[magick-users] Color to B&W

[Hugemann]

Post Scriptum:

For anyone with deeper interest, I would suggest reading the following 
article on different strategies for grayscale conversion:
http://www.fho-emden.de/~hoffmann/gray10012001.pdf

Especially the Photoshop result is drastically different from that of 
other formulae. Perhaps IM should allow to choose between different 
luminance models when converting to grayscale.

Of course, you can implement any algorithm by the fx operator but that 
would be rather slow for batch processing a bulk of images.

Wolfgang Hugemann