Method of and apparatus for establishing a reference point on a

Details Method of and apparatus for establishing a reference point on a Method of and apparatus for establishing a reference point on a

1989-12-05

1991-01-08

Britton, Howard W.

Facsimile and static presentation processing

Static presentation processing

Attribute control

358 75, H04N 146

Patent

active

049840711

ABSTRACT:
A highlight point (HL.sub.R, HL.sub.G, HL.sub.B) and/or a shadow point (SD.sub.R, SD.sub.G, SD.sub.B) on a gradation correction curve are established in consideration of decoloration and color fog of an original. Density values of respective primary colors are obtained for each pixel on an original. Average density is computed for each pixel and a cumulative histogram of average density distribution is generated. Temporary reference density values corresponding to prescribed cumulative frequencies are found on the cumulative histogram. Reference color density values (D.sub.RH, D.sub.GH, D.sub.BH) are computed by averaging the density of each color for the pixels having average density between the temporary reference density and terminal density on the cumulative histogram. The highlight and shadow points are specified with one of the reference color density values.

REFERENCES:
patent: 4899216 (1990-02-01), Yonezawa

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