Automatic correction for color printing
First Claim
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1. A method to process color component signals for printing accurate color image reproductions comprising steps of:
- scanning a color image to be reproduced to derive said color component signals from the color image;
adjusting the color component signals to correct errors in the signals introduced by the scanning step including extending a dynamic range of each color component signal to pass through its white and black points;
converting said adjusted color component signals to intermediate color printing signals to regulate hue values;
correcting the intermediate color printing signals for non-linearities in reproduction characteristics of inks used to print the reproduction;
transforming corrected intermediate color printing signals to compensate color printing signals by steps ofderiving a factor for each of said color printing signals depending on its black paint, andmultiplying one of the intermediate color printing signal by a nonlinear factor proportional to its derived factor to obtain a first compensated color printing signals value and each of the other two intermediate color printing signals by a nonlinear multiplier proportional to its derived factor and the first compensated color printing signal value to obtain the other two compensated color printing signals; and
printing a color reproduction of the color image to be reproduced according to the values of the compensated color printing signals.
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Abstract
Automatic processing of color signals to print an accurate reproduction of an original color image. The RGB scan signals are processed to use the full dynamic range of the system and to adjust the values such that the gray scale lines of the color components pass through the white points. The additive color signals are converted to subtractive color signals that are adjusted so that the gray scale lines pass through the black points to produce automatically an accurate reproduction with a proper neutral gray scale. The processing is arranged to make the adjustments and corrections as fast as possible.
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6 Claims
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1. A method to process color component signals for printing accurate color image reproductions comprising steps of:
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scanning a color image to be reproduced to derive said color component signals from the color image; adjusting the color component signals to correct errors in the signals introduced by the scanning step including extending a dynamic range of each color component signal to pass through its white and black points; converting said adjusted color component signals to intermediate color printing signals to regulate hue values; correcting the intermediate color printing signals for non-linearities in reproduction characteristics of inks used to print the reproduction; transforming corrected intermediate color printing signals to compensate color printing signals by steps of deriving a factor for each of said color printing signals depending on its black paint, and multiplying one of the intermediate color printing signal by a nonlinear factor proportional to its derived factor to obtain a first compensated color printing signals value and each of the other two intermediate color printing signals by a nonlinear multiplier proportional to its derived factor and the first compensated color printing signal value to obtain the other two compensated color printing signals; and printing a color reproduction of the color image to be reproduced according to the values of the compensated color printing signals. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification