添加依赖：

<!-- google图片处理 -->
<dependency><groupId>net.coobird</groupId><artifactId>thumbnailator</artifactId><version>0.4.11</version>
</dependency>

代码

package com.solar.oa.card.util;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.math.BigDecimal;
import javax.imageio.ImageIO;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import net.coobird.thumbnailator.Thumbnails;/*** 图片处理* @ClassName: ImageUtil.java* @Description: TODO * @date 2020年6月30日 下午2:24:55* @author yqwang*/
public class ImageUtil {private final static Logger logger = LoggerFactory.getLogger(ImageUtil.class);/*** 【压缩图片】到要求的图片标准:  宽[300,500],高[300,500];100kb;jpg/jpeg* 先按宽高压缩，压缩后如果还不满足100kb,则按质量递归压缩* @Title:compressPhoto* @Description: TODO * @date 2020年6月30日 下午2:11:52* @author yqwang* @param imgFile 源图片文件* @param maxkb 目标kb* @param photoWidth 目标宽度* @param photoHeight 模板高度* @param quality 质量* @return 处理后的文件byte[]* @throws Exception*/public static byte[] compressPhoto(File imgFile,Integer maxkb,Integer photoWidth,Integer photoHeight,Float quality) throws Exception{// 1.压缩图片是否存在if(imgFile == null || !imgFile.exists()){throw new Exception("图片文件不存在。");}byte[] bytes = readFileToByteArray(imgFile);if(bytes == null || bytes.length == 0){throw new Exception("图片文件为空。");}// 2.是否超过100kb?没超过就不处理图片long fileSize = bytes.length;if (fileSize <= maxkb * 1024) {logger.info("图片不超过{}kb,无需压缩。",maxkb);return bytes;}// 3.压缩到300-500宽高，100kbBufferedImage bim = ImageIO.read(new ByteArrayInputStream(bytes));int imgWidth = bim.getWidth();int imgHeight = bim.getHeight();// 3.1.先按宽高判断是否需要缩放  outputQuality=1确保画质清晰if(imgWidth >= photoWidth && imgHeight >= photoHeight){logger.info("先按宽{}高{}压缩。",photoWidth,photoHeight);ByteArrayOutputStream out = new ByteArrayOutputStream();//Closing a <tt>ByteArrayOutputStream</tt> has no effect.   因此无需closeThumbnails.of(new ByteArrayInputStream(bytes)).size(photoWidth, photoHeight).outputQuality(1).outputFormat("jpg").toOutputStream(out);bytes = out.toByteArray();}// 3.2.判断按宽高缩放后是否超过100kb,超过递归就按质量压缩（图片会变得跟模糊！）bytes = compressPhotoByQuality(bytes, quality, maxkb);return bytes;}/*** 递归按quality质量处理，压缩到maxkb后返回新的bytes值* @Title:compressPhotoByQuality* @Description: TODO * @date 2020年6月30日 下午2:24:36* @author yqwang* @param bytes 源文件字节* @param quality 压缩质量 （如果为1则不处理）* @param maxkb 要求压缩到的最大kb* @return* @throws IOException*/public static byte[] compressPhotoByQuality(byte[] bytes,Float quality,long maxkb) throws IOException{if(bytes == null){return bytes;}logger.info("开始按质量压缩图片({}kb)。",bytes.length/1024);// 如果配置的1，则不再处理,多说无益if(quality == 1){logger.info("quality=1,不执行压缩。");return bytes;}// 满足目标kb值，则返回long fileSize = bytes.length;if (fileSize <= maxkb * 1024) {logger.info("图片文件{}kb<={}kb,不再压缩质量。",fileSize/1024,maxkb);return bytes;}// Closing a <tt>ByteArrayOutputStream</tt> has no effect.   因此无需closeByteArrayOutputStream out = null;out = new ByteArrayOutputStream();BufferedImage bim = ImageIO.read(new ByteArrayInputStream(bytes));int imgWidth = bim.getWidth();int imgHeight = bim.getHeight();// 如果不处理size,只用quality,可能导致一致压缩不到目标值，一致递归在当前方法中！！int desWidth = new BigDecimal(imgWidth).multiply(new BigDecimal(quality)).intValue();int desHeight = new BigDecimal(imgHeight).multiply(new BigDecimal(quality)).intValue();logger.info("图片文将按照width={}*height={}进行压缩，画质quality={}。",desWidth,desHeight,quality);Thumbnails.of(new ByteArrayInputStream(bytes)).size(desWidth, desHeight).outputQuality(quality).outputFormat("jpg").toOutputStream(out);//递归return compressPhotoByQuality(out.toByteArray(), quality, maxkb);}/**File to bytes[]*/public static byte[] readFileToByteArray(File f) throws Exception {byte[] fileb = null;InputStream is = null;ByteArrayOutputStream out = new ByteArrayOutputStream();try {is = new FileInputStream(f);byte[] b = new byte[1024];int n;while ((n = is.read(b)) != -1) {out.write(b, 0, n);}fileb = out.toByteArray();return fileb;} catch (Exception var16) {throw new Exception("readFileToByteArray", var16);} finally {if (is != null) {try {is.close();} catch (Exception var15) {;}}if (out != null) {try {out.close();} catch (Exception var14) {;}}}}
}

 测试

package com.solar.oa.card.util;import java.io.File;
import java.io.FileOutputStream;
import org.apache.commons.codec.binary.Base64;public class ImageTest {public static void main(String[] args) throws Exception {// 图片压缩File file = new File("D://test/1.jpg");/*@Parameters:imgFile 源图片文件；maxkb 目标kb；photoWidth 目标宽度；photoHeight 模板高度；quality 质量*/byte[] bytes = ImageUtil.compressPhoto(file, 100, 300, 300, 0.9f);// 输出到文件File desFile = new File("D://test/2.jpg"); FileOutputStream fos = new FileOutputStream(desFile);fos.write(bytes);fos.close();// 转base64System.out.println("data:image/jpg;base64,"+ Base64.encodeBase64String(bytes));}
}

效果：1.86MB-->58kb,且压缩后图片依然清晰！

source.jpg: 2708x3085  1.86MB

result.jpg:263x300  58kb

result: