将png图片的白色背景转为透明背景

代码实现

BufferedImage sourceImage = ImageIO.read(imageFile);
int height = sourceImage.getHeight();
int width = sourceImage.getWidth();
BufferedImage newImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = newImage.createGraphics();
g2d.drawImage(sourceImage, 0, 0, null);
int alpha = 0;
for (int y = newImage.getMinY(); y < newImage.getHeight(); y++) {
    for (int x = newImage.getMinX(); x < newImage.getWidth(); x++) {
        int rgb = newImage.getRGB(x, y);
        alpha = includeColor(rgb) ? 0 : 255;
        rgb = (alpha << 24) | (rgb & 0X00FFFFFF);
        newImage.setRGB(x, y, rgb);
    }
}
g2d.dispose();
ByteArrayOutputStream imageOutPutStream = new ByteArrayOutputStream();
ImageIO.write(newImage, "png", imageOutPutStream);


/**
 * 判断当前色块是否属于设定值的范围
 * @param color 当前颜色
 * @return false|true
 */
public static boolean includeColor(int color) {
    int red = (color & 0xFF0000) >> 16;
    int green = (color & 0x00FF00) >> 8;
    int blue = (color & 0x0000FF);
    int color_range = 215;
    return (red >= color_range && green >= color_range && blue >= color_range);
}