I am working with an old system of palletes. When I export an image, it also creates an pallete with 15/16 colors. But when I try to replicate the same result, the program does not recognize the image which I just created. To analyse what happened, I opened some images with notepad and compared them with my "creation" and I noticed quite some differences.
But the most interesting thing was that at the beginning of my images' code was the type "BM6", while they should be "png" or "bmp". I think that is some thing of codification, but I cannot find anything about it.
If the image file is properly formed, then you can take your .bm6 file and simple change / rename the extension to .bmp. And it should suddenly be an image.
.bm6 can result from creating an image file using a text editor, as seen here.