Adding the last bit to a mask that covers everything but an image of the iPhone...

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2020-02-10 01:07:49

Struggling to get everything outside a photo of the iPhone not to show. Learning about masks but not great at it.

Seems like there should be a way to select the extra bit with a wand, but even when I merge all the layers so I can do that, and copy the resulting bit, I don't know how to add that bit to the mask. I describe the problem in this little video:

Appreciate any tips!
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2020-02-10 07:40:50

Hi ajg23.
There are two ways of commonly masking things: masks (a.k.a. opacity masks, layer masks) and clipping masks. They work in different ways but achieve similar results. Although I'm a big fan of clipping masks, I'll stick to layer masks here as they are (in my opinion) a little easier to use.

A layer mask is a supplementary bitmap added to a layer (or group) that modifies its opacity. Where the mask is white, the layer (or group) is opaque, where it is black the layer (or group) is transparent.

Let's start with your unmasked image. Here's my 1 minute mock-up:
Let's add a mask to the group of objects. When you create a mask, it is affected by any active selections, so let's deselect before we do anything.
1. Cmd-D to deleclect.
2. Right-click on the group of objects and select Add Mask.
Now, you can paint on the mask itself.
3. In the layers palette click one the mask so that it is selected and in the canvas, with a sharp-edged black brush, paint out the bits you don't want.
Job done. If you go to far and paint out something you want to keep, switch to a white brush and paint it back in.

That's it, that's all you need to get this done, but I did mention something earlier about selections. If you have a selection active when you create a mask, rather than creating an all-white mask, Pixelmator will create a mask that is white where the selection was active and black everywhere else.
If you have a bit of time on your hands, now is the time try it. To remove your mask, right click on it in the layers panel and Remove Mask. Make the selection that you want then right-click and Add Mask again. If this isn't exactly what you want, you can always paint in/out more of the mask later. You may need to deselect first, though, as a selection will affect where you can/cannot paint.
Hope this helps. If anything is unclear, just come back and I (or someone else) will be bound to come back and help.
- Stef.