ArcGIS for JavaScript继承TiledMapServiceLayer来实现“动态切图”

这种方式可以提高出图速度于效果，算法见http://blog.newnaw.com/?p=633，我用ArcGIS for JavaScript API来实现。具体代码为：

       function initDynamicMapLayer() {
         dojo.declare("ogc.DynamicMapLayer", esri.layers.TiledMapServiceLayer, { // create DynamicMapLayer by extending esri.layers.TiledMapServiceLayer
           datetime: "",
           constructor: function(datetime) {
             this.datetime = datetime;
             this.spatialReference = new esri.SpatialReference({
               wkid: 4326
             });
             this.initialExtent = new esri.geometry.Extent(-180, -90, 180, 90, this.spatialReference);
             this.fullExtent = new esri.geometry.Extent(-180, -90, 180, 90, this.spatialReference);
             //
             this.tileInfo = new esri.layers.TileInfo({
               "dpi": "90.71428571428571",
               "format": "image/png",
               "compressionQuality": 0,
               "spatialReference": {
                 "wkid": "4326"
               },
               "rows": 256,
               "cols": 256,
               "origin": {
                 "x": -180,
                 "y": 90
               },

               // Scales in DPI 96
               "lods" : [
                   {"level" : 1, "resolution" : 0.7031249999891485, "scale" : 2.958293554545656E8},
                   {"level" : 2, "resolution" : 0.35156249999999994, "scale" : 1.479146777272828E8},
                   {"level" : 3, "resolution" : 0.17578124999999997, "scale" : 7.39573388636414E7},
                   {"level" : 4, "resolution" : 0.08789062500000014, "scale" : 3.69786694318207E7},
                   {"level" : 5, "resolution" : 0.04394531250000007, "scale" : 1.848933471591035E7},
                   {"level" : 6, "resolution" : 0.021972656250000007, "scale" : 9244667.357955175},
                   {"level" : 7, "resolution" : 0.01098632812500002, "scale" : 4622333.678977588},
                   {"level" : 8, "resolution" : 0.00549316406250001, "scale" : 2311166.839488794},
                   {"level" : 9, "resolution" : 0.0027465820312500017, "scale" : 1155583.419744397},
                   {"level" : 10, "resolution" : 0.0013732910156250009, "scale" : 577791.7098721985},
                   {"level" : 11, "resolution" : 0.000686645507812499, "scale" : 288895.85493609926},
                   {"level" : 12, "resolution" : 0.0003433227539062495, "scale" : 144447.92746804963},
                   {"level" : 13, "resolution" : 0.00017166137695312503, "scale" : 72223.96373402482},
                   {"level" : 14, "resolution" : 0.00008583068847656251, "scale" : 36111.98186701241},
                   {"level" : 15, "resolution" : 0.000042915344238281406, "scale" : 18055.990933506204},
                   {"level" : 16, "resolution" : 0.000021457672119140645, "scale" : 9027.995466753102},
                   {"level" : 17, "resolution" : 0.000010728836059570307, "scale" : 4513.997733376551},
                   {"level" : 18, "resolution" : 0.000005364418029785169, "scale" : 2256.998866688275},
                   {"level" : 19, "resolution" : 2.68220901485e-6, "scale": 1128.499433344138},
                   {"level" : 20, "resolution" : 1.341104507425e-6, "scale": 564.2497166720688}
                 ]

             });
             this.loaded = true;
             this.onLoad(this);
           },

           getTileUrl: function(level, row, col) {
               var resolution = 0;
               for (var i = 0; i < this.tileInfo.lods.length; i++){
                     var lod = this.tileInfo.lods[i];
                     if (lod.level == level){
                         resolution = lod.resolution;
                     }
               }
               var xmin, ymin, xmax, ymax;
               xmin = -180 + resolution * 256 * col;
               ymin = 90 - resolution * 256 * (row + 1);
               xmax = -180 + resolution * 256 * (col + 1);
               ymax = 90 - resolution * 256 * row;
               var bbox=xmin+"%2C"+ymin+"%2C"+xmax+"%2C"+ymax;
               return "http://xxx.xxx.xxx.xxx/arcgis/rest/services/WeatherServices/MapServer/export?dpi=96&transparent=true&format=png8&dynamicLayers=%5B%7B%22id%22%3A999%2C%22source%22%3A%7B%22type%22%3A%22dataLayer%22%2C%22dataSource%22%3A%7B%22type%22%3A%22raster%22%2C%22workspaceId%22%3A1%2C%22dataSourceName%22%3A%22"+this.datetime+".gif%22%7D%7D%2C%22minScale%22%3A0%2C%22maxScale%22%3A0%7D%5D&bbox="+bbox+"&bboxSR=4326&imageSR=4326&size=256%2C256&f=image";
           }
         });
       }

以上基于天地图底图，效果如下：

效果杠杠的，云图播放一点都不卡了。