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CHAPTER 11 274
Using Layers
4
Select Preview to preview the results in the
image window.
5
Select Invert to use the negative of the channel
contents in the calculation.
6
For Blending, choose the blending option you
want to apply.
Descriptions of the Add and Subtract options
appear at the end of this section. Other blending
options are the same ones listed in the Options
palette of the painting and editing tools and in the
Layers palette (see “Selecting a blending mode” on
page 205).
7
Enter an opacity for the effect’s strength.
8
Select Preserve Transparency to apply the
results only to opaque areas in the result layer.
9
Select Mask if you want to apply the blending
through a mask. Then choose the image and layer
containing the mask. For Channel, you can choose
any color or alpha channel to use as the mask. You
can also use a mask based on the active selection or
the boundaries of the chosen layer (Transparency).
Select Invert to reverse the masked and unmasked
areas of the channel. (See “About masks” on
page 249.)
10
Click OK to apply the blending effect.
Using the Calculations command
The Calculations command lets you blend two
individual channels from one or more source
images. You can then apply the results to a new
image or to a new channel or selection in the active
image. You cannot apply the Calculations
command to composite channels.
To use the Calculations command:
1
Open the source image or images. The pixel
dimensions of the images must match for image
names to appear in the Calculations dialog box.
2
Choose Image > Calculations.
3
To preview the calculation results in the image
window, select Preview.
4
Choose the first source image, layer, and
channel. To use all the layers in the source image,
choose Merged for Layer.
Select Invert to use the reversed contents, or
negative, of the channel. For Channel, choose Gray
to get the same effect as converting the image to a
grayscale image.
5
Choose the second source image, layer, and
channel, specifying further options as described in
the previous step.
6
For Blending, choose the blending option you
want to apply.
A description of the Add and Subtract options
appears at the end of this section. Other blending
options are the same ones listed in the Options
palette of the painting and editing tools and in the
Layers palette (see “Selecting a blending mode” on
page 205).
7 Enter an opacity for the effect’s strength.