How to map OSMSharp view point to Geo coordinate? - ios

Question

I am using OSMSharp for an iOS project.
I'll like to be able to convert a given point in the view/map to GeoCoordinates (based on the current MapCenter, view size, zoom, etc).
I thought mapView.Map.Project.ToGeoCoordinates would do that, but the result is not correct. The inverse function (mapView.Map.Project.ToPixel) returns values in a coordinate system that doesn't correspond to the actual view (it returns value up to 10000 or so, and the size of my view is 1024x768).
So, how do I convert a given pixel coordinate in a OsmSharp.iOS.UI.MapView to its corresponding GeoCoordinate?.

Answer 1

Right now there's no method to get it. But it's easy to get
Add below method to MapView class in OsmSharp.iOS.UI project
public GeoCoordinate PointToCoordinate(int PointX, int PointY)
{
View2D view = _cacheRenderer.Create(this.Width, this.Height, this.Map,
(float)this.Map.Projection.ToZoomFactor(this.MapZoom), this.MapCenter, false, true);
// get scene coordinates.
double x, y;
var fromMatrix = view.CreateFromViewPort(this.Width, this.Height);
fromMatrix.Apply(PointX, PointY, out x, out y);
return this.Map.Projection.ToGeoCoordinates(x, y);
}
If you want the Point from Geocoordinate, add below method to the same class
public Point CoordinateToPoint(GeoCoordinate gc)
{
var gcPx = this.Map.Projection.ToPixel(gc);
View2D view = _cacheRenderer.Create(this.Width, this.Height, this.Map,
(float)this.Map.Projection.ToZoomFactor(this.MapZoom), this.MapCenter, false, true);
// get scene coordinates.
double x, y;
var fromMatrix = view.CreateFromViewPort(this.Width, this.Height);
fromMatrix.Remove(gcPx[0], gcPx[1], out x, out y);
return new Point((int)System.Math.Round(x, 0), (int)System.Math.Round(y, 0));
}
And below method to Matrix2D class in OsmSharp.UI.Renderer project
public void Remove(double x, double y, out double xNew, out double yNew)
{
xNew = (x * this.E11 - this.E02 * this.E11 + this.E01 * this.E12 - this.E01 * y) / (this.E00 * this.E11 - this.E01 * this.E10);
yNew = (y - this.E12 - this.E10 * xNew) / this.E11;
}