代码说话

package com.example.demo.image;

import sun.misc.BASE64Decoder;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.ArrayList;
import java.util.List;

public class PicImageTest {


    public static void main(String[] args) throws Exception{
        List<File> files = new ArrayList<>();
        File file1 = new File("D:/1.jpg");
        File file2 = new File("D:/11.jpg");
        files.add(file1);
        files.add(file2);
        String path = "D:/222.jpg";
        mergeHorizontal(files, path);
    }
    //竖向合成
    public static void mergeVertical(List<File> files, String path){
        try {
            Integer allWidth = 0;	//计算画布总宽
            Integer allHeight = 0;	//计算画布总高
            List<BufferedImage> imgs = new ArrayList<>();
            for(int i=0; i<files.size(); i++){
                imgs.add(ImageIO.read(files.get(i)));
                //因为是竖向合成，拿图片里最大的一个宽度就行
                allWidth = Math.max(allWidth,imgs.get(i).getWidth());
                allHeight += imgs.get(i).getHeight();
            }
            BufferedImage combined = new BufferedImage(allWidth, allHeight,BufferedImage.TYPE_INT_RGB);
            Graphics g = combined.getGraphics();
            //设置画布背景颜色 ，默认黑色
            g.setColor(Color.white);
            g.fillRect(0, 0, allWidth, allHeight);
            Integer height = 0;
            for(int i=0; i< imgs.size(); i++){
                g.drawImage(imgs.get(i), 0, height,null);
                //+10为了设置上下两个图片间距
                height +=  imgs.get(i).getHeight()+10;
            }
            ImageIO.write(combined, "jpg", new File(path));
            System.out.println("===合成成功====");
        } catch (Exception e) {
            System.out.println("===合成失败====");
            e.printStackTrace();
        }
    }

    //横向合成
    public static void mergeHorizontal(List<File> files, String path){
        try {
            Integer allWidth = 0;
            Integer allHeight = 0;
            List<BufferedImage> imgs = new ArrayList<>();
            for(int i=0; i<files.size(); i++){
                imgs.add(ImageIO.read(files.get(i)));
                allHeight = Math.max(allHeight,imgs.get(i).getHeight());
                allWidth += imgs.get(i).getWidth();
            }
            BufferedImage combined = new BufferedImage(allWidth, allHeight, BufferedImage.TYPE_INT_RGB);
            Graphics g = combined.getGraphics();
            g.setColor(Color.white);
            g.fillRect(0, 0, allWidth, allHeight);
            Integer width = 0;
            for(int i=0; i< imgs.size(); i++){
                g.drawImage(imgs.get(i), width, 0, null);
                //设置横向间距
                width +=  imgs.get(i).getWidth()+10;
            }
            ImageIO.write(combined, "jpg", new File(path));
            System.out.println("===合成成功====");
        } catch (Exception e) {
            System.out.println("===合成失败====");
            e.printStackTrace();
        }
    }
	//字符串类型图片转换
    public static BufferedImage base64StringToImg(String base64String) {
        try {
          byte[] bytes = Base64.getDecoder().decode(data);
         ByteArrayInputStream in = new ByteArrayInputStream(bytes);
         return ImageIO.read(in);
        } catch (final IOException ioe) {
            throw new UncheckedIOException(ioe);
        }
    }

}

首先弄两张图片，如下：

将这两张图片合成一张图片到本地，代码如下：

package org.example.test;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.WritableRaster;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * 把两张图片合并一张
 */
public class Picture {

    /**
     * 压缩图片
     */
    private static BufferedImage resize(BufferedImage source, int targetW, int targetH) {
        // targetW，targetH分别表示目标长和宽
        int type = source.getType();
        BufferedImage target = null;
        int width = source.getWidth();
        int height = source.getHeight();
        double sx = (double) targetW / width;
        double sy = (double) targetH / height;
        // 这里想实现在targetW，targetH范围内实现等比缩放
        if (sx > sy) {
            sx = sy;
            targetW = (int) (sx * source.getWidth());
        } else {
            sy = sx;
            targetH = (int) (sy * source.getHeight());
        }
        if (type == BufferedImage.TYPE_CUSTOM) {
            ColorModel cm = source.getColorModel();
            WritableRaster raster = cm.createCompatibleWritableRaster(targetW,
                    targetH);
            boolean alphaPremultiplied = cm.isAlphaPremultiplied();
            target = new BufferedImage(cm, raster, alphaPremultiplied, null);
        } else {
            target = new BufferedImage(targetW, targetH, type);
        }
        Graphics2D g = target.createGraphics();
        // smoother than exlax:
        g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
        g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));
        g.dispose();
        return target;
    }


    /**
     * 待合并的两张张图必须满足这样的前提，如果水平方向合并，则高度必须相等；如果是垂直方向合并，宽度必须相等。
     *
     * @param img1 待合并的第一张图
     * @param img2 带合并的第二张图
     * @return 返回合并后的BufferedImage对象
     */
    private static BufferedImage mergeImage(BufferedImage img1, BufferedImage img2) {
        int w1 = img1.getWidth();
        int h1 = img1.getHeight();
        int w2 = img2.getWidth();
        Graphics2D graphics2D = null;
        // 生成新图片
        BufferedImage destImage = null;
        destImage = new BufferedImage(w1 + w2, h1, BufferedImage.TYPE_INT_RGB);
        graphics2D = destImage.createGraphics();
        graphics2D.drawImage(img1, 0, 0, w1, h1, null);
        graphics2D.drawImage(img2, w1, 0, w2, h1, null);
        graphics2D.dispose();
        return destImage;
    }

    /**
     * 生成新图片到本地
     */
    public static void writeImageLocal(String newImage, BufferedImage img) {
        if (newImage != null && img != null) {
            try {
                File outputfile = new File(newImage);
                ImageIO.write(img, "jpg", outputfile);
            } catch (IOException e) {
                System.out.println(e.getMessage());
            }
        }
    }


    public static void main(String[] args) throws Exception {
        InputStream is1 = new FileInputStream("D:\\photo\\01_皖R6982_20200620082639_1636A_77_60_1.jpg");
        InputStream is2 = new FileInputStream("D:\\photo\\01_皖R6982_20200620082639_1636A_77_60_2.jpg");
        BufferedImage readImg1 = ImageIO.read(is1);
        BufferedImage readImg2 = ImageIO.read(is2);
        // 图像压缩  保证每张图片大小一致
        int width = readImg1.getWidth();
        int height = readImg1.getHeight();
        readImg2 = resize(readImg2, width, height);
        BufferedImage mergeImg = mergeImage(readImg1, readImg2);
        writeImageLocal("D:\\photo\\new.jpg", mergeImg);
    }
}

成功合成一张图片，结果如下：