解决微信及360浏览器无法读取本地图片问题

近期做移动端项目发现360浏览器及微信不能读取本地图片,究其原因是无法获取文件格式,导致base64编码时文件头丢失文件类型信息,无法生成正确的图片编码,所以添加文件头即可解决此问题。

正确的编码

data:image/jpeg;base64,...

微信的编码

data:;base64,...

 

解决微信及360浏览器无法读取本地图片问题
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=0">
<title>图片压缩</title>
<style>
body { margin:0; padding:0; }
html { font-size:62.5%; }

.imgzip { padding:1em; }
.imgzip .itm { padding-bottom:1em; word-break:break-all; font-size:1.2rem; line-height:1.5em; }
.imgzip .itm .tit { margin-bottom:.5em; background-color:#e71446; color:#FFF; padding:.5rem 1rem; border-radius:3px; }
.imgzip .itm .cnt { padding:1rem; }
.imgzip .itm .cnt img { display:block; max-width:100%; }
</style>
</head>

<body>
<input type="file" accept="image/*;capture=camera" class="input">
<div class="imgzip"></div>
<script>
document.addEventListener(DOMContentLoaded, init, false);

function init() {
  var u = new UploadPic();
  u.init({
    input: document.querySelector(.input),
    callback: function (base64) {
      var html = ‘‘;
            
      html = <div class="itm"><div class="tit">图片名称:</div><div class="cnt"> + this.fileName + </div></div>
           + <div class="itm"><div class="tit">原始大小:</div><div class="cnt"> + (this.fileSize / 1024).toFixed(2) + KB<\/div><\/div>
           + <div class="itm"><div class="tit">编码大小:</div><div class="cnt"> + (base64.length / 1024).toFixed(2) + KB<\/div><\/div>
           + <div class="itm"><div class="tit">原始尺寸:</div><div class="cnt"> + this.tw + px *  + this.th + px<\/div><\/div>
           + <div class="itm"><div class="tit">编码尺寸:</div><div class="cnt"> + this.sw + px *  + this.sh + px<\/div><\/div>
           + <div class="itm"><div class="tit">图片预览:</div><div class="cnt"><img src=" + base64 + "><\/div><\/div>
           + <div class="itm"><div class="tit">Base64编码:</div><div class="cnt"> + base64 + <\/div><\/div>;

      document.querySelector(.imgzip).innerHTML = html;
    },
    loading: function () {
      document.querySelector(.imgzip).innerHTML = 读取中,请稍候...;
    }
  });
}

function UploadPic() {
  this.sw = 0;
  this.sh = 0;
  this.tw = 0;
  this.th = 0;
  this.scale = 0;
  this.maxWidth = 0;
  this.maxHeight = 0;
  this.maxSize = 0;
  this.fileSize = 0;
  this.fileDate = null;
  this.fileType = ‘‘;
  this.fileName = ‘‘;
  this.input = null;
  this.canvas = null;
  this.mime = {};
  this.callback = function () {};
  this.loading = function () {};
}

UploadPic.prototype.init = function (options) {
  this.maxWidth = options.maxWidth || 800;
  this.maxHeight = options.maxHeight || 600;
  this.maxSize = options.maxSize || 3 * 1024 * 1024;
  this.input = options.input;
  this.mime = {png: image/png, jpg: image/jpeg, jpeg: image/jpeg, bmp: image/bmp};
  this.callback = options.callback || function () {};
  this.loading = options.loading || function () {};
    
  this._addEvent();
};

/**
 * @description 绑定事件
 * @param {Object} elm 元素
 * @param {Function} fn 绑定函数
 */
UploadPic.prototype._addEvent = function () {
  var _this = this;
    
  function tmpSelectFile(ev) {
    _this._handelSelectFile(ev);
  }
    
  this.input.addEventListener(change, tmpSelectFile, false);
};

/**
 * @description 绑定事件
 * @param {Object} elm 元素
 * @param {Function} fn 绑定函数
 */
UploadPic.prototype._handelSelectFile = function (ev) {
  var file = ev.target.files[0];
  var type = file.type;
  
  // 如果没有文件类型,则通过后缀名判断(解决微信及360浏览器无法获取图片类型问题)
  if (!type) {
    type = this.mime[file.name.match(/\.([^\.]+)$/i)[1]];
  }
  
  if (!/image.(png|jpg|jpeg|bmp)/.test(type)) {
    alert(选择的文件类型不是图片);
    return;
  }
    
  if (file.size > this.maxSize) {
    alert(选择文件大于 + this.maxSize / 1024 / 1024 + M,请重新选择);
    return;
  }

  this.fileName = file.name;
  this.fileSize = file.size;
  this.fileType = type;
  this.fileDate = file.lastModifiedDate;
    
  this._readImage(file);
};

/**
 * @description 读取图片文件
 * @param {Object} image 图片文件
 */
UploadPic.prototype._readImage = function (file) {
  var _this = this;
    
  function tmpCreateImage(uri) {
    _this._createImage(uri);
  }
  
  this.loading();
    
  this._getURI(file, tmpCreateImage);
};

/**
 * @description 通过文件获得URI
 * @param {Object} file 文件
 * @param {Function} callback 回调函数,返回文件对应URI
 * return {Bool} 返回false
 */
UploadPic.prototype._getURI = function (file, callback) {
  var reader = new FileReader();
  var _this = this;

  function tmpLoad() {
    // 头不带图片格式,需填写格式
    var re = /^data:base64,/;
    var ret = this.result + ‘‘;
        
    if (re.test(ret)) ret = ret.replace(re, data: + _this.mime[_this.fileType] + ;base64,);
        
    callback && callback(ret);
  }
    
  reader.onload = tmpLoad;
    
  reader.readAsDataURL(file);
    
  return false;
};

/**
 * @description 创建图片
 * @param {Object} image 图片文件
 */
UploadPic.prototype._createImage = function (uri) {
  var img = new Image();
  var _this = this;
    
  function tmpLoad() {
    _this._drawImage(this);
  }
    
  img.onload = tmpLoad;
    
  img.src = uri;
};

/**
 * @description 创建Canvas将图片画至其中,并获得压缩后的文件
 * @param {Object} img 图片文件
 * @param {Number} width 图片最大宽度
 * @param {Number} height 图片最大高度
 * @param {Function} callback 回调函数,参数为图片base64编码
 * return {Object} 返回压缩后的图片
 */
UploadPic.prototype._drawImage = function (img, callback) {
  this.sw = img.width;
  this.sh = img.height;
  this.tw = img.width;
  this.th = img.height;
    
  this.scale = (this.tw / this.th).toFixed(2);

  if (this.sw > this.maxWidth) {
    this.sw = this.maxWidth;
    this.sh = Math.round(this.sw / this.scale);
  }
    
  if (this.sh > this.maxHeight) {
    this.sh = this.maxHeight;
    this.sw = Math.round(this.sw * this.scale);
  }
  
  this.canvas = document.createElement(canvas);
  var ctx = this.canvas.getContext(2d);
    
  this.canvas.width = this.sw;
  this.canvas.height = this.sh;
    
  ctx.drawImage(img, 0, 0, img.width, img.height, 0, 0, this.sw, this.sh);
    
  this.callback(this.canvas.toDataURL(image/jpeg));
    
  ctx.clearRect(0, 0, this.tw, this.th);
  this.canvas.width = 0;
  this.canvas.height = 0;
  this.canvas = null;
};
</script>
</body>
</html>
解决微信及360浏览器无法读取本地图片问题

解决微信及360浏览器无法读取本地图片问题,布布扣,bubuko.com

解决微信及360浏览器无法读取本地图片问题

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