Using Opacity Mask to Crop the Images and
create varying effects in Illustrator
We
may use the phrase "object mask" to describe any type of opacity mask
based on a vector object and we may use the phrase “opacity mask” to describe
the mask on a raster image.
Reason: There is slightly different process for
creating masks based on raster images. Object masks are much more
straightforward.
We open up the Transparency
palette. Choose the flyaway menu on the right, and select the "Make
Opacity Mask" option.
Instantly your text
will disappear. To make it reappear, deselect the "Clip" checkbox in
the Transparency palette.
Now click on the opacity mask
that you've created in order to select it.
Notice what happens
in your Layers palette?
You've entered into a sort of
nested layer system in Illustrator in which any object you create becomes a
sub-layer of your text object. You can't select any object that's currently in
your document. You can only select and create objects within this special
opacity mask layer. So now pick a drawing tool. We may use the rectangle tool
and draw a box around my text object, which happens to have the same fill color
as my text.
And then we may
apply a gradient swatch to that box. The gradient I chose, seen below in the
Layers palette and the Transparency palette, has a white center, fading out to
black. Because Illustrator uses the luminance values of objects in the opacity
mask, this means that my text fades from full opaque to fully transparent from
the center.
Now we may continue
to add objects to the mask, if desired, or modify the current object. We may
also convert the radial gradient to a linear gradient; adjust the brightness
value of the black to make it a dark gray so that the text doesn't disappear
completely.
Then, in the
Transparency palette we may again select the main object to manipulate the
object rather than the mask. We may drag it on top of an image in the composition,
and now have live, editable text with a gradient mask!
Second Phase
Select your text
object once again, and, if you haven't already, create a new opacity mask for
it, just as before, then select the opacity mask, and choose Edit > Paste in
Front (Command-F on the Mac/Control-F on Windows) to paste it in place so that
it doesn't get lost on your canvas. Move the image around to make it fit better
into your text.
If you're effect looks
inverted--if, say, you have the masked object on top of a light background, you
can select the "Invert Mask" option in the transparency palette,
which will flip around the luminance values of your opacity mask.
You may also continue to make
adjustments to the image in the mask. One way would be to select the mask, and
adjust its transparency in the Transparency palette. Reducing the mask object's
opacity value will make the text less transparent, which can help in certain
circumstances. (Note: If you have multiple objects within your opacity mask,
you can select individual objects to adjust their transparency values.)
Similarly, you could
also apply an Adjust Colors filter to the mask image to adjust individual color
channels, accentuating and deemphasizing portions of the image as you see fit.
If you wish, you can use the
"Clip" option in the Transparency palette, which will cut off (or
"clip") your object outside the bounds of your opacity mask
object(s).
Finally, you can also disable and
delete opacity masks. To disable them, simply choose "Disable Opacity
Mask" from the flyaway menu in the Transparency palette. To delete the
mask and its contents, select the opacity mask in the Transparency palette,
then select and delete the objects within the mask. After this, choose the
flyaway menu in the Transparency palette, and select "Release Opacity
Mask." Alternately, if you
wish to keep the contents of the opacity mask but not use them in an opacity
mask, simply release the mask without deleting the objects.
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