Claims
- 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 (.DELTA.D.sub.B, .DELTA.D.sub.G, .DELTA.D.sub.R) between desired finish densities and the output density signals (D.sub.i ') 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(D.sub.i ')) 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 F.sub.i are within a specified inclination range (F.sub.imin <F.sub.i <F.sub.imax), wherein F.sub.imin is a minimum inclination and F.sub.imax 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.
- 2. A method as claimed in claim 1, wherein said original is positioned at a coordinate input device so that the specified points can be specified by color patches.
- 3. A method as claimed in claim 2, wherein said coordinate input device is a digitizer.
- 4. A method as claimed in claim 1, wherein, if said output density signals for each color are D.sub.Bj ', D.sub.Gj ' and D.sub.Rj ' and said desired finish densities are D.sub.Bj, D.sub.Gj and D.sub.Rj, then said differences are calculated in accordance with the following equations:
- .DELTA.D.sub.Bj =D.sub.Bj.sup.o -D.sub.Bj '
- .DELTA.D.sub.Gj =D.sub.Gj.sup.o -D.sub.Gj '
- .DELTA.D.sub.Rj =D.sub.Rj.sup.o -D.sub.Rj '
- wherein j=1, 2, . . . N, and further wherein said gradation conversion table is determined when the curves are obtained by repeatedly processing the following equations: ##EQU6## based upon said difference and said reference gradation conversion curves F.sub.B, F.sub.G, F.sub.R.
- 5. A method as claimed in claim 4, wherein an optimization function OPF is defined and minimized in accordance with the following equations: ##EQU7## wherein: i=Y,M,C
- j=Y,M,C,B,G,R
- Q.sub.ij : color correction coefficients
- Q.sub.ij.sup.o : reference color correction coefficients ##EQU8## wherein: i=B,G,R
- F.sub.i =corrected gradation conversion curve
- a, b, c.sub.k =weight.
Priority Claims (1)
Number |
Date |
Country |
Kind |
60-251573 |
Nov 1985 |
JPX |
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Parent Case Info
This application is a continuation of application Ser. No. 06/928,824 filed Nov. 10, 1986, now abandoned.
US Referenced Citations (5)
Foreign Referenced Citations (4)
Number |
Date |
Country |
58-175055 |
Oct 1983 |
JPX |
60-37878 |
Feb 1985 |
JPX |
60-216350 |
Oct 1985 |
JPX |
60-216353 |
Oct 1985 |
JPX |
Continuations (1)
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Number |
Date |
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Parent |
928824 |
Nov 1986 |
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