Clipping Masks

Masks in Illustrator come in two varieties: clipping and opacity. Clipping masks hide part of an object or image. Opacity masks use a pattern or gradient to selectively expose parts of an object or image. A practical difference is that opacity masks can be semitransparent, whereas clipping masks cannot. Figure 17.1 shows an image and how it can be affected by the two types of masks.

Figure 17.1. The selection in the center shows how the clipping mask hides part of the image. To the right is an opacity mask using a pattern.