Problems Importing Flats

I imported some flats and this is the result:



Why is it doing this and how can I fix this?

Those images are right now in Doom image format. The flats however should be in flat format. You can save an image as a flat by clicking Image|Save as Doom Flat.

If you are using the latest version, you can avoid this. Just make sure you click the "Floors" button at the bottom toolbar. This will filter your WAD to only floors, and when you import images, they will automatically be saved as flats.

You can also double-click the "Floors" button, that's a one-step do-it-all flat import function. It will even create the FF_START/FF_END markers if needed.

Alright, Thanks... It works :)