Analyzes a ChromaKey image to guess its key color (by examining nine areas of the image and using the one with the least hue variance). If a selection is active it only analyzes the selection.

Analyzes a ChromaKey image to guess its key color (by examining nine areas of the image and using the one with the least hue variance). If a selection is active it only analyzes the selection. This overload will return a level of Tolerance that would remove all the background color from the selection. If this is used without a selection it is likely to return a level that is too low (a default tolerance of 0.21 is usually better).