Acorn: Shapes in Layer Masks

Shapes in Layer Masks

The workaround for getting a shape into a layer mask.

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Layer masks are currently bitmap only, which means vector shapes cannot be used in the mask. There is a nifty work around you can use if you want a shape in your mask. If you aren't familiar with layer masks, be sure to read the layer masks documentation, and fun with layer masks tutorial first.

In this example, a layer mask with a circle shape will be used to focus on the rubber duck in the image.

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Add a layer mask to the rubber duck layer. Draw out the shape you would like to eventually be present in your layer mask in the color black. The shape will currently be on its own layer since it is vector based. If you want to base the size of your shape on something in the image, temporarily turn the opacity down on the shape layer so you can see the layer below. In the image below the shape's opacity has been turned down to 50% so the circle shape can be adjusted to the size of the rubber duckie.

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Adjust the shape layer opacity back up to 100%. Go to Select ▸ Make Selection from Layer.

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Hide your shape layer by clicking on the eye located to its left in the layers list. Click on the layer mask.

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Go to Select ▸ Inverse. Hit the delete key. Deselect (⌘D). Since the selection is inverted, black fills the layer mask except for the circle made over the duckie. Below the rubber duckie image layer is transparency, so that is what shows through on the mask.

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If you didn't get your shape lined up perfectly on the first try, you can click the '+' button located just to the left of the layer mask in order to move the layer around separately from the mask.

Layer masks are a great way to play around with your images non-destructively!

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Additional Example

This time a red frame will be added around the rubber duckie using a layer mask. A layer filled with red has been added below the duckie layer

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Click on the rubber duckie layer in the layers list. Now click on the shape tool and draw out a rectangle with no fill and a black stroke.

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Go to Select ▸ Make Selection from Layer. Hide the shape layer by clicking on the eye. Add a layer mask to the rubber duckie layer. Hit the delete key. Deselect (⌘D).

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Photo Credit