把图片的白色背景换成透明色

package com.xixi;

import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.DirectColorModel;
import java.awt.image.FilteredImageSource;
import java.awt.image.RGBImageFilter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

import javax.imageio.ImageIO;

public class ChangeBack {
	public static void main(String[] args) {
		new ChangeBack().changBackPic("D:\\jazm.png");
	}

	public void changBackPic(String path) {
		File file = new File(path);
		int height = getPicHeight(file);
		int width = getPicWidth(file);
		try {
			BufferedImage bimg = ImageIO.read(new FileInputStream(path));
			FilteredImageSource fis = new FilteredImageSource(bimg.getSource(), new MyFilter(255));
			Image im = Toolkit.getDefaultToolkit().createImage(fis);
			BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
			Graphics2D ig2 = bi.createGraphics();
			ig2.drawImage(im, 0, 0, width, height, null);
			ig2.dispose();
			String[] array = path.split("\\.");
			String gs = array[array.length - 1];
			path = path.replace("." + gs, "_changeBack." + gs);
			ImageIO.write(bi, "PNG", new File(path));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public static int getPicHeight(File file) {
		try {
			return ImageIO.read(new FileInputStream(file)).getHeight();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return 0;
	}

	public static int getPicWidth(File file) {
		try {
			return ImageIO.read(new FileInputStream(file)).getWidth();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return 0;
	}
}

class MyFilter extends RGBImageFilter {
	int alpha = 0;

	public MyFilter(int alpha) {
		this.canFilterIndexColorModel = true;
		this.alpha = alpha;
	}

	public int filterRGB(int x, int y, int rgb) {
		DirectColorModel dcm = (DirectColorModel) ColorModel.getRGBdefault();
		int red = dcm.getRed(rgb);
		int green = dcm.getGreen(rgb);
		int blue = dcm.getBlue(rgb);
		int alp = dcm.getAlpha(rgb);
		if (red == 255 && blue == 255 && green == 255) {
			alpha = 0;
		} else {
			alpha = 255;
		}
		return alpha << 24 | red << 16 | green << 8 | blue;
	}
}
​

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