Leandro,
I am sorry to say that we do not support the Garmin img format directly. While, it seems (may be incorrect) that some open source projects can parse the format.
sourceforge.net/projects/garmin-img/
I did not do any investigations on this format up to now, while I think if we can parse the format somehow, we probably can support it very easily. Basically the solution is to create our own RasterSource and RasterLayer, in the following API override method, use the open source project to parse the Garmin img format file and return back an image representing the extent image with specified width and height.
protected abstract GeoImage GetImageCore(RectangleShape worldExtent, int canvasWidth, int canvasHeight);
Any more questions just feel free to let me know.
Thanks.
Yale