IMAGE PROCESSING24 February, 1999
Auto Letter/Photo Separation
Text Area
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In auto text/photo mode, the original image is separated into text and photo areas
(dot screen areas).
"Text" refers to an original or area of an original that contains text and/or line
drawings.
Generally, text areas have strong contrast between the image and the background.
However, photo areas (dot screen areas) have a less extreme range of contrast
levels.
Using these characteristics, the original image is separated into black text areas,
colored text areas, and photo areas. The machine uses the following three
separation methods to detect the different data areas, and the final evaluation
circuit analyzes the output from these three processes to determine the result.
Edge Separation
? Black Text
? Colored Text
Dot Screen Separation? Photo
Colored Text Separation
A259D513.WMF
(1) Edge separation
The edges of text and line diagram elements are identified by using the following
characteristics: strong contrast, continuity of black or color pixels, continuity of
white pixels around the black or color pixels
The machine can do this by only referring to the green signal.
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