Lighten or Darken pixel selection by Color Intensity

[anthony]

The Intensity variants of Lighten and Darken as now been added to the SVN, and will be published in IM v6.6.9-5

Examples of its use are in IM Usage (which takes longer to update than the actual coding).
http://www.imagemagick.org/Usage/compos ... _intensity

It has two modes of operation, a default 'alpha-weighted intensity' whole pixel selection mode,
or a 'no-weighting' mode but allowing you to just transfer specific (or 'ALL') channels.

That second mode makes it relatively easy to generate a 'shaped mask' using alpha channel coping, if a mask is all you want.

You could even use it as a funny type of "Select this alpha on this, otherwise select that alpha" type of selection.

I am still looking for a more formal definition of "Lighten by Intensity", as it is not covered by the normal SVG or Photoshop definitions I use for composition methods.