java如何去除图片中的白色背景

package com.wdg.util;  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 ImageUtil {   public static void main(String[] args) {     transferAlpha();   }    public static byte[] transferAlpha() {      ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();     File file = new File("D://08//11.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("D://08//12.png"));// 直接输出文件     } catch (Exception e) {       e.printStackTrace();     } finally {      }     return byteArrayOutputStream.toByteArray();   } }