Applying a Mask to a Layer


  1. Read the tutorial on Layer Composition which covers opacity and blend modes.
  2. Read the tutorial on Adding an FX to a layer.

The project file for this tutorial can be downloaded here.

Step 1: In the Workspace Inspector create an extra layer, inspect it, and hide it by setting its opacity to 0 or clicking the 'Hide' button.

Tip: In the Layer Source controls choose a built-in source such as CoreImage Checkboard or Quartz Composer Gradient to create a test masking image.

Note the Show/Hide button state in the layer composition controls for this hidden 'Mask Layer'

Step 2: Add the "Layer Mask.fs" FX to the layer to be masked (the top layer), and in the "maskImage" pop-up menu, select the hidden layer's video stream.

Tip: The Layer Mask is in the Masking FX category.

Tip: Set the composition mode of the foreground layer to OpenGL Over or Source-Atop-VV for best results when compositing over another layer.

Previews of the Foreground and Masking layers at various stages of processing and the final output.