Js local preview of a simple implementation

  • 2020-03-30 01:44:30
  • OfStack


// JavaScript Document
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var ImagePreview = function(file, img, options) {

 this.file = $(file);//The file object
 this.img = $(img);//Preview image object

 this._preload = null;//Preload the image object
 this._data = "";//Image data
 this._upload = null;//remote Mode used for uploading The file object

 var opt = this._setOptions(options);

 this.action = opt.action;
 this.timeout = opt.timeout;
 this.ratio = opt.ratio;
 this.maxWidth = opt.maxWidth;
 this.maxHeight = opt.maxHeight;

 this.onCheck = opt.onCheck;
 this.onShow = opt.onShow;
 this.onErr = opt.onErr;

 //Set up the data acquisition program
 this._getData = this._getDataFun(opt.mode);
 //Set the preview display program
 this._show = opt.mode !== "filter" ? this._simpleShow : this._filterShow;
};
//Get mode based on the browser
ImagePreview.MODE = $B.ie7 || $B.ie8 ? "filter" :
 $B.firefox ? "domfile" :
 $B.opera || $B.chrome || $B.safari ? "remote" : "simple";
//Transparent image
ImagePreview.TRANSPARENT = $B.ie7 || $B.ie6 ?
 "mhtml:" + document.scripts[document.scripts.length - 1].getAttribute("src", 4) + "!blankImage" :
 "data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==";
ImagePreview.prototype = {
  //Set default properties
  _setOptions: function(options) {
    this.options = {//The default value
  mode:  ImagePreview.MODE,//Preview mode
  ratio:  0,//Custom scale
  maxWidth: 0,//Thumbnail width
  maxHeight: 0,//Thumbnail height
  onCheck: function(){},//Preview detection when executed
  onShow:  function(){},//Execute when previewing the image
  onErr:  function(){},//Execute when preview error occurs
  //The following is valid in remote mode
  action:  undefined,//Set up the action
  timeout: 0//Set timeout (0 is not set)
    };
    return $.extend(this.options, options || {});
  },
  //To preview
  preview: function() {
 if ( this.file && false !== this.onCheck() ) {
  this._preview( this._getData() );
 }
  },

  //Returns the data according to the mode to get the program
  _getDataFun: function(mode) {
 switch (mode) {
  case "filter" :
   return this._filterData;
  case "domfile" :
   return this._domfileData;
  case "remote" :
   return this._remoteData;
  case "simple" :
  default :
   return this._simpleData;
 }
  },
  //Filter data acquisition program
  _filterData: function() {
 this.file.select();
 try{
  return document.selection.createRange().text;
 } finally { document.selection.empty(); }
  },
  //Domfile data acquisition program
  _domfileData: function() {
 return this.file.files[0].getAsDataURL();
  },
  //Remote data acquisition program
  _remoteData: function() {
 this._setUpload();
 this._upload && this._upload.upload();
  },
  //General data acquisition program
  _simpleData: function() {
 return this.file.value;
  },

  // Set up the remote Mode upload The file object
  _setUpload: function() {
 if ( !this._upload && this.action !== undefined && typeof QuickUpload === "function" ) {
  var oThis = this;
  this._upload = new QuickUpload(this.file, {
   onReady: function(){
    this.action = oThis.action; this.timeout = oThis.timeout;
    var parameter = this.parameter;
    parameter.ratio = oThis.ratio;
    parameter.width = oThis.maxWidth;
    parameter.height = oThis.maxHeight;
   },
   onFinish: function(iframe){
    try{
     oThis._preview( iframe.contentWindow.document.body.innerHTML );
    }catch(e){ oThis._error("remote error"); }
   },
   onTimeout: function(){ oThis._error("timeout error"); }
  });
 }
  },

  //The preview program
  _preview: function(data) {
 //Null values or identical values are not displayed
 if ( !!data && data !== this._data ) {
  this._data = data; this._show();
 }
  },

  // Set the general Preload the image object
  _simplePreload: function() {
 if ( !this._preload ) {
  var preload = this._preload = new Image(), oThis = this,
   onload = function(){ oThis._imgShow( oThis._data, this.width, this.height ); };
  this._onload = function(){ this.onload = null; onload.call(this); }
  preload.onload = $B.ie ? this._onload : onload;
  preload.onerror = function(){ oThis._error(); };
 } else if ( $B.ie ) {
  this._preload.onload = this._onload;
 }
  },
  //General display
  _simpleShow: function() {
 this._simplePreload();
 this._preload.src = this._data;
  },

  // Set the filter Preload the image object
  _filterPreload: function() {
 if ( !this._preload ) {
  var preload = this._preload = document.createElement("div");
  //Hide and set the filter
  $D.setStyle( preload, {
   width: "1px", height: "1px",
   visibility: "hidden", position: "absolute", left: "-9999px", top: "-9999px",
   filter: "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod='image')"
  });
  //Insert the body
  var body = document.body; body.insertBefore( preload, body.childNodes[0] );
 }
  },
  //Filter shows
  _filterShow: function() {
 this._filterPreload();
 var preload = this._preload,
  data = this._data.replace(/[)'"%]/g, function(s){ return escape(escape(s)); });
 try{
  preload.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = data;
 }catch(e){ this._error("filter error"); return; }
 //Set the filter and display it
 this.img.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod='scale',src="" + data + "")";
 this._imgShow( ImagePreview.TRANSPARENT, preload.offsetWidth, preload.offsetHeight );
  },

  //According to preview
  _imgShow: function(src, width, height) {
 var img = this.img, style = img.style,
  ratio = Math.max( 0, this.ratio ) || Math.min( 1,
    Math.max( 0, this.maxWidth ) / width  || 1,
    Math.max( 0, this.maxHeight ) / height || 1
   );
 //Set preview size
 style.width = Math.round( width * ratio ) + "px";
 style.height = Math.round( height * ratio ) + "px";
 //Set the SRC
 img.src = src;
 this.onShow();
  },

  //Destruction of program
  dispose: function() {
 // Destruction of upload The file object
 if ( this._upload ) {
  this._upload.dispose(); this._upload = null;
 }
 // The destruction Preload the image object
 if ( this._preload ) {
  var preload = this._preload, parent = preload.parentNode;
  this._preload = preload.onload = preload.onerror = null;
  parent && parent.removeChild(preload);
 }
 //Destroy related objects
 this.file = this.img = null;
  },
  // error 
  _error: function(err) {
 this.onErr(err);
  }
}

The method to invoke is as follows

<input id="idFile" type="file" name="pic" /><img id="idImg" alt="" src="//www.jb51.net/" />
<script>
var ip = new ImagePreview( $$("idFile"), $$("idImg"), {
 maxWidth: 200, maxHeight: 2000, action: "ImagePreview.ashx"
});
ip.img.src = ImagePreview.TRANSPARENT;
ip.file.onchange = function(){ ip.preview(); };
</script>


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