内存中完成：图片压缩+Base64编码

一、引入thumbnailator

1. maven:

        <dependency>
            <groupId>net.coobird</groupId>
            <artifactId>thumbnailator</artifactId>
            <version>0.4.8</version>
        </dependency>

2. gradle:

implementation  'net.coobird:thumbnailator:0.4.8'

二、单元测试代码

public class ThumnailTEst {
    @Test
    public void test1() throws Exception {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        URL url = Thread.currentThread().getContextClassLoader()
                .getResource("cage1.jpeg");

        //压缩后转向到内存中
        Thumbnails
                .of(url)//可以是文件名或输入流
                .size(100, 100)
                .rotate(90)//转90度
                .keepAspectRatio(true)//保持比例(默认)
                .toOutputStream(out);

        //将压缩后的图片变成Base64
        String s=Base64.getEncoder().encodeToString(out.toByteArray());
        System.out.println(s);

    }

}