Patent Document ID: 5488491
Application ID: 08086391
Patent Status: 1

Claim One:
1. An electrostatographic reproduction apparatus comprising: scanning means for scanning and outputting first signals representing intensity variations in an original image on a document sheet; designating means for generating second signals representing information relative to a determined image area of the document sheet containing both foreground information and background density; area operation means responsive to the first and second signals for generating third signals representing parameters for substantially eliminating the background density while substantially preserving information with foreground density; and an electrostatographic marking engine including means responsive to said third signals for reproducing a copy of the document sheet with the foreground information without the background density in the area corresponding to the determined area; and wherein the area operation means includes: means for generating a histogram of pixel densities and their frequencies for pixels residing within the determined image area; means for subjecting data in said histogram to a low pass filter and outputting filtered data; means for determining a slope of points in said filtered data; means for defining a geometric minimum within a predetermined amount of a statistical average of the histogram data; means for determining geometric maximums on each side of the geometric minimum; and means for comparing a maximum on one side with a maximum on the other side and defining said parameters if one particular maximum is greater than the other.