Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-05-26
2003-11-04
Nguyen, Madeleine (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S518000, C382S167000
Reexamination Certificate
active
06643029
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an image processing method, an image processing apparatus and a computer readable memory. More particularly, the invention relates to an image processing method, an image processing apparatus and a computer readable memory for matching the color expressions of input and output devices having different color characteristics.
In order to achieve color matching between image data entered by an input device such as a monitor or scanner and image data output by an output device such as a color ink-jet printer based upon the entered image data, there is a known image processing system in which data (referred to as “profile data” below) that describes the input/output characteristics of various input/output devices is retained in the form of a database. The image processing system executes processing between the input image data and the output image data utilizing input/output profile data, which corresponds to these input/output devices, in actual image processing such as color matching.
ICC (International Color Consortium) profile data is well known as an industrial standard and is an example of profile data used in such an image processing system.
In regard to each item of profile data, a color space (Profile Connection Space, or PCS) that is independent of input/output devices is defined by CIE XYZ color space or CIE L*a*b* color space. The intermediate color space is established to make possible color matching between various input and output devices by performing processing in two steps, namely by making a conversion from color space dependent upon the input device to PCS and then making a conversion from PCS to color space dependent upon the output device. One PCS is defined for the data of each profile.
In regard to the data of each profile, data composed of a 3-input N-output look-up table or the like is retained as a database for performing the conversion from PCS to the color space dependent upon the input/output device or the conversion from the color space dependent upon the input/output device to PCS. These items of data are referred to in actual image processing such as color matching and either the data referred to is output or, in certain cases, interpolated data obtained by applying interpolation processing to the same data is output.
Further, in regard to the data of each profile, data consisting of a 3-input 1-output look-up table or the like is retained as a database which indicates whether a color specified by PCS is capable of being reproduced by the input/output devices. These items of data are referred to in color-reproduction range examination processing, which is for determining whether a specific color is capable of being reproduced by a certain input/output device, and either the data referred to is output or, in certain cases, interpolated data obtained by applying interpolation processing to the same data is output.
The structure of the data referred to at the time of such image processing as color matching is referred to as being of the Lut8Type or Lut16Type in regard to ICC profile data and, as shown in
FIG. 9A
, is composed of a 3×3 matrix
20
, a set
21
of three one-dimensional look-up tables (one-dimensional LUTs), a three-dimensional look-up table (three-dimensional LUT)
22
having d
0
×d
0
×d
0
grid points each of which possesses N components, and a set
23
of N one-dimensional look-up tables (one-dimensional LUTs), where N represents the number of components in the color space of the output device. For example, N is equal to 3 in RGB color space and 4 in CMYK color space. Further, d
0
represents the number of grid points along each color-space axis of the three-dimensional LUT.
Similarly, the structure of the data referred to at the time of such image processing as color matching is referred to as being of the Lut8Type or Lut16Type in regard to ICC profile data and, as shown in
FIG. 9B
, is composed of a 3×3 matrix
20
, a set
21
of three one-dimensional LUTs, a three-dimensional LUT
22
having d
1
×d
1
×d
1
grid points each of which possesses one component, and a one-dimensional LUT
23
, where d
1
represents the number of grid points along each color-space axis of the three-dimensional LUT.
Consider a case where an image displayed on a color monitor in which color space is defined by RGB space is output to a color printer in which color space is defined by CMYK space. In accordance with the example of the prior art described above, first the RGB data is converted to device-independent PCS (RGB→PCS) in accordance with the processing flow shown in
FIG. 9A
, then PCS is converted to CMYK data (PCS→CMYK) in similar fashion in accordance with the processing flow shown in FIG.
9
B.
However, since the 3×3 matrix is used in the initial step of processing, this matrix can be employed in the RGB→PCS conversion but not in a CMYK→PCS conversion. Accordingly, the processing procedure is used upon modifying a part of the procedure in such a manner that the data defined in PCS will enter the one-dimensional LUT as is. By contrast, in a case where the printer that outputs the image handles image data that has been defined in YMC space, this matrix can be used.
Thus, with the processing of the prior art, there are cases where the standard processing procedure can be used as is and cases where it must be used after being partially modified, depending upon how the color space of the output device is defined. Such a processing technique lacks versatility.
In order to provide a preview of an output, it is necessary that an image be displayed on a color monitor, in which color space is defined by RGB, so as to reflect the output characteristic of the printer serving as the output device. To achieve this, it is desired that the image be output by performing the color space conversion by following a process that is the reverse of above-described process RGB→PCS, PCS→CMYK. In order to execute such processing, it would be ideal if the color-space matching processing also possessed a reversible characteristic.
In addition, the color reproduction characteristic of a printer varies depending upon the aging of the very components that construct the printer. For example, if the printer is a laser printer, the color reproduction characteristic varies owing to a change in the optical characteristic of the semiconductor laser, the reflection characteristic of the photosensitive drum, etc., with the passage of time.
Furthermore, regardless of the type of color matching processing executed, it is vital that the user of the apparatus executing this processing know in advance the kind of image processing being executed. It is required that the type of processing being executed be managed accurately at all times especially in an image processing system composed of various input and output devices.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an image processing method and apparatus wherein it is possible to preview an image that takes into account a change in the color reproduction characteristic of an output device with the passage of time, as well as a computer readable memory storing a program for executing this preview processing.
According to one aspect of the present invention, the foregoing object is attained by providing an image processing method comprising a generating step of executing calibration of an output device, which outputs an image, in regard to an image output characteristic thereof, and generating a set of one-dimensional LUTs that conforms to a color reproduction characteristic of the output device, a first modifying step of modifying, on the basis of the set of one-dimensional LUTs, content of a first set of one-dimensional LUTs used when device-independent data that has been stored in a profile corresponding to the output device is converted to data dependent upon the output device, and a second modifying step of modifying, on the basis of the set of one-dimensional LUTs, a se
Kumada Shuichi
Ohta Ken-ichi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Madeleine
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