Using Map Editor and wmLibEditor.
When in Map editor u open the map u want to make a minimap for, and export as a bmp file.
Then u look at the size, in my case
2100 x 1400 then u ?4. But on the First Dimention u add 2.
Example: 2100 ?4 = 525 then u add 2 so its 527.
then u do 1400 ?4 = 350...