1、wkt简介
WKT(Well-known text)是一种文本标记语言，用于表示矢量几何对象、空间参照系统及空间参照系统之间的转换。它的二进制表示方式，，亦即WKB(well-known-binary)则胜于在传输和在数据库中存储相同的信息。该格式由开放地理空间联盟(OGC)制定。WKT可以表示的几何对象包括：点，线，多边形，TIN（不规则三角网）及多面体。以下为几何WKT字串样例：POINT(6 10)LINESTRING(3 4,10 50,20 25)POLYGON((1 1,5 1,5 5,1 5,1 1),(2 2,2 3,3 3,3 2,2 2))MULTIPOINT(3.5 5.6, 4.8 10.5)MULTILINESTRING((3 4,10 50,20 25),(-5 -8,-10 -8,-15 -4))MULTIPOLYGON(((1 1,5 1,5 5,1 5,1 1),(2 2,2 3,3 3,3 2,2 2)),((6 3,9 2,9 4,6 3)))GEOMETRYCOLLECTION(POINT(4 6),LINESTRING(4 6,7 10))POINT ZM (1 1 5 60)POINT M (1 1 80)POINT EMPTYMULTIPOLYGON EMPTY
2、geometry
geometry为Arcgis中的几何对象，包括Extent、Multipoint、Point 、Polygon 、Polyline。
3、相互转换
实现相互转换，封装成了两个js文件，内容如下：
WKTUtil.js
var WKTUtil = function(options){this.initialize(options);}WKTUtil.prototype = {/*** Constructor: OpenLayers.Format.WKT* Create a new parser for WKT** Parameters:* options – {Object} An optional object whose properties will be set on*this instance** Returns:* {<OpenLayers.Format.WKT>} A new WKT parser.*/initialize: function(options) {this.regExes = {'typeStr': /^\s*(\w+)\s*\(\s*(.*)\s*\)\s*$/,'spaces': /\s+/,'parenComma': /\)\s*,\s*\(/,'doubleParenComma': /\)\s*\)\s*,\s*\(\s*\(/, // can't use {2} here'trimParens': /^\s*\(?(.*?)\)?\s*$/};for(var i in options){this[i] = options[i];}},/*** APIMethod: read* Deserialize a WKT string and return a vector feature or an* array of vector features. Supports WKT for POINT, MULTIPOINT,* LINESTRING, MULTILINESTRING, POLYGON, MULTIPOLYGON, and* GEOMETRYCOLLECTION.** Parameters:* wkt – {String} A WKT string** Returns:* {<OpenLayers.Feature.Vector>|Array} A feature or array of features for* GEOMETRYCOLLECTION WKT.*/read: function(wkt) {var features, type, str;wkt = wkt.replace(/[\n\r]/g, " ");var matches = this.regExes.typeStr.exec(wkt);if(matches) {type = matches[1].toLowerCase();str = matches[2];if(this.parse[type]) {features = this.parse[type].apply(this, [str]);//console.log(features);}}return features;},/*** Method: extractGeometry* Entry point to construct the WKT for a single Geometry object.** Parameters:* geometry – {<OpenLayers.Geometry.Geometry>}** Returns:* {String} A WKT string of representing the geometry*/extractGeometry: function(geometry) {var type = geometry.CLASS_NAME.split('.')[2].toLowerCase();if (!this.extract[type]) {return null;}if (this.internalProjection && this.externalProjection) {geometry = geometry.clone();geometry.transform(this.internalProjection, this.externalProjection);}var wktType = type == 'collection' ? 'GEOMETRYCOLLECTION' : type.toUpperCase();var data = wktType + '(' + this.extract[type].apply(this, [geometry]) + ')';return data;},trim: function(str){return str.replace(/^\s\s*/, '').replace(/\s\s*$/, '');},/*** Object with properties corresponding to the geometry types.* Property values are functions that do the actual parsing.*/parse: {/*** Return point feature given a point WKT fragment.* @param {String} str A WKT fragment representing the point* @returns {OpenLayers.Feature.Vector} A point feature* @private*/'point': function(str) {var coords = this.trim(str).split(this.regExes.spaces);return coords;//new esri.geometry.Point(coords[0], coords[1]);},/*** Return a multipoint feature given a multipoint WKT fragment.* @param {String} str A WKT fragment representing the multipoint* @returns {OpenLayers.Feature.Vector} A multipoint feature* @private*/'multipoint': function(str) {var point;var points = this.trim(str).split(',');var components = [];for(var i=0, len=points.length; i<len; ++i) {point = points[i].replace(this.regExes.trimParens, '$1');components.push(this.parse.point.apply(this, [point]).geometry);}return new OpenLayers.Feature.Vector(new OpenLayers.Geometry.MultiPoint(components));},/*** Return a linestring feature given a linestring WKT fragment.* @param {String} str A WKT fragment representing the linestring* @returns {OpenLayers.Feature.Vector} A linestring feature* @private*/'linestring': function(str) {var points = this.trim(str).split(',');var components = [];for(var i=0, len=points.length; i<len; ++i) {components.push(this.parse.point.apply(this, [points[i]]));}return components//new esri.geometry.Polyline(components);},/*** Return a multilinestring feature given a multilinestring WKT fragment.* @param {String} str A WKT fragment representing the multilinestring* @returns {OpenLayers.Feature.Vector} A multilinestring feature* @private*/'multilinestring': function(str) {var line;var lines = OpenLayers.String.trim(str).split(this.regExes.parenComma);var components = [];for(var i=0, len=lines.length; i<len; ++i) {line = lines[i].replace(this.regExes.trimParens, '$1');components.push(this.parse.linestring.apply(this, [line]).geometry);}return new OpenLayers.Feature.Vector(new OpenLayers.Geometry.MultiLineString(components));},/*** Return a polygon feature given a polygon WKT fragment.* @param {String} str A WKT fragment representing the polygon* @returns {OpenLayers.Feature.Vector} A polygon feature* @private*/'polygon': function(str) {var ring, linestring, linearring;var rings = this.trim(str).split(this.regExes.parenComma);var components = [];for(var i=0, len=rings.length; i<len; ++i) {ring = rings[i].replace(this.regExes.trimParens, '$1');linestring = this.parse.linestring.apply(this, [ring]);components.push(linestring);}return components;}}}mapTran.js
不甚酒力，体会不了酒的美味，但却能感受知已的妙处。
