I.R.I.S. Readiris Pro 12 for Windows User Guide - Manual (Page 40)

Chapter 6 – Adjusting scanned documents
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o Select Smoothen color image to even out the image.
This option renders grayscale and color images more homogeneous by
smoothening out differences in intensity. As a result, a stronger
contrast is created between the foreground (text) and background
(artwork).
Note: sometimes smoothening is the only way to separate text from a
colored background.
(Original image)
(Binarized black-and-white image)
(Smoothened image)
o Use the slider to increase or decrease the Brightness.
The Brightness settings determine the overall brightness of the image.
Use these settings to darken or lighten the image when the text is
illegible.