Editing a world map

[Deadshade]

I'm not sure what your original image looks like. A sample of that image (or even the whole image, if you're willing) would be helpful.

Sorry I don't know how to post a picture but it probably doesn't matter as I only need to find a succession of transformations which start with a PNG (or other usual) format and finishing in FT3 where the coastline should be conserved. Nothing else matters as I will recreate the details (rivers, lakes, mountains etc) anyway so that if it is destroyed by the transformations, it is not a problem.
To get an idea, it is basically a planet with a perimeter of 11 000 miles (about half Earth) where between latitudes of about 50° and - 50° and longitude -60 and + 60 lies an island system. The island system is composed of 4 large islands (the largest being ~ 1000x1000 miles) relatively near to each other and a dozen of smaller islands around. Everything else is sea. I will perhaps add ice caps but this is irrelevant for the moment.


It is because I have an island system that the total coastline is relatively long and I need that it be conserved before starting editing.

As I said above, surprisingly the PNG is conserved (with false and strange colors) and clearly visible when loaded into Wilbur but I am absolutely unable to edit anything.
On the other hand I am able to edit in FT3 but I am unable to transfer the coastline into it.

EDIT :
Ah I forgot. The projection I am working with is equirectangular what is called "flat world" in FT3. It was precisely to avoid distorsions at higher latitudes that I concentrated my landmasses between +50 and - 50.
And so I am stuck.