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I am trying to understand what is going on under the hood when I invert a selection. Situation: I have an image with a selection. The selection consists of two parts, one (at the left hand side) done with the freehand selection tool, the other (to the right) with the elliptical marquee tool. The freehand part has a blurry boundary, the elliptical part has a sharp boundary. I now want to create two layer masks, one from the selection and the other from whatever is outside of it. I use Invert Selection for that. The idea is to stack two layers with the original image, with one of the masks applied to each of them. Hopefully, each mask will let through just enough so that together they will blend into the original image. I expect normal blending mode should do the trick. My way of working is the following: - the original selection I save into a channel that I call "base selection". - I then invert the selection, and save the result in a channel called "base selection inverted". - I create a pixel layer and fill it with pink colour. - I duplicate that layer. - For each of the two layers I create a mask. The "base selection" channel I load into alpha of the first mask, the "base selection inverted" channel into alpha of the second mask. - I stack the two layers with normal blending mode. - I activate both layers and their masks. - Finally, to see clearly what is happening I create an extra blue pixel layer that I use as background. This is the resulting layer panel: I would now expect, perhaps naively, that I would see the original pink image back, since the masks are complementary and both let their own part of the original through. Instead, I see the following: Whereas the elliptical selection to the right is invisible, the blurry freehand selection to the left lets part of the blue background shine through. I now have the following questions: - how exactly is the selection converted into a mask through the channel? As I understand it, a mask is a mapping that tells what opacity to assign to each pixel of the (pixel) layer it is assigned to. White has 100% opacity, black is fully transparant. Fine. For black and white positions in the mask, this works. But if there is a position in the mask with "grey tonal value", an opacity between 0 and 1 is assigned. What is the formula for that? How is this "gray tonal value" determined, and once you have it, how does it translate to an opacity number? - How do the opacity numbers relate between a mask derived from a selection, and a mask derived from its inverse? Are they complementary, i.e., add up to 1 in every case? - From what I am seeing, it looks like inverting a selection does not necessarily lead to masks that are complementary in the sense that they can work together to restore a full image. They may leave spots with less than full opacity, if selections have blurry edges. This leads to the following question: is there a way to achieve what I am aiming for? Or am I missing the obvious here? Thanks to everyone who read through all this. I do hope you can shed some light. For reference, I attach the project (done with AP 184.108.40.206). Jeroen. selection inversion test.afphoto