How to manage the color format in the PNG file ?

[VGD]

In the tutorials about the maps editing the authors point to the 16-bit gray scale as the best format but the question arose: What software can control the color format in PNG image?
For example:
- http://community.bistudio.com/wiki/Visitor_3_Manual, section "Terrain", fourth item, quote: "Import PNG Image (Projects/Import from Picture): Imports 8 or 16 bit PNG image, ...", by the way, the correct path is Project > Import Terrain from picture ... But "Project > Export Terrain into picture ..." produces a 32-bit PNG image!
- the BIStudio utility "EmfToPng" produces a 24-bit PNG image;
- Photoshop does not have options for the color management in PNG image.