Java上传图片预览并通过JS压缩

- 日理万妓 2022-05-17 05:16 296阅读 0赞

**1.前端上传图片JS压缩**

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
    <%
    	String contextPath = request.getContextPath();
    %>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no,width=device-width,height=device-height">
    <script src="<%=contextPath%>/js/jquery-1.11.3.js"></script>
    <title>图片上传</title>
    <style type="text/css">   
        .float_zm{    
            float_zm:left;    
            width : 200px;    
            height: 200px;    
            overflow: hidden;    
            border: 1px solid #CCCCCC;    
            border-radius: 10px;    
            padding: 5px;    
            margin: 5px;    
            
            position:absolute;
            left:50%;
            margin-left: -100px;
        }     
        .result{    
            width: 200px;    
            height: 200px;    
            text-align: center;    
            box-sizing: border-box;    
        }      
    </style> 
    <script type="text/javascript">
    $(function(){
        var input = document.getElementById("file_input_zm");         
         　　　　
        if(typeof FileReader==='undefined'){    
            alert("抱歉，你的浏览器不支持 FileReader");    
            input.setAttribute('disabled','disabled');    
        }else{    
            input.addEventListener('change',readFile,false);    
        }
            
        function readFile(){       
            var iLen = this.files.length;  
            var index = 0;  
            for(var i=0;i<iLen;i++){  
                if (!input['value'].match(/.jpg|.gif|.png|.jpeg|.bmp/i)){　　//判断上传文件格式    
                    return alert("上传的图片格式不正确，请重新选择");    
                }  
                /* if (this.files[i].size > 1048576){
                	return alert("上传的图片大小超过1M，请重新选择");	//判断上传图片大小
                } */ 
                var reader = new FileReader();  
                reader.index = i;    
                reader.readAsDataURL(this.files[i]); //转成base64    
                reader.fileName = this.files[i].name;  
                $("#sfzzm_name").val(reader.fileName);
                reader.onload = function(e){ 
                    $("#zmtp").empty();
                    var result = '<div class="float_zm"><div onclick="select_zm()" class="result"><img id="sfzzm" src="'+this.result+'" /></div></div>';  
                    $("#zmtp").html(result);
                    var img = document.getElementById('sfzzm');
                    img.onload = function(){   
                        var nowHeight = ReSizePic(this); //设置图片预览大小  
                        this.parentNode.style.display = 'block';    
                        var oParent = this.parentNode;    
                        if(nowHeight){    
                            oParent.style.paddingTop = (oParent.offsetHeight - nowHeight)/2 + 'px';    
                        }  
                    	//压缩照片
                        var base64 = yszp(img,this);
                        $("#sfzzm_base64").val(base64);    
                    }   
                }    
            }    
        }    
                     
    })
    
    //压缩照片
    function yszp(img,ThisPic){
    	//缩放图片需要的canvas
    	var canvas = document.createElement('canvas');
    	var context = canvas.getContext('2d');
    	// 图片原始尺寸
    	 var originWidth = ThisPic.width;
    	 var originHeight = ThisPic.height;
    	 // 最大尺寸限制
    	 var maxWidth = 200, maxHeight = 200;
    	 // 目标尺寸
    	 var targetWidth = originWidth, targetHeight = originHeight;
    	 // 图片尺寸超过200x200的限制
    	 if (originWidth > maxWidth || originHeight > maxHeight) {
    	     if (originWidth / originHeight > maxWidth / maxHeight) {
    	         // 更宽，按照宽度限定尺寸
    	         targetWidth = maxWidth;
    	         targetHeight = Math.round(maxWidth * (originHeight / originWidth));
    	     } else {
    	         targetHeight = maxHeight;
    	         targetWidth = Math.round(maxHeight * (originWidth / originHeight));
    	     }
    	 }	     
    	 // canvas对图片进行缩放
    	 canvas.width = targetWidth;
    	 canvas.height = targetHeight;
    	 // 清除画布
    	 context.clearRect(0, 0, targetWidth, targetHeight);
    	 // 图片压缩
    	 context.drawImage(img, 0, 0, targetWidth, targetHeight);
    	 // 返回压缩后的base64
    	 return canvas.toDataURL();
    }
                    
    function ReSizePic(ThisPic) {    
        var RePicWidth = 200; //目标宽度       
        var TrueWidth = ThisPic.width; //图片实际宽度    
        var TrueHeight = ThisPic.height; //图片实际高度  
        if(TrueWidth>TrueHeight){   
            //宽大于高    
            var reWidth = RePicWidth;    
            ThisPic.width = reWidth;    
            //垂直居中    
            var nowHeight = TrueHeight * (reWidth/TrueWidth);    
            return nowHeight;  //将图片修改后的高度返回，供垂直居中用    
        }else{    
            //宽小于高    
            var reHeight = RePicWidth;    
            ThisPic.height = reHeight;    
        }    
    }    
    
    //选择照片
    function select_zm(){
    	$("#file_input_zm").click();
    }  
    
    //上传
    function myCheck(){
    	var sfzzm = $("#sfzzm").attr("src");
    	if(sfzzm == ''){
    		alert("请选择照片");
    		return false;
    	}
    	$("#form").submit();
    }
    </script>
    </head>
    <body>
    	<form id="form" action="wap_ajbj_upload_save.htm" method="post" enctype="multipart/form-data">
    	<input type="hidden" id="sfzzm_name" name="sfzzm_name">
    	<input type="hidden" id="sfzzm_base64" name="sfzzm_base64">
    	<input type="file" id="file_input_zm" name="file_input_zm" style="display: none;"/>
    	<div id="zmtp" style="width: 100%;height: 240px;position:relative;">			
    	    <div class="float_zm">
           		<div class="result" onclick="select_zm()">
           			<img id="sfzzm" name="sfzzm" />
           			<span id="zpbz" style="font-size: 16px;line-height: 200px;">照片(点击上传)</span>
           		</div> 
            </div>
    	</div>	
    	<div style="text-align: center;margin: 0 auto;">
    		<button style="width: 80%;" type="button" onclick="myCheck()">上传</button>
    	</div> 
    	</form>
    </body>
    </html>

**2.后端保存图片**

@RequestMapping(value = "wap_ajbj_upload_save.htm", method = { RequestMethod.GET,RequestMethod.POST })
    	public ModelAndView wap_ajbj_upload_save(MultipartHttpServletRequest request) throws Exception {
    		ModelAndView mv = new ModelAndView("wap/ajbj_index");
    		String sfzzm_base64 = request.getParameter("sfzzm_base64");
    		String sfzzm_name = request.getParameter("sfzzm_name");
    		String suffix = sfzzm_name.substring(sfzzm_name.lastIndexOf(".") + 1);
    		String filename = System.currentTimeMillis() + "." + suffix;
    		String path = filePath + "/ajbj/zm/"+filename;
    		sfzzm_base64 = sfzzm_base64.split(",")[1];
    		GenerateImage(sfzzm_base64, path);
    		return mv;
    	}
    	
    	/**
    	 * @Description: 将base64编码字符串转换为图片
    	 * @param imgStr base64编码字符串
    	 * @param path 图片路径-具体到文件
    	*/ 
        public static boolean GenerateImage(String imgStr,String imgFilePath){     
            if (imgStr == null) //图像数据为空  
                return false;  
            BASE64Decoder decoder = new BASE64Decoder();  
            try{  
                //Base64解码  
                byte[] b = decoder.decodeBuffer(imgStr);  
                for(int i=0;i<b.length;++i){  
                    if(b[i] < 0){//调整异常数据  
                        b[i] += 256;  
                    }  
                }  
                OutputStream out = new FileOutputStream(imgFilePath);      
                out.write(b);  
                out.flush();  
                out.close();  
                return true;  
            }   
            catch (Exception e){  
                return false;  
            }  
        }