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js图片裁剪原理

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项目需求有个功能要实现头像，让我这个后端开发来做这个确实有点为难，结合网上大神的例子，做了个简单的功能，以备不时之需

实现效果

JAVA spring+jcrop.js实现简单的头像剪裁

页面+js

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
%>



  
    
    
    My JSP 'face.jsp' starting page
    
    
    
        
    
    
    
<%--     --%>
    
    
    <script type="text/javascript" src="/n/<%=basePath%>static/js/jquery-1.9.1.min.js"></script>
    <script type="text/javascript" src="/n/<%=basePath%>static/js/ajaxfileupload.js"></script>
    <script type="text/javascript" src="/n/<%=basePath%>static/js/bootstrap.js"></script>
    <script type="text/javascript" src="/n/<%=basePath%>static/js/jquery.json-2.4.js" charset="UTF-8"></script> 
    <script type="text/javascript" src="/n/<%=basePath%>static/js/jquery.validate.js"></script> 
    <script type="text/javascript" src="/n/<%=basePath%>static/js/jquery.Jcrop.js"></script>
     
    <script type="text/javascript">
        /* jcrop对象，全局变量方便操作 */
        var api = null;
        /* 原图宽度 */
        var boundx;
        /* 原图高度 */
        var boundy;
        
        /* 选择图片事件 */
        function readURL(URL){
            var reader = new FileReader();
            reader.readAsDataURL(URL.files[0]);
            reader.onload = function(e){
                $("#faceId").removeAttr("src");
                $("#lookId").removeAttr("src");
                $("#faceId").attr("src",e.target.result);
                $("#lookId").attr("src",e.target.result); 
                $("#faceId").Jcrop({
                    onChange: showPreview,
                    onSelect: showPreview,
                    aspectRatio: 1,
                    boxWidth:600
                  },function(){
                    // Use the API to get the real image size
                    //使用API来获得真实的图像大小
                    var bounds = this.getBounds();
                    boundx = bounds[0];
                    boundy = bounds[1];
                    // Store the API in the jcrop_api variable
                    //jcrop_api变量中存储API
                    api = this;
                    
                    $("#boundx").val(boundx);
                    $("#boundy").val(boundy);
                    
                  });
             };
              /* 移除jcrop */
              if (api != undefined) {
                  api.destroy();
              }
              
            //简单的事件处理程序，响应自onChange,onSelect事件，按照上面的Jcrop调用
            function showPreview(coords){
                /* 设置剪切参数 */
                $("#x").val(coords.x);
                $("#y").val(coords.y);
                $("#w").val(coords.w);
                $("#h").val(coords.h);
                if(parseInt(coords.w) > 0){
                    //计算预览区域图片缩放的比例，通过计算显示区域的宽度(与高度)与剪裁的宽度(与高度)之比得到
                    var rx = $("#preview_box").width() / coords.w; 
                    var ry = $("#preview_box").height() / coords.h;
                    $("#lookId").css({
                        width:Math.round(rx * $("#faceId").width()) + "px", //预览图片宽度为计算比例值与原图片宽度的乘积
                        height:Math.round(rx * $("#faceId").height()) + "px",   //预览图片高度为计算比例值与原图片高度的乘积
                        marginLeft:"-" + Math.round(rx * coords.x) + "px",
                        marginTop:"-" + Math.round(ry * coords.y) + "px"
                    });
                }
            }

        }
    
    
    </script>
    

  
  
  
    

        
        
            

                

                    
                        头像：
                        
                    
                    
                            
                            附件


                        
                         
                         
                         
                        
                        
                        

                    
                

                
                

                    
                        头像预览：
                    
                    
                        
                        预览
                        
                    
                

                

                    
                        用户名：
                    
                    
                        艺名：

后端控制器

package com.lovo.controller;

import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;

import com.lovo.utils.CutImgeUtil;
import com.lovo.utils.FileUploadCheck;


@Controller
public class FaceController {
    
    private static Logger logger = Logger.getLogger(FaceController.class);

    @RequestMapping(value = "/faceUpload.do",method = RequestMethod.POST)
    public void faceLoginController(HttpServletRequest request,HttpServletResponse response,Model model,
            @RequestParam("imgFile") MultipartFile imgFile,String userName,String artName){
        
        //剪裁图片坐标
        String x = request.getParameter("x");
        String y = request.getParameter("y");
        String w = request.getParameter("w");
        String h = request.getParameter("h");
        
        //原始图片坐标
        String boundx = request.getParameter("boundx");
        String boundy = request.getParameter("boundy");
        
        //切图参数
        int imgeX = (int) Double.parseDouble(x);
        int imgeY = (int) Double.parseDouble(y);
        int imegW = (int) Double.parseDouble(w);
        int imgeH = (int) Double.parseDouble(h);
        int srcX = (int) Double.parseDouble(boundx);
        int srcY = (int) Double.parseDouble(boundy);
        
        //文件保存文件夹
        String path = request.getSession().getServletContext().getRealPath("/")+"fileUpload"+File.separator;
        //文件重命名
        Date day = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
        String newName = sdf.format(day)+System.currentTimeMillis()+".jpg";

        try 
        {
            //处理头像附件
            if(imgFile !=null)
            {
                //判断是否为图片文件
                if(FileUploadCheck.allowUpload(imgFile.getContentType()))
                {
                    boolean cut = CutImgeUtil.cutImge(imgFile.getInputStream(), imgeX, imgeY, imegW, imgeH, srcX, srcY, path+newName);
                    if(cut)
                    {
                        //当头像剪切成功进行用户信息数据库存储
                        System.out.println(userName+" "+artName+" "+newName);
                    }
                    
                }
            }
            
        } catch (Exception e)
        {
            e.printStackTrace();
            logger.error("上传失败");
        }
        
        
    }
}

工具类

package com.lovo.utils;

import java.awt.Graphics;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.awt.image.CropImageFilter;
import java.awt.image.FilteredImageSource;
import java.awt.image.ImageFilter;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.InputStream;

import javax.imageio.ImageIO;

import org.apache.log4j.Logger;



public class CutImgeUtil {
    
    private static Logger logger = Logger.getLogger(CutImgeUtil.class);
    
    /**
     * 图片剪切工具类
     * @param input 图片输入流
     * @param x 截取时的x坐标
     * @param y 截取时的y坐标
     * @param desWidth 截取的宽度
     * @param desHeight 截取的高度
     * @param srcWidth 页面图片的宽度
     * @param srcHeight 页面图片的高度
     * @param newFilePath 保存路径+文件名
     * @return
     */
    public static boolean cutImge(InputStream input, int x, int y, int desWidth, int desHeight, int srcWidth,int srcHeight,String newFilePath){
            
        boolean cutFlag = true;
        
        try 
        {
            //图片类
            Image imge ;
            ImageFilter cropFilter;
            
            //读取图片
            BufferedImage bi = ImageIO.read(input);
            
            //当剪裁大小小于原始图片大小才执行
            if(srcWidth >= desWidth && srcHeight >= desHeight)
            {
                //获取原始图
                Image image = bi.getScaledInstance(srcWidth, srcHeight, Image.SCALE_DEFAULT);
                //获取新图
                cropFilter = new CropImageFilter(x, y, desWidth, desHeight);
                imge = Toolkit.getDefaultToolkit().createImage(new FilteredImageSource(image.getSource(), cropFilter));
                BufferedImage tag = new BufferedImage(desWidth, desHeight, BufferedImage.TYPE_INT_RGB);
                Graphics g = tag.getGraphics();
                g.drawImage(imge, 0, 0, null);
                g.dispose();
                
                File out = new File(newFilePath);
               // 输出文件
                ImageIO.write(tag, "JPEG", out);
            }
            
        } catch (Exception e) 
        {
            cutFlag = false;
            e.printStackTrace();
            logger.error("剪切失败");
        }
        return cutFlag;
        
    }
}

package com.lovo.utils;

import java.util.Arrays;
import java.util.List;

public class FileUploadCheck {
    
    //支持的文件类型
    public static final List ALLOW_TYPES = Arrays.asList("image/jpg","image/jpeg","image/png","image/gif");

    //校验文件类型是否是被允许的
    public static boolean allowUpload(String postfix){
        return ALLOW_TYPES.contains(postfix);
    }
}

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