In DM -- select import data.
Set the image size, select binary as the image format and put file size - image size (widthxheight) as offset. Also set data type as integer 1 byte unsigned.

In NIH image -- select import.
Select custom and click on set. enter the image size and again put (file size - image size) as offset.

This method seems to introduce some artifacts sometimes, but you can fix it by using any of these programs.