Thanks for the update jxp! This Filetype Plugin of yours should be part of PDN.
Oh! While using your Plugin, I came across a bug (error). Here is a simple way to reproduce it:
1) Set the size of a blank canvas (doesn't have to be blank, the bug shows up either way) to "256 x 384". (I haven't tried other sizes, but I'm sure the bug might show up again in a different resolution.)
2) Click "File > Save As..."
3) Use any "Low color" Save as type. I used "Bitmap (Low color) (*.bmp)".
Now, in the Save Configuration window, there is no preview of the image. And at the top where it normally says the size of the image, it says "Preview. file size (error)". If you were to click "OK" to save the image when this error occurred in the Save Configuration window, the saved file would not have any data of the image within it, therefore, it would be blank and with a different resolution.