摘要：時間年月日星期六說明本文部分內容均來自慕課網。可以更加專注于業務邏輯開發，縮短項目開發周期，提高項目開發速度。

時間：2017年07月15日星期六
說明：本文部分內容均來自慕課網。@慕課網：http://www.imooc.com
教學源碼：無
學習源碼：https://github.com/zccodere/s...

在用戶進行信息概略瀏覽的時候，提供縮略圖

提升程序性能
提升程序效率

課程內容

Java圖片等比縮略圖實現方式介紹
課程項目案例介紹
實現圖片等比縮略圖的生成

實現方式

Thumbnailator類庫：
    推薦使用
    size()API方法
Java AWT類庫：
    根據縮略比例計算縮略圖高度和寬度
    使用Image類獲得原圖的縮放版本
    使用ImageIO類保存縮略圖
    BufferedImage類
    ImageIO類
    Graphics類

案例介紹

基于springmvc框架的Java Web應用程序，允許上傳圖片，并生成圖片的縮略圖

效果示意圖

個人學習時，使用springboot+freemaker+mavem搭建，POM文件如下

    4.0.0

    com.myimooc
    thumbnail
    0.0.1-SNAPSHOT
    jar

    thumbnail
    http://maven.apache.org

    
        org.springframework.boot
        spring-boot-starter-parent
        1.5.1.RELEASE
         
    

    
        UTF-8
        UTF-8
    

    
        
            org.springframework.boot
            spring-boot-starter
        

        
            org.springframework.boot
            spring-boot-starter-web
        

        
            org.springframework.boot
            spring-boot-starter-freemarker
        

        
            commons-io
            commons-io
            2.5
        

        
        
            net.coobird
            thumbnailator
            0.4.8
        

    

    
        
            
                org.apache.maven.plugins
                maven-compiler-plugin
                
                    1.8
                    1.8
                
            
        
    

項目層級結構如下

代碼演示：

    
圖片上傳
    
    

        
請上傳圖片
        
        
    
    

代碼演示：

package com.myimooc.thumbnail.controller;

import javax.servlet.http.HttpServletRequest;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.ModelAndView;

import com.myimooc.thumbnail.service.ThumbnailService;
import com.myimooc.thumbnail.service.UploadService;

/**
 * Thumbnail 控制器類
 * @author ZhangCheng on 2017-07-19
 *
 */
@Controller
@RequestMapping("/")
public class ThumbnailController {
    
    private static Logger logger = LoggerFactory.getLogger(ThumbnailController.class);
    
    @Autowired
    private UploadService uploadService;
    @Autowired
    private ThumbnailService thumbnailService;
    
    @PostMapping("thumbnail")
    public ModelAndView thumbnail(MultipartFile image,HttpServletRequest request){
        
        ModelAndView mav = new ModelAndView();
        
        String uploadPath = "static/images/";
        String realUploadPath = getClass().getClassLoader().getResource(uploadPath).getPath();
        
        logger.info("上傳相對目錄：{}",uploadPath);
        logger.info("上傳絕對目錄：{}",uploadPath);
        
        String imageUrl = uploadService.uploadImage(image, uploadPath, realUploadPath);
        String thumImageUrl = thumbnailService.thumbnail(image, uploadPath, realUploadPath);
        
        mav.addObject("imageURL", imageUrl);
        mav.addObject("thumImageUrl", thumImageUrl);
        mav.setViewName("thumbnail");
        return mav;
    }
    
}

代碼演示：

package com.myimooc.thumbnail.service;

import java.io.File;
import java.io.IOException;
import org.apache.commons.io.FileUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;

/**
 * 圖片上傳服務類
 * @author ZhangCheng on 2017-07-19
 *
 */
@Service
public class UploadService {
    
    private static Logger logger = LoggerFactory.getLogger(UploadService.class);
    
    public String uploadImage(MultipartFile file,String uploadPath,String realUploadPath){
        
        logger.info("上傳的相對路徑：{}",uploadPath);
        logger.info("上傳的絕對路徑：{}",realUploadPath);
        
        String filePath = realUploadPath + file.getOriginalFilename();
        
        try {
            File targetFile=new File(filePath);
            logger.info("將圖片寫入文件："+ filePath);
            FileUtils.writeByteArrayToFile(targetFile, file.getBytes());
        } catch (IOException e) {
            logger.info("圖片寫入失敗");
            e.printStackTrace();
        }
        return uploadPath + "/" + file.getOriginalFilename();
    }
}

代碼演示：

package com.myimooc.thumbnail.service;

import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;

import net.coobird.thumbnailator.Thumbnails;

/**
 * 縮略圖服務類
 * @author ZhangCheng on 2017-07-19
 *
 */
@Service
public class ThumbnailService {
    
    public static final int WIDTH = 100;
    public static final int HEIGHT = 100;
    
    public String thumbnail(MultipartFile file,String uploadPath,String realUploadPath){
        try{
            String des = realUploadPath + "/thum_" + file.getOriginalFilename();
            Thumbnails.of(file.getInputStream()).size(WIDTH, HEIGHT).toFile(des);
        }catch (Exception e) {
            e.printStackTrace();
        }
        return uploadPath + "/thum_" + file.getOriginalFilename();
    }
}

代碼演示：

package com.myimooc.thumbnail.service;

import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import javax.imageio.ImageIO;

import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;

/**
 * 縮略圖服務類
 * 
 * @author ZhangCheng on 2017-07-19
 *
 */
@Service
public class ThumbnailAWTService {

    public static final int WIDTH = 100;
    public static final int HEIGHT = 100;

    @SuppressWarnings("static-access")
    public String thumbnail(MultipartFile file, String uploadPath, String realUploadPath) {

        OutputStream os = null;

        try {
            String des = realUploadPath + "/thum_" + file.getOriginalFilename();

            os = new FileOutputStream(des);

            Image image = ImageIO.read(file.getInputStream());
            int width = image.getWidth(null);// 原圖狂寬度
            int height = image.getHeight(null);// 原圖高度

            int rateWidth = width / WIDTH;// 寬度縮略比例
            int rateHeight = height / HEIGHT;// 高度縮略比

            // 寬度縮略比例大于高度縮略比例，使用寬度縮略比例
            int rate = rateWidth > rateHeight ? rateWidth : rateHeight;

            // 計算縮略圖最終的寬度和高度
            int newWidth = width / rate;
            int newHeight = height / rate;

            BufferedImage bufferedImage = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_RGB);

            bufferedImage.getGraphics().drawImage(image.getScaledInstance(newWidth, newHeight, image.SCALE_SMOOTH), 0,
                    0, null);

            String imageType = file.getContentType().substring(file.getContentType().indexOf("/") + 1);
            ImageIO.write(bufferedImage, imageType, os);

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (os != null) {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return uploadPath + "/thum_" + file.getOriginalFilename();
    }
}

代碼演示：

    
操作結果
    
    
    

    返回
    

效果演示：

啟動項目，訪問主頁

點擊選擇圖片

點擊上傳，結果顯示如下

通過使用開源組件，可以很方便的實現自己需要的功能。可以更加專注于業務邏輯開發，縮短項目開發周期，提高項目開發速度。