如何获取阿里云上的图片压缩后再上传

本文用到了一个谷歌的图片处理插件 thumbnailator

		<!-- 图片处理 -->
        <dependency>
            <groupId>net.coobird</groupId>
            <artifactId>thumbnailator</artifactId>
            <version>0.4.8</version>
        </dependency>

• 图片压缩工具类

package com.zl.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import net.coobird.thumbnailator.Thumbnails;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;

/**
 * <br>
 * 文件名称： PicUtil<br>
 * 初始作者： Lynn <br>
 * 创建日期： 2021/4/16 14:07<br>
 * 功能说明： Thumbnails 图片处理工具类 <br>
 * <br>
 * ================================================<br>
 * 修改记录：<br>
 * 修改作者 日期 修改内容<br>
 * <br>
 * ================================================<br>
 * Copyright Lynn 2021/4/16 .All rights reserved.<br>
 *
 * @author Lynn
 */
public class PicUtil {

    private static Logger logger = LoggerFactory.getLogger(PicUtil.class);

    /**
     * 根据指定大小压缩图片
     *
     * @param imageBytes  源图片字节数组
     * @param desFileSize 指定图片大小，单位kb
     * @return 压缩质量后的图片字节数组
     */
    public static byte[] compressPicForScale(byte[] imageBytes, long desFileSize) {
        if (imageBytes == null || imageBytes.length <= 0 || imageBytes.length < desFileSize * 1024) {
            return imageBytes;
        }
        long srcSize = imageBytes.length;
        double accuracy = getAccuracy(srcSize / 1024);
        try {
            while (imageBytes.length > desFileSize * 1024) {
                ByteArrayInputStream inputStream = new ByteArrayInputStream(imageBytes);
                ByteArrayOutputStream outputStream = new ByteArrayOutputStream(imageBytes.length);
                Thumbnails.of(inputStream)
                        .scale(accuracy)
                        .outputQuality(accuracy)
                        .toOutputStream(outputStream);
                imageBytes = outputStream.toByteArray();
            }
            logger.info("图片原大小={}kb | 压缩后大小={}kb", srcSize / 1024, imageBytes.length / 1024);
        } catch (Exception e) {
            logger.error("【图片压缩】msg=图片压缩失败!", e);
        }
        return imageBytes;
    }

    /**
     * 自动调节精度(经验数值)
     *
     * @param size 源图片大小
     * @return 图片压缩质量比
     */
    private static double getAccuracy(long size) {
        double accuracy;
        if (size < 2048) {
            accuracy = 0.8;
        } else if (size < 7168) {
            accuracy = 0.7;
        } else if (size < 10240){
            accuracy = 0.5;
        }else {
            accuracy = 0.4;
        }
        return accuracy;
    }
}

• 如何使用? 上代码

package com.zl.service.impl.ocr;

import com.zl.framework.validator.annotation.NotEmpty;
import com.zl.service.ocr.CommonOssService;
import com.zl.framework.util.OssUtil;
import com.zl.util.PicUtil;
import org.apache.commons.collections.MapUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Map;

/**
 * <br>
 * 文件名称： CommonOssServiceImpl<br>
 * 初始作者： Lynn <br>
 * 创建日期： 2021/4/15 17:39<br>
 * 功能说明：  <br>
 * <br>
 * ================================================<br>
 * 修改记录：<br>
 * 修改作者 日期 修改内容<br>
 * <br>
 * ================================================<br>
 * Copyright Lynn 2021/4/15 .All rights reserved.<br>
 *
 * @author Lynn
 */
@Service
public class CommonOssServiceImpl implements CommonOssService {

    private static Logger logger = LoggerFactory.getLogger(CommonOssServiceImpl.class);

    /**
     * 【公共接口】获取图片压缩并上传
     * @param params sourcefile 原图名称。即不包括Bucket名称在内的原图完整访问路径，例如example/image.png
     * @return String
     */
    @NotEmpty(params = {"sourcefile"})
    @Override
    public Map<String, Object> commonPersistPic(Map<String, Object> params) {
        // 获取导入源文件
        String sourceFile = MapUtils.getString(params, "sourcefile");
        String ossSourceFile = getOssUploadKey(sourceFile);
        params.put("ossurl",ossSourceFile);
        InputStream inputStream = null;

        try {
            inputStream = OssUtil.getObjectContent(sourceFile);
            byte[] sourceByte = toByteArray(inputStream);
            byte[] resultByte = PicUtil.compressPicForScale(sourceByte, 1500);
            InputStream sbs = new ByteArrayInputStream(resultByte);
            OssUtil.uploadFile2OSS(sbs,ossSourceFile);
            return params;
        } catch (Exception e) {
            try {
                throw e;
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return params;
    }

    /**
     * 输入流转byte[]数组
     * @param input InputStream
     * @return byte[]
     * @throws IOException IOException
     */
    private static byte[] toByteArray(InputStream input) throws IOException {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024*4];
        int n ;
        while (-1 != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
        }
        return output.toByteArray();
    }

    /**
     * 根据文件名前缀生成上传文件key
     * @return String
     */
    private String getOssUploadKey(String sourceFile) {
        // 文件上传存放路径
        return "attachment/incoming/" + sourceFile;
    }
}