map.js

用来在地图上做操作GIS,在地图上做标记

     */
    getMaxExtent: function () {
        var maxExtent = null;
        if (this.baseLayer != null) {
            maxExtent = this.baseLayer.maxExtent;
        }        
        return maxExtent;
    },
    
    /**
     * APIMethod: getNumZoomLevels
     * 
     * Returns:
     * {Integer} The total number of zoom levels that can be displayed by the 
     *           current baseLayer.
     */
    getNumZoomLevels: function() {
        var numZoomLevels = null;
        if (this.baseLayer != null) {
            numZoomLevels = this.baseLayer.numZoomLevels;
        }
        return numZoomLevels;
    },

  /********************************************************/
  /*                                                      */
  /*                 Baselayer Functions                  */
  /*                                                      */
  /*    The following functions, all publicly exposed     */
  /*       in the API?, are all merely wrappers to the    */
  /*       the same calls on whatever layer is set as     */
  /*                the current base layer                */
  /*                                                      */
  /********************************************************/

    /**
     * APIMethod: getExtent
     * 
     * Returns:
     * {<OpenLayers.Bounds>} A Bounds object which represents the lon/lat 
     *                       bounds of the current viewPort. 
     *                       If no baselayer is set, returns null.
     */
    getExtent: function () {
        var extent = null;
        if (this.baseLayer != null) {
            extent = this.baseLayer.getExtent();
        }
        return extent;
    },

    /**
     * APIMethod: getResolution
     * 
     * Returns:
     * {Float} The current resolution of the map. 
     *         If no baselayer is set, returns null.
     */
    getResolution: function () {
        var resolution = null;
        if (this.baseLayer != null) {
            resolution = this.baseLayer.getResolution();
        }
        return resolution;
    },

     /**
      * APIMethod: getScale
      * 
      * Returns:
      * {Float} The current scale denominator of the map. 
      *         If no baselayer is set, returns null.
      */
    getScale: function () {
        var scale = null;
        if (this.baseLayer != null) {
            var res = this.getResolution();
            var units = this.baseLayer.units;
            scale = OpenLayers.Util.getScaleFromResolution(res, units);
        }
        return scale;
    },


    /**
     * APIMethod: getZoomForExtent
     * 
     * Parameters: 
     * bounds - {<OpenLayers.Bounds>}
     * closest - {Boolean} Find the zoom level that most closely fits the 
     *     specified bounds. Note that this may result in a zoom that does 
     *     not exactly contain the entire extent.
     *     Default is false.
     * 
     * Returns:
     * {Integer} A suitable zoom level for the specified bounds.
     *           If no baselayer is set, returns null.
     */
    getZoomForExtent: function (bounds, closest) {
        var zoom = null;
        if (this.baseLayer != null) {
            zoom = this.baseLayer.getZoomForExtent(bounds, closest);
        }
        return zoom;
    },

    /**
     * APIMethod: getZoomForResolution
     * 
     * Parameter:
     * resolution - {Float}
     * closest - {Boolean} Find the zoom level that corresponds to the absolute 
     *     closest resolution, which may result in a zoom whose corresponding
     *     resolution is actually smaller than we would have desired (if this
     *     is being called from a getZoomForExtent() call, then this means that
     *     the returned zoom index might not actually contain the entire 
     *     extent specified... but it'll be close).
     *     Default is false.
     * 
     * Returns:
     * {Integer} A suitable zoom level for the specified resolution.
     *           If no baselayer is set, returns null.
     */
    getZoomForResolution: function(resolution, closest) {
        var zoom = null;
        if (this.baseLayer != null) {
            zoom = this.baseLayer.getZoomForResolution(resolution, closest);
        }
        return zoom;
    },

  /********************************************************/
  /*                                                      */
  /*                  Zooming Functions                   */
  /*                                                      */
  /*    The following functions, all publicly exposed     */
  /*       in the API, are all merely wrappers to the     */
  /*               the setCenter() function               */
  /*                                                      */
  /********************************************************/
  
    /** 
     * APIMethod: zoomTo
     * Zoom to a specific zoom level
     * 
     * Parameters:
     * zoom - {Integer}
     */
    zoomTo: function(zoom) {
        if (this.isValidZoomLevel(zoom)) {
            this.setCenter(null, zoom);
        }
    },
    
    /**
     * APIMethod: zoomIn
     * 
     * Parameters:
     * zoom - {int}
     */
    zoomIn: function() {
        this.zoomTo(this.getZoom() + 1);
    },
    
    /**
     * APIMethod: zoomOut
     * 
     * Parameters:
     * zoom - {int}
     */
    zoomOut: function() {
        this.zoomTo(this.getZoom() - 1);
    },

    /**
     * APIMethod: zoomToExtent
     * Zoom to the passed in bounds, recenter
     * 
     * Parameters:
     * bounds - {<OpenLayers.Bounds>}
     */
    zoomToExtent: function(bounds) {
        var center = bounds.getCenterLonLat();
        if (this.baseLayer.wrapDateLine) {
            var maxExtent = this.getMaxExtent();

            //fix straddling bounds (in the case of a bbox that straddles the 
            // dateline, it's left and right boundaries will appear backwards. 
            // we fix this by allowing a right value that is greater than the
            // max value at the dateline -- this allows us to pass a valid 
            // bounds to calculate zoom)
            //
            bounds = bounds.clone();
            while (bounds.right < bounds.left) {
                bounds.right += maxExtent.getWidth();
            }
            //if the bounds was straddling (see above), then the center point 
            // we got from it was wrong. So we take our new bounds and ask it
            // for the center. Because our new bounds is at least partially 
            // outside the bounds of maxExtent, the new calculated center 
            // might also be. We don't want to pass a bad center value to 
            // setCenter, so we have it wrap itself across the date line.
            //
            center = bounds.getCenterLonLat().wrapDateLine(maxExtent);
        }
        this.setCenter(center, this.getZoomForExtent(bounds));
    },

    /** 
     * APIMethod: zoomToMaxExtent
     * Zoom to the full extent and recenter.
     */
    zoomToMaxExtent: function() {
        this.zoomToExtent(this.getMaxExtent());
    },

    /** 
     * APIMethod: zoomToScale
     * Zoom to a specified scale 
     * 
     * Parameters:
     * scale - {float}
     */
    zoomToScale: function(scale) {
        var res = OpenLayers.Util.getResolutionFromScale(scale, 
                                                         this.baseLayer.units);
        var size = this.getSize();
        var w_deg = size.w * res;
        var h_deg = size.h * res;
        var center = this.getCenter();

        var extent = new OpenLayers.Bounds(center.lon - w_deg / 2,
                                           center.lat - h_deg / 2,
                                           center.lon + w_deg / 2,
                                           center.lat + h_deg / 2);
        this.zoomToExtent(extent);
    },
    
  /********************************************************/
  /*                                                      */
  /*             Translation Functions                    */
  /*                                                      */
  /*      The following functions translate between       */
  /*           LonLat, LayerPx, and ViewPortPx            */
  /*                                                      */
  /********************************************************/
      
  //
  // TRANSLATION: LonLat <-> ViewPortPx
  //

    /**
     * APIMethod: getLonLatFromViewPortPx
     * 
     * Parameters:
     * viewPortPx - {<OpenLayers.Pixel>}
     * 
     * Returns:
     * {<OpenLayers.LonLat>} An OpenLayers.LonLat which is the passed-in view 
     *                       port <OpenLayers.Pixel>, translated into lon/lat
     *                       by the current base layer.
     */
    getLonLatFromViewPortPx: function (viewPortPx) {
        var lonlat = null; 
        if (this.baseLayer != null) {
            lonlat = this.baseLayer.getLonLatFromViewPortPx(viewPortPx);
        }
        return lonlat;
    },

    /**
     * APIMethod: getViewPortPxFromLonLat
     * 
     * Parameters:
     * lonlat - {<OpenLayers.LonLat>}
     * 
     * Returns:
     * {<OpenLayers.Pixel>} An OpenLayers.Pixel which is the passed-in 
     *                      <OpenLayers.LonLat>, translated into view port 
     *                      pixels by the current base layer.
     */
    getViewPortPxFromLonLat: function (lonlat) {
        var px = null; 
        if (this.baseLayer != null) {
            px = this.baseLayer.getViewPortPxFromLonLat(lonlat);
        }
        return px;
    },

    
  //
  // CONVENIENCE TRANSLATION FUNCTIONS FOR API
  //

    /**
     * APIMethod: getLonLatFromPixel
     * 
     * Parameters:
     * px - {<OpenLayers.Pixel>}
     *
     * Returns:
     * {<OpenLayers.LonLat>} An OpenLayers.LonLat corresponding to the given
     *                       OpenLayers.Pixel, translated into lon/lat by the 
     *                       current base layer
     */
    getLonLatFromPixel: function (px) {
        return this.getLonLatFromViewPortPx(px);
    },

    /**
     * APIMethod: getPixelFromLonLat
     * 
     * Parameters:
     * lonlat - {<OpenLayers.LonLat>}
     * 
     * Returns: 
     * {<OpenLayers.Pixel>} An OpenLayers.Pixel corresponding to the 
     *                      <OpenLayers.LonLat> translated into view port 
     *                      pixels by the current base layer.
     */
    getPixelFromLonLat: function (lonlat) {
        return this.getViewPortPxFromLonLat(lonlat);
    },



  //
  // TRANSLATION: ViewPortPx <-> LayerPx
  //

    /**
     * APIMethod: getViewPortPxFromLayerPx
     * 
     * Parameters:
     * layerPx - {<OpenLayers.Pixel>}
     * 
     * Returns:
     * {<OpenLayers.Pixel>} Layer Pixel translated into ViewPort Pixel 
     *                      coordinates
     */
    getViewPortPxFromLayerPx:function(layerPx) {
        var viewPortPx = null;
        if (layerPx != null) {
            var dX = parseInt(this.layerContainerDiv.style.left);
            var dY = parseInt(this.layerContainerDiv.style.top);
            viewPortPx = layerPx.add(dX, dY);            
        }
        return viewPortPx;
    },
    
    /**
     * APIMethod: getLayerPxFromViewPortPx
     * 
     * Parameters:
     * viewPortPx - {<OpenLayers.Pixel>}
     * 
     * Returns:
     * {<OpenLayers.Pixel>} ViewPort Pixel translated into Layer Pixel 
     *                      coordinates
     */
    getLayerPxFromViewPortPx:function(viewPortPx) {
        var layerPx = null;
        if (viewPortPx != null) {
            var dX = -parseInt(this.layerContainerDiv.style.left);
            var dY = -parseInt(this.layerContainerDiv.style.top);
            layerPx = viewPortPx.add(dX, dY);
            if (isNaN(layerPx.x) || isNaN(layerPx.y)) {
                layerPx = null;
            }
        }
        return layerPx;
    },
    
  //
  // TRANSLATION: LonLat <-> LayerPx
  //

    /**
     * APIMethod: getLonLatFromLayerPx
     * 
     * Parameters:
     * px - {<OpenLayers.Pixel>}
     *
     * Returns:
     * {<OpenLayers.LonLat>}
     */
    getLonLatFromLayerPx: function (px) {
       //adjust for displacement of layerContainerDiv
       px = this.getViewPortPxFromLayerPx(px);
       return this.getLonLatFromViewPortPx(px);         
    },
    
    /**
     * APIMethod: getLayerPxFromLonLat
     * 
     * Parameters:
     * lonlat - {<OpenLayers.LonLat>} lonlat
     *
     * Returns:
     * {<OpenLayers.Pixel>} An OpenLayers.Pixel which is the passed-in 
     *                      <OpenLayers.LonLat>, translated into layer pixels 
     *                      by the current base layer
     */
    getLayerPxFromLonLat: function (lonlat) {
       //adjust for displacement of layerContainerDiv
       var px = this.getViewPortPxFromLonLat(lonlat);
       return this.getLayerPxFromViewPortPx(px);         
    },

    CLASS_NAME: "OpenLayers.Map"
});

/**
 * Constant: TILE_WIDTH
 * {Integer} 256 Default tile width (unless otherwise specified)
 */
OpenLayers.Map.TILE_WIDTH = 256;
/**
 * Constant: TILE_HEIGHT
 * {Integer} 256 Default tile height (unless otherwise specified)
 */
OpenLayers.Map.TILE_HEIGHT = 256;