Hello Cartographers.
It's my first post on that forum and it caught my eye, because of how passionate it seems about making maps.

Right now I'm making a fantasy world map in Photoshop CC and it's rectangular, so it's like it's in mercator projection.
But does anyone know how can I convert a raster image (like .JPG or .PNG) from mercator to winkel tripel projection?

I saw some post about FlexProject, but it seems like this program is just for manipulating a real world map.
So do You have any ideas how to solve that problem?