util.js

用来在地图上做操作GIS,在地图上做标记

 * 
 * Parameters:
 * to - {Object}
 * from - {Object}
 */
OpenLayers.Util.applyDefaults = function (to, from) {
    for (var key in from) {
        if (to[key] == null) {
            to[key] = from[key];
        }
    }
};

/**
 * Function: getParameterString
 * 
 * Parameters:
 * params - {Object}
 * 
 * Returns:
 * {String} A concatenation of the properties of an object in 
 *          http parameter notation. 
 *          (ex. <i>"key1=value1&key2=value2&key3=value3"</i>)
 *          If a parameter is actually a list, that parameter will then
 *          be set to a comma-seperated list of values (foo,bar) instead
 *          of being URL escaped (foo%3Abar). 
 */
OpenLayers.Util.getParameterString = function(params) {
    paramsArray = [];
    
    for (var key in params) {
      var value = params[key];
      if ((value != null) && (typeof value != 'function')) {
        var encodedValue;
        if (typeof value == 'object' && value.constructor == Array) {
          /* value is an array; encode items and separate with "," */
          var encodedItemArray = [];
          for (var itemIndex=0; itemIndex<value.length; itemIndex++) {
            encodedItemArray.push(encodeURIComponent(value[itemIndex]));
          }
          encodedValue = encodedItemArray.join(",");
        }
        else {
          /* value is a string; simply encode */
          encodedValue = encodeURIComponent(value);
        }
        paramsArray.push(encodeURIComponent(key) + "=" + encodedValue);
      }
    }
    
    return paramsArray.join("&");
};

/**
 * Property: ImgPath
 * {String} Default is ''.
 */
OpenLayers.ImgPath = '';

/** 
 * Function: getImagesLocation
 * 
 * Returns:
 * {String} The fully formatted image location string
 */
OpenLayers.Util.getImagesLocation = function() {
    return OpenLayers.ImgPath || (OpenLayers._getScriptLocation() + "img/");
};


/** 
 * Function: Try
 * Execute functions until one of them doesn't throw an error. 
 *     Capitalized because "try" is a reserved word in JavaScript.
 *     Taken directly from OpenLayers.Util.Try()
 * 
 * Parameters:
 * [*] - {Function} Any number of parameters may be passed to Try()
 *    It will attempt to execute each of them until one of them 
 *    successfully executes. 
 *    If none executes successfully, returns null.
 * 
 * Returns:
 * {*} The value returned by the first successfully executed function.
 */
OpenLayers.Util.Try = function() {
    var returnValue = null;

    for (var i = 0; i < arguments.length; i++) {
      var lambda = arguments[i];
      try {
        returnValue = lambda();
        break;
      } catch (e) {}
    }

    return returnValue;
}


/** 
 * Function: getNodes
 * 
 * These could/should be made namespace aware?
 * 
 * Parameters:
 * p - {}
 * tagName - {String}
 * 
 * Returns:
 * {Array}
 */
OpenLayers.Util.getNodes=function(p, tagName) {
    var nodes = OpenLayers.Util.Try(
        function () {
            return OpenLayers.Util._getNodes(p.documentElement.childNodes,
                                            tagName);
        },
        function () {
            return OpenLayers.Util._getNodes(p.childNodes, tagName);
        }
    );
    return nodes;
};

/**
 * Function: _getNodes
 * 
 * Parameters:
 * nodes - {Array}
 * tagName - {String}
 * 
 * Returns:
 * {Array}
 */
OpenLayers.Util._getNodes=function(nodes, tagName) {
    var retArray = [];
    for (var i=0;i<nodes.length;i++) {
        if (nodes[i].nodeName==tagName) {
            retArray.push(nodes[i]);
        }
    }

    return retArray;
};



/**
 * Function: getTagText
 * 
 * Parameters:
 * parent - {}
 * item - {String}
 * index - {Integer}
 * 
 * Returns:
 * {String}
 */
OpenLayers.Util.getTagText = function (parent, item, index) {
    var result = OpenLayers.Util.getNodes(parent, item);
    if (result && (result.length > 0))
    {
        if (!index) {
            index=0;
        }
        if (result[index].childNodes.length > 1) {
            return result.childNodes[1].nodeValue; 
        }
        else if (result[index].childNodes.length == 1) {
            return result[index].firstChild.nodeValue; 
        }
    } else { 
        return ""; 
    }
};

/**
 * Function: getXmlNodeValue
 * 
 * Parameters:
 * node - {XMLNode}
 * 
 * Returns:
 * {String} The text value of the given node, without breaking in firefox or IE
 */
OpenLayers.Util.getXmlNodeValue = function(node) {
    var val = null;
    OpenLayers.Util.Try( 
        function() {
            val = node.text;
            if (!val)
                val = node.textContent;
            if (!val)
                val = node.firstChild.nodeValue;
        }, 
        function() {
            val = node.textContent;
        }); 
    return val;
};

/** 
 * Function: mouseLeft
 * 
 * Parameters:
 * evt - {Event}
 * div - {HTMLDivElement}
 * 
 * Returns:
 * {Boolean}
 */
OpenLayers.Util.mouseLeft = function (evt, div) {
    // start with the element to which the mouse has moved
    var target = (evt.relatedTarget) ? evt.relatedTarget : evt.toElement;
    // walk up the DOM tree.
    while (target != div && target != null) {
        target = target.parentNode;
    }
    // if the target we stop at isn't the div, then we've left the div.
    return (target != div);
};

/**
 * Function: rad
 * 
 * Parameters:
 * x - {Float}
 * 
 * Returns:
 * {Float}
 */
OpenLayers.Util.rad = function(x) {return x*Math.PI/180;};

/**
 * Function: distVincenty
 * 
 * Parameters:
 * p1 - {Float}
 * p2 - {Float}
 * 
 * Returns:
 * {Float}
 */
OpenLayers.Util.distVincenty=function(p1, p2) {
    var a = 6378137, b = 6356752.3142,  f = 1/298.257223563;
    var L = OpenLayers.Util.rad(p2.lon - p1.lon);
    var U1 = Math.atan((1-f) * Math.tan(OpenLayers.Util.rad(p1.lat)));
    var U2 = Math.atan((1-f) * Math.tan(OpenLayers.Util.rad(p2.lat)));
    var sinU1 = Math.sin(U1), cosU1 = Math.cos(U1);
    var sinU2 = Math.sin(U2), cosU2 = Math.cos(U2);
    var lambda = L, lambdaP = 2*Math.PI;
    var iterLimit = 20;
    while (Math.abs(lambda-lambdaP) > 1e-12 && --iterLimit>0) {
        var sinLambda = Math.sin(lambda), cosLambda = Math.cos(lambda);
        var sinSigma = Math.sqrt((cosU2*sinLambda) * (cosU2*sinLambda) +
        (cosU1*sinU2-sinU1*cosU2*cosLambda) * (cosU1*sinU2-sinU1*cosU2*cosLambda));
        if (sinSigma==0) return 0;  // co-incident points
        var cosSigma = sinU1*sinU2 + cosU1*cosU2*cosLambda;
        var sigma = Math.atan2(sinSigma, cosSigma);
        var alpha = Math.asin(cosU1 * cosU2 * sinLambda / sinSigma);
        var cosSqAlpha = Math.cos(alpha) * Math.cos(alpha);
        var cos2SigmaM = cosSigma - 2*sinU1*sinU2/cosSqAlpha;
        var C = f/16*cosSqAlpha*(4+f*(4-3*cosSqAlpha));
        lambdaP = lambda;
        lambda = L + (1-C) * f * Math.sin(alpha) *
        (sigma + C*sinSigma*(cos2SigmaM+C*cosSigma*(-1+2*cos2SigmaM*cos2SigmaM)));
    }
    if (iterLimit==0) return NaN  // formula failed to converge
    var uSq = cosSqAlpha * (a*a - b*b) / (b*b);
    var A = 1 + uSq/16384*(4096+uSq*(-768+uSq*(320-175*uSq)));
    var B = uSq/1024 * (256+uSq*(-128+uSq*(74-47*uSq)));
    var deltaSigma = B*sinSigma*(cos2SigmaM+B/4*(cosSigma*(-1+2*cos2SigmaM*cos2SigmaM)-
        B/6*cos2SigmaM*(-3+4*sinSigma*sinSigma)*(-3+4*cos2SigmaM*cos2SigmaM)));
    var s = b*A*(sigma-deltaSigma);
    var d = s.toFixed(3)/1000; // round to 1mm precision
    return d;
};

/**
 * Function: getParameters
 * Parse the parameters from a URL or from the current page itself into a 
 *     JavaScript Object. Note that parameter values with commas are separated
 *     out into an Array.
 * 
 * Parameters:
 * url - {String} Optional url used to extract the query string.
 *                If null, query string is taken from page location.
 * 
 * Returns:
 * {Object} An object of key/value pairs from the query string.
 */
OpenLayers.Util.getParameters = function(url) {
    //if no url specified, take it from the location bar
    url = url || window.location.href
    if(url == null) {
        url = window.location.href;
    }

    //parse out parameters portion of url string
    var paramsString = "";
    if (OpenLayers.String.contains(url, '?')) {
        var start = url.indexOf('?') + 1;
        var end = OpenLayers.String.contains(url, "#") ?
                    url.indexOf('#') : url.length;
        paramsString = url.substring(start, end);
    }
        
    var parameters = {};
    var pairs = paramsString.split(/[&;]/);
    for(var i = 0; i < pairs.length; ++i) {
        var keyValue = pairs[i].split('=');
        if (keyValue[0]) {
            var key = decodeURIComponent(keyValue[0]);
            var value = keyValue[1] || ''; //empty string if no value

            //decode individual values
            value = value.split(",");
            for(var j=0; j < value.length; j++) {
                value[j] = decodeURIComponent(value[j]);
            }

            //if there's only one value, do not return as array                    
            if (value.length == 1) {
                value = value[0];
            }                
            
            parameters[key] = value;
         }
     }
    return parameters;
};

/**
 * Function: getArgs
 * Deprecated - Will be removed in 3.0. 
 *     Please use instead OpenLayers.Util.getParameters
 * 
 * Parameters:
 * url - {String} Optional url used to extract the query string.
 *                If null, query string is taken from page location.
 * 
 * Returns:
 * {Object} An object of key/value pairs from the query string.
 */
OpenLayers.Util.getArgs = function(url) {
    var err = "The getArgs() function is deprecated and will be removed " +
            "with the 3.0 version of OpenLayers. Please instead use " +
            "OpenLayers.Util.getParameters().";
    OpenLayers.Console.warn(err);
    return OpenLayers.Util.getParameters(url);
};

/**
 * Property: lastSeqID
 * {Integer} The ever-incrementing count variable.
 *           Used for generating unique ids.
 */
OpenLayers.Util.lastSeqID = 0;

/**
 * Function: createUniqueID
 * 
 * Parameters:
 * prefix {String} String to prefix unique id. 
 *                 If null, default is "id_"
 * 
 * Returns:
 * {String} A unique id string, built on the passed in prefix
 */
OpenLayers.Util.createUniqueID = function(prefix) {
    if (prefix == null) {
        prefix = "id_";
    }
    OpenLayers.Util.lastSeqID += 1; 
    return prefix + OpenLayers.Util.lastSeqID;        
};

/**
 * Constant: INCHES_PER_UNIT
 * {Object} Constant inches per unit -- borrowed from MapServer mapscale.c
 */
OpenLayers.INCHES_PER_UNIT = { 
    'inches': 1.0,
    'ft': 12.0,
    'mi': 63360.0,
    'm': 39.3701,
    'km': 39370.1,
    'dd': 4374754
};
OpenLayers.INCHES_PER_UNIT["in"]= OpenLayers.INCHES_PER_UNIT.inches;
OpenLayers.INCHES_PER_UNIT["degrees"] = OpenLayers.INCHES_PER_UNIT.dd;

/** 
 * Constant: DOTS_PER_INCH
 * {Integer} 72 (A sensible default)
 */
OpenLayers.DOTS_PER_INCH = 72;

/**
 * Function: normalzeScale
 * 
 * Parameters:
 * scale - {float}
 * 
 * Returns:
 * {Float} A normalized scale value, in 1 / X format. 
 *         This means that if a value less than one ( already 1/x) is passed
 *         in, it just returns scale directly. Otherwise, it returns 
 *         1 / scale
 */
OpenLayers.Util.normalizeScale = function (scale) {
    var normScale = (scale > 1.0) ? (1.0 / scale) 
                                  : scale;
    return normScale;
};

/**
 * Function: getResolutionFromScale
 * 
 * Parameters:
 * scale - {Float}
 * units - {String} Index into OpenLayers.INCHES_PER_UNIT hashtable.
 *                  Default is degrees
 * 
 * Returns:
 * {Float} The corresponding resolution given passed-in scale and unit 
 *         parameters.
 */
OpenLayers.Util.getResolutionFromScale = function (scale, units) {

    if (units == null) {
        units = "degrees";
    }

    var normScale = OpenLayers.Util.normalizeScale(scale);

    var resolution = 1 / (normScale * OpenLayers.INCHES_PER_UNIT[units]
                                    * OpenLayers.DOTS_PER_INCH);
    return resolution;
};

/**
 * Function: getScaleFromResolution
 * 
 * Parameters:
 * resolution - {Float}
 * units - {String} Index into OpenLayers.INCHES_PER_UNIT hashtable.
 *                  Default is degrees
 * 
 * Returns:
 * {Float} The corresponding scale given passed-in resolution and unit 
 *         parameters.
 */
OpenLayers.Util.getScaleFromResolution = function (resolution, units) {

    if (units == null) {
        units = "degrees";
    }

    var scale = resolution * OpenLayers.INCHES_PER_UNIT[units] *
                    OpenLayers.DOTS_PER_INCH;
    return scale;
};

/**
 * Function: safeStopPropagation
 * Deprecated.
 * 
 * This function has been deprecated. Please use directly 
 *     OpenLayers.Event.stop() passing 'true' as the 2nd 
 *     argument (preventDefault)
 * 
 * Safely stop the propagation of an event *without* preventing
 *   the default browser action from occurring.
 * 
 * Parameter:
 * evt - {Event}
 */
OpenLayers.Util.safeStopPropagation = function(evt) {
    OpenLayers.Event.stop(evt, true);
};

/**
 * Function: pagePositon
 * Calculates the position of an element on the page. 
 *
 * Parameters:
 * forElement - {DOMElement}
 * 
 * Returns: