Factorio's map editor is fine and dandy, but can be a bit slow when you want to do large-scale terraforming. Image editors have a bunch of convenient features for what you want to use Factorio's editor to do. So why not use an image editor to create maps? Right now you can only edit the terrain since everything needs a unique color - and imagine assigning a color to every single entity - though it's very convenient to just load up your favorite image editor and use the myriad of features they tend to have.
You can also keep map generation settings if you generate a map, export it, edit it, and import it. As long as you keep the edges as they were the game will still generate the map normally as you approach the edges of the map.
Here's a link to the thread: https://forums.factorio.com/forum/vie ... =14&t=7243
- Mod to export map to files
- Program to convert mod output to an image file
- Same program to convert an image to a new version of the mod
- Use new version of mod to import the map into the game