG("C:\\Documents and Settings\\Administrator\\桌面\\8d9e9c82d158ccbf8b31059319d8bc3eb035414e.jpg", "C:\\Documents and Settings\\Administrator\\桌面\\ell.png",200, 100,true);  
    		
    		        System.out.println("OK");  
    		
    		    }
    		
}