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2. Basics of Image Processing

## 2.8 Layer Masks

Layer masks are a special kind of clipping layer (see chapter 2.7). While a clipping layer is clipping all its predecessor layers, a layer mask is clipping its parent layer. Therefore a layer mask is always the child (see chapter 2.3.5) of the layer it is clipping. Layer masks are used, if only one layer has to be clipped. The text example of chapter 2.7 is a typical example of a layer mask. Furthermore layer masks are used in traditional image processing to hide unwanted parts of images on the layer stack.

If layer masks are used on image layers, they offer several helping functions in order to combine them with or create them from an alpha channel or a mask (see chapter 7.5.15 and following).