convertPictureToImage method
Converts the underlying ui.Picture to a ui.Image.
If this TilePicture already contains an image, that image is returned directly.
Implementation
ui.Image convertPictureToImage() {
if (_image != null) return _image!;
_image = _picture!.toImageSync(MapsforgeSettingsMgr().tileSize.round(), MapsforgeSettingsMgr().tileSize.round());
return _image!.clone();
}