Method of and apparatus for electronic contrast enhancement of r

Details Method of and apparatus for electronic contrast enhancement of r Method of and apparatus for electronic contrast enhancement of r

1987-08-14

1989-04-25

Groody, James J.

Facsimile and static presentation processing

Facsimile

Recording apparatus

358 36, 358 37, 358 75, 358 80, 358166, 358167, 358280, H04N 140, H04N 146, H04N 514, H04N 964

Patent

active

048252972

ABSTRACT:
The invention relates to a method and apparatus for electronic contrast valuation of two-dimensional transparent original images, in which the original images are electro-optically scanned by rows and columns. The image signals, corresponding to the image elements or pixels, and possibly needing correction, are subjected to frequency filtering, in which they are modified by a low-pass filter. The resulting low-pass signals are summed with corresponding high-pass signals obtained by subtraction of low-pass signals from the original image signals. The amplification factor for the high-pass signal is determined according to a non-linear transfer characteristic function K2, such that small signals corresponding to low image contrast are more greatly amplified (amplification S.sub.1) than are large signals corresponding to high image contrast (amplification S.sub.2), and that the low-pass signals are modified according to a non-linear gradation characteristic function K1 prior to the addition of the high-pass and low-pass signals.

REFERENCES:
patent: 3715477 (1973-02-01), Olson et al.
patent: 4009334 (1977-02-01), Sypula
patent: 4245237 (1981-01-01), Lagoni
patent: 4365266 (1982-12-01), Lagoni
patent: 4626903 (1986-12-01), Giesche et al.
patent: 4661843 (1987-04-01), Sekizawa et al.
patent: 4689666 (1987-08-01), Hatanaka

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