U.S. patent application number 09/066865 was filed with the patent office on 2001-11-29 for image processing method and apparatus for transforming thecolor space of entered image data.
Invention is credited to OHTA, KENICHI.
Application Number | 20010046319 09/066865 |
Document ID | / |
Family ID | 14807605 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010046319 |
Kind Code |
A1 |
OHTA, KENICHI |
November 29, 2001 |
IMAGE PROCESSING METHOD AND APPARATUS FOR TRANSFORMING THECOLOR
SPACE OF ENTERED IMAGE DATA
Abstract
Data for color conversion stored beforehand in a ROM is
transferred to a three-dimensional look-up table when a color
copier is started. By referring to R, G, B signals, which have been
stored beforehand in a buffer memory, in accordance with signal of
M, C, Y, Bk signals output in synchronization with the printing
operation of a printer, a CPU rewrites the data in the look-up
table to appropriate data (M, C, Y, Bk output signal values). A
color signal processing circuit refers to the updated look-up table
and outputs M, C, Y, Bk color signals that correspond to entered R,
G, B signals.
Inventors: |
OHTA, KENICHI;
(KAWASAKI-SHI, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
14807605 |
Appl. No.: |
09/066865 |
Filed: |
April 28, 1998 |
Current U.S.
Class: |
382/167 |
Current CPC
Class: |
H04N 1/6011 20130101;
G06T 11/001 20130101; H04N 1/6025 20130101 |
Class at
Publication: |
382/167 |
International
Class: |
G06K 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 12, 1997 |
JP |
9-121290 |
Claims
What is claimed is:
1. An image processing apparatus for transforming the color space
of input image data, comprising: dividing means for dividing image
data into data of high-order and low-order bits; a look-up table
memory in which color data of a different color space corresponding
to the number of high-order bits is stored in advance; color signal
processing means for interpolating, on the basis of the data of the
low-order bits, color data read out of said look-up table memory
using the data of the high-order bits as an address, and outputting
the interpolated color data; and rewriting means for selectively
rewriting the color data at a prescribed address of said look-up
table memory.
2. The apparatus according to claim 1, wherein said rewriting means
includes: designating means for designating data of at least one
color; generating means, in which high-order bits of the data that
has been designated by said designating means are used as an
address, for generating an address in the neighborhood of this
address; and color data rewriting means for rewriting the color
data of said look-up table memory that corresponds to the address
generated by said generating means.
3. The apparatus according to claim 2, wherein said designating
means includes: area designating means for designating a desired
area in the image of an original; and extracting means for
extracting image data of the area that has been designated by said
area designating means.
4. The apparatus according to claim 3, further comprising reading
means for reading the image of the original and separating the
image into colors pixel by pixel in order to generate the data of
said at least one color.
5. The apparatus according to claim 4, wherein said rewriting means
generates data to be rewritten based upon a corresponding
relationship between a drive signal of output means which outputs a
reproduced image of the image of the original and data obtained by
separating a color output by said output means into color
components, and the image data of the designated area.
6. The apparatus according to claim 4, further comprising
colorimetry means for measuring data obtained by said reading
means; said rewriting means generating data to be rewritten based
upon a corresponding relationship between a drive signal of output
means and a value obtained by said colorimetry means, and the image
data of the designated area.
7. The apparatus according to claim 1, wherein said color data is
magenta, cyan and yellow color data.
8. The apparatus according to claim 1, wherein said color data is
magenta, cyan, yellow and black color data.
9. An image processing apparatus for subjecting image data to color
processing, comprising: storage means for storing a look-up table
having multi-dimensional inputs; input means for inputting color
data of a specific color; arithmetic means for obtaining a
relationship between input and output data of said look-up table
that corresponds to a color in the neighborhood of the specific
color; and modifying means for modifying a portion of said look-up
table based upon the relationship between the input and output data
obtained by said arithmetic means.
10. The apparatus according to claim 9, further comprising second
input means for inputting color data that is based upon a manual
designation made by a user.
11. The apparatus according to claim 9, wherein the color
processing conforms to an output characteristic of image output
means.
12. An image processing method for transforming the color space of
input image data, comprising: a dividing step of dividing image
data into data of high-order and low-order bits; a color signal
processing step of interpolating, on the basis of the data of the
low-order bits, color data that has been read out of a look-up
table memory using the data of the high-order bits as an address,
wherein color data of a different color space corresponding to the
number of high-order bits has been stored in the look-up table
memory in advance; and a rewriting step of selectively rewriting
the color data at a prescribed address of the look-up table
memory.
13. The method according to claim 12, wherein said rewriting step
includes the steps of: designating data of at least one color;
adopting high-order bits of the designated data as an address and
generating an address in the neighborhood of this address; and
rewriting the color data of the look-up table memory that
corresponds to the generated address.
14. The method according to claim 13, wherein the step of
designating data includes the steps of: designating a desired area
in the image of an original; and extracting image data of the area
that has been designated.
15. The method according to claim 14, further comprising a reading
step of reading the image of the original in advance and separating
the image into colors pixel by pixel in order to generate the data
of said at least one color.
16. The method according to claim 15, wherein said rewriting step
generates data to be rewritten based upon a corresponding
relationship between a drive signal for outputting a reproduced
image and data obtained by separating a color output by said the
drive signal into color components, and the image data of the
designated area.
17. The method according to claim 15, further comprising a
colorimetry step of measuring color of data obtained by said
reading step; said rewriting step generating data to be rewritten
based upon a corresponding relationship between a drive signal for
outputting a reproduced image and a value obtained by said
colorimetry step, and the image data of the designated area.
18. The method according to claim 12, wherein the color data that
has been stored in the look-up table memory in advance is obtained
by: outputting a combination of color data in regard to a
respective one of a plurality of combinations of color data
prepared in advance; reading the output obtained as a result; and
storing data obtained as a result of reading the output as data
corresponding to the combination of the image data.
19. An image processing method for subjecting image data to color
processing using a stored look-up table having multi-dimensional
inputs, comprising the steps of: inputting color data of a specific
color; obtaining a relationship between input and output data of
the look-up table that corresponds to a color in the neighborhood
of the specific color; and modifying a portion of the look-up table
based upon the relationship between the input and output data.
20. The method according to claim 19, further comprising a step of
inputting color data that is based upon a manual designation made
by a user.
21. The method according to claim 19, wherein the color processing
conforms to an output characteristic of image output means.
22. A computer readable memory storing program codes of image
processing for transforming the color space of input image data,
comprising: a code of a dividing step of dividing image data into
data of high-order and low-order bits; a code of a color signal
processing step of interpolating, on the basis of the data of the
low-order bits, color data that has been read out of a look-up
table memory using the data of the high-order bits as an address,
wherein color data of a different color space corresponding to the
number of high-order bits has been stored in the look-up table
memory in advance; and a code of a rewriting step of selectively
rewriting the color data at a prescribed address of the look-up
table memory.
23. A computer readable memory storing program codes of image
processing for executing color processing using a multi-dimensional
input look-up table that has been stored in memory, comprising: a
code of an input step of inputting color data of a specific color;
a code of an arithmetic step of obtaining a relationship between
input and output data of the look-up table that corresponds to a
color in the neighborhood of the specific color; and a code of a
modifying step of modifying a portion of the look-up table based
upon the relationship between the input and output data obtained at
step arithmetic step.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to an image processing apparatus and
method for transforming the color space of entered image data, by
way of example.
[0002] One typical example of an image processing apparatus that
has become popular in recent years is a color copier which reads a
color document upon separating the document into each of its colors
pixel by pixel and prints a reproduced image of the color document
based upon the digital separated color component signals obtained
by reading the document. A color copier of this type executes
processing to separate the color document into the three colors R
(red), G (green) and B (blue) and converts these colors to the
three primary colors C (cyan), M (magenta) and Y (yellow) of a
subtractive color mixture.
[0003] FIGS. 10 and 11 are diagrams useful in describing processing
for the conversion of color signals in accordance with an example
of the prior art.
[0004] As shown in FIG. 10, image signals of the three primary
colors R, G, B obtained by color separation enter signal processing
circuits 1, 2, 3, respectively, whence there are obtained the C, M
and Y color signals, respectively.
[0005] A conversion method for generating the C, M, Y signals from
the R. G, B color signals is so-called masking, expressed by the
following equations (where Aij are coefficients decided in
dependence upon the characteristic of the output device), executed
by the signal processing circuits 1, 2, 3:
[0006] Signal processing circuit 1:
C=A11.times.R+A12.times.G+A13.times.B
[0007] Signal processing circuit 2:
M=A21.times.R+A22.times.G+A23.times.B
[0008] Signal processing circuit 3:
Y=A31.times.R+A32.times.G+A33.times.B
[0009] Another available method does not rely upon taking the sum
of products by the signal processing circuits 1, 2, 3. According to
this method, the results of the arithmetic operations are stored
beforehand in a memory serving as a look-up table and the results
of these operations are read out of the look-up table and delivered
as outputs in response to R, G, B signal values input to the
table.
[0010] In the arrangement where the results of arithmetic
operations are read out of a look-up table, the number of required
addresses for the storage areas will be 2.sup.24 (i.e., more
16,000,000) if each of the entered R, G, B signal values is
expressed by eight bits. Consequently, this approach is not
realistic in view of the high cost of the memory required.
[0011] Accordingly, a converting circuit of the kind shown in FIG.
11 is provided for each of the C, M, Y signals. This arrangement
divides the input R, G, B signals into high-order bit data Ru, Gu,
Bu and low-order bit data Rl, Gl, Bl by a high-order/low-order bit
dividing circuit 11. Only calculated results (namely the C, M, Y
color signal values) that correspond to the high-order bit data Ru,
Gu, Bu are stored beforehand in a table memory 13, which is a
three-dimensional R, G, B look-up table. When the high-order bit
data Ru, Gu, Bu of certain R, G, B color signal values is input to
the table memory 13, the latter produces an output value 14
corresponding to this high-order bit data. The output value 14 and
the low-order bit data Rl, Gl, Bl enter an interpolating circuit
15, which outputs a color signal 16 that is the result of
subjecting the output value 14 to linear interpolation in
dependence upon the low-order bit data Rl, Gl, Bl. (FIG. 11
illustrates a state in which the interpolating circuit 15 outputs
the C signal.) In accordance with this arrangement, the number of
storage area addresses of the table memory 13 need only be that
required by the number of high-order bits. For example, if the
high-order bits consist of three bits for each color, then the
number of storage area addresses required will be 2.sup.9 (i.e.,
512), thereby making it possible to reduce storage area
capacity.
[0012] It should be noted that the data stored in the table memory
13 in advance is not a data continuum. Accordingly, if the
low-order bit data Rl, Gl, Bl is zero, the output signal 16 of the
interpolating circuit 15 will correspond to the high-order bit data
Ru, Gu, Bu and therefore correct color reproduction will be
obtained. On the other hand, if the low-order bit data Rl, Gl, Bl
is not zero, the output signal value 14 from the table memory 13
undergoes linear interpolation in the interpolating circuit 15 in
conformity with the low-order bit data. As a consequence, the
linear interpolation gives rise to interpolation error and color
reproduction of the desired accuracy is not obtained.
SUMMARY OF THE INVENTION
[0013] Accordingly, the present invention has been devised in view
of the aforesaid problem and its object is to provide an image
processing apparatus and method in which it is possible to obtain
accurate color reproduction using a look-up memory having a small
storage capacity.
[0014] Another object of the present invention is to provide an
image processing apparatus and method in which it is possible to
readily generate a look-up table compensated for color
reproducibility in relation to a specific color.
[0015] According to the present invention, the foregoing objects
are attained by providing an image processing apparatus for
transforming the color space of input image data, comprising:
dividing means for dividing image data into data of high-order and
low-order bits; a look-up table memory in which color data of a
different color space corresponding to the number of high-order
bits is stored in advance; color signal processing means for
interpolating, on the basis of the data of the low-order bits,
color data read out of the look-up table memory using the data of
the high-order bits as an address, and outputting the interpolated
color data; and rewriting means for selectively rewriting the color
data at a prescribed address of the look-up table memory.
[0016] By way of example, the rewriting means includes: designating
means for designating data of at least one color; generating means,
in which high-order bits of the data that has been designated by
the designating means are used as an address, for generating an
address in the neighborhood of this address; and color data
rewriting means for rewriting the color data of the look-up table
memory that corresponds to the address generated by the generating
means.
[0017] In another aspect of the present invention, the foregoing
objects are attained by providing an image processing apparatus for
subjecting image data to color processing, comprising: storage
means for storing a look-up table having multi-dimensional inputs;
input means for inputting color data of a specific color;
arithmetic means for obtaining a relationship between input and
output data of the look-up table that corresponds to a color in the
neighborhood of the specific color; and modifying means for
modifying a portion of the look-up table based upon the
relationship between the input and output data obtained by the
arithmetic means.
[0018] Further, according to the present invention, the foregoing
objects are attained by providing an image processing method for
transforming color space of input image data, comprising: a
dividing step of dividing image data into data of high-order and
low-order bits; a color signal processing step of interpolating, on
the basis of the data of the low-order bits, color data that has
been read out of a look-up table memory using the data of the
high-order bits as an address, wherein color data of different
color spaces corresponding to the number of high-order bits is
stored in the look-up table memory in advance; and a rewriting step
of selectively rewriting the color data at a prescribed address of
the look-up table memory.
[0019] By way of example, the rewriting step includes the steps of:
designating data of at least one color; adopting high-order bits of
the designated data as an address and generating an address in the
neighborhood of this address; and rewriting the color data of the
look-up table memory that corresponds to the generated address.
[0020] In another aspect of the present invention, the foregoing
objects are attained by providing an image processing method for
subjecting image data to color processing using a stored look-up
table having multi-dimensional inputs, comprising the steps of:
inputting color data of a specific color; obtaining a relationship
between input and output data of the look-up table that corresponds
to a color in the neighborhood of the specific color; and modifying
a portion of the look-up table based upon the relationship between
the input and output data.
[0021] Other features and advantages of the present invention will
be apparent from the following description taken in conjunction
with the accompanying drawings, in which like reference characters
designate the same or similar parts throughout the figures
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a diagram schematically showing the construction
of a color copier according to a first embodiment of the present
invention;
[0023] FIG. 2 is a block diagram showing a signal processing
section according to the first embodiment of the present
invention;
[0024] FIG. 3 is a block diagram of a color signal processing
circuit included in the signal processing section of FIG. 2
according to the first embodiment of the present invention;
[0025] FIG. 4 is a diagram useful in describing the structure of a
three-dimensional look-up table according to the first embodiment
of the present invention;
[0026] FIG. 5 is a diagram illustrating, in two dimensions, the
rewriting of the three-dimensional look-up table according to the
first embodiment of the present invention;
[0027] FIG. 6 is a flowchart illustrating the operation of the
color copier according to the first embodiment of the present
invention;
[0028] FIG. 7 is a block diagram showing a signal processing
section according to a second embodiment of the present
invention;
[0029] FIG. 8 is a block diagram showing a signal processing
section according to a third embodiment of the present
invention;
[0030] FIG. 9 is a diagram useful in describing the rewriting of
the three-dimensional look-up table according to the first
embodiment of the present invention;
[0031] FIG. 10 is a diagram useful in describing processing for
converting color signals according to the prior art;
[0032] FIG. 11 is a diagram useful in describing processing for
converting color signals according to the prior art.
[0033] FIG. 12 is a block diagram useful in describing an image
processing apparatus according to a fifth embodiment of the present
invention;
[0034] FIG. 13 is a diagram showing an example of a simulation
screen used in the apparatus according to the fifth embodiment;
and
[0035] FIG. 14 is a diagram useful in describing a user interface
used in the apparatus according to the fifth embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Preferred embodiments in which a color image processing
apparatus according to the present invention is applied to a color
copier will now be described in detail with reference to the
drawings.
[0037] First Embodiment
[0038] FIG. 1 is a diagram is a diagram schematically showing the
construction of a color copier to which the present invention is
applied.
[0039] The color copier shown in FIG. 1 includes an image scanner
201 for reading an original and executing digital signal
processing, and a printer 202 for printing the image of the
original, which has been read by the image scanner 201, on
recording paper in full color.
[0040] The image scanner 201 has a retaining plate provided with a
mirror surface and a glass platen 203 on which an original 204 is
placed. The original 204 is illuminated with light from a lamp 205
and light reflected from the original 204 is introduced to a lens
209 via mirrors 206, 207 and 208. The lens 209 forms an image of
the reflected light on a three-line solid-state image sensor
(referred to as a "CCD" below) 210. As a result, analog image
signals of the three colors R, G, B constituting full-color
information output by the CCD 210 are sent to an image processing
section 211. The lamp 205 and mirror 206 are moved mechanically at
a speed V, and the mirrors 207, 208 at a speed V/2, in a direction
perpendicular to the electrical scanning (main-scan) direction of
the CCD, whereby the entire surface of the original on the platen
203 is scanned (in the sub-scan direction). Here the original 204
is read as a resolution of 400 dpi (dots per inch) in both the
main- and sub-scan directions.
[0041] The signal processing section 211 electrically processes the
read image signal, separates the image signal into M, C, Y and Bk
(black) components and sends the color components to the printer
202. With this color copier, one component of each of the color
components M, C, Y, Bk is sent to the printer 202 per scan of the
original in the image scanner 201 so that the printout of one copy
of the original is completed by a total of four scans of the
original.
[0042] The M, C, Y, Bk image signals sent from the image scanner
201 are delivered to a laser driver 212. The latter modulates and
drives a semiconductor laser 213 in conformity with the image
signals received. The laser beam is caused to scan a photosensitive
drum 217 via a polygon mirror 214, f-.theta. lens 215 and mirror
216, whereby an electrostatic latent image is formed on the
photosensitive drum 217 at a resolution of 400 dpi.
[0043] A revolving developing unit 218 comprises a magenta
developing unit 219, a cyan developing unit 220, a yellow
developing unit 221 and a black developing unit 222. The four
developing units contact the photosensitive drum 217 one after
another so that the electrostatic latent image that has been formed
on the photosensitive drum 217 is developed by toners. Recording
paper supplied from a paper cassette 224 or 225 is wound upon a
transfer drum 223 so that the toner image that has been developed
on the photosensitive drum 217 is transferred to the recording
paper. The toner image is fixed to the recording paper by a fixing
unit 226, after which the recording paper is discharged from the
copier.
[0044] The image processing section 211 of the image scanner 201
will now be described.
[0045] FIG. 2 is a block diagram showing the image processing
section 211 according to the first embodiment of the present
invention.
[0046] As shown in FIG. 2, the R, G, B signals obtained by
separating the image of a color original into its color components
pixel by pixel using the CCD 210 are converted to digital signals
by an analog/digital (A/D) converting circuit 103, and the digital
signals obtained by the conversion are sent to a shading correction
circuit 104, which compensates the signals for sensitivity
unevenness of the CCD 210 and uneven illumination of the original
illuminating lamp. The resulting signals are sent from the shading
circuit 104 to a selector 105.
[0047] In accordance with a control signal from a CPU 101, the
selector 105 is changed over to send the R, G, B signals, which
have been obtained by the shading correction circuit 104, to a
color signal processing circuit 106 for processing to be described
later, or to a buffer memory 107.
[0048] The color signal processing circuit 106 generates color
signals M, C, Y, Bk 110 in order that the R, G, B signals (digital)
may be printed by the printer 202. More specifically, in accordance
with an indication from a control unit such as the CPU 101, the
colors M, C, Y, Bk are converted to field-sequential color signals
and the color signals are output in synchronization with the
printing operation of the printer 202.
[0049] A look-up table 108 according to this embodiment is a
writable memory that requires a storage holding operation to
storage data in the memory.
[0050] When the color copier is started up, the CPU 101 transfers
data for color conversion stored beforehand in a ROM 109 to the
three-dimensional look-up table 108. An ordinary method may be used
to obtain the data that is stored in the ROM and the method need
not be described here.
[0051] The operation of the color copier having the construction
set forth above will now be described with reference to FIG. 6.
[0052] FIG. 6 is a flowchart illustrating the operation of the
color copier according to the first embodiment of the present
invention.
[0053] The CPU 101 determines, at step S1, whether the user has
selected a copying mode at a control panel (not shown). Ordinary
copying processing is executed at step S2 if the copying mode has
been selected ("YES" at step S1). If the copying mode has not been
selected ("NO" at step S1), then processing (described later) for
rewriting the look-up table is executed at step S3.
[0054] According to this embodiment, the CPU 101 of the color
copier refers to the R, G, B signals, which have been stored
beforehand in the buffer memory 107, in accordance with any signal
of the M, C, Y, Bk signals output in synchronization with the
printing operation of the printer 202, and updates (rewrites) the
data in the three-dimensional look-up table 108 to the appropriate
data (M, C, Y, Bk output signal values). The method through which
appropriate data to be rewritten is obtained will be described
later.
[0055] The color signal processing circuit 106 refers to the
updated look-up table 108 and outputs the M, C, Y, Bk color signals
that correspond to the entered R, G, B signals.
[0056] Furthermore, in accordance with this embodiment, the printer
202 performs printing in the four colors M, C, Y, Bk. However, it
goes without saying that printing may be performed only in the
three colors M, C, Y or in five of more colors using special
colors.
[0057] Color signal processing circuit 106
[0058] The details of the color signal processing circuit 106 will
now be described.
[0059] FIG. 3 is a block diagram of the color signal processing
circuit 106 according to the first embodiment of the present
invention.
[0060] As shown in FIG. 3, R, G, B signals 31 from the selector 105
are digital signals each composed of eight bits. These signals
enter a bit dividing circuit 32 in parallel. The R, G, B signals 31
are divided into high-order bit signals Ru, Gu, Bu and low-order
bit signals Rl, Gl, Bl, respectively, by the bit dividing circuit
32. If N represents the number of bits constituting each of the
high-order bit signals Ru, Gu, Bu, then the number of bits
constituting each of the low-order bit signals Rl, Gl, Bl will be
8-N because each of the input signals (the R, G, B signals 31) is
composed of eight bits.
[0061] The high-order bit signals Ru, Gu, Bu enter the look-up
table 108 as address signals and one set of data (the details of
which will be described later) corresponding to these address
signals are read from the data, which has been stored beforehand in
the look-up table 108, as an output signal value 37. Meanwhile, the
low-order bit signals Rl, Gl, Bl enter a weighting coefficient
generating circuit 36, which generates a weighting coefficient 38
for an interpolation operation.
[0062] A linear interpolating circuit 39 uses the output signal
value 37 from the look-up table 108 and the weighting coefficient
38 to perform linear interpolation (described later) and generates
a magenta color signal, for example, as a first output signal.
[0063] Three-dimensional look-up table 108
[0064] The construction of the look-up table 108 and the method of
obtaining the data that is stored beforehand in the ROM 109 will
now be described. The data stored beforehand in the ROM 109 is
decided at the design state and is set in the ROM at the time of
shipping.
[0065] Construction of look-up table 108
[0066] FIG. 4 is a diagram useful in describing the structure of
the three-dimensional look-up table according to the first
embodiment of the present invention. To simplify the description,
only the R and G input signals in two dimensions from among the
three-dimensional input signals R, G, B will be discussed. The
input signals R, G (each of which is an 8-bit digital signal) of
the look-up table 108 are each represented by numerical values
0.about.255 arrayed horizontally and vertically on a
two-dimensional plane, as shown in FIG. 4.
[0067] As illustrated in FIG. 4, output signal values from the
look-up table 108 corresponding to input signal values of R and G
have been stored in the look-up table 108 at positions stipulated
in terms of coordinates by each of the input signal values of R
(plotted along the horizontal axis) and G (plotted along the
vertical axis), i.e., at positions indicated by the white or black
circles. The positions of these white or black circles shall be
referred to as "lattice points" below.
[0068] The number Q of lattice points and the spacing .DELTA.d
between neighboring lattice points are decided by the number N of
high-order bits. That is, we have the following:
Q=2.sup.(N.times.2)
.DELTA.d=2.sup.(8-N)
[0069] Since FIG. 4 illustrates a case in which N=2 holds, we have
Q=16, .DELTA.d=32.
[0070] First, with regard to arbitrary input signals R, G
(indicated by the x mark in FIG. 4), the data at the four lattice
points (the black circles in FIG. 4) decided by the high-order bit
signals Ru, Gu is read out of the look-up table 108. Specifically,
in FIG. 4 the four lattice points are C00, C10, C01, C11.
[0071] Next, the weighting coefficients 38 for linear interpolation
are generated by the weighting coefficient generating circuit 36
from the low-order bit signals Rl, Gl. The calculation of the
weighting coefficients 38 is equivalent to obtaining, by linear
interpolation from the data at the four lattice points in the
neighborhood of the point at the coordinates designated by the
arbitrary input signals R, G, a signal to be output from the
look-up table 108 to which the arbitrary input signals R. G
(indicated by the x mark) have been applied.
[0072] A total of four of the weighting coefficients 38, namely one
for each of the four items of lattice-point data (C00, C10, C01,
C11), are required. Letting these coefficients be represented by
A00, A10, A01, A11 in regular order, the coefficients are obtained
in accordance with the following equations:
A00=(.DELTA.d-Rl).times.(.DELTA.d-Gl)
A10=Rl.times.(.DELTA.d-Gl)
A01=(.DELTA.d-Rl).times.Gl
A11=Rl.times.Gl
[0073] Next, the linear interpolating circuit 39 performs the
operation indicated by the following equation using the calculated
weighting coefficients A00, A10, A01, A11 and generates the output
signal M, for example, as a first output signal:
M=(A00.times.C00+A10.times.C10+A01.times.C01+A11.times.C11)/(.DELTA.d.sup.-
2)
[0074] The foregoing is the method of calculation in regard to the
two-dimensional input signals R, G. The case for three-dimensional
input signals will now be described with reference to FIG. 9 based
upon the two-dimensional case described above.
[0075] FIG. 9 is a diagram useful in describing the rewriting of
the three-dimensional look-up table according to the first
embodiment.
[0076] As shown in FIG. 9, data at eight lattice points on the
vertices of a cube in three-dimensional space is necessary in case
of input signals in three dimensions. Let the lattice-point data be
represented by C000, C100, C010, C001, C110, C101, C001, C111 in a
manner similar to that of the two-dimensional case described
above.
[0077] One weighting coefficient is required for each of the
lattice points, for a total of eight. These are obtained in
accordance with the following equations, in which the low-order bit
signals of the three-dimensional input signals are represented by
Rl, Gl, Bl:
A000=(.DELTA.d-Rl).times.(.DELTA.d-Gl).times.(.DELTA.d-Bl)
A100=Rl.times.(.DELTA.d-Gl).times.(.DELTA.d-Bl)
A010=(.DELTA.d-Rl).times.Gl.times.(.DELTA.d-Bl)
A001=(.DELTA.d-Rl).times.(.DELTA.d-Gl).times.Bl
A110=Rl.times.Gl).times.(.DELTA.d-Bl)
A101=Rl.times.(.DELTA.d-Gl).times.Bl
A011=(.DELTA.d-Rl).times.Gl.times.Bl
A111=Rl.times.Gl.times.Bl
[0078] Next, the linear interpolating circuit 39 performs the
operation indicated by the following equation using the calculated
weighting coefficients A000, A100, A010, A001, A110, A101, A011,
A111 and generates the output signal M, for example, as a first
output signal:
M=(A000.times.C000+A100.times.C100+A010.times.C010+A001.times.C001+A110.ti-
mes.C110+A101.times.C101+A011.times.C011+A111.times.C11)/(.DELTA.d.sup.3)
[0079] Further, the number Q of lattice points relating to the
capacity of the three-dimensional look-up table and the lattice
point spacing .DELTA.d that has an influence upon the accuracy of
the output signal are calculated as follows in case of the
three-dimensional input signals R, G, B:
Q=2.sup.(N.times.3)
.DELTA.d=2.sup.(8-N)
[0080] The number N of bits of each of the high-order bit signals
Ru, Gu, Bu is decided in dependence upon the accuracy desired to be
achieved by color signal conversion. The larger the value of N is
made, the smaller .DELTA.d becomes and the closer the spacing of
the lattice points in FIG. 4. Accordingly, though enlarging the
value of N raises the accuracy of the output signal from the
look-up table, the storage capacity of the look-up table required
increases correspondingly (e.g., if N=2 holds, then we have Q=64,
.DELTA.d=32).
[0081] Thus, as will be understood from the description rendered
above, it is required that M, C, Y, Bk signals sufficient for the
separated color signals R, G, B indicative of a color original to
be reproduced accurately by the printer 202 be stored beforehand in
the three-dimensional look-up table 108.
[0082] Method of deciding data stored beforehand in ROM 109 and
read into look-up table 108
[0083] The data is decided as follows: The printer 202 drives the
above-described printing mechanism to reproduce one certain color
on recording paper based upon the M, C, Y, Bk color signals
provided by the color signal processing circuit 106. Accordingly,
in regard to one certain color on the original, the printer 202
compares the separated color signals R, G, B input to the color
signal processing circuit 106 with separated color signals R, G, B,
which correspond to the one certain color, obtained by converting
the first-mentioned color signals R. G, B to M, C, Y, Bk signals,
reproducing these on the recording paper by the printer 202 and
performing color separation again by the scanner 201. If the
compared R, G, B color signals agree, this means that the color on
the original has been reproduced accurately.
[0084] Accordingly, the color that has been output on the recording
paper by the printer 202 using the M, C, Y, Bk color signals is
again subjected to color separation by the scanner 201 to obtain
the separated color signals R, G, B, and these signals are
represented as functions F of M, C, Y, Bk, as indicated by the
following equations:
R=Fr(M,C,Y,Bk)
G=Fg(M,C,Y,Bk)
B=Fb(M,C,Y,Bk) (1)
[0085] If a certain original is subjected to color separation by
the image scanner 201 to obtain R, G. B signals, then, in order to
realize accurate color reproduction, the values of R, G, B are
substituted into the left side of Equations (1) and the inverse
functions of these equations are found, whereby the M, C, Y, Bk
signals are obtained. If the printer 202 is driven using the values
of these signals, then a color the same as that of the original
will be reproduced. If we let G represent the inverse function of
the function F, then the M, C, Y, Bk sought will be expressed by
the following:
M=Gm(R,G,B)
C=Gc(R,G,B)
Y=Gy(R,G,B)
Bk=Gk(R,G,B) (2)
[0086] However, the relations represented by Equations (1) are
highly non-linear and it is difficult to obtain the functions Fr,
Fg, Fb analytically. Accordingly, Gm, Gc, Gy, Gk, which are the
inverse functions, also are difficult to obtain analytically.
Therefore, rather than obtaining the M, C, Y, Bk that correspond to
the R, G, B signals by way of Equations (1), a plurality of
combinations of M, C, Y, Bk are prepared beforehand as output
signals to be obtained from the look-up table 108, printing is
actually performed by the printer 202 with regard to a certain
combination of M, C, Y, Bk among these combinations, and the output
obtained is subjected to color separation by the scanner 201,
thereby obtaining R, G, B signal values that correspond to the
certain combination of M, C, Y, Bk.
[0087] In actuality, where M, C, Y, Bk are represented by eight
bits each, printout is performed in regard to all combinations
of
Mp=0, 64, 128, 192, 255 (p=1.about.5)
Cq=0, 64, 128, 192, 255 (q=1.about.5)
Yr=0, 64, 128, 192, 255 (r=1.about.5)
Bks=0, 64, 128, 192, 255 (s=1.about.5) (3)
[0088] [for a total of 625 colors (=5.times.5.times.5 colors)], and
these outputs are subjected to color separation by the scanner 201
to obtain the resulting separated color signals R, G, B in advance.
In other words,
Rpqrs=R (Mp,Cq,Yr,Bks)
Gpqrs=G (Mp,Cq,Yr,Bks)
Bpqrs=B (Mp,Cq,Yr,Bks) (4)
[0089] are found beforehand and these are substituted for the
functions Fr, Fg, Fb in Equations (1). That is, it is so arranged
that the separated colors signals R, G, B corresponding to M, C, Y,
Bk are obtained by interpolation from the aforesaid 625 values.
[0090] Since it is also difficult to analytically obtain Gm, Gc,
Gy, Gk, which are the inverse functions of the function F, certain
functions are presumed. For example, the linear functions given by
the equations below are presumed to hold, where the coefficient Aij
is an unknown number.
M=Gm(R,G,B)=A11.times.R+A12.times.G+A13.times.B
C=Gc(R,G,B)=A21.times.R+A22.times.G+A23.times.B
Y=Gy(R,G,B)=A31.times.R+A32.times.G+A33.times.B
Bk=Gk(R,G,B)=A41.times.R+A42.times.G+A43.times.B (5)
[0091] The relationship between M, C, Y, Bk and R, G, B also is
highly non-linear and approximation is difficult with the linear
functions of the kind indicated by Equations (5). In accordance
with this embodiment, the above-mentioned relationship is dealt
with as holding true only with regard to R, G, B signals in the
neighborhood of a lattice point of interest, and the value of the
coefficient Aij is found for every lattice point. This makes it
possible to employ these simple approximate equations.
[0092] What are sought now are the M, C, Y, Bk color signal values
that are to be stored in the three-dimensional look-up table 108.
These signal values are values for accurately reproducing R, G, B
input values, which are represented as a certain color at a lattice
point, by the M, C, Y, Bk color components when printout is
performed. Accordingly, first the coefficient Aij is set to a
certain initial value and the R, G, B input signals corresponding
to a certain lattice point are substituted into Equations (5) as
R0, G0, B0 to find the M, C, Y, Bk values. Next, thevalues of the
separated color signals of Equations (4) are interpolated based
upon the M, C, Y, Bk values that have been obtained, whereby the
corresponding R, G, B values are found. It will then suffice to
decide the coefficients Aij of Equations (5) in such a manner that
the R, G, B values obtained will become equal to the original R0,
G0, B0 values. To accomplish this, an error function E is defined
as follows:
E=[(R-R0).sup.2+(G-G0).sup.2+(B-B0).sup.2].sup.1/2 (6)
[0093] the above-described procedure is applied repeatedly and the
unknown coefficients Aij are decided using a well-known
optimization technique such as the method of steepest descent so as
to minimize the error function E.
[0094] Further, an arrangement may be adopted in which N sets R0i,
G0i, B0i (where i=1-N) of color signals in the neighborhood of the
lattice point of interest are set as R0, G0, B0, the separated
color signal values Ri, Gi, Bi are obtained with regard to these
sets through the above-described method, and the mean deviations of
these values are evaluated. In this case the evaluation equation
would be as follows:
E=.SIGMA.[(Ri-R0i).sup.2+(Gi-G0i).sup.2+(Bi-B0i).sup.2].sup.1/2
[0095] where .SIGMA. represents the sum total from 1 to N.
[0096] Thus, the coefficients Aij are found and the R, G, B values
at the lattice point are substituted into the Equations (5) to
obtain M, C, Y, Bk. This processing is executed for all lattice
points and the M, C, Y, Bk obtained in correspondence with each of
the lattice points are stored, whereby the three-dimensional
look-up table 108 is obtained.
[0097] The data stored in the look-up table 108 is found through
the procedure described above. In this embodiment, this data is
registered in the ROM 109 beforehand and is transferred to the
look-up table 108 by a command from the CPU 101 when the color
copier is started or reset.
[0098] Method of obtaining rewritten data in look-up table 108
[0099] If the separated color signals R, G, B input to the color
signal processing circuit 106 constitute data at a lattice point of
the look-up table 108, then an accurate color reproduction is
possible. However, the data stored beforehand in the look-up table
108 is not continuous data (a data continuum), as mentioned
earlier. In a case where the separated color signals R, G, B are
color signals offset from a lattice point, therefore, the M, C, Y,
Bk signals output by the look-up table 108 are linearly
interpolated by the linear interpolating circuit 39. Hence there is
the possibility that color reproduction will not be performed
accurately. According to the present invention, therefore, the R,
G, B values in the look-up table 108 are updated (rewritten) by
applying a procedure described below to improve the reproducibility
of a color that is desired to be reproduced with particular
accuracy.
[0100] Improving reproducibility of designated color
[0101] First, in order for a color (referred to below as a
"specific color") desired to be reproduced with particular accuracy
to be subjected to color separation by the scanner 201, the
operator operates the scanner 201 and uses a position designating
device or the like to read in the area of the specific color
contained in the original. (It is also possible to read in the
specific color from a color chip.)
[0102] When the specific color is read in, the CPU 101 switches the
selector 105 of FIG. 2 to the side of the buffer memory 107 so that
the image (the separated color signal values Rs, Gs, Bs) of the
specific color is written to the buffer memory 107. Next, the CPU
101 extracts, from the image that has been written to the buffer
memory 107, the R, G, B values Rs, Gs, Bs of the area (the area of
the specific color) designated by the operator. Here E' of the
following equation is used instead of Equation (6) as the error
evaluation equation E:
E'=[(R-Rs).sup.2+(G-Gs).sup.2+(B-Bs).sup.2].sup.1/2 (7)
[0103] Through the procedure described above, R0, G0, B0 are
substituted for Rs, Gs, Bs and the coefficients Aij of Equations
(5) are obtained in accordance with the evaluation equation E'. If
the coefficients Aij have been found, then the lattice point R0,
G0, B0 of the look-up table 108 is substituted into Equations (5)
that now employ these coefficients Aij, thereby obtaining M, C, Y,
Bk. These values are written to the look-up table 108 as the M, C,
Y, Bk values of the above-mentioned lattice point. The lattice
point at which the M, C, Y, Bk values are written is made only the
lattice point in the neighborhood of Rs, Gs, Bs. In regard to other
lattice points, the values obtained beforehand through the
above-described procedure are stored as they are. Accordingly,
since only the separated color signals in the neighborhood of the
specific color are rewritten, the reproduction of the other colors
remains based upon the M, C, Y, Bk values stored previously in the
look-up table 108. The conditions at this time are shown
diagrammatically in FIG. 5.
[0104] FIG. 5 is a diagram illustrating, in two dimensions, the
rewriting of the three-dimensional look-up table according to the
first embodiment of the present invention. In order to facilitate
the description, the three-dimensional look-up table will be
described based upon a one-dimensional look-up table.
[0105] As shown in FIG. 5, the input signals R, G, B of the look-up
table 108 are plotted along the horizontal axis, and the output
signal values M, C, Y, Bk are plotted along the vertical axis.
Further, points at which the low-order bit signals Rl, Gl, Bl of
the input signal R, G, B become zero are indicated by the triangle
marks along the horizontal axis. The lattice points corresponding
to these points are indicated by the white circle marks.
Accordingly, the lattice points indicated by the white circles
represent the output signal values M, C, Y, Bk that have been
stored beforehand in the look-up table 108.
[0106] In this embodiment, output signal values are linearly
interpolated from output signal values at the lattice points marked
by the white circles in regard to input signals for which the
low-order bit signals Rl, Gl, Bl are not zero. For example, in a
case where input signal values are Rs, Gs, Bs along the horizontal
axis in FIG. 5, an output signal value 503 is obtained by linear
interpolation based upon the values at the two lattice points 502
marked by the white circles. However, since the output signal value
503 is interpolated from the two items at the aforementioned
lattice points, the input signal colors Rs, Gs, Bs will not be
reproduced accurately.
[0107] Accordingly, the above-described procedure for rewriting the
look-up table 108 is applied to update the value at the lattice
points 502 to values at lattice points 504 marked by black circles
in FIG. 5, whereby a new output signal value 505 is obtained. The
Rpqrs, Gpqrs, Bpqrs values are obtained by interpolation from the
data of Equation (4) using the color signals M, C, Y, Bk indicated
by the output signal 505, and the lattice points 504 are moved in
such a manner that these values will approach Rs, Gs, Bs. The
processing through which the Rpqrs, Gpqrs, Bpqrs values obtained by
interpolation are thus made to approach the input signal values Rs,
Gs, Bs is equivalent to moving the output signal values 504
corresponding to Rs, Gs, Bs by changing the coefficients Aij of
Equation (5).
[0108] In accordance with the rewriting processing described above,
only lattice points in the neighborhood of an input signal value
regarding a specific color are shifted for the purpose of improving
the reproducibility of the specific color. As a result, it is
possible to reduce the influence on the input signals of other
areas.
[0109] Second Embodiment
[0110] FIG. 7 is a block diagram showing a signal processing
section according to a second embodiment of the present
invention.
[0111] Blocks 103 through 105 and block 107 in FIG. 7 are the same
as the identically numbered blocks in FIG. 1 and need not be
described again. A color signal processing circuit 601 executes
color signal processing substantially the same as that of the color
signal processing circuit 106. However, the color signal processing
circuit 106 shown in FIG. 3 is provided in the color signal
processing circuit 601 to correspond to each of the colors M, C, Y
and produces M, C, Y output signals 603. Accordingly, data for
generating the three outputs M, C, Y is stored in a
three-dimensional look-up table 602 as well.
[0112] The output signals of the color signal processing circuit
601 enter a black-component extracting circuit 604, which generates
a black signal Bk in accordance with the following equation:
Bk=min(C,M,Y)
[0113] A UCR (undercolor removal) circuit 605 executes the
processing indicated by the following equations to produce final
output signals M', C', Y', Bk':
M'=M-.alpha.m.times.Bk
C'=C-.alpha.c.times.Bk
Y'=Y-.alpha.y.times.Bk
Bk'=.alpha.y.times.Bk
[0114] where .alpha.m, .alpha.c, .alpha.y, .alpha.k represent
predetermined values.
[0115] By adopting this arrangement, only the three signals M, C, Y
need be dealt with, as opposed to the aforementioned case where the
four signals M, C, Y, Bk must be used in the Equations
(2).about.(5). This makes it possible to simplify the arithmetic
operations.
[0116] Third Embodiment
[0117] FIG. 8 is a block diagram showing a signal processing
section according to a third embodiment of the present
invention.
[0118] Blocks 103 through 110 in FIG. 8 are the same as the
identically numbered blocks in FIG. 1 and need not be described
again. In this embodiment, a matrix converting circuit 701 is
provided at the output of the shading correction circuit 104. This
circuit converts the separated R, G, B color signals to signals in
a standard colorimetric system stipulated by the CIE (Commission
Internationale de l'Eclairage). Specifically, the matrix converting
circuit 701 performs the operations indicated by the following
equations:
X=.beta.11.times.R+.beta.12.times.G+.beta.13.times.B
Y=.beta.21.times.R+.beta.22.times.G+.beta.23.times.B
Z=.beta.31.times.R+.beta.32.times.G+.beta.33.times.B
[0119] Here the coefficients Bij are constants decided by the color
separation characteristic of the CCD, etc., in the scanner 201. The
X, Y, Z signals thus obtained are sent to the selector 105 in the
same manner as set forth in the first embodiment.
[0120] In accordance with this arrangement, the color signals input
to the color signal processing circuit 106 are standard
colorimetric values. As a result, when the data stored in the
look-up table 108 (the data stored beforehand in the ROM 109) is
obtained, it is no longer necessary to read the printout from the
printer 202 by the scanner 201. That is, it is possible to use
values obtained by measurement in a standard calorimetric
system.
[0121] It should be noted that the color signals are not limited to
X, Y, Z and it is of course permissible to apply other standard
color-space signals defined by the CIE.
[0122] Fourth Embodiment
[0123] In each of the embodiments described above, the object is to
faithfully reproduce, at the time of printout, the separated color
component signals Rs, Gs, Bs of a specific color desired to be
reproduced with particular accuracy. With the fourth embodiment, it
is possible to make a designation in such a manner that the
specific color will be reproduced as a desired color different from
the color on the original.
[0124] For example, the separated color component signals of the
color on the original are Rs, Gs, Bs. In order to reproduce these
as a color having somewhat more red than the precise color, the R,
G, B values plugged into Equations (5) are left as Rs, Gs, Bs and
the evaluation equation (7) is written as follows:
E={[R-(Rs+.DELTA.R)].sup.2+(G-Gs).sup.2+(B-Bs).sup.2}.sup.1/2
(8)
[0125] where .DELTA.R may be specified by the operator or read in
separately from the scanner 201 as the data of the color desired to
be reproduced.
[0126] Fifth Embodiment
[0127] In the fifth embodiment, a user interface relating to a
color adjustment for modifying lattice-point data will be described
with reference to FIGS. 12 through 14 as a modification of the
foregoing embodiment.
[0128] According to this embodiment, the degree of color adjustment
applied to an image that will be printed can be modified by the
user at will based upon a displayed image that simulates the image
that will be printed.
[0129] The construction of the image processing apparatus for
generating the displayed image will be described first with
reference to FIG. 12.
[0130] A display image is generated by a simulation processor 204
based upon the field-sequential digital signals M, C, Y, Bk 606
output by the color signal processing circuit 106 in FIG. 2. The
first page of the field-sequential signals 606 is stored in a
memory 201, Y, M, C, Bk indicating the same pixel are read out in
parallel from the signals stored as digital data in the memory 201,
and the signals that have been read out are output to a color
converter 202. The entered Y, M, C, Bk image signals are converted
to R, G, B signals by the color converter 22 based upon the output
characteristic of the printer 202 and the display characteristic of
a monitor 203, and the R, G, B signals resulting from the
conversion are output to the monitor 203.
[0131] Read/write control of the memory 201 and control of the
color converter 202 is carried out by the CPU 101.
[0132] It should be noted that the processing performed by the
color converter 202 can be implemented by using the processing
described in the specification of U.S. Ser. No. 683,704 (filed on
Jul. 17, 1996), by way of example.
[0133] FIG. 13 illustrates an example of a simulation screen
displayed on the monitor 203. As shown in FIG. 13, a simulation
image 210 and the type 211 of the simulation image are displayed.
In FIG. 13, the simulation image 210 corresponds to the image of an
original that has been read by the image scanner 201.
[0134] It should be noted that the simulation screen differs
depending upon the particulars specified by the user at a control
panel (not shown).
[0135] The user interface for adjusting the color displayed on the
control panel will be described with reference to FIG. 14.
[0136] First, the user operates the control panel (not shown) to
select a color adjustment mode, whereupon a screen 220 is displayed
on the monitor 203. Displayed on the screen 220 are a registration
list button 221 for displaying a list of color adjustment
conditions that have been registered, a registration button 222 for
adding adjusted color adjustment conditions to the registration
list, and a fine adjustment button 223 for performing a fine
adjustment, described below.
[0137] If the fine adjustment button 223 has been selected by the
user, then the monitor 203 displays a screen 230. Displayed on this
screen are a read button 231 for executing the processing,
illustrated in the first embodiment, that reads in a specific color
from an original, a color adjustment range bar 232 for controlling
the range of lattice points modified based upon the specific color
that has been read in, a representative color adjustment button 233
for finely setting a representative color generally referred to as
an "original color" and considered to be important in terms of
image reproduction, and a sample button 234 for displaying a sample
image that has been registered beforehand as a simulation
image.
[0138] In the first embodiment, only a lattice point in the
neighborhood of a color that has been read in is treated as a
lattice point to be modified. However, a user preference is to be
able to perform an overall adjustment of the color within a
prescribed color range, as when performing a flesh color
adjustment. According to the present embodiment, therefore, it is
so arranged that an adjustment color range (i.e., a range of
lattice points to be modified) can be controlled at will by the
color adjustment range bar 232.
[0139] For example, assume that the three-dimensional look-up table
108 in FIG. 3 has a number of lattice points corresponding to N=3.
If the color adjustment range bar 232 is shifted one step to the
right from the leftmost position, which is the default position,
the cube to which the signal values representing the color read in
belong and data at the 64 lattice points in a cube contiguous to
this cube are adjusted in the three-dimensional look-up table 108.
To achieve the adjustment, lattice points constituting the cube to
which the signal values representing the color read in belong are
adjusted in the same manner as set forth in the first embodiment,
and other lattice points are adjusted in such a manner that color
continuity with lattice points not adjusted is maintained.
[0140] Further, the sample image is the image of a person suitable
for performing a flesh color adjustment, by way of example. The
manufacturer may prepare a plurality of sample images of persons,
scenery and the like, or the user can register any desired image by
reading in the user using the image scanner 201. In other words,
color adjustment is carried out using an image other than the image
on an original.
[0141] If the user selects the representative color adjustment
button 233 on the screen 230, then the monitor 203 displays a
screen 240. By performing a color adjustment using the screen 240,
a fine adjustment can be applied in simple fashion in relation to
representative colors (flesh color, the color blue used to depict
the sky or sea, and the color green used to depict foliage or the
like) generally referred to as "original colors" and considered to
be important in terms of image reproduction.
[0142] When the representative color to undergo color adjustment is
selected by the user on screen 240, a pallet 212 (see FIG. 13)
composed of colors related to the selected representative color is
displayed on the display screen. A specific color used in
adjustment can be selected by specifying, at the control panel, a
number representing any color indicated in the pallet 212. By thus
using the pallet 212, the required color can be simply selected by
the user.
[0143] The screen 240 has a slide bar for each representative color
so that the range of color adjustment can be set independently for
each representative color. The default value of each slide bar is
based upon the experience of the manufacturer and set for each
color. For example, the range of adjustment of the flesh color is
set by default to be narrower than that for the color blue or the
color green.
[0144] In accordance with this embodiment, as described above, the
user is capable of adjusting the three-dimensional look-up table
108 in a simple manner.
[0145] Further, in the foregoing embodiment, designating the
specific color used in color adjustment is performed by reading the
image on the original using the image scanner 201 and by specifying
a pallet number using the control panel. However, the selection can
be made by displaying a pointer on the monitor 203 and moving the
pointer using a mouse or the like. If such an arrangement is
adopted, a specific color can be designated from a sample image
being displayed on the monitor as the simulation image. This makes
it even easier for the user to designate the specific color
required.
[0146] Other Embodiments
[0147] In the foregoing embodiments, only one output signal is
produced for every color printed out. However, if an apparatus
capable of printing M, C, Y, K simultaneously is used as the
printer 202, then it can be so arranged that four different signals
M, C, Y, K will be output in parallel.
[0148] The present invention can be applied to a system constituted
by a plurality of devices (e.g., a host computer, interface,
reader, printer, etc.) or to an apparatus comprising a single
device (e.g., a copier or facsimile machine, etc.).
[0149] Further, it goes without saying that the object of the
present invention can also be achieved by providing a storage
medium storing program codes for performing the aforesaid functions
of the foregoing embodiments to a system or an apparatus, reading
the program codes with a computer (e.g., a CPU or MPU) of the
system or apparatus from the storage medium, and then executing the
program.
[0150] In this case, the program codes read from the storage medium
implement the functions according to the embodiments, and the
storage medium storing the program codes constitutes the
invention.
[0151] The storage medium, such as a floppy disk, hard disk,
optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape,
non-volatile type memory card or ROM can be used to provide the
program codes.
[0152] Furthermore, besides the case where the aforesaid functions
according to the embodiments are implemented by executing the
program codes read by a computer, it goes without saying that the
present invention covers a case where an operating system or the
like working on the computer performs a part of or the entire
process in accordance with the designation of program codes and
implements the functions according to the embodiment.
[0153] Furthermore, it goes without saying that the present
invention further covers a case where, after the program codes read
from the storage medium are written to a function extension board
inserted into the computer or to a memory provided in a function
extension unit connected to the computer, a CPU or the like
contained in the function extension board or function extension
unit performs a part of or the entire process in accordance with
the designation of program codes and implements the function of the
above embodiments.
[0154] Thus, in accordance with the each embodiments described
above, there are provided an image processing apparatus and an
image processing method in which it is possible to obtain accurate
color reproduction using a look-up memory having a small storage
capacity.
[0155] Further, there are provided an image processing apparatus
and an image processing method in which it is possible to readily
generate a look-up table compensated for color reproducibility in
relation to a specific color. It is also possible to adjust color
reproducibility in regard to a desired color specified by the
user.
[0156] As many apparently widely different embodiments of the
present invention can be made without departing from the spirit and
scope thereof, it is to be understood that the invention is not
limited to the specific embodiments thereof except as defined in
the appended claims.
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