Comment 3 for bug 679974

Could we use the alpha channel to indicate an image priority?

alpha=0 -> no image data.
alpha=1.0 -> normal: use this image.

alpha1 < alpha2 -> prefer using image 2.

this would lead to "special case" of alpha 1.0. It should be considered "medium priority" where images can come above and below. It would be most consistent, but have a painful transition period if we'd set the alpha to 0.5 by default.

Suppose I have two images.
11111111111111111111111111111111111111111111111111111111111
...............................2222222222222222222...................................

Of course "2" was taken with longer focal length, so it has more details. So I'd prefer image 2 to image 1. Currently enblend would say something like excessive overlap, and forget all about image 2. In fact it should cut everything on image 1 that is "far from the edge" of image 2 away and then do a normal blend.

Of course this requires some interesting coding in enblend......