I agree, the Problem is, if you make a large map like a continent or a world map. Once you save as an image file you will not be able to zoom in to see the details. if you can't see it when you are zoomed out it will only be a blur when you zoom in.
I have spent a long time making a map that is to scale of an old map that my D&D group uses only to find out that once I have finished I could not use it unless I do screen shots. I Tried setting the Anti-alias to 80% "which is the highest I can do with my PC" Quality of 100%, 24 bit and saved as each of the formats. To no Avail, Blur, just blur.
Solution, don't make large and/ or Detail maps cause it just won't work. Honestly, My favorite map designer is the "Map Maker" that you find in AD&D Core Rules 2.0. Unfortunately there just isn't a lot of Symbols to use.