网上有很多封装好的包，我用的是这个，如下坐标，项目地址

文档github
文档gitee

<!-- 图片合成 -->
<dependency>
    <groupId>com.freewayso</groupId>
    <artifactId>image-combiner</artifactId>
    <version>2.6.3</version>
</dependency>

或者

<dependency>
    <groupId>io.github.chichengyu</groupId>
    <artifactId>java-image-combiner</artifactId>
    <version>1.1.0</version>
</dependency>

新建工具类MerageImageUtil.java，内容如下：

package com.zyq.util;

import com.freewayso.image.combiner.ImageCombiner;
import com.freewayso.image.combiner.enums.Direction;
import com.freewayso.image.combiner.enums.OutputFormat;
import com.freewayso.image.combiner.enums.ZoomMode;
import lombok.Data;
import org.springframework.lang.Nullable;
import org.springframework.util.FileCopyUtils;
import org.springframework.web.multipart.MultipartFile;

import javax.imageio.ImageIO;
import java.awt.Color;
import java.awt.Font;
import java.awt.GraphicsEnvironment;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.Base64;
import java.util.Objects;

/** 合并图片工具
 * author xiaochi
 * date 2024/9/2
 */
public class MerageImageUtil {

    /**
     * 显示所有可用字体
     */
    public static void showFonts() throws InterruptedException {
        GraphicsEnvironment e = GraphicsEnvironment.getLocalGraphicsEnvironment();
        String[] fontName = e.getAvailableFontFamilyNames();
        for (int i = 0; i < fontName.length; i++) {
            System.out.println(fontName[i]);
        }
    }

    /**
     * Base64格式图片转MultipartFile对象
     * @throws Exception
     */
    public static MultipartFile base64ToMultipartFile(String fileName,String originalFilename,String contentType,String base64Str) throws Exception {
        byte[] bytes = base64ToByteArray(base64Str);
        return new DefaultMultiPartFile(fileName,originalFilename,contentType, bytes);
    }

    /**
     * Base64格式图片转input输入流
     * @throws Exception
     */
    public static InputStream base64ToInputStream(String base64Str) throws Exception {
        byte[] bytes = base64ToByteArray(base64Str);
        return new ByteArrayInputStream(bytes);
    }

    /**
     * Base64格式图片转byte[]数组
     * @throws Exception
     */
    public static byte[] base64ToByteArray(String base64Str) throws Exception {
        base64Str = base64Str.replaceAll("data:image/(jpg|png|jpeg);base64,","");
        return Base64.getDecoder().decode(base64Str);
    }

    /**
     * InputStream转Base64格式
     * @throws Exception
     */
    public static String toBase64(InputStream in) throws Exception {
        return toBase64(in,"jpg");
    }

    /**
     * InputStream转Base64格式
     * @throws Exception
     */
    public static String toBase64(InputStream in,String imageType) throws Exception {
        byte[] bytes = new byte[4096];
        int len;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        while ((len = in.read(bytes)) != -1){
            out.write(bytes,0,len);
        }
        return "data:image/"+imageType+";base64,"+ new String(Base64.getEncoder().encode(out.toByteArray()), StandardCharsets.UTF_8);
    }

    /**
     * 合并图片与文字并输出Base64格式
     * @throws Exception
     */
    public static String toBase64(Params params) throws Exception {
        InputStream in = merageImageAndTxt(params);
        return toBase64(in,"jpg");
    }

    /**
     * 合并图片与文字
     * @throws Exception
     */
    public static InputStream merageImageAndTxt(Params params) throws Exception {
        //showFonts();
        /*String bg = "https://img.thebeastshop.com/combine_image/funny_topic/resource/bg_3x4.png";
        ImageCombiner combiner = new ImageCombiner(bg, OutputFormat.JPG);*/
        int top = 1248;
        ImageCombiner combiner = new ImageCombiner(ImageIO.read(new File(params.getBackImage())), OutputFormat.JPG);
        BufferedImage cover = ImageIO.read(params.getCoverImage());
        //叠加人物
        combiner.addImageElement(cover, 0, 0,1248,top, ZoomMode.WidthHeight)
                .setCenter(true)
                .setRotate(0);

        //Font font = new Font("Smiley Sans", Font.ITALIC, 150);//"微软雅黑"
        String font = "微软雅黑";
        if (!Objects.equals(params.getTitleFont(),null) && !Objects.equals(params.getTitleFont(),"")){
            font = params.getTitleFont();
        }
        combiner.addTextElement(params.getTitle(), font,150, 150,100)
                .setColor(Color.getHSBColor(223,212,184))
                .setAutoBreakLine(0)
                .setDirection(Direction.CenterLeftRight);
        combiner.addTextElement(params.getDesc(),"楷体",48,250,850)
                .setColor(Color.WHITE)
                .setAutoBreakLine(0)
                .setAlpha(.5F);
        Font authorFont = new Font("黑体", Font.BOLD, 48);//"微软雅黑"
        combiner.addTextElement(params.getAuthor(),authorFont,100,top+30)
                .setColor(Color.BLACK)
                .setSpace(.5F);
        /*combiner.addImageElement("http://img.thebeastshop.com/images/index/imgs/8wzZ7St7KH.jpg", 10, 30)
                .setCenter(true)
                .setRotate(45);*/

        combiner.combine();
        if (Objects.equals(params.getSavePath(),null) || Objects.equals(params.getSavePath(),"")){
            return combiner.getCombinedImageStream();
        }
        combiner.save(params.getSavePath());
        return null;
    }

    @Data
    public static class Params{
        private String title;
        private String desc;
        private String author;
        private String titleFont = "/font/SmileySans2.ttf";//如果是字体文件路径,放到resource的font目录下，必须/开头，如：/font/SmileySans2.ttf
        private String savePath;
        private String backImage;//背景图
        //private String coverImage;//封面图
        private InputStream coverImage;//封面图
    }

    public static class DefaultMultiPartFile implements MultipartFile {
        private final String name;
        private String originalFilename;
        @Nullable
        private String contentType;
        private final byte[] content;

        public DefaultMultiPartFile(String name, @Nullable byte[] content) {
            this(name, name, (String)null, content);
        }

        public DefaultMultiPartFile(String name, String originalFilename, @Nullable String contentType, byte[] content) {
            this.name = name;
            this.originalFilename = originalFilename;
            this.contentType = contentType;
            this.content = content;
        }

        @Override
        public String getName() {
            return this.name;
        }

        @Override
        public String getOriginalFilename() {
            return this.originalFilename;
        }

        @Override
        public String getContentType() {
            return this.contentType;
        }

        @Override
        public boolean isEmpty() {
            return content.length==0;
        }

        @Override
        public long getSize() {
            return content.length;
        }

        @Override
        public byte[] getBytes() throws IOException {
            return content;
        }

        @Override
        public InputStream getInputStream() throws IOException {
            return new ByteArrayInputStream(content);
        }

        @Override
        public void transferTo(File file) throws IOException, IllegalStateException {
            FileCopyUtils.copy(this.content, file);
        }
    }

    public static void main(String[] args) throws Exception {
        Params params = new Params();
        params.setTitle("生活时光机");
        params.setDesc("以时光为单位");
        params.setAuthor("汪新元.回忆录111");
        params.setTitleFont("/font/SmileySans2.ttf");// params.setTitleFont("微软雅黑");
        params.setSavePath("D:\\workspace\\demo2\\test.jpg");
        params.setBackImage("D:\\image_test\\bg.jpg");
        params.setCoverImage(new FileInputStream(new File("D:\\image_test\\people.jpg")));
        merageImageAndTxt(params);
    }
}

这时直接调用就好了。如果需要转换 MultipartFile对象，可以如下调用

MultipartFile file = MerageImageUtil.base64ToMultipartFile("123.jpg", "123.jpg", "jpg", "Base64图片字符串");

这样就可以转成 MultipartFile对象了，注：123.jpg 是随便给的，只是给 Base64 图片字符串一个源文件名称，因为Base64图片是没名称的，后面获取file原名称就会null。