Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
2000-10-10
2003-09-16
Bella, Matthew C. (Department: 2676)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
C345S589000, C345S591000, C345S603000, C345S597000, C345S601000, C382S162000, C382S167000
Reexamination Certificate
active
06621497
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to data processing used for a full-color printing related equipment such as a printer, a video printer, a scanner or the like, an image processor for forming computer graphic images or a display device such as a monitor. More specifically, the invention relates to a color conversion device and a color conversion method for performing color conversion from image data in the form of a first set of three color data of red, green and blue, or cyan, magenta and yellow, to a second set of three color data of red, green and blue, or cyan, magenta and yellow.
Color conversion in printing is an indispensable technology for compensating deterioration of image quality due to color mixing property due to the fact that the ink is not of a pure color, or the non-linearity (in the hue) of the image-printing, and to output a printed image with a high color reproducibility. Also, in a display device such as a monitor or the like, color conversion is performed in order to output (display) an image having desired color reproducibility in accordance with conditions under which the device is used or the like when an inputted color signal is to be displayed.
Conventionally, two methods have been available for the foregoing color conversion: a table conversion method and a matrix calculation method.
A representative example of the table conversion method is a three-dimensional look-up table method, in which the image data represented by red, green and blue (hereinafter referred to as R, G, and B) are input, to output an image data of R, G, and B stored in advance in a memory, such as a ROM, or complementary color data of yellow, cyan and magenta (hereinafter referred to as Y, M, and C). Because any desired conversion characteristics can be achieved, color conversion with a good color reproducibility can by performed.
However, in a simple structure for storing data for each combination of image data, a large-capacity memory of about 400 Mbit must be used. For example, even in the case of a compression method for memory capacity disclosed in Japanese Patent Kokai Publication No. S63-227181, memory capacity is about 5 Mbit. Therefore, a problem inherent in the table conversion system is that since a large-capacity memory is necessary for each conversion characteristic, it is difficult to implement the method by means of an LS
1
, and it is also impossible to deal with changes in the condition under which the conversion is carried out.
On the other hand, in the case of the matrix calculation method, for example, for obtaining printing data of Y, M and C from image data of R, G and B, the following formula (11) is used as a basic calculation formula.
[
Y
M
C
]
=
(
Aij
)
[
R
G
B
]
(
11
)
Here, Aij represents coefficients, with i=1 to 3, and j=1 to 3.
However, by the simple linear calculation of the formula (11), it is impossible to provide a good conversion characteristic because of a non-linearity of an image-printing or the like.
A method has been proposed for providing a conversion characteristic to improve the foregoing characteristic. This method is disclosed in Japanese Patent Application Kokoku Publication H2-30226, directed to a color correction calculation device, and employs a matrix calculation formula (12) below.
[
Y
M
C
]
=
(
Dij
)
[
R
G
B
R
*
G
G
*
B
B
*
R
R
*
R
G
*
G
B
*
B
N
]
(
12
)
Here, N is a constant, i=1 to 3, and j=1 to 10.
In the foregoing formula (12), since image data having a mixture of an achromatic component and a color component is directly used, mutual interference occur in computation. In other words, if one of the coefficients is changed, influence is given to the components or hues other than the target component or hue (the component or hue for which the coefficient is changed). Consequently, a good conversion characteristic cannot be realized.
A color conversion method disclosed in Japanese Patent Application Kokai Publication H7-170404 is a proposed solution to this problem.
FIG. 20
is a block circuit diagram showing the color conversion method for conversion of image data of R, G and B into printing data of C, M and Y, disclosed in Japanese Patent Application Kokai Publication H7-170404. In the drawing, reference numeral
100
denotes a complement calculator;
101
, a minimum and maximum calculator;
102
, a hue data calculator;
103
, a polynomial calculator;
104
, a matrix calculator;
105
, a coefficient generator; and
106
, a synthesizer.
Next, the operation will be described. The complement calculator
100
receives image data R, G and B, and outputs complementary color data Ci, Mi and Yi which have been obtained by determining
1
's complements.
The determination of
1
's complement of an input data can be achieved by subtracting the value of the input data of n bits (n being an integer) from (2
n
−1). For example, in the case of 8-bit data, the value of the input data is deducted from “255”.
The minimum and maximum calculator
101
outputs a maximum value &bgr; and a minimum value &agr; of this complementary color data and an identification code S for indicating, among the six hue data, data which are zero.
The hue data calculator
102
receives the complementary color data Ci, Mi and Yi and the maximum and minimum values &bgr; and &agr;, and outputs six hue data r, g, b, y, m and c which are obtained by executing the following subtraction:
r=&bgr;−Ci,
g=&bgr;−Mi,
b=&bgr;−Yi,
y=Yi−&agr;,
m=Mi−&agr;, and
c=Ci−&agr;.
Here, among the six hue data, at least two assume the value zero.
The polynomial calculator
103
receives the hue data and the identification code S, selects, from r, g and b, two data Q
1
and Q
2
which are not zero and, from y, m and c, two data P
1
and P
2
which are not zero. Based on these data, the polynomial calculator
103
computes polynomial data:
T
1
=P
1
*P
2
;
T
3
=Q
1
*Q
2
,
T
2
=T
1
/(P
1
+P
2
), and
T
4
=T
3
/(Q
1
+Q
2
),
and then outputs the results of the calculation.
It is noted that asterisks “*” are sometimes used in this specification to indicate multiplication.
The coefficient generator
105
generates calculation coefficients U(Fij) and fixed coefficients U(Eij) for the polynomial data based on information of the identification code S. The matrix calculator
104
receives the hue data y, m and c, the polynomial data T
1
to T
4
and the coefficients U, and outputs the result of the following formula (13) as color ink data C
1
, M
1
and Y
1
.
[
C1
M1
Y1
]
=
(
Eij
)
[
c
m
y
]
+
(
Fij
)
[
c
*
m
m
*
y
y
*
c
r
*
g
g
*
b
b
*
r
c
*
m
/
(
c
+
m
)
m
*
y
/
(
m
+
y
)
y
*
c
/
(
y
+
c
)
r
*
g
/
(
r
+
g
)
g
*
b
/
(
g
+
b
)
b
*
r
/
(
b
+
r
)
]
(
13
)
The synthesizer
106
adds together the color ink data C
1
, M
1
and Y1 and data &agr; which is the achromatic data, and outputs printing data C, M and Y. Accordingly, the following formula (14) is used for obtaining printing data.
[
C
M
Y
]
=
(
Eij
)
[
c
m
y
]
+
(
Fij
)
[
c
*
m
m
*
y
y
*
c
r
*
g
g
*
b
b
*
r
c
*
m
/
(
c
+
m
)
m
*
y
/
(
m
+
y
)
y
*
c
/
(
y
+
c
)
r
*
g
/
(
r
+
g
)
g
*
b
/
(
g
+
b
)
b
*
r
/
(
b
+
r
)
]
+
[
α
α
α
]
(
14
)
The formula (14) shows a general formula for a group of pixels.
FIG. 21A
to
FIG. 21F
, which are schematic diagrams, show relations between six hues of red (R), green (G), blue (B), yellow (Y), cyan (C) and magenta (M), and hue data y, m, c, r, g and b. As shown, each hue data relates to three hues (i.e., extends over the range of three hues). For instance the hue data c relates to the hues g, c and b.
FIG. 22A
to
FIG. 22F
, which are schematic diagrams, show relations between the six hues and product terms y*m, r*g, c*y, g*b, m*c and b*r.
As shown, each of the six product terms y*m, m*c, c*y, r*g, g*b and b*r in the formula (14) relates to only one hue among the six hues of red, blue, green, yellow, cyan and magenta. That is, only y*m is an effective product term for red; m*c for blue;
Kagawa Shuichi
Sugiura Hiroaki
Bella Matthew C.
Mitsubishi Denki & Kabushiki Kaisha
Rahmjoo Manucher
LandOfFree
Color conversion device and color conversion method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Color conversion device and color conversion method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color conversion device and color conversion method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3086515