如何将OSMSharp视点映射到地理坐标？

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;
    }