java处理png

使png图片背景透明的方法：
首先png图片背景设置为白色或者纯黑色 总之就是图片中用不到的颜色区间
然后使用java的bufferedImage将图片根据点阵读出，并将图片的每一个点的rgb区出来判断是否在将要被设置为透明的区间内
如果在该区间内 将该点的颜色移为如xxxxxx--〉00xxxxxx 这样透明度的位置就可以设置为0 这样该点的颜色就是透明的了

public static byte[] test(Image image) {
		ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
		try {
ImageIcon imageIcon = new ImageIcon(image);
BufferedImage bufferedImage = new BufferedImage(imageIcon.getIconWidth(), 

imageIcon.getIconHeight(),BufferedImage.TYPE_4BYTE_ABGR);
Graphics2D g2D = (Graphics2D) bufferedImage.getGraphics();
g2D.drawImage(imageIcon.getImage(), 0, 0, imageIcon.getImageObserver());
int alpha = 0;
for (int j1 = bufferedImage.getMinY(); j1 < bufferedImage.getHeight(); j1++) {
	for (int j2 = bufferedImage.getMinX();j2 < bufferedImage.getWidth();j2++){
		int rgb = bufferedImage.getRGB(j2, j1);
		int R = (rgb & 0xff0000) >> 16;
		int G = (rgb & 0xff00) >> 8;
		int B = (rgb & 0xff);
		if(...){//r，g，b都在透明区间中
rgb = (alpha << 24) | (rgb & 0x00ffffff);
		}
		bufferedImage.setRGB(j2, j1, rgb);
	}
}
g2D.drawImage(bufferedImage, 0, 0, imageIcon.getImageObserver());
ImageIO.write(bufferedImage, "png", byteArrayOutputStream);
} catch (Exception e) {
	e.printStackTrace();
}
  return byteArrayOutputStream.toByteArray();
}
public static void main(String[] args) throws IOException {
		File inputFile = new File("c:/bbb.png");
		BufferedImage input = ImageIO.read(inputFile);
		byte[] byte1=test(input);
		FileOutputStream out=new FileOutputStream("e:/aaa.png");
		out.write(byte1);
		out.close();
	}