zoukankan html css js c++ java

H5图片预览、压缩、上传

目标实现：

　　1、选择图片，前端预览效果

　　2、图片大于1.2M的时候，对图片进行压缩

　　3、以表单的形式上传图片

　　4、图片删除

预览效果图：

代码说明：

1、input:file选择图片

<!-- html部分 -->
<ul id="preview" class="clear">
    <li class="fl">
        <img src="/images/audition/icon_upload.png">
        <input id="fileImage" type="file" name="file[]" multiple />
        <div class="num">0/4</div>
    </li>
</ul>

var imgId = 0;  //图片id标志, 方便删除预览图片

/* 选择图片 */
function choosePic() {
    $('#fileImage').change(function() {
        var files = this.files,
            len = $('#preview').find('.pic').length;
        if (len + files.length > 4) {
            showTip('最多只能上传4张图片哦~');
            return;
        }
        for (var i = 0; i < files.length; i++) {
            var file = files[i];
            if (file.type.indexOf("image") == 0) {
                if (file.size >= 1024 * 1024 * 3) {
                    showTip('图片大小过大，应小于3M');
                } else {
                    showPic(file); //图片预览
                }
            } else {
                showTip('文件"' + file.name + '"不是图片类型')
                break;
            }
        }
    });
}

2、图片预览（base64）

/* 渲染图片 */
function showPic(file) {
    var html = '',
        $wap = $('#preview'),
        reader = new FileReader();
    reader.readAsDataURL(file);
    reader.onload = function(e) {
        var image_base64 = this.result;

        html = '<li class="fl pic" id="imgItem_' + imgId + '">' +
                    '<img src="' + image_base64 + '" alt="">' +
                    '<i class="del-img"></i>' +
                '</li>';
        imgId++;        
        $wap.append(html);
        $('#fileImage').next().text($wap.find('.pic').length + '/4');    

        //图片压缩上传，大于1.2M压缩图片
        if (file.size / 1024 > 1024 * 1.2) {
            dealImage(image_base64, {
                quality: 0.5
            }, function(base64Codes) {
                var bl = processData(base64Codes, file.type);
                uploadPic(bl, imgId);
            });
        } else {
            uploadPic(file, imgId);
        }
    }
}

3、图片压缩

/**
 * 图片压缩（利用canvas）
 * @param  path     图片路径
 * @param  obj      压缩配置width,height,quality，不传则按比例压缩
 * @param  callback  回调函数
 */
function dealImage(path, obj, callback) {
    var img = new Image();
    img.src = path;
    img.onload = function() {
        var that = this;
        // 默认按比例压缩
        var w = that.width,
            h = that.height,
            scale = w / h;
        w = obj.width || w;
        h = obj.height || (w / scale);

        //生成canvas
        var canvas = document.createElement('canvas'),
        ctx = canvas.getContext('2d');
        canvas.width = w;
        canvas.height = h;
        ctx.drawImage(that, 0, 0, w, h);

        // 默认图片质量为0.7
        var quality = 0.7;
        if (obj.quality && obj.quality <= 1 && obj.quality > 0) {
            quality = obj.quality;
        }

        // 回调函数返回base64的值
        var base64 = canvas.toDataURL('image/jpeg', quality);
        callback(base64);
    }
}

压缩后的文件是base64格式，我们希望用file图片的形式上传

/* 将以base64的图片url数据转换为Blob */
function processData(dataUrl, type) {
    var binaryString = window.atob(dataUrl.split(',')[1]),
    arrayBuffer = new ArrayBuffer(binaryString.length),
    intArray = new Uint8Array(arrayBuffer);
    for (var i = 0, j = binaryString.length; i < j; i++) {
        intArray[i] = binaryString.charCodeAt(i);
    }

    var data = [intArray], blob;

    try {
        blob = new Blob(data);
    } catch (e) {
        window.BlobBuilder = window.BlobBuilder ||
            window.WebKitBlobBuilder ||
            window.MozBlobBuilder ||
            window.MSBlobBuilder;
        if (e.name === 'TypeError' && window.BlobBuilder) {
            var builder = new BlobBuilder();
            builder.append(arrayBuffer);
            blob = builder.getBlob(type);
        } else {
            showTip('版本过低，不支持图片压缩上传');
        }
    }
    return blob;
}

4、图片上传

/* 上传图片 */
function uploadPic(file, id) {
    var formData = new FormData();
    formData.append('img', file);
    $.ajax({
        url: '/upload',
        type: 'post',
        dataType: 'json',
        data: formData,
        contentType: false,
        processData: false,           
        success: function(res){
            if(res.respCode == 1000) {
                $('#imgItem_' + id).find('.del-img').attr('data-src', res.data.src);                    
            }else {
                showTip('文件上传失败！'); 
            }
        }
    });  
}

5、其他

function showTip(str) {
    //TODO:信息提示
    console.log(str);
}

/* 删除图片 */
function delPic() {
    var $wap = $('#preview');
    $wap.on('click', '.del-img', function() {
        //TODO:从数据库删除图片
        $(this).parent().remove();
        $('#fileImage').next().text($wap.find('.pic').length + '/4');    
    });
}

源码：

  1 <!DOCTYPE html>
  2 <html lang="en">
  3 <head>
  4     <meta charset="UTF-8">
  5     <title>前端图片预览压缩上传</title>
  6     <style>
  7         .clear::after {
  8           content: '';
  9           clear: both;
 10           display: block;
 11         }
 12         .fl {
 13             float: left;
 14         }
 15         .list-img li {
 16             position: relative;
 17             margin-right: 10px;
 18             list-style: none;
 19         }
 20         .list-img img {
 21             display: inline-block;
 22             width: 50px;
 23             height:50px;    
 24         }
 25         .list-img input {
 26             position: absolute;
 27             top: 0;
 28             left: 0;
 29             z-index: 10;
 30             width: 50px;
 31             height:50px;
 32             opacity: 0;    
 33         }
 34         .list-img i {
 35             position: absolute;
 36             top: 0;
 37             right: 0;
 38             width: 15px;
 39             height: 15px;
 40             background: url(../images/icon_del.png) no-repeat center;
 41             background-size: 100%;
 42         }
 43         .list-img .num {
 44             position: absolute;
 45             left: 0;
 46             bottom: 0;
 47             width: 100%;
 48             text-align: center;
 49             color: #999;
 50             font-size: 12px;    
 51         }
 52     </style>
 53 </head>
 54 <body>
 55     <div class="list-img">
 56         <ul id="preview" class="clear">
 57             <li class="fl">
 58                 <img src="/images/icon_upload.png">
 59                 <input id="fileImage" type="file" name="file[]" multiple />
 60                 <div class="num">0/4</div>
 61             </li>
 62         </ul>
 63     </div>    
 64 
 65     <script src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
 66     <script>
 67         var pageCtrl = {
 68             imgId : 0, //图片id标志, 方便删除预览图片
 69             maxNum : 4, //最多上传图片张数
 70 
 71             /* 选择图片 */
 72             _choosePic : function() {
 73                 var _self = this;
 74                 $('#fileImage').change(function() {
 75                     var files = this.files,
 76                         len = $('#preview').find('.pic').length;
 77                     if (len + files.length > _self.maxNum) {
 78                         _self._showTip('最多只能上传' + _self.maxNum + '张图片哦~');
 79                         return;
 80                     }
 81                     for (var i = 0; i < files.length; i++) {
 82                         var file = files[i];
 83                         if (file.type.indexOf("image") == 0) {
 84                             if (file.size >= 1024 * 1024 * 3) {
 85                                 _self._showTip('图片大小过大，应小于3M');
 86                             } else {
 87                                 _self._showPic(file); //图片预览
 88                             }
 89                         } else {
 90                             _self._showTip('文件"' + file.name + '"不是图片类型')
 91                             break;
 92                         }
 93                     }
 94                 });
 95             },
 96 
 97             /* 渲染图片 */
 98             _showPic : function(file) {
 99                 var _self = this,
100                     html = '',
101                     $wap = $('#preview'),
102                     reader = new FileReader();
103                 reader.readAsDataURL(file);
104                 reader.onload = function(e) {
105                     var image_base64 = this.result,
106                     imgId = _self.imgId;
107 
108                     html = '<li class="fl pic" id="imgItem_' + imgId + '">' +
109                                 '<img src="' + image_base64 + '" alt="">' +
110                                 '<i class="del-img"></i>' +
111                             '</li>';
112                     imgId++;        
113                     $wap.append(html);
114                     $('#fileImage').next().text($wap.find('.pic').length + '/' + _self.maxNum);    
115 
116                     //图片压缩上传，大于1.2M压缩图片
117                     if (file.size / 1024 > 1024 * 1.2) {
118                         _self._dealImage(image_base64, {
119                             quality: 0.5
120                         }, function(base64Codes) {
121                             var bl = _self._processData(base64Codes, file.type);
122                             _self._uploadPic(bl, imgId);
123                         });
124                     } else {
125                         _self._uploadPic(file, imgId);
126                     }
127                 }
128             },
129 
130 
131             /**
132              * 图片压缩（利用canvas）
133              * @param  path     图片路径
134              * @param  obj      压缩配置width,height,quality，不传则按比例压缩
135              * @param  callback  回调函数
136              */
137             _dealImage : function(path, obj, callback) {
138                 var img = new Image();
139                 img.src = path;
140                 img.onload = function() {
141                     var that = this;
142                     // 默认按比例压缩
143                     var w = that.width,
144                         h = that.height,
145                         scale = w / h;
146                     w = obj.width || w;
147                     h = obj.height || (w / scale);
148 
149                     //生成canvas
150                     var canvas = document.createElement('canvas'),
151                     ctx = canvas.getContext('2d');
152                     canvas.width = w;
153                     canvas.height = h;
154                     ctx.drawImage(that, 0, 0, w, h);
155 
156                     // 默认图片质量为0.7
157                     var quality = 0.7;
158                     if (obj.quality && obj.quality <= 1 && obj.quality > 0) {
159                         quality = obj.quality;
160                     }
161 
162                     // 回调函数返回base64的值
163                     var base64 = canvas.toDataURL('image/jpeg', quality);
164                     callback(base64);
165                 }
166             },
167 
168             /* 将以base64的图片url数据转换为Blob */
169             _processData : function(dataUrl, type) {
170                 var binaryString = window.atob(dataUrl.split(',')[1]),
171                 arrayBuffer = new ArrayBuffer(binaryString.length),
172                 intArray = new Uint8Array(arrayBuffer);
173                 for (var i = 0, j = binaryString.length; i < j; i++) {
174                     intArray[i] = binaryString.charCodeAt(i);
175                 }
176 
177                 var data = [intArray], blob;
178 
179                 try {
180                     blob = new Blob(data);
181                 } catch (e) {
182                     window.BlobBuilder = window.BlobBuilder ||
183                         window.WebKitBlobBuilder ||
184                         window.MozBlobBuilder ||
185                         window.MSBlobBuilder;
186                     if (e.name === 'TypeError' && window.BlobBuilder) {
187                         var builder = new BlobBuilder();
188                         builder.append(arrayBuffer);
189                         blob = builder.getBlob(type);
190                     } else {
191                         _showTip('版本过低，不支持图片压缩上传');
192                     }
193                 }
194                 return blob;
195             },
196 
197             /* 上传图片 */
198             _uploadPic : function(file, id) {
199                 var _self = this,
200                 formData = new FormData();
201                 formData.append('img', file);
202                 $.ajax({
203                     url: '/upload',
204                     type: 'post',
205                     dataType: 'json',
206                     data: formData,
207                     contentType: false,
208                     processData: false,           
209                     success: function(res){
210                         if(res.respCode == 1000) {
211                             $('#imgItem_' + id).find('.del-img').attr('data-src', res.data.src);                    
212                         }else {
213                             _self._showTip('文件上传失败！'); 
214                         }
215                     }
216                 });  
217             },
218 
219             /* 删除图片 */
220             _delPic : function() {
221                 var _self = this,
222                 $wap = $('#preview');
223                 $wap.on('click', '.del-img', function() {
224                     //TODO:从数据库删除图片
225                     $(this).parent().remove();
226                     $('#fileImage').next().text($wap.find('.pic').length + '/' + _self.maxNum);    
227                 });
228             },
229 
230             _showTip : function(str) {
231                 //TODO信息提示
232                 console.log(str);
233             },
234 
235             init: function() {
236                 this._choosePic();
237                 this._delPic();        
238             }
239         };
240 
241         $(function() {
242             pageCtrl.init();
243         });
244     </script>
245 </body>
246 </html>
247 
248 完整代码

完整代码

参考文章：

https://www.cnblogs.com/007sx/p/7583202.html

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原文地址：https://www.cnblogs.com/ww03/p/9507039.html