: How to knock out same-color overlap in Photoshop Let's say I have two layers with some black pixels on them: What can I do with blending, masks, knockouts, etc, such that when these two

@Hamaas979

Others have given answers here that will work in PS, however have you considered using Illustrator for this? It has a new feature called the Shaper Tool, which is used for making non-destructive combinations of shapes exactly like that.

I know you asked for Photoshop, but Illustrator makes such tasks super easy.

Here's an example of moving one of the shapes around inside a Shaper Group - with the overlap set to knock out.

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@Berryessa866

This is a bit convoluted and won't easily translate to more complex artwork (i.e. anything other than solid black/white blocks of color), but it's the only way I can think to do this with pixel layers and have the effect "live" and update with any changes to the layers...

You can use the "Difference" blending mode on the top layer, which subtracts the color values of one layer from the other. The only problem being that blending with black produces no change; blending white with white however produces black...

If you can change the rectangles to white, set the top layer to "Difference" and invert the result (with an "Invert" adjustment layer), you can get close to the result you want:



Then if you want the background color to show through you can group the two rectangles, clip the invert adjustment layer to the group so that it doesn't affect the background, then set the group's blend mode to "Multiply":



If you can't change the black pixel layers to actually be white, you can just add a white color overlay to each of the black layers:

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@Cofer715

I'm betting there's a simpler way, but this way works without another layer and you could easily turn it into an action:


Step 1: Overlap two layers

Step 2: Ctrl/command-click the first layer in the layer panel to select its outline, then click the second layer. Press the 'add layer mask' button at the bottom of the layers panel. This hides anything but the A overlap from B.

Step 3: Repeat in reverse order. Ctrl/command-click the second layer, select the first layer, add layer mask. Now only the overlap is visible. We want to opposite though.

Step 4: Invert the layer masks by selecting each layer mask in the layers panel and pressing ctrl/command-I



You'll have to remove the layer masks and redo all the steps every time you move a layer, but it's actually relatively quick. Experiment with creating an action for it, perhaps? This technique works with more than two layers, as well.

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