I have an RGB image and a Gray scale image. I would like to merge them in a 4 bands image. How can I do that? Is there a simple way to do it from QGIS or I have to modify the image before to load them in QGIS.Thanks a lot!
Enable the GDALTools plugin (Plugins->Manage Plugins... menu) and use the Merge tool (Raster->Miscellaneous menu) and tick the Layer stack option.