Using transparency to shape a knockout


    Use the Opacity & Mask Define Knockout Shape option to make a knockout effect proportional to the object's opacity--in areas of the mask that are close to 100% opacity, the knockout effect will be strong; in areas with less opacity, the knockout effect will be weaker. For example, if you use a gradient-masked object as a knockout, the underlying object will be knocked out progressively, as if it were being shaded by a gradient. You can create knockout shapes with both vector and raster objects.

    Note: The Opacity & Mask Define Knockout Shape option is most useful for objects that use a blending mode other than Normal.

    Illustration of Knocking out shapes using a gradient mask with these callouts: A. Original objects B. Rectangle and wave made into an opacity mask C. Opacity mask and lighthouse grouped and then Knockout Group option selected D. Opacity mask targeted and Opacity & Mask Define Knockout Shape option selected.
    Knocking out shapes using a gradient mask A. Original objects B. Rectangle and wave made into an opacity mask C. Opacity mask and lighthouse grouped and then Knockout Group option selected D. Opacity mask targeted and Opacity & Mask Define Knockout Shape option selected
    Illustration of Knocking out shapes using a bitmap object with these callouts: A. Lighthouse with transparent background B. Darken blending mode applied to lighthouse C. Lighthouse and moon grouped and Knockout Group option selected D. Opacity & Mask Define Knockout shape option applied to lighthouse
    Knocking out shapes using a bitmap object A. Lighthouse with transparent background B. Darken blending mode applied to lighthouse C. Lighthouse and moon grouped and Knockout Group option selected D. Opacity & Mask Define Knockout shape option applied to lighthouse

To create a shaped knockout:

  1. Do one of the following:
    • To use an opacity mask to shape the knockout, select the mask, and then group it with the objects you want to knock out.
    • To use the alpha channel of a bitmap object to shape the knockout, select a bitmap object that contains transparency, and then group it with the objects you want to knock out.
  2. Select the group.
  3. In the Transparency palette, select Knockout Group until the option displays a checkmark.
  4. Among the grouped objects, target the masking objects or transparent image in the Layers palette. (See Targeting layers, groups, and containers.)
  5. In the Transparency palette, select Opacity & Mask Define Knockout Shape.