1.什么是Thumbnailator？

Thumbnailator是一个用于Java的缩略图生成库。通过Thumbnailator提供的流畅接口(fluent interface)的方式可以完成复杂的缩略图处理任务，无需访问Image I/O API并通过Graphics2D对象手动操作BufferedImages。

2 缩略图可以做什么？

缩略图是应用极其广泛的，像头像、图片消息、商品图片等，都会用到缩略图。比如，当你有了一个新的微信好友，你就能看到他的头像，一开始这个头像是一个比原图更小的缩略图。而你点击查看原图时，微信客户端才会给你下载原图。因为你并不会对每个人的头像都感兴趣，都会去查看清晰的原图，一个小小的缩略图已经能满足了。这样可以减轻网络传输的负担，加快响应速度。微信传图片和视频也是同样的道理，先给你传一个比较小的预览，你点击查看原图或视频播放才给你传更大的文件。

3.代码工程

实验目的

生成缩略图（缩放、旋转、裁剪、水印）

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">    <parent>        <groupId>org.springframework.bootgroupId>        <artifactId>spring-boot-starter-parentartifactId>        <version>3.2.1version>    parent>    <modelVersion>4.0.0modelVersion>
    <artifactId>thumbnailatorartifactId>
    <properties>        <maven.compiler.source>17maven.compiler.source>        <maven.compiler.target>17maven.compiler.target>    properties>    <dependencies>        <dependency>            <groupId>net.coobirdgroupId>            <artifactId>thumbnailatorartifactId>            <version>0.4.19version>        dependency>        <dependency>            <groupId>org.springframework.bootgroupId>            <artifactId>spring-boot-starter-webartifactId>        dependency>
        <dependency>            <groupId>org.springframework.bootgroupId>            <artifactId>spring-boot-autoconfigureartifactId>        dependency>        <dependency>            <groupId>org.springframework.bootgroupId>            <artifactId>spring-boot-starter-testartifactId>            <scope>testscope>        dependency>
    dependencies>project>

工具类

package com.et.thumbnailtor.util;
import net.coobird.thumbnailator.Thumbnails;import net.coobird.thumbnailator.geometry.Positions;import net.coobird.thumbnailator.name.Rename;
import javax.imageio.ImageIO;import java.io.File;import java.io.IOException;import java.util.Objects;
public class ThumbnailatorUtil {    public static void main(String[] args) throws IOException {        String originalPic = "/Users/liuhaihua/IdeaProjects/springboot-demo/thumbnailator/src/main/resources/origin-image/pexels-mike-b-130851.jpg";        String picturePath = "/Users/liuhaihua/IdeaProjects/springboot-demo/thumbnailator/src/main/resources/output/";
        // Then output the result according to the parameters        Thumbnails.of(originalPic)                .size(400, 300)                .toFile(picturePath + "climb-up.size.400X300.jpeg");
        // Then enlarge it proportionally and take the smallest value        Thumbnails.of(originalPic)                .size(4400, 3400)                .toFile(picturePath + "climb-up.size.4400X3300.jpeg");
      //Then scale down and take the smallest value        Thumbnails.of(originalPic)                .size(200, 150)                .toFile(picturePath + "climb-up.size.200X150.jpeg");
        // keepAspectRatio        Thumbnails.of(originalPic)                .size(200, 300)                .keepAspectRatio(false)                .toFile(picturePath + "climb-up.size.notKeepRatio.200X300.jpeg");
        // forcesize        Thumbnails.of(originalPic)                .forceSize(200, 300)                .toFile(picturePath + "climb-up.forceSize.200X300.jpeg");
        // The width and height are reduced to 0.1 times of the original        Thumbnails.of(originalPic)                .scale(0.1f)                .toFile(picturePath + "climb-up.scale.403X302.jpeg");

        // The width and height are both enlarged to 1.1 times the original        Thumbnails.of(originalPic)                .scale(1.1f)                .toFile(picturePath + "climb-up.scale.4435X3326.jpeg");
        // rotate        Thumbnails.of(originalPic)                .size(400,300)                .rotate(45)                .toFile(picturePath + "climb-up.rotate.45.jpeg");

        // add watermark        Thumbnails.of(originalPic)                .size(2000,1500)                .watermark(Positions.TOP_RIGHT, ImageIO.read(                        new File("/Users/liuhaihua/IdeaProjects/springboot-demo/thumbnailator/src/main/resources/origin-image/watermark.jpg")), 0.5f)                .toFile(picturePath + "climb-up.watermark.jpeg");

        // crop        Thumbnails.of(originalPic)                .sourceRegion(Positions.TOP_RIGHT, 1800, 1800)                .size(400, 400)                .toFile(picturePath + "climb-up.crop.jpeg");
        // batch operator        Thumbnails.of(Objects.requireNonNull(new File(picturePath).listFiles()))                .size(400, 400)                .toFiles(Rename.PREFIX_DOT_THUMBNAIL);
    }}