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 EMPTY
MULTIPOLYGON 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
/**
*wkt转化成arcgis的Point对象
* @param wkt
* @returns {Polyline}
* @constructor
*/
function WktToPoint(wkt,spatialreference){
var wktUtil = new WKTUtil();
var pt = wktUtil.read(wkt);
var json = {
x:pt[0],
y:pt[1],
spatialReference: spatialreference
}
var point = new esri.geometry.Point(json);
return point;
}
/**
*wkt转化成arcgis的Polyline对象
* @param wkt
* @returns {Polyline}
* @constructor
*/
function WktToPolyline(wkt, spatialreference){
var wktUtil = new WKTUtil();
var points = wktUtil.read(wkt);
var json = {
paths: [points],
spatialReference: spatialreference
}
var polyline = new esri.geometry.Polyline(json);
return polyline;
}
/**
* wkt转化成arcgis的Polygon对象
* @param wkt
* @returns {Polygon}
* @constructor
*/
function WktToPolygon(wkt, spatialreference){
var wktUtil = new WKTUtil();
var points = wktUtil.read(wkt);
var json = {
rings: points,
spatialReference: {"wkid":4326}
}
var polygon = new esri.geometry.Polygon(json);
return polygon;
}
/**
* @param geometry
*/
function PointToWKT(geometry){
console.log(geometry);
return "POINT ("+geometry.x+" "+geometry.y+")";
}
/**
* @param geometry
*/
function PolygonToWKT(geometry){
var wkt = [];
var rings = geometry.rings;
for(var i in rings){
var ring = rings[i];
for(var j in ring){
var p = ring[j];
wkt.push(p.join(" "));
}
}
return "POLYGON (("+wkt.join(",")+"))";
}
/**
* @param geometry
*/
function LineToWKT(geometry){
var wkt = [];
var paths = geometry.paths;
for(var i in paths){
var path = paths[i];
for(var j in path){
var p = path[j];
wkt.push(p.join(" "));
}
}
return "LINESTRING ("+wkt.join(",")+")";
}使用的时候，直接调用对应的函数即可。
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