慕课网_《Java实现图片等比例缩略图》学习总结

摘要：时间年月日星期六说明本文部分内容均来自慕课网。可以更加专注于业务逻辑开发，缩短项目开发周期，提高项目开发速度。

时间：2017年07月15日星期六
说明：本文部分内容均来自慕课网。@慕课网：http://www.imooc.com
教学源码：无
学习源码：https://github.com/zccodere/s...

在用户进行信息概略浏览的时候，提供缩略图

提升程序性能
提升程序效率

课程内容

Java图片等比缩略图实现方式介绍
课程项目案例介绍
实现图片等比缩略图的生成

实现方式

Thumbnailator类库：
    推荐使用
    size()API方法
Java AWT类库：
    根据缩略比例计算缩略图高度和宽度
    使用Image类获得原图的缩放版本
    使用ImageIO类保存缩略图
    BufferedImage类
    ImageIO类
    Graphics类

案例介绍

基于springmvc框架的Java Web应用程序，允许上传图片，并生成图片的缩略图

效果示意图

个人学习时，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
                
            
        
    

项目层级结构如下

代码演示：

    
图片上传
    
    

        
请上传图片
        
        
    
    

代码演示：

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 控制器类
 * @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("上传相对目录：{}",uploadPath);
        logger.info("上传绝对目录：{}",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;
    }
    
}

代码演示：

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;

/**
 * 图片上传服务类
 * @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("上传的相对路径：{}",uploadPath);
        logger.info("上传的绝对路径：{}",realUploadPath);
        
        String filePath = realUploadPath + file.getOriginalFilename();
        
        try {
            File targetFile=new File(filePath);
            logger.info("将图片写入文件："+ filePath);
            FileUtils.writeByteArrayToFile(targetFile, file.getBytes());
        } catch (IOException e) {
            logger.info("图片写入失败");
            e.printStackTrace();
        }
        return uploadPath + "/" + file.getOriginalFilename();
    }
}

代码演示：

package com.myimooc.thumbnail.service;

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

import net.coobird.thumbnailator.Thumbnails;

/**
 * 缩略图服务类
 * @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();
    }
}

代码演示：

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;

/**
 * 缩略图服务类
 * 
 * @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);// 原图狂宽度
            int height = image.getHeight(null);// 原图高度

            int rateWidth = width / WIDTH;// 宽度缩略比例
            int rateHeight = height / HEIGHT;// 高度缩略比

            // 宽度缩略比例大于高度缩略比例，使用宽度缩略比例
            int rate = rateWidth > rateHeight ? rateWidth : rateHeight;

            // 计算缩略图最终的宽度和高度
            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();
    }
}

代码演示：

    
操作结果
    
    
    

    返回
    

效果演示：

启动项目，访问主页

点击选择图片

点击上传，结果显示如下

通过使用开源组件，可以很方便的实现自己需要的功能。可以更加专注于业务逻辑开发，缩短项目开发周期，提高项目开发速度。