Color reproduction system
AssigneeMassachusetts Institute of Technology
InventorWilliam F. Schreiber
Life of this patent
Estimating the term…
Abstract
A system for reproducing a color original in a medium using a selected multiplicity of reproduction colorants, comprising: a scanner for producing from said color original a train of appearance signals dependent on at least three color values of said original; aesthetic correction circuitry for introducing aesthetically desired alteration into said appearance signals to produce modified appearance signals; and colorant selection mechanism for receiving said modified appearance signals and for selecting corresponding reproduction signals representing values of said reproduction colorants to produce in said medium a color match of said modified appearance signals.
Claims21
A system for reproducing a color original in a medium using a selected multiplicity of reproduction colorants, the system comprising in serial order:
- a. a scanner for producing from said color original a set of three tristimulus appearance signals dependent on the colors in said original;
- b. display means connected to the scanner for receiving the appearance signals and aesthetic correction circuitry for interactively introducing aesthetically desired alterations into said appearance signals to produce modified appearance signals;
- and
- c. colorant selection mechanism for receiving said modified appearance signals and for selecting corresponding reproduction signals representing values of said reproduction colorants to produce in said medium a colorimetrically-matched reproduction.
In a color reproduction system in which a lookup table is used to calculate the desired amount of colorant, the method of finding the entries of said table comprising the following steps:
- a. printing a multiplicity of combination of amounts of colorants spanning the full range of such physically realizable combinations;
- b. measuring the appearance values of all the combinations using a colorimetric and calculating the corresponding lookup table inputs;
- c. choosing a trial set of entries of said table on the basis of the results of steps (a) and (b);
- d. printing color patches corresponding to each of said entries, measuring their appearance values with a colorimeter, and calculating the corresponding lookup table inputs;
- e. determining the lookup table outputs corresponding to the said inputs;
- f. printing the colorants of step (e), measuring the corresponding appearance values, and calculating the corresponding lookup table inputs;
- g. on the basis of the results of steps (d) through (f), adjusting the lookup table entries in such a direction as to reduce the discrepancy between successive sets of lookup table inputs;
- and
- h. repeating the process until the discrepancy between results on successive iterations is acceptably small.
A method for reproducing a color original using a selected multiplicity of reproduction colorants, the method comprising:
- (a) scanning said original to produce a set of three tristimulus appearance signals dependent on the colors in said original;
- (b) surrounding and illuminating the original with a reference white border;
- (c) displaying said appearance signals as an image on a television display device having three phosphor light sources, the intensities of which are directly proportional to the appearance signals, the display device also comprising an illuminated reference white element;
- (d) modifying the appearance signals until the displayed image is a colorimetric match of the reference white illuminated original;
- (e) translating the modified appearance signals into colorant value signals;
- (f) selecting the amounts of particular colorants in response to the colorant value signals;
- and
- (g) using said colorants to form a reproduction.
In a color reproduction system in which a lookup table is used to calculate the desired amount of colorant, the method of finding the entries of said table comprising the following steps:
- a. printing a plurality of colorant combinations with varying amounts of colorants spanning the full range of physically realizable combinations;
- b. measuring the appearance values of each of said combinations using a colorimeter and calculating a corresponding lookup table input value;
- c. choosing a set of initial entries for said table on the basis of the results of steps (a) and (b);
- d. determining the lookup table outputs corresponding to the said inputs;
- and
- e. filling said table with additional input and output values by interpolating between said input and output values of said initial entries.
Dependencies are inferred from the claim text.