User Guide

Operating VRS
VRS User’s Manual
41
converted to a color photograph, an image cannot be converted to color if that original
color data was never captured.
Like the color image, an 8-bit grayscale or 256-level grayscale image also looks like a
photographic representation of the original, but without the color. Because it can
display up to 256 gray levels, it is suited for representing documents containing
different shades of text. Black and white only document scanners capture the
documents in 8-bit grayscale, but convert these images to single bit or pure black and
white images before sending the images to your application.
In this example, we will scan a document and show the effects of VRS Contrast,
Brightness, and Gamma settings on it. In the image shown in Figure 2-32, we have
scanned a document we will refer to as the “CORE” document as a Black and White
image at 200 DPI. If we first set the Contrast value to 0, then set the Brightness value
to 20 (remember that setting the Contrast to 0 is basically like using VRS as a simple
thresholding device), the faint text on the top of the page is visible, but the text behind
the highlighter is unreadable.
Figure 2-32. Brightness with a Low Setting
With a high Brightness setting, such as 45, the highlighted text appears, but the faint
text becomes unreadable.
This text is
revealed.
This text
disappears.