inStorium Games’ tool, “Image Atlasser”, is now available on Unity Asset Store!
Image Atlasser is a tool that uses the most efficient image packing method, out of several ones (can be overriden to manual selection).
The generated Atlas is a PNG image imported as Sprite texture that auto-assigns your selected texture parts. It can also extract your packed textures from the very own atlas (using the exported codings or sprite meta data!).
Check it out HERE.
Video tutorial HERE.