import java.awt.Graphics2D;

import java.awt.image.BufferedImage;

import java.io.File;

import java.io.IOException;

import javax.imageio.ImageIO;

import javax.swing.ImageIcon;

public class Application {

    public static void main(String[] args) throws IOException {

        BufferedImage image = ImageIO.read(new File("D:\\郑州-买房\\subway-graph.jpg"));

        // 高度和宽度

        int height = image.getHeight();

        int width = image.getWidth();

        // 生产背景透明和内容透明的图片

        ImageIcon imageIcon = new ImageIcon(image);

        BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_4BYTE_ABGR);

        Graphics2D g2D = (Graphics2D) bufferedImage.getGraphics(); // 获取画笔

        g2D.drawImage(imageIcon.getImage(), 0, 0, null); // 绘制Image的图片

        int alpha = 0; // 图片透明度

        // 外层遍历是Y轴的像素

        for (int y = bufferedImage.getMinY(); y < bufferedImage.getHeight(); y++) {

            // 内层遍历是X轴的像素

            for (int x = bufferedImage.getMinX(); x < bufferedImage.getWidth(); x++) {

                int rgb = bufferedImage.getRGB(x, y);

                // 对当前颜色判断是否在指定区间内

                if (colorInRange(rgb)) {

                    alpha = 0;

                } else {

                    // 设置为不透明

                    alpha = 255;

                }

                // #AARRGGBB 最前两位为透明度

                rgb = (alpha << 24) | (rgb & 0x00ffffff);

                bufferedImage.setRGB(x, y, rgb);

            }

        }

        // 绘制设置了RGB的新图片

        g2D.drawImage(bufferedImage, 0, 0, null);

        // 生成图片为PNG

        ImageIO.write(bufferedImage, "png", new File("D:\\郑州-买房\\subway-graph2.jpg"));

        System.out.println("完成画图");

    }

    // 判断是背景还是内容

    public static boolean colorInRange(int color) {

        int red = (color & 0xff0000) >> 16;// 获取color(RGB)中R位

        int green = (color & 0x00ff00) >> 8;// 获取color(RGB)中G位

        int blue = (color & 0x0000ff);// 获取color(RGB)中B位

        // 通过RGB三分量来判断当前颜色是否在指定的颜色区间内

        if (red >= color_range && green >= color_range && blue >= color_range) {

            return true;

        }

        ;

        return false;

    }

    // 色差范围0~255

    public static int color_range = 210;

}