Legacy ImageMagick Discussions Archive

-threshold is described as "Apply simultaneous black/white threshold to the image."
http://www.imagemagick.org/script/comma ... #threshold

But "-threshold 50%" gives a different result than "-black-threshold 50% -white-threshold 50%". The former looks at the pixel as a whole while the latter looks at one channel at a time. "-channel RGB -threshold 50%%" switches how the first is handled. Is there a similarly simple way to switch how -black-threshold is handled?

Some commands handling -channel in different ways. There is a slow consolidation of how channel is handled.

-threshold by default maps images to greyscale first, unless the -channel setting has changed. This was due to historical reasons.

The other two are straight channel only 'half threshold' operators. That is they only threshold one side of the given value.