Java操作透明图片并保持背景透明的实现

public static void pressText2(String sourceImg,String targetImg) {
    try {
        File file = new File(sourceImg);
        File targetfile = new File(targetImg);
        Image image = ImageIO.read(file);
        int width = image.getWidth(null);
        int height = image.getHeight(null);
        BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = bufferedImage.createGraphics();
        bufferedImage = g.getDeviceConfiguration()
                .createCompatibleImage(width, height, Transparency.TRANSLUCENT);
        g = bufferedImage.createGraphics();
        g.drawImage(image, 0, 0, null);
        g.setColor(Color.BLACK);
        g.drawString("wudididi",20,20);
        ImageIO.write(bufferedImage, "png", targetfile);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

/**
* 设置源图片为背景透明，并设置透明度
* @param srcFile 源图片
* @param desFile 目标文件
* @param alpha 透明度
* @param formatName 文件格式
* @throws IOException
*/
public static void transparentImage(String srcFile,String desFile,int alpha,String formatName) throws IOException{
    BufferedImage temp =  ImageIO.read(new File(srcFile));//取得图片
        transparentImage(temp, desFile, alpha, formatName);
    }
/**
* 设置源图片为背景透明，并设置透明度
* @param srcImage 源图片
* @param desFile 目标文件
* @param alpha 透明度
* @param formatName 文件格式
* @throws IOException
*/
public static void transparentImage(BufferedImage srcImage,
String desFile, int alpha, String formatName) throws IOException {
int imgHeight = srcImage.getHeight();//取得图片的长和宽
        int imgWidth = srcImage.getWidth();
        int c = srcImage.getRGB(3, 3);
        //防止越位
        if (alpha < 0) {
            alpha = 0;
         } else if (alpha > 10) {
            alpha = 10;
         }
        BufferedImage bi = new BufferedImage(imgWidth, imgHeight,
                BufferedImage.TYPE_4BYTE_ABGR);//新建一个类型支持透明的BufferedImage
        for(int i = 0; i < imgWidth; ++i)//把原图片的内容复制到新的图片，同时把背景设为透明
        {
            for(int j = 0; j < imgHeight; ++j)
            {
            //把背景设为透明
                if(srcImage.getRGB(i, j) == c){
                    bi.setRGB(i, j, c & 0x00ffffff);
                }
                //设置透明度
                else{
                int rgb = bi.getRGB(i, j);
                    rgb = ((alpha * 255 / 10) << 24) | (rgb & 0x00ffffff);
                    bi.setRGB(i, j, rgb);
                }
            }
        }
ImageIO.write(bi, StringUtils.isEmpty(formatName)?FORMAT_PNG:formatName, new File(desFile));
}