There is still one wrong or misleading sentence now:
http://www.imagemagick.org/script/comma ... hp#quality
This second sentence could be deleted. (I already saw users here with commands like "convert input -quality 100 output.png" - wich makes no sense..)For the MNG and PNG image formats, the quality value sets the zlib compression level (quality / 10) and filter-type (quality % 10). Compression levels range from 0 (fastest compression) to 100 (best but slowest).
But I won't bug you anymore with this..
Thanks for all your efforts!