Facsimile and static presentation processing – Natural color facsimile – Black signal synthesis
Reexamination Certificate
1997-06-12
2001-02-20
Grant, II, Jerome (Department: 2724)
Facsimile and static presentation processing
Natural color facsimile
Black signal synthesis
C358S530000, C358S518000, C382S162000, C382S167000
Reexamination Certificate
active
06191874
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image processing apparatus and method, and more particularly, to an image processing apparatus and method for performing color processing, and to a recording medium.
2. Description of the Related Art
FIG. 1
is a flowchart illustrating processing when printing on a color printer a color image which is displayed on a CRT (cathode-ray tube). In
FIG. 1
, processing for converting R, G and B image data for CRT display into C, M, Y and K image data corresponding to inks of four colors (cyan (C), magenta (M), yellow (Y) and black (K)) for printing on a color printer.
By performing luminance-to-density conversion in step S
102
for R, G and B image data (Rin, Gin and Bin) input in step S
101
, C, M and Y image data (Cin, Min and Yin) are obtained. Inks of three primary colors, cyan, magenta and yellow, do not have ideal colors, and also have other color components (unnecessary components). In order to compensate for the influence by these unnecessary components, color correction is performed for the C, M and Y image data in step S
103
. For example, a masking method is known as a method for such color correction.
C, M and Y image data (C1, M1 and Y1) subjected to color correction are converted, in step S
104
, into C, M, Y and K image data (C2, M2, Y2 and K2) according to black-generation processing. In general, the minimum value of the C, M and Y image data is made to be an achromatic-color component and is used as black-image data K (black generation). By subtracting the value of K from the respective original C, M and Y image data (removal of under color), C, M, Y and K image data (C2, M2, Y2 and K) are obtained. Then, in step S
105
, density correction desired by the user is performed. Then, in step S
106
, output correction is performed, and obtained output data (Cout, Mout, Yout and Kout) are transmitted to a color printer.
FIG. 2
is a flowchart also illustrating processing when printing on a color printer a color image which is displayed on a CRT. In the flowchart of
FIG. 2
, however, black-generation processing (step S
104
) is performed before performing color correction (step S
103
).
The above-described techniques, however, have the following problems.
In the processing shown in
FIG. 1
, the minimum value of C, M and Y image data after performing luminance-to-density conversion is made to be a black component. When, for example, the C component from among the C, M and Y image data has a minimum value, if the C component is included in unnecessary components of inks corresponding to the remaining M and Y components, achromatic-color components are produced due to the unnecessary components, thereby degrading saturation in the entire image.
In order to prevent degradation in saturation by removing influence by the unnecessary components of inks in the processing shown in
FIG. 1
, it is necessary to perform conversion in which the unnecessary components are taken into consideration in the luminance-to-density conversion in step S
102
. For that purpose, it is necessary to form a large number of color patches, to measure the densities of the respective color patches, and to calculate a conversion table or the like from the results of the measurement. This requires a significant number of operations. Furthermore, when performing luminance-to-density conversion in which unnecessary components in inks are taken into consideration, it is difficult to make achromatic colors represented by C=M=Y to be achromatic colors after the correction. That is, it is very difficult to prevent degradation in saturation in the entire image while maintaining reproducibility for achromatic colors (gray balance).
When performing color correction after performing black-generation processing shown in
FIG. 2
, also, influence of unnecessary components in inks is not removed, thereby degrading saturation in the entire image.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-described problems.
It is another object of the present invention to prevent degradation in saturation in the entire image while maintaining gray balance, and to obtain a high-picture-quality image.
It is still another object of the present invention to provide an image processing apparatus and method which can maintain gray balance according to density correction based on a user's manual instruction.
According to one aspect, the present invention which achieves these objectives relates to an image processing apparatus which includes input means for inputting an image signal including a plurality of color-component signals, extraction means for extracting an achromatic-color component from the input image signal and for subtracting the achromatic-color component from the plurality of color-component signals, color correction means for performing color correction for the plurality of color-component signals output from the extraction means and for outputting a plurality of color-component signals subjected to color correction indicated by real numbers, and generation means for generating an achromatic-color-component signal based on the achromatic-color component extracted by the extraction means and for adding the achromatic-color component to the plurality of color-component signals subjected to the color correction by the color correction means.
According to another aspect, the present invention which achieves these objectives relates to an image processing method which includes an input step of inputting an image signal including a plurality of color-component signals, an extraction step of extracting an achromatic-color component from the input image signal and for subtracting the achromatic-color component from the plurality of color-component signals, a color correction step of performing color correction for the plurality of color-component signals obtained in the extraction step and outputting a plurality of color-component signals subjected to color correction indicated by real numbers, and a generation step of generating an achromatic-color-component signal based on the achromatic-color component extracted in the extraction step and adding the achromatic-color component to the plurality of color-component signals subjected to the color correction in the color correction step.
According to still another aspect, the present invention which achieves these objectives relates to a memory which can be read by a computer and which stores program codes for image processing. The memory includes a code of an input step of inputting an image signal including a plurality of color-component signals, a code of an extraction step of extracting an achromatic-color component from the input image signal and for subtracting the achromatic-color component from the plurality of color-component signals, a code of a color correction step of performing color correction for the plurality of color-component signals obtained in the extraction step and outputting a plurality of color-component signals subjected to color correction indicated by real numbers, and a code of a generation step of generating an achromatic-color-component signal based on the achromatic-color component extracted in the extraction step and adding the achromatic-color component to the plurality of color-component signals subjected to the color correction in the color correction step.
According to still another aspect, the present invention which achieves these objectives relates to an image processing apparatus which includes extraction means for extracting an achromatic-color component and chromatic-color components in an input color image signal, and generation means for performing color correction for the chromatic-color components, for adding the achromatic-color component to the chromatic-color components subjected to the color correction indicated by real numbers, and for generating an ink signal.
According to still another aspect, the present invention which achieves these objectives relates to an image processing method which in
Hirabayashi Hiromitsu
Yamada Akitoshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grant II Jerome
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