I'm trying to derive tree cover from a topographical map (unfortunately I've got no appropriate Landsat or other imagery for the area (it's hard to separate tree cover and fields on summer imagery) for deriving tree cover from satellite imagery). Unforunately cluster processing with diverse programs (as IDRISI or SAGA) haven't given good results. Therefore I installed the trial version of Avenzas Photohsop Addon and chose the tree cover simply with the magic wand tool. This is working quite well, but unfortunately contour lines, text and grid line are leaving white spaces.
In a GIS I could probably use the buffer function, no? Is there any possibility in Photoshop to solve this? I've tried Gaussian blur and other filters for filling the spaces (after that once again use the magic wand tool, inverting the selection and refilling the selection with only one color). Results are not bad, but in some cases the tree areas are growing too much into all directions and do not only close the white spaces within the area.
Do you have any ideas how to solve that problem?