ashatora/openlayers
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Estimate point resolution for Proj4js projections

Browse Source
This commit is contained in:
Tom Payne
2013-03-03 17:19:18 +01:00
parent 343768df6a
commit a8760108d4
2 changed files with 70 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
src/ol/projection.js
View File

@@ -8,6 +8,7 @@ goog.require('goog.object');
goog.require('ol.Coordinate');
goog.require('ol.Extent');
goog.require('ol.TransformFunction');
goog.require('ol.sphere.NORMAL');
/**
@@ -129,10 +130,49 @@ ol.Proj4jsProjection_ = function(code, proj4jsProj) {
*/
this.proj4jsProj_ = proj4jsProj;
/**
* @private
* @type {?ol.TransformFunction}
*/
this.toEPSG4326_ = null;
};
goog.inherits(ol.Proj4jsProjection_, ol.Projection);
/**
* @inheritDoc
*/
ol.Proj4jsProjection_.prototype.getPointResolution =
function(resolution, point) {
if (this.getUnits() == ol.ProjectionUnits.DEGREES) {
return resolution;
} else {
// Estimate point resolution by transforming the center pixel to EPSG:4326,
// measuring its width and height on the normal sphere, and taking the
// average of the width and height.
if (goog.isNull(this.toEPSG4326_)) {
this.toEPSG4326_ = ol.projection.getTransform(
this, ol.projection.getProj4jsProjectionFromCode_('EPSG:4326'));
}
var vertices = [
point.x - resolution / 2, point.y,
point.x + resolution / 2, point.y,
point.x, point.y - resolution / 2,
point.x, point.y + resolution / 2
];
vertices = this.toEPSG4326_(vertices, vertices, 2);
var width = ol.sphere.NORMAL.haversineDistance(
new ol.Coordinate(vertices[0], vertices[1]),
new ol.Coordinate(vertices[2], vertices[3]));
var height = ol.sphere.NORMAL.haversineDistance(
new ol.Coordinate(vertices[4], vertices[5]),
new ol.Coordinate(vertices[6], vertices[7]));
return (width + height) / 2;
}
};
/**
* @return {Proj4js.Proj} Proj4js projection.
*/