Comment 2 for bug 673995

Both requests are the same:
transparent parts of an image should be ignored during the image search (in the first case the outer parts in the second some inner parts of the reference image).

This is a special case for an option to define some masking (in this case use transparency), to exclude parts of an image from the matching process.

In the second case transparency would not be needed, if it was possible, to have an option for the Pattern object like
Pattern(image).exclude(offset, region)
where offset is the upper left offset of region inside the image, that should be ignored.
This could even be supported in the Preview window like TargetOffset.
I am not sure, wether it makes sense, to have more than one of these exclude-regions per image.

additional:
Pattern.getExclude()
Pattern.setExclude()

to dynamically adjust the exclude regions.