geotools draw symbol on overlay

Question

I'm new to Geotools. I am developing a simple application that shows a map and I would like to dynamically place a bitmap or vector symbol on it (for example to show where the current position is, like in navigation systems). Now, what I've done already is:

• showing a map given one or more shapefile.
• center the map on the last inserted position.
• add shapes to new layers when needed.

What I need to do is to create an overlay with images at given coordinates on the map area (to be clear, I don't want to generate a raster layer on disk, I just want to paint on the screen). My guess is that I have to somehow directly use the Graphics2D instance inside JMapPane, is that correct? In this case how can I convert from the geographic coordinates to pixel coordinates on the drawing pane? Or are there some geotools functions/classes that I should be looking for?

Thank you.

Answer 1

Answering myself, since I found the solution.

I did it by extending class org.geotools.map.DirectLayer, which provides a way to define a custom layer by extending its draw(Graphics2D, MapContent) method. Graphic elements are placed at the correct coordinates by using the worldToScreen affine transform provided by geotools. For example, to define a Point2D placed at the current position given real-world coordinates:

AffineTransform worldToScreen = viewport.getWorldToScreen();
Point2D worldPoint = new Point2D.Double(currentPosition.x, currentPosition.y);
Point2D screenPoint = worldToScreen.transform(worldPoint, null);

Once the draw() method is defined, just instantiate and add as a layer to your MapContent instance.