Mapsui: CenterCrossWidget - required

[lukaszpitulski]

Hi Team,

as we discussed in #504 with @charlenni , will be nice... is needed to have a widget which will give us a Center Cross above all layers, and from the code will be possibility to get the position (geo-position) of it on the map easily.

Our solution now (top secret ;) ):
```c#
public static Bitmap RedCrossBmp(int pixels)
{
var b = new Bitmap(pixels + 1, pixels + 1);
using (var g = Graphics.FromImage(b))
{
var pen = new Pen(Color.Red, 1);
g.DrawLine(pen,0,pixels/2,pixels+1,pixels/2);
g.DrawLine(pen,pixels/2,0,pixels/2,pixels+1);
}
return b;
}

private static readonly Bitmap RedCross = RedCrossBmp(10);

internal static int GetBitmapId(byte[] bitmap)
{
var imageMS = new MemoryStream();

System.Drawing.Image.FromStream(new MemoryStream(bitmap)).Save(imageMS, System.Drawing.Imaging.ImageFormat.Png);

if (imageMS.Length <= 0)
    throw new Exception();

imageMS.Position = 0;

return BitmapRegistry.Instance.Register(imageMS);

}

private static IStyle CreateRedCrossStyle()
{
var bitmapId = GetBitmapId(RedCross.ToByteArray(System.Drawing.Imaging.ImageFormat.Png));

return new SymbolStyle
{
    BitmapId = bitmapId,
    SymbolType = SymbolType.Bitmap,
    SymbolScale = 1
};

}

private WritableLayer RedCrossLayer;
private Point RedCrossLocation = null;

RedCrossLayer = new WritableLayer
{
Name = "RedCrossPointLayer",
Style = CreateRedCrossStyle()
};
RedCrossLayer.Transformer.FromCRS = "EPSG:4326";
MapControl.Map.Layers.Add(RedCrossLayer);

RedCrossLocation = null;

MapControl.Map.Viewport.ViewportChanged += Map_CurrentExtentChanged; //https://github.com/Mapsui/Mapsui/issues/398

private void Map_CurrentExtentChanged(object sender, PropertyChangedEventArgs e)
{
try
{
if (MapControl?.Map?.Viewport == null || !MapControl.Map.Viewport.Initialized) return; //https://github.com/Mapsui/Mapsui/issues/399

    var worldLocation = MapControl.Map.Viewport.Center;

    if (RedCrossLayer != null && worldLocation != null)
    {
        {
            var mapLocation = new Point(worldLocation.X, worldLocation.Y);
            //here Transformation of the mapLocation values from one CRS to another - if required; eg. base map layer (OSM) "EPSG:3857"->"EPSG:4326" used coordinate system

            if (RedCrossLocation == mapLocation) return;

            RedCrossLocation = mapLocation;
        }

        RedCrossLayer.Clear();

        //var symbolStyle = CreateRedCrossStyle(); -> Memory Leaking! #503
        //
        var feature = new Feature
        {
            Geometry = worldLocation,
        //  Styles = new StyleCollection
        //  {
        //      symbolStyle,
        //  }
        };

        RedCrossLayer.Add(feature);
    }
}
catch(Exception ex) { /*ex.Message*/ }

}

//later somewhere in the code
point = RedCrossLayer.GetFeatures().First(f => f != null).Geometry as Mapsui.Geometries.Point
```

Many Thanks,
Łukasz

[lukaszpitulski]

oo, if you have any ideas on how the above solution could be improved, do not hesitate to comment and give a clue, advice

thanks!

[pauldendulk]

The red cross is always right in the center of the map right? So, why don't you split your requirements into two parts:

• Get the position of the center of the map (and perhaps MapInfo from the center of the map)
• Draw a red cross on the center of the MapControl. There might be something available in WinForms for that.

[lukaszpitulski]

You're probably right, it could be one of the solutions, another one might be a widget (as I ask in this issue)
Such a widget could be used outside of WinForms also, am I right?

[pauldendulk]

Yes. But a custom widget is only possible in v2.

[lukaszpitulski]

1.4.* :(

[lukaszpitulski]

"a custom widget" ? What do you mean?

I'm asking you to create and implement a default/build-in CenterCross widget in the Mapsui, available for all.
Those widgets that are already available (ScaleBarWidget, ZoomInOutWidget), can't there be one more?

[josesimas]

I did exactly what Paul says and it works quite well. Simply overlay a text element on top of the map. The user moves the map underneath and I get the map position from the map's center.

[lukaszpitulski]

yes, sure it is one of solutions of the case and I'm not saying I will not do this but still I request for the widget in Mapsui, not my own solution on my side in my code :)

[pauldendulk]

There will only be bug fixes in 1.4, so this will have to wait for 2.0.

[lukaszpitulski]

Yupiii :)

Many Thanks!

I'm looking forward to the next release of Mapsui 1.4

[pauldendulk]

I released 1.4.8 with @charlenni s center cross widget.

[jin-khera-eastpoint]

That's a great addition! Is there a way to change the image for the cross?

[lukaszpitulski]

CenterCrossWidget is the cross image ;)
I don't think the image should be changed, that would be too much for that specific widget ;)

Again MANY THANKS guys!

[lukaszpitulski]

For me, the widget works perfectly! :)

map.Widgets.Add(new Mapsui.Widgets.CenterCross.CenterCrossWidget(map) { Color = Color.Red, Halo = Color.Transparent, Height = 10, Width = 6 });
and then I can do:
var RedCrossLocation = MapControl.Map.Viewport.Center;

Or (not nice ;) )
map.Widgets.Add(new Mapsui.Widgets.CenterCross.CenterCrossWidget(map) { Color = Color.Red, Halo = Color.Transparent, Height = 10, Width = 6, Envelope = map.Viewport.Extent });
and then I can do:
var RedCrossLocation = MapControl.Map.Widgets.Find(w => w is Mapsui.Widgets.CenterCross.CenterCrossWidget).Envelope.GetCentroid();

Best Regards,
Łukasz

[pauldendulk]

@jin-khera-eastpoint This is not planned. 1.4 should only get bugfixes. In 2.0 you could add this widget as a custom widget and change it too your liking.