US 5,477,335 A · Method and apparatus of copying of black text on documents using a color scanner

Abstract

A document reproduction method and apparatus wherein a scanner scans a document to determine the color components of pixels forming the image information on the document. The color signals generated by the scanner are transformed into lightness space and each pixel is examined as part of a window that includes neighboring pixels. The examination involves a first determination of whether or not the neighboring pixels are white pixels, second and third determinations of whether or not the current pixel is a grey pixel and has high contrast, and a fourth determination of whether or not the window has text structure. In accordance with combination of these determinations, a decision is made to recast the pixel as a pixel to be reproduced with a black colorant to thereby minimize color fringing errors at the edge of text-like information.

Claims20

Dependent claims

In a reproduction apparatus for copying color information, the apparatus comprising:

first means for scanning an original containing color information to be reproduced and generating signals representing plural color components of pixels of the information scanned;
second means for examining a current pixel to determine if the current pixel meets a first criterion of having any neighboring pixels that meet a criterion for a white pixel;
third means for examining the current pixel to determine if the current pixel meets a second criterion for a gray pixel;
fourth means for testing the current pixel that meets the first criterion but not the second criterion to determine in accordance with a third criterion that the current pixel is in a region of high contrast;
fifth means for substituting for the current pixel meeting the first criterion and the third criterion but not meeting the second criterion a signal indicative that the current pixel has only black color content and
means, responsive to said signal, for reproducing said current pixel in black.

3 more elements

Dependencies are inferred from the claim text.

Method and apparatus of copying of black text on documents using a color scanner

Life of this patent

Method and apparatus of copying of black text on documents using a color scanner

Life of this patent

Abstract

Claims20