java将白色背景图片转换成无色

package com.cxf.dao;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;import javax.imageio.ImageIO;
import javax.swing.ImageIcon;public class Alpha {
public static void main(String[] args) {
transferAlpha();
}public static byte[] transferAlpha() { ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
File file = new File("E:/07.png");
InputStream is;
try {
is = new FileInputStream(file);
//如果是MultipartFile类型，那么自身也有转换成流的方法：is = file.getInputStream();
BufferedImage bi=ImageIO.read(is);
Image image=(Image)bi;
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(((255-R)<30) && ((255-G)<30) && ((255-B)<30)){
rgb = ((alpha + 1) << 24) | (rgb & 0x00ffffff);
} bufferedImage.setRGB(j2, j1, rgb); }
} g2D.drawImage(bufferedImage, 0, 0, imageIcon.getImageObserver());
ImageIO.write(bufferedImage, "png", new File("e:/67.png"));//直接输出文件 // ImageIO.write(bufferedImage, "png", byteArrayOutputStream);//转换成byte数组
} catch (Exception e) {
e.printStackTrace();
}finally{ }
return byteArrayOutputStream.toByteArray();
}
}