Acorn: Layer Masks

Layer Masks

What is a Layer Mask?

Layer masks allow you to show or hide certain parts of a layer without actually having to modify the layer itself. This can be tremendously helpful when working with layers that you want to keep intact for easy alteration later without committing to permanent modification.

Creating a Layer Mask

Select the layer that you would like to add on a layer mask. At the bottom of the tools palette, click on the cogwheel and select "add layer mask". Or, you can control-click on the layer to bring up the canvas contextual menu with the option to add layer mask.

Pasted Graphic.tiff

The mask shows up to the right on the layer as you can see highlighted below.

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Important Tip: Be sure that the layer mask is selected if you want to work on it. Click on the mask in the layers section of the palette and a black bar will appear towards the bottom of the mask as shown on the highlighted layer mask above. If you want to work on the image rather than the mask, click on the image to select it and the black line will move from the mask to the selected image.

Working with Layer Masks

In layer masks, black that is drawn or painted on the mask hides pixels in the linked layer thus exposing the layer below in those areas. In this example the Seattle skyline has the layer mask, and Godzilla is in the layer below. By selecting a brush and the color black, Godzilla can be exposed by drawing on the layer mask.

White does the opposite of black in layer masks. Anything drawn or painted in white on the layer mask will preserve that area of the linked layer. If you feel like you have exposed too much of the layer below, you can correct this by changing the color of your pen or brush to white, and draw on the layer mask until you have achieved your desired effect. Play around with the opacity and style of your pen or brush to maximize smoothness between your layers.

Moving, Disabling, and Deleting Layer Masks

To move a layer around on the canvas without also moving the layer mask, click on the "+" that is located between the layer and layer mask in the layers list. Re-clicking in this location will cause the "+" to appear again and allow the layer mask to move with its layer in the canvas.

Disabling a layer mask allows you to see what things look like in your project without the layer mask present. You can disable a layer mask by clicking on the cogwheel and selecting "disable layer mask". The layer mask will turn dark gray to show that it is disabled. The layer mask can be turned on again by selecting "enable layer mask" from the cogwheel.

To delete a layer mask, make sure you have the mask selected. Then you can click on the cogwheel and select "delete layer mask". Another way to accomplish this is to control-click on the layer mask to bring up the canvas contextual menu and the option to delete the layer mask will be presented.

Vector Shapes and Layer Masks

Currently layer masks are bitmap only, which means you cannot draw shapes in them. If you would like a shape in a layer mask, there is a work around you can perform as outlined in the Shapes in Layer Masks tutorial.

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