04812903 is referenced by 84 patents and cites 19 patents.

A colored original to be reproduced is scanned point-by-point in each of the three primary colors. The resulting imaging signals are processed to generate a luminance signal and a pair of chrominance signals. The luminance signal is branched into a high-pass filter channel and a low-pass filter channel. The high-pass portion of the luminance signal is amplified in accordance with a sublinear characteristic function which causes signals of small amplitude to be amplified to a greater degree than signals of large amplitude. The low-pass portion of the luminance signal is modified per a non-linear characteristic gradation function. The thus-modified high-pass and low-pass portions of the luminance signal are added to yield an enhanced luminance signal. The enhanced luminance signal is divided by the original luminance signal and each of the chrominance signals is multiplied by the resulting quotient. This automatially compensates for the changes in color saturation which accompany changes in brightness. After the multiplication, the chrominance signals are amplified in accordance with a sublinear characteristic function which causes signals of small amplitude to be amplified to a greater degree than signals of large amplitude. This characteristic function further has a form such that no additional ampification takes place beyond a predetermined threshold limit.

Title
Method of electronically improving the sharpness and contrast of a colored image for copying
Application Number
7/85942
Publication Number
4812903
Application Date
August 14, 1987
Publication Date
March 14, 1989
Inventor
Klaus Birgmeir
Putzbrunn
DE
Hermann Fuchsberger
Ismaning
DE
Wolfgang Ruf
Munich
DE
Eduard Wagensonner
Aschheim
DE
Agent
Peter K Kontler
Assignee
AGFA Gevaert Aktiengesellschaft
DE
IPC
H04N 9/64
H04N 1/46
G03F 3/08
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