4.5.3 Finding the Natural Mask
Performing a selection requires separating the subject, the part of
the image that interests us, from the background. Often the subject
has colorspace features that differentiate it from the background, and
the goal of this section is to explain how to exploit this fact.
Since the techniques described in this section depend on using an
image's natural color features to make the selection, I call this finding the natural mask. The methods are based on using two primary
tools: Threshold, found in the Image:Image/Colors menu,
and Decompose, found in Image:Image/Mode. The natural
mask approach often allows the subject to be extracted in a single,
bold operation.
