Clip with Opacity Masks


An opacity mask reveals part (and only part) of an underlying object. But, though it reveals a section of the underlying object, it does it through an opacity lens; that is, it distorts the brightness of the section of the underlying image that it masks.

Opacity masks are a little confusing because they combine two concepts (transparency and masking) that are both kind of confusing themselves . But you can create some of my favorite effects by using them, and you ll see how it s done in the steps in this section.

You can get a better handle on the impact of the opacity mask effect if you use a gradient fill in your mask object. Though fill doesn t matter when you apply a regular mask, it does matter when you apply an  opacity mask. The lighter the fill, the more the masked illustration shows through the opacity mask. The darker the fill of the opacity mask, the less the underlying illustration shows through.

Follow these steps to apply a gradient fill as an opacity mask:

  1. Create or open an illustration that you will use as a masked object. It will be easier to keep track of your masked object and your masking object if you group the underlying masked object.

  2. Create a circle to use as an opacity mask, and fill it with a black-to-white gradient fill, like the one shown in Figure 17-6.


    Figure 17-6: Preparing an object to serve as an opacity mask

  3. Move the masking object (the circle with the gradient fill) over the illustration.

  4. Open the Transparency palette.

  5. Select both the mask object (the circle) and the underlying illustration.

  6. From the menu in the Transparency palette, choose Make Opacity Mask, as shown in Figure 17-7.

    click to expand
    Figure 17-7: Applying an opacity mask

  7. Click outside the masked set to reveal the results of the opacity mask. By default the Clip checkbox in the Transparency palette is selected when you apply an opacity mask. Figure 17-8 shows the result of applying an opacity mask to an image.

    click to expand
    Figure 17-8: The overlaying object both masks and applies transparency to the underlying object.

If you deselect the Clip check box in the Transparency palette after you apply an opacity mask, the mask functions like a regular transparency, not a mask. If you select the Invert Mask check box, you reverse the effect that dark and light colors have on the underlying image. If you reduce the opacity of the masking object, the resulting mask is more transparent.

You can click on the Link button in the Transparency palette ”it s visible when an opacity mask is selected ”to unlink the opacity mask from the underlying image. When you unlink the opacity mask from the underlying image, you can move either the underlying (masked) image or the opacity mask to change the area that is revealed through the mask.




How to Do Everything with Illustrator CS
How to Do Everything with Adobe Illustrator CS
ISBN: 0072230924
EAN: 2147483647
Year: 2002
Pages: 175
Authors: David Karlins

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