In fact, it is 
Macs have a built-in ability to take a screenshot of the whole screen, a selected rectangle, or a specific window, and dump it directly to a .png.
...though, in all fairness, I have been given to understand that more recent versions of Windows have less crippled screenshot functionality than XP and previous.
In any case, DF has its own image-dumping functionality, accessed from the [esc] menu (same place as where you save & quit). This simply dumps images of entire z-levels to .bmp files. On no account should one try to upload these .bmp files anywhere, however; they're absurdly large. DF comes bundled with a copy of optipng, which is a command-line tool that allows you to take the .bmp files and convert them into .png files of various sizes.
If you want to do any editing to the image dumps, though (cropping, annotating, etc), you should do it before converting, because MS Paint uses .bmp as a native format anyway, and it's non-lossy.
I'm familiar with using the Print Screen button on my windows pc and then cropping.
The z level is nice, though sometimes I think I'd want to show text and warnings and other stuff.
So... we will only use one of the magma channels?
I don't quite understand how they work or how many we need.
