Adaptive technique for providing accurate tone reproduction cont

Details Adaptive technique for providing accurate tone reproduction cont Adaptive technique for providing accurate tone reproduction cont

1992-04-22

1993-10-19

Coles, Sr., Edward L.

Facsimile and static presentation processing

Natural color facsimile

Color photography previewer

358406, 358455, H04N 140, H04N 146

Patent

active

052550850

ABSTRACT:
Apparatus and associated methods employed therewith for accurately providing a desired ("Aim") tone reproduction characteristic in an output image through a DDCP (direct digital color proofing) imaging chain (such as that implemented by a raster image processor (200), particularly a screening process (660) occurring therein, and a marking engine (130)) and for significantly reducing the number of test proof images that need to be produced and measured to achieve this result. Specifically, "Benchmark" operating conditions and intrinsic performance (i.e. "Benchmark" entry point data) of the DDCP imaging chain thereat are first defined. Then, based upon differences (such as in screen ruling and solid area density) between a desired operating condition and an appropriate "Benchmark" condition, "Benchmark" values associated with the latter are adapted, through use of a pre-defined model and associated sensitivity coefficients that collectively predict the performance of the DDCP imaging chain, to determine corresponding "Adapted" values that accurately specify the intrinsic process tone reproduction characteristic of the imaging chain at the desired operating condition. Thereafter, in response to both "Aim" (400) and the "Adapted" values for the desired operating condition, a look-up table is fabricated to contain, for all possible input dot areas, the "Aim" dot gain modified by the inverse of this expected intrinsic process tone reproduction characteristic applied to the desired tone reproduction characteristic. Incoming dot area values (i.e. contone values) for a corresponding separation are then routed through this table, prior to screening and writing, in order to intentionally vary the tone reproduction value of each such value so that the resulting dots in the proof image will accuratel exhibit the desired "Aim" tone reproduction characteristic substantially free from corruption due to the native tone reproduction characteristic of the imaging chain.

REFERENCES:
patent: 4657831 (1987-04-01), Ambro et al.
patent: 4708459 (1987-11-01), Cowan et al.
patent: 4816863 (1989-03-01), Lee
patent: 4962421 (1990-10-01), Murai
F. N. Fritsch et al., "Monotone Piecewise Cubic Interpolation", SIAM Journal of Numerical Analysis, vol. 17, No. 2, Apr. 1980, pp. 238-246.
J. A. C. Yule, Principles of Color Reproduction (1967: John Wiley & Sons Inc., New York), specifically pp. 205-216 of Chapter 8 "Additivity and Proportionality of Densities".

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