JS实现上传图片的三种方法并实现预览图片功能

时间:2024-03-07 10:42:53

转载地址:https://www.cnblogs.com/OldJack/p/7163725.html


在常见的用户注册页面,需要用户在本地选择一张图片作为头像,并同时预览。

常见的思路有两种:一是将图片上传至服务器的临时文件夹中,并返回该图片的url,然后渲染在html页面;另一种思路是,直接在本地内存中预览图片,用户确认提交后再上传至服务器保存。

这两种方法各有利弊,方法一很明显,浪费流量和服务器资源;方法二则加重了浏览器的负担,并且对浏览器的兼容性要求更高(在某些低版本中的IE浏览器不支持)。

以下是实现上述思路的方法:

1. 模板文件

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <title>Title</title>
 6 </head>
 7 <body>
 8     <div style="margin-left: 30px; margin-top: 30px">
 9         <form action="">
10             {% csrf_token %}
11         <h3>用户注册</h3>
12         <p>用户名:<input type="text" name="userName"></p>
13         <p>密码:<input type="password" name="password"></p>
14         <p>邮箱:<input type="text" name="email"></p>
15             <input id="avatar" type="text" value="/static/images/sample.png" name="avatar" style="width: 400px"> {# 实际应用中要将该input标签隐藏,display:none; #}
16             <p><input type="submit" value="注册"></p>
17             </form>
18         <div style="position: absolute; top: 85px; left: 300px;">
19         <input id="avatarSlect" type="file" style="position: absolute;float: left; z-index: 10; opacity: 0;width: 100px; height: 100px;">
20         <img id="avatarPreview" src="/static/images/sample.png" title="点击更换图片" style="position: absolute; z-index: 9; float: left; width: 100px; height: 100px">
21             </div>
22     </div>
23 </body>
24 
25 <script src="/static/jquery-3.2.1.js"></script>
26 <script>
27     $(function () {
28             bindAvatar();
29   });
30     function bindAvatar() {
31             if(window.URL.createObjectURL){
32                 bindAvatar3();
33             }else if(window.FileReader){
34                 bindAvatar2();
35             }else {
36                 bindAvatar1();
37             }
38   }
39 
40     /*Ajax上传至后台并返回图片的url*/
41     function bindAvatar1() {
42         $("#avatarSlect").change(function () {
43         var csrf = $("input[name=\'csrfmiddlewaretoken\']").val();
44         var formData=new FormData();
45         formData.append("csrfmiddlewaretoken",csrf);
46         formData.append(\'avatar\', $("#avatarSlect")[0].files[0]);    /*获取上传的图片对象*/
47         $.ajax({
48             url: \'/upload_avatar/\',
49                     type: \'POST\',
50                     data: formData,
51                     contentType: false,
52                     processData: false,
53                     success: function (args) {
54                 console.log(args);    /*服务器端的图片地址*/
55                             $("#avatarPreview").attr(\'src\',\'/\'+args);    /*预览图片*/
56                             $("#avatar").val(\'/\'+args);    /*将服务端的图片url赋值给form表单的隐藏input标签*/
57           }
58             })
59   })
60     }
61     /*window.FileReader本地预览*/
62     function bindAvatar2() {
63         console.log(2);
64              $("#avatarSlect").change(function () {
65                      var obj=$("#avatarSlect")[0].files[0];
66                      var fr=new FileReader();
67                      fr.onload=function () {
68                              $("#avatarPreview").attr(\'src\',this.result);
69                              console.log(this.result);
70                              $("#avatar").val(this.result);
71            };
72            fr.readAsDataURL(obj);
73        })
74   }
75   /*window.URL.createObjectURL本地预览*/
76   function bindAvatar3() {
77       console.log(3);
78             $("#avatarSlect").change(function () {
79                     var obj=$("#avatarSlect")[0].files[0];
80                     var wuc=window.URL.createObjectURL(obj);
81                      $("#avatarPreview").attr(\'src\',wuc);
82                      $("#avatar").val(wuc);
83 {#                     $("#avatarPreview").load(function () {#}        /*当图片加载后释放内存空间,但在jQuery3.2.1中会报错。浏览器关闭后也会自动释放*/
84 {#                             window.URL.revokeObjectURL(wuc);#}
85 {#           })#}
86       })
87   }
88 
89 </script>
90 </html>
test.html

2. 视图函数

 1 from django.shortcuts import render, HttpResponse
 2 
 3 
 4 def test(request):
 5     return render(request, \'test.html\')
 6 
 7 
 8 def upload_avatar(request):
 9     file_obj = request.FILES.get(\'avatar\')
10     file_path = os.path.join(\'static/images\', file_obj.name)
11     with open(file_path, \'wb\') as f:
12         for chunk in file_obj.chunks():
13             f.write(chunk)
14     return HttpResponse(file_path)
upload_avatar.py

3. 路由系统

1 from django.conf.urls import url
2 from django.contrib import admin
3 from home import views as homeViews
4 
5 urlpatterns = [
6     url(r\'^admin/\', admin.site.urls),
7     url(r\'^upload_avatar/\', homeViews.upload_avatar),  # 上传头像
8     url(r\'^test/\', homeViews.test),  # 测试页面
9 ]
urls.py

验证效果:

选择图片前:

 

Ajax上传图片至服务器,并返回浏览器该图片的url:

 

window.FileReader本地预览,form表单提交:

 

 window.URL.createObjectURL本地预览,form表单提交:

 


转载地址:https://www.cnblogs.com/OldJack/p/7163725.html