How to change downloaded map size?

[disa 0]

I have recently downloaded a map of the STEX. The map was in size 1025*1025, which as I have understood it, is the same size of 8*8 or 16 large maps.
I would like to change to whole region size to 2*2 or 4 large maps. I tried doing this by halfing the size of the original .jpeg map file, but it won't work. SC4 won't load it. It works just fine when the map is in it's original size.
I have changed the config.bmp file to only 4 large cities (blue). The size of the .jpeg file after I changed it is 513*513, the same as another map file I downloaded from the STEX.

I have searched the forums but I can't find any information about how big the .jpeg files should be? Could someone please help me?

[Constantina 5]

JPEG files can be of any size, provided it is 8-bit greyscale, and the value of the width/height of the map is a factor of:

x×64+1

[vester_DK 477]

There is a tool call Landscape Designer, which can help you with the config.bmp's. You can find it in the Modds & Downloads.

[sim1234 62]

Here is a link to the Landscape Designer which vester_DK mentioned:
https://www.simtropolis.com/stex/details.cfm?id=12679&v=1

[disa 0]

Thank you all for your feedback. I finally figured out what the problem was. I though that I had saved the picture as 8 bit greyscale, which I in fact hadn't. After I had saved the picture as a greyscale using InfraView, it worked out fine, so it worked out evetually, cheers.