Color image signal processing method
First Claim
1. A color image signal processing method for a color image input/output system which is adapted to read an original by an image input section, to correct in color and gradation thus obtained image signals, and to feed output density signals for each color to an image output device, which comprises the steps of;
- calculating differences (Δ
DB, Δ
DG, Δ
DR) between desired finish densities and the output density signals (Di '"'"') at specified points on said original which are obtained by converting input density signals at said specified points based upon reference gradation conversion curves;
preparing characteristic curves (f(Di '"'"')) of said differences with respect to said output density signals utilizing a same function for the respective colors, said same function satisfying specified restraint conditions;
preparing corrected gradation conversion curves by adding said reference gradation conversion curves to said functions; and
determining said functions so that said corrected gradation conversion curves Fi are within a specified inclination range (Fimin <
Fi <
Fimax), wherein Fimin is a minimum inclination and Fimax is a maximum inclination;
thereby correcting a gradation conversion table as well as correcting a color correction table by limiting the values of color correction coefficients so as to remove color distortion of output images.
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Abstract
A color image signal processing method for a color image input/output system reads an original by an image input section and corrects the color and gradation of the thus obtained image signals and feeds output density signals for each color to an image output device. The processing method includes the steps of calculating differences between desired finished densities and the output density signals at specified points on the original which are obtained by converting input density signals on the specified points based upon reference gradation conversion curves and then prepares characteristic curves of the differences with respect to the output density signals using the same functions for the respective colors and then prepares corrected gradation conversion curves by adding the reference gradation conversion curves to the functions. The functions are then determined so that the corrected gradation conversion curves are within a specified inclination range so as to thereby correct a gradation conversion table as well as correcting a color correction table by limiting the values of color correction coefficients so as to remove color distortion of output images.
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Citations
5 Claims
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1. A color image signal processing method for a color image input/output system which is adapted to read an original by an image input section, to correct in color and gradation thus obtained image signals, and to feed output density signals for each color to an image output device, which comprises the steps of;
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calculating differences (Δ
DB, Δ
DG, Δ
DR) between desired finish densities and the output density signals (Di '"'"') at specified points on said original which are obtained by converting input density signals at said specified points based upon reference gradation conversion curves;preparing characteristic curves (f(Di '"'"')) of said differences with respect to said output density signals utilizing a same function for the respective colors, said same function satisfying specified restraint conditions; preparing corrected gradation conversion curves by adding said reference gradation conversion curves to said functions; and determining said functions so that said corrected gradation conversion curves Fi are within a specified inclination range (Fimin <
Fi <
Fimax), wherein Fimin is a minimum inclination and Fimax is a maximum inclination;thereby correcting a gradation conversion table as well as correcting a color correction table by limiting the values of color correction coefficients so as to remove color distortion of output images. - View Dependent Claims (2, 3, 4, 5)
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Specification