TileSplitter: extract tiles from tileset image

You may know the problem: you found a really nice tileset, but it comes as a pre-made tileset image (atlas). But you'd really like to (or need to):

- re-arrange the tiles to have the layout fit your needs (or any logic at all)
- only use some of the tiles, not all of them
- figure out what the tileset image's grid size, spacing and margin actually are
- have all the tiles as individual files, for whatever reason (ie using Tiled's image collection tileset and packing the tileset with the tool of your choice)

With TileSplitter you would have a tool that allows you to load a tileset (atlas) image and experiment with spacing, margin and grid size until it seems about right, then extract the tiles as individual, sequentially numbered images. You could also extract the same image multiple times with different settings in case the tiles aren't all aligned on the same grid (yeah, apparently some artists do not understand the whole purpose of aligning tiles on the same grid).

The problem with existing tools that do this are:

- they were not made for tilemap tiles but rather tiling website images
- they may have worked once before, but they are now dysfunctional and abandoned projects
- they are command-line only tools that are hard to understand and you can't modify them because they were written in one of those really, really weird languages like Ruby or Perl
- they are inflexible, don't allow to specify (important or any) parameters
- they may only read from proprietary map or "game making tool" formats
- they output in an unusable format (gif, bmp, jpg, tiff, proprietary) that would (at best) require additional conversion
- some cost a lot more for what they're worth (ie 40$ and more) -- TileSplitter is intended to be bundled with TilemapKit

Estimate: 2 weeks (OS X app with GUI)