[mapguide-trac] #1245: Map Image format automatic optimization

[MapGuide Open Source]

#1245: Map Image format automatic optimization
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   Reporter:  msuing       |       Owner:                          
       Type:  enhancement  |      Status:  new                     
   Priority:  medium       |   Milestone:                          
  Component:  AJAX Viewer  |     Version:  2.1.0                   
   Severity:  major        |    Keywords:  image, format, png, png8
External_id:               |  
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 Hi all,

 Since the quality of PNG8 is still not ideal (see
 http://trac.osgeo.org/mapguide/ticket/634), we often face a dilemma :
 quality OR speed (PNG or PNG8).
 It would be great to allow MapGuide to adapt automatically the map image
 format depending on the client connection speed.

 The idea would be to define the image format as a parameter in
 ajaxmappane.templ :
     var mapImageFormat = 'PNG';         // default map image format
     var mapImageAutoFormat = true;      //automatic optimization of map
 image format
     var connectionSpeedLimit = 5000;    //minimum connection speed for
 high quality

 Then to change the map url to allow a dynamic map image format :
 function RequestMapImage(reqId, viewParams){
     url = webAgent + "?OPERATION=GETDYNAMICMAPOVERLAYIMAGE&FORMAT=" +
 mapImageFormat + "&VERSION=2.1.0&SESSION="...

 After the first map has been loaded we could evaluate the connection speed
 to change the format to PNG if it's good or PNG8 if it's bad (below
 connectionSpeedLimit Kbps), for the rest of the session :

 function AutoImageFormat()
 {
         var st = new SpeedTest();
         st.run({
           onStart: function() {
             //alert('Before Running Speed Test');
           }
           ,onEnd: function(speed) {
             //alert( 'Speed test complete:  ' + speed.Kbps + ' Kbps  ' +
 speed.KBps + ' KBps');
             if( speed.Kbps > connectionSpeedLimit )
                 mapImageFormat = 'PNG';
             else
                 mapImageFormat = 'PNG8';
           }
         });
 }


 var SpeedTest = function() {
 };

 SpeedTest.prototype = {
   imgUrl: "../stdicons/speedtest.png"    // Where the image is located at
   ,size: 258048                         // size in bytes
   ,run: function( options ) {

     if( options && options.onStart )
       options.onStart();

     var imgUrl = this.imgUrl + "?r=" + Math.random();
     this.startTime = (new Date()).getTime() ;

     var testImage = new Image();
     var me = this;
     testImage.onload = function() {
       me.endTime = (new Date()).getTime();
       me.runTime = me.endTime - me.startTime;

       if( options && options.onEnd )
         options.onEnd( me.getResults() );
     };
     testImage.src = imgUrl;
   }

   ,getResults: function() {
     if( !this.runTime )
       return null;

     return {
       runTime: this.runTime
       ,Kbps: ( this.size * 8 / 1024 / ( this.runTime / 1000 ) )
       ,KBps: ( this.size / 1024 / ( this.runTime / 1000 ) )
     };
   }
 }

 To go one step further, we could :

 - evaluate this connection speed directly on the map image previously
 loaded instead of "../stdicons/speedtest.png"

 - choose to put automatically JPG format if one of the displayed layers is
 based on a raster datasource.

 Cheers,

 Max.

-- 
Ticket URL: <http://trac.osgeo.org/mapguide/ticket/1245>
MapGuide Open Source <http://mapguide.osgeo.org/>
MapGuide Open Source Internals