package com.example.eochadmin.controller;


import com.example.eochadmin.util.DrawImage;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import static com.example.eochadmin.util.DrawImage.*;


@RestController
public class StudentController {
    private static final Random random = new Random();

    @GetMapping("/image")
    public void image(HttpServletResponse response) throws IOException {
        BufferedImage image = new BufferedImage(DEFAULT_IMAGE_WIDTH, DEFAULT_IMAGE_HEIGHT, BufferedImage.TYPE_INT_RGB);
        // 绘制图像内容
        int num1 = random.nextInt(100);
        int num2 = random.nextInt(100);
        char operator = random.nextBoolean() ? '+' : '-';
        String equation = num1 + " " + operator + " " + num2 + " = ";
        if (operator == '+') {
            // 加法计算操作存入redis
        } else {
            System.out.println(num1 - num2);
        }
        DrawImage.drawImage(image, equation);
        // 将图像写入HTTP响应
        DrawImage.writeToResponse(response, image);
    }
}

package com.example.eochadmin.util;

import jakarta.servlet.http.HttpServletResponse;


import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

public class DrawImage {
    private static final Random random = new Random();
    public static final int DEFAULT_IMAGE_WIDTH = 150;
    public static final int DEFAULT_IMAGE_HEIGHT = 40;
    private static final int MAX_FONT_SIZE = 70;



    public static void drawImage(BufferedImage image, String equation) {
        Graphics2D graphics = image.createGraphics();
        try {
            // 填充背景
            graphics.setColor(Color.WHITE);
            graphics.fillRect(0, 0, DEFAULT_IMAGE_WIDTH, DEFAULT_IMAGE_HEIGHT);
            // 绘制方程
            drawEquationOnImage(graphics, equation);
            // 绘制干扰线
            int numOfLines = random.nextInt(3) + 4;
            for (int i = 0; i < numOfLines; i++) {
                int x1 = random.nextInt(DEFAULT_IMAGE_WIDTH);
                int y1 = random.nextInt(DEFAULT_IMAGE_HEIGHT);
                int x2 = random.nextInt(DEFAULT_IMAGE_WIDTH);
                int y2 = random.nextInt(DEFAULT_IMAGE_HEIGHT);
                Color lineColor = new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256));
                drawLineOnImage(graphics, x1, y1, x2, y2, lineColor);
            }
        } finally {
            graphics.dispose();
        }
    }

    public static void writeToResponse(HttpServletResponse response, BufferedImage image) throws IOException {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        try {
            ImageIO.write(image, "PNG", outputStream);
            byte[] imageData = outputStream.toByteArray();
            response.setContentType("image/png");
            response.setContentLength(imageData.length);
            try (OutputStream responseStream = response.getOutputStream()) {
                responseStream.write(imageData);
            }
        } finally {
            outputStream.close();
        }
    }

    private static void drawEquationOnImage(Graphics2D graphics, String equation) {
        int fontSize = Math.min(DEFAULT_IMAGE_HEIGHT / 2, MAX_FONT_SIZE);
        graphics.setFont(new Font("Arial", Font.BOLD, fontSize));
        FontMetrics fontMetrics = graphics.getFontMetrics();
        int textWidth = fontMetrics.stringWidth(equation);
        int textHeight = fontMetrics.getAscent(); // 获取文字的上升高度（基线到最高点的距离）
        int x = (DEFAULT_IMAGE_WIDTH - textWidth) / 2;
        int y = (DEFAULT_IMAGE_HEIGHT - textHeight) / 2 + fontMetrics.getAscent(); // 计算垂直居中位置
        graphics.setColor(new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256)));
        graphics.drawString(equation, x, y);
    }


    private static void drawLineOnImage(Graphics2D graphics, int x1, int y1, int x2, int y2, Color color) {
        graphics.setColor(color);
        graphics.drawLine(x1, y1, x2, y2);
    }
}

效果图