Adobe PHOTOSHOP 5.0 User Manual page 139

To invert an image:
Choose Image > Adjust > Invert.
Original image, and Invert command applied
Using the Equalize command
The Equalize command redistributes the
brightness values of the pixels in an image so that
they more evenly represent the entire range of
brightness levels. When you choose this
command, Photoshop finds the brightest and
darkest values in the image so that the darkest
value represents black (or as close to it as possible)
and the brightest value represents white.
Photoshop then attempts to equalize the
brightness—that is, to distribute the intermediate
pixel values evenly throughout the grayscale.
You might use this command when a scanned
image appears darker than the original and you
want to balance the values to produce a lighter
image. Using the Equalize command together with
the Histogram command lets you see before-and-
after brightness comparisons.
To equalize the brightness values of pixels:
Choose Image > Adjust > Equalize.
1
If you selected an area of the image, in the
2
Equalize dialog box select what to equalize:.
Equalize Selected Area Only to distribute evenly
•
only the selection's pixels.
Equalize Entire Image Based on Selected Area to
•
distribute evenly all image pixels based on those in
the selection.
Click OK to equalize the image or the
3
selection.
Original image, and Equalize command applied
Using the Threshold command
Use the Threshold command to convert grayscale
or color images to high-contrast, black-and-white
images. This command lets you specify a certain
level as a threshold. All pixels lighter than the
threshold are converted to white and all pixels
darker to black.
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User Guide