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image, called unsharp mask. The unsharp mask is then subtracted from the
original image, removing low frequencies.
The Unsharp Mask tool has the following parameters:
■ Unsharp Mask Radius X, Radius Y, and Link Control the radius of the
blur (just like in the Blur tool). By default, the X and Y radii are linked and
set to 1.20; otherwise, their range is the same as that of the Blur tool.
■ Strength Controls the strength of the effect of masking that is added.
Basically, the output image is computed as I+s*(I-M) where I is the original
image, M is the unsharp mask, and s is the strength parameter (in 0 to 500
percent; default 100%).
■ Threshold Defines how large the difference between the original image
and unsharp mask must be before the original pixels are changed. A pixel
is changed if the difference in any of its components is larger than or equal
to the threshold (in 0 to 100%; default is 0%).
NOTE This tool can either affect the RGB components or the Alpha component,
but not both at the same time.
Formatting Tools
In some cases you will be working with images of different sizes and color
depths. Use Formatting tools to change these parameters.
There are five image formatting tools:
Description:Tool:
Changes an image's color depth—see Convert Depth Tool on page 410.Convert
Depth
Removes rows or columns of pixels next to the edges of the input im-
age—see Crop Tool on page 410.
Crop
Formatting Tools | 409