System and method of determining a reference value for the intensity associated with a color indication variable obtained by scanning an original with a color scanning unit
First Claim
1. A method of determining a reference value for the intensity associated with a color indication variable, obtained by scanning an original with a color scanning unit, the color scanning unit being adapted to scan said original point-by-point, said method comprising determining a locally valid reference value for each scanned point and for each associated color indication variable, provided the intensity value related thereto deviates from a defined standard value by less than a preset value, by adapting, starting from the data concerning the then locally available reference value, said locally available reference value, using a fraction of the value representing the intensity in the case of the color indication variable concerned.
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Abstract
A method and system of determining a reference value for the intensity associated with a color indication variable and obtained by scanning an original with a color scanning unit the color scanning unit being adapted to scan the original point-by-point, the method comprising determining a locally valid reference value for each scanned point and for each color indication variable, provided the intensity value related thereto deviates from a defined standard value by less than a preset value, by adapting the then locally available reference value by using a fraction of the value representing the intensity in the case of the color indication variable concerned. For example, a white reference value (white point) can be determined for an original point by point, with the result that weak color tones which are perceived as white are also regarded as white, while in addition small variations in these weak color tones (e.g. uneven yellowing) are also noted as white.
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Citations
14 Claims
- 1. A method of determining a reference value for the intensity associated with a color indication variable, obtained by scanning an original with a color scanning unit, the color scanning unit being adapted to scan said original point-by-point, said method comprising determining a locally valid reference value for each scanned point and for each associated color indication variable, provided the intensity value related thereto deviates from a defined standard value by less than a preset value, by adapting, starting from the data concerning the then locally available reference value, said locally available reference value, using a fraction of the value representing the intensity in the case of the color indication variable concerned.
- 13. A color reproduction system, comprising a color scanning unit for point-by-point scanning of an original and generation of associated color information and an image processing and control unit for correcting and processing said color information to give control signals for controlling a color printing unit, said system being adapted to determine a reference value for the intensity associated with a color indication variable, said color reproduction system being further provided with a first computing means for determining a locally valid reference value for each scanned point and for each color indication variable, provided the intensity value related thereto deviates from a defined standard value by less than a preset value, by adapting, starting from the data concerning the then locally available reference value, this available reference value, using a fraction of the value representing the intensity in the case of the color indication variable concerned, and is also provided with a second computing means for establishing an adapted intensity value by reference to the intensity value determined for that scanned point for each color component, using a scale conversion function based on the locally valid reference value for said scanned point, in order to give color information to be supplied to said image processing and control unit.
Specification