Canon CanoScan D646U User Manual page 91

Glossary
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Glossary
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Grayscale
Grayscale refers to a single-channel image made up of 256 shades of
gray, ranging from white to black, that represent all tones in an image.
Halftoning
A method of simulating intermediate tones in black-and-white images by
varying the patterns dots and lines. Halftoning is usually used for
photographs, or other images with intermediate tones, scanned in Black
and White.
Height
The Height text box contains the height of the current selection, or, if
there is no selection, the maximum vertical output size, based on the
currently selected Paper Size.
Histogram
The Histogram displays the distribution of bright and dark pixels for each
color channel in the previewed image. The Eyedropper tool on the
histogram graph lets you redefine the tonal profile.
Keep Proportions button
The Keep Proportions button affects the selection and the Width and
Height text boxes. When you click the Keep Proportions button, the
image size is maintained in the same proportion whenever you change
either the width or the height.
Low contrast
An image that has low contrast does not have many distinct differences
between tones.
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