U.S. patent application number 08/353906 was filed with the patent office on 2002-05-23 for apparatus and method for processing color image.
Invention is credited to KANNO, AKIKO, SUZUKI, TAKASHI.
Application Number | 20020060796 08/353906 |
Document ID | / |
Family ID | 27463244 |
Filed Date | 2002-05-23 |
United States Patent
Application |
20020060796 |
Kind Code |
A1 |
KANNO, AKIKO ; et
al. |
May 23, 2002 |
APPARATUS AND METHOD FOR PROCESSING COLOR IMAGE
Abstract
A color image signal is generated and an arbitrary color in the
color image signal is set as a color to be converted. A color after
conversion is designated. The color to be converted or a color
similar to the color to be converted is converted into the color
after conversion or a color similar to the color after conversion.
By this processing, a good color-converted image in which a
conversion boundary is unnoticeable.
Inventors: |
KANNO, AKIKO; (YOKOHAMA-SHI,
JP) ; SUZUKI, TAKASHI; (TOKYO, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
27463244 |
Appl. No.: |
08/353906 |
Filed: |
December 12, 1994 |
Current U.S.
Class: |
358/1.9 ;
358/518 |
Current CPC
Class: |
H04N 1/6075
20130101 |
Class at
Publication: |
358/1.9 ;
358/518 |
International
Class: |
G06K 015/02; H04N
001/60 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 1993 |
JP |
5-318739 |
Dec 28, 1993 |
JP |
5-337599 |
Mar 25, 1994 |
JP |
6-55729 |
Mar 31, 1994 |
JP |
6-62963 |
Claims
What is claimed is:
1. A color image processing apparatus comprising: means for
generating a color image signal; first color designation means for
designating an arbitrary color in the color image signal as a color
to be converted; second color designation means for designating a
color after conversion; and color conversion means for converting
the color to be converted or a color similar to the color to be
converted into the color after conversion or a color similar to the
color after conversion.
2. An ap aratus according to claim 1, wherein said color image
signal has values representing the hue, brightness and saturation
of a color.
3. An apparatus according to claim 2, wherein each of said first
and second color designation means designates the hue of the
color.
4. An apparatus according to claim 3, wherein said similar color is
a color having a hue positioned at a predetermined distance Hue
circle from the designated hue.
5. An apparatus according to claim 4, wherein the predetermined
distance varies according to the designated hue.
6. An apparatus according to claim 1, wherein said color conversion
means comprises a look-up table.
7. An apparatus according to claim 1, wherein said first and second
color designation means comprise a pointing device.
8. An apparatus according to claim 1, further comprising read means
for reading a color image.
9. An a paratus according to claim 8, wherein said color image
signal is a signal read by said read means.
10. An apparatus according to claim 8, further comprising area
designation means for designating a particular area on the color
image.
11. An apparatus according to claim 8, wherein said color
conversion means makes color conversion independently with respect
to areas designated by said area designation means.
12. A color image processing apparatus comprising: coordinate
transformation means for converting an input image into three
coordinates indicating the hue, saturation and brightness of a
color; function conversion means for converting an output from said
coordinate transformation means by a predetermined function freely
selected; and coordinate reverse transformation means for reversely
converting an output from said function conversion means into an
image signal having said plural kinds of components.
13. An apparatus according to claim 12, further comprising read
means for reading a color image.
14. An apparatus according to claim 13, wherein the input image
signal having plural components is a signal read by said read
means.
15. An apparatus according to claim 13, further comprising area
designation means for designating a particular area on the color
image.
16. An apparatus according to claim 15, wherein said function
conversion means makes conversion independently with respect to
areas designated by said area designation means.
17. An apparatus according to claim 12, wherein functions for
plural kinds of processing can be set in said function conversion
means.
18. An apparatus according to claim 17, wherein said plural kinds
of processing include color conversion.
19. An apparatus according to claim 17, wherein said plural kinds
of processing include color space compression.
20. A color image processing comprising: supply means for supplying
image signals having plural component including at least hue
components and saturation components; designation means for
selecting particular one or all of the hue components and for
designating the same as a hue to be adjusted; setting means for
setting a rate of change in at least one of a hue component and a
saturation component of an image signal of the hue to be adjusted
designated by said designation means.
21. An apparatus according to claim 20, wherein said designation
means has, in an initial state, all the hue components set as a hue
to be adjusted.
22. An apparatus according to claim 20 wherein said supply means
converts an input signal of three primary colors into said plural
components and supplies the converted components.
23. An apparatus according to claim 20, further comprising
adjustment means for adjusting the level of the image signal having
the hue to be adjusted according to the setting of said setting
means.
24. An apparatus according to claim 23, wherein said adjustment
means simultaneously adjusts the level of the hue component and the
saturat on component if the degree of adjustment has been set with
respect to each of the hue component and the saturation
component.
25. An apparatus according to claim 20, further comprising display
means for displaying the state of designation made by designation
means and the state of setting made by said setting means.
26. An apparatus according to claim 25, wherein said display means
the state of designation and the state of setting in the same
image.
27. An apparatus according to claim 20, further comprising area
designation means for designating an area represented by an
arbitrary one of the image signals having the plural kind of
components as an area with which a hue to be converted is
designated by said designation means and with which a degree of
change is set by said setting means.
28. apparatus according to claim 27, wherein said area designation
means designates at least one area as the designated area.
29. A color image processing apparatus comprising: setting means
for setting an area processing characteristic with respect to image
data having plural components; processing means for performing area
processing with a characteristic selected according to the setting
made by said setting means with respect to the image data having
plural components; and determination means for determining a color
of the image data having plural components on the basis of the same
image data processed by said processing means.
30. An apparatus according to claim 29, wherein said setting means
is an operating unit of said color image processing apparatus.
31. An apparatus according to claim 29, wherein the area processing
includes at least one of filtering processing and majority decision
processing.
32. An apparatus according to claim 31, wherein said filtering
processing is smoothing using a spatial filter.
33. An apparatus according to claim 29, wherein said determination
means has equal color determination means which determines image
data having the same color as a color previously designated in the
processed image data having plural components.
34. A color image processing apparatus comprising: detection means
for detecting the number of screen lines of a halftone dot image;
control means for controlling an area processing characteristic
with respect to image data having plural components on the halftone
dot image according to the result of detection made by said
detection means; processing means for processing the image data
having plural components according to the area processing
characteristic controlled by said control means; and determination
means for determining a color on the basis of the image data having
plural components processed by said processing means.
35. An apparatus according to claim 34, wherein said setting means
is an operating unit of said color image processing apparatus.
36. An apparatus according to claim 34, wherein the area processing
includes at least one of filtering processing and majority decision
processing.
37. An apparatus according to claim 36, wherein said filtering
processing is smoothing using a spatial filter.
38. An apparatus according to claim 34, wherein said determination
means has equal color determination means which determines image
data having the same color as a color previously designated in the
processed image data having plural components.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an apparatus and a method
for processing color images and, more particularly, to a color
image processing apparatus having a function of replacing a
particular color in an original with a different color and a color
image processing method using such a function.
[0003] 2. Description of the Related Art
[0004] FIG. 6 shows a conventional color image processing
apparatus.
[0005] Three image color signals R (red), G (green) and B (blue)
representing an image are converted into an intensity signal I, a
hue signal H and a saturation signal S by a matrix calculation in a
coordinate conversion section 61. Comparators 62a to 62f compare
the three signals with the intensity, hue and saturation,
respectively, of a color set as a color to be converted. The color
of the image represented by the signals is regarded as the "color
to be converted" and a selector 63 replaces the color of the image
with a "color after conversion" if the comparison result is that
the difference of each signal from the corresponding value of the
set color is not larger than a predetermined value. The selector 63
outputs the unchanged original color if any one of the signals is
largely different from the predetermined value.
[0006] In the above-described conventional image processing
apparatus, colors before and after conversion are changed according
to binary information as to whether a color of an original
corresponds to a "color to be converted". Therefore, in a portion
close to the boundary of the converted color, the colors before and
after conversion may remain as mottles or speckles because of
chattering due to reading non-uniformity or the like, resulting in
a considerable deterioration in image quality.
[0007] Functions for converting colors of images include color
conversion processing for converting a particular color of an
original color image into a different color, monochromatic
conversion processing for converting an image having a plurality of
colors into a monochromatic image of a selected single color, color
balance adjustment, and posterization for forming a poster-like
image by reducing the number of colors of an image. In a color
processing system, these kinds of processing can be practiced using
independent circuits.
[0008] Regarding color conversion processing for changing a
particular color in an original color image into a different color,
a method described below is known as a method of discriminating a
particular color. It is possible to identify the color of pixels by
conforming whether the ratios of red signal R, green signal G an
blue signal B coincide with predetermined ratios in certain
allowance ranges. For example, the largest one of R1, G1 and B1 is
selected as a maximum value M1 to obtain the ratios of the other
two values to M1. Then, if the following inequalities are
satisfied, it is determined that the corresponding pixel has the
same color as the particular color to be converted. For example,
with respect to input pixel signals (R, G, B), if M1=R1,
R.times.(G/M1).times..alpha.1.ltoreq.G
.ltoreq.R.times.(G/M1).times..alpha- .2
R.times.(B/M1).times..beta.1.ltoreq.B
.ltoreq.R.times.(B/M1).times..beta.2
M1.times..gamma.1.ltoreq.R .ltoreq.M1.times..gamma.2
[0009] Each of .alpha.1, .beta.1 and .gamma.1 is a value equal to
or smaller than 1, and each of .alpha.2, .beta.2 and .gamma.2 is a
value equal to or larger than 1. Color identification allowances
are determined by selecting these set values. If all the pixels
whose colors are identified as the particular color are replaced
with the color (R2, G2, B2), a color-converted image having a solid
density is obtained.
[0010] It is also possible to convert a particular color while
maintaining its gradation in such a manner that the largest one of
R2, G2 and B2 (e.g., M2=G2) is selected to obtain the ratios of the
other two values to the maximum valu the R value is set to
(M1.times.(R2/M2)), the G value is set to M1, and the B value to
(M1.times.(B2/M2)).
[0011] Monochromatic conversion processing for converting an image
having a plurality of colors into a monochromatic image of a
selected single color is performed as described below. A designated
color (R1, G1, B1) is converted into density signals (C1 (cyan), M1
(magenta), and Y1 (yellow) and Bk1 (black)), and a maximum value MX
in these values is stored. A signal ND (neutral density)
representing a density is calculated by the following equation from
density signals (C, M, Y) converted from input image signals (R, G,
B). That is,
ND=(C+M+Y)/3.
[0012] For example, if MX=C1, then the density (C0, M0, Y0, Bk0)/
of a target pixel which is presently processed is calculated by the
following equations:
C0=ND.times.MX
M0=ND.times.(M1/MX)
Y0=ND.times.(Y1/MX)
Bk0=ND.times.(Bk1/MX).
[0013] Thus, it possible to change the density of an image while
maintaining the same color.
[0014] Color balance adjustment for adjusting a color tone is
performed in such a manner that different gain offsets set with
respect to necessary colors are added to correction coefficients
provided in an F correction table with respect to the colors to
adjust the tone of color when the colors are superposed.
[0015] For posterization, lower 6 bits of each of R, G and B input
signals, for example, are fixed to set four gradations of each
color. In this case, it is possible to obtain a limited color image
of 64 colors.
[0016] Conventionally, the above-described functions are realized
by separate circuits. Therefore, the circuit scale and the
manufacturing cost of the processing apparatus are increased if the
number of functions is increased.
[0017] In a case where an ordinary user performs color balance
adjustment, there is a need to convert, for example, an (R, G, B)
system into a (C, M, Y, Bk) system and to perform adjustment
operation with respect to each color component. For intuitive
adjustment satisfying a demand for a "lighter", "slightly bluish"
tone or the like, long experience, i.e., a great deal of skill, is
required.
[0018] There are two kinds of color adjustment processing: one in
which an amount of change is set with respect to a particular color
on an original selected as a color to be modified, and the selected
particular color is modified by the set amount, and one in which
all colors on the entire original surface are selected to be
modified and are changed by equal amounts on the hue circle.
However, none of conventional color image processing systems has
both these two kinds of adjustment processing.
[0019] In the case of color conversion processing on input color
image data read from a halftone dot image formed by a color copying
machine or the like, if the input color image data and a color to
be converted are simply converted, and if the color is examined
with respect to each pixel of the image, each of pixels formed of
non-superposed color dots cannot be determined as the same color as
the color to be converted even if its color can be visually
perceived as the same color because of the specific formation of
the halftone dot image in which constellati of dots having a
plurality of colors are superposed in a manner, resulting in
failure to achieve accurate color conversion.
[0020] To solve this problem, a color conversion method has
recently been practiced in which image data obtained by filtering
an input color image read from a halftone dot image is used for
determination of a color as a color to be converted.
[0021] In this conventional method, however, a filter used for such
filtering is fixed and, therefore, image data after filtering,
which is used for color identification, is limited to one set.
Therefore, the image after color conversion cannot always be the
same as the desired image imaged by an operator, and the converted
color cannot be modified.
[0022] Moreover, since a uniform filter is used regardless of the
number of lines of dots, there is a possibility of the accuracy of
the image after filtering being reduced to such an extent that
color identification cannot be made with the desired fidelity.
SUMMARY OF THE INVENTION
[0023] In view of the above-described problems, an object of the
present invention is to provide a color image processing apparatus
and a color image processing method which make it possible to
suitably convert a color.
[0024] Another object of the present invention is to provide a
color image processing apparatus in which the circuit scale of a
color processing section is reduced.
[0025] Still another object of the present invention is to provide
a color image processing apparatus which can be easily operated for
color conversion processing.
[0026] A further object of the present invention is to provide a
color image processing apparatus and a color image processing
method which make is possible to obtain a color-converted image in
which a color tone is smoothly converted even at a color
boundary.
[0027] To achieve these objects, according to the present
invention, there is provided a color image processing apparatus
comprising means for generating a color image signal, first color
designation means for designating an arbitrary color in the color
image signal as a color to be converted, second color designation
means for designating a color after conversion, and color
conversion means for converting the color to be converted or a
color similar to the color to be converted into the color after
conversion or a color similar to the color after conversion.
[0028] Still another object of the present invention is to provide
a color image processing apparatus having a novel function and a
color image processing method using such a function.
[0029] 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
[0030] FIG. 1 is a block diagram of a first embodiment of the
present invention;
[0031] FIG. 2 is a diagram of the external appearance of an
operating/display panel of a digital color copying machine in
accordance with the first embodiment;
[0032] FIGS. 3(a), 3(b), and 3(c) are graphs of an example the
content of a look-up table 109;
[0033] FIG. 4 is a block diagram showing the configuration of a
color conversion unit 104 of a second embodiment of the present
invention;
[0034] FIG. 5 is a block diagram of a color conversion unit 104 of
a third embodiment of the present invention;
[0035] FIG. 6 is a block diagram of a conventional color image
processing apparatus;
[0036] FIG. 7 is a block diagram schematically showing a fourth
embodiment of the present invention;
[0037] FIG. 8 is a block diagram showing image processing functions
of a digital full-color copying machine utilizing the fourth
embodiment;
[0038] FIG. 9 is a diagram of an HSL color space used in the
embodiment shown in FIG. 7;
[0039] FIG. 10 is a block diagram schematically showing a circuit
arranged to change color conversion processing with respect to
arbitrary areas of an image;
[0040] FIG. 11 is a diagram showing an example of a
visually-recognizable change depending upon the hue;
[0041] FIG. 12 is a block diagram schematically showing a circuit
arranged to use a lightness conversion table as a hue correction
coefficient table;
[0042] FIG. 13 is a diagram of examples of conversion tables f(E),
f(S), and f(L) for processing of "changing red into blue";
[0043] FIG. 14 is a block diagram schematically showing a circuit
arranged to set a converted color through three components, i.e.,
hue, lightness and saturation values;
[0044] FIG. 15 is a diagram showing an example of a result of
determination in the case of determining a particular color in a
color halftone dot original;
[0045] FIG. 16 is a block diagram of schematically showing a color
onversion circuit having a smoothing function for unsharpening a
halftone dot image before converting the image;
[0046] FIG. 17 is a diagram of a color space;
[0047] FIGS. 18(a) through 18(d) are diagrams showing an operating
unit when hue adjustment processing is performed in accordance with
a fifth embodiment of the present invention;
[0048] FIG. 19 is a graph of an H-f(H) characteristic when Y is
changed two steps in the direction G while C is changed one step in
the direction G;
[0049] FIGS. 20(a) through 20(d) are diagrams of an operating unit
when area designation processing is performed;
[0050] FIG. 21 is a diagram showing an operating unit 1214 in a
sixth embodiment of the present invention;
[0051] FIG. 22 is a block diagram of a control unit 1213;
[0052] FIG. 23 is a diagram showing an operating unit at the time
of color selection before conversion in the sixth embodiment;
[0053] FIG. 24 is a diagram showing the operating unit at the time
of color selection after conversion in the sixth embodiment;
[0054] FIG. 25 is a diagram of the operating unit at the time of
adjustment of the degree of smoothing in the sixth embodiment;
and
[0055] FIG. 26 is a diagram of filters in accordance with the sixth
embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0056] The preferred embodiments of the present invention will be
described in detail with reference to the drawings.
[0057] <First Embodiment>
[0058] FIG. 1 shows an example of a circuit of a digital color
copying machine in accordance with the first embodiment of the
present invention, and FIG. 2 shows the external appearance of a
display and an operating panel of the copying machine.
[0059] Referring to FIG. 2, the copying machine has an image
display 201, a copying start key 202, a ten key cluster 203,
function keys 204, and control keys 205.
[0060] When color conversion processing is started by operating the
color conversion mode function keys 204 after setting an original,
the original is scanned and an original image is displayed on the
image display 201. A color before conversion and a color after
conversion, which are selected from colors in the image or from
color samples (not shown), are then designated by using a pointing
device (not shown) such as a so-called mouse. An image converted in
accordance with the designation is displayed. When the start key
202 is pressed, the displayed image is printed out.
[0061] If it is desirable to adjust the color-converted area and
the designated color by observing the displayed image, the color
conversion mode function keys 204 are operated to designate area
adjustment or adjustment of the designated color. Thereafter,
adjustment is made by using the ten key cluster 203 or control keys
205. The image after adjustment is displayed again on the image
display 201, and the above-described process is thereafter repeated
to output the resulting image.
[0062] Referring to FIG. 1, an image reading section 101 reads an
original image and outputs digital signals which represent three
colors, red (R), green (G) and blue (B), and which are each an
8-bit signal. A shading correction circuit 102 corrects a
nonuniformity of the reading section 101 and an optical system. An
input masking circuit 103 forms standard three color signals
(NTSC-RGB signals in this embodiment) from three color image
signals obtained from the image reading section by calculations.
These signals are supplied to a color conversion unit 104. A LOG
table 105 converts the light quantity signals R, G, and B into cyan
(C), magenta (M) and yellow (Y) toner density signals. An
UCR/output masking circuit 106 forms color recording signals C, M,
Y, and Bk (black) from the density signals C, M, and Y in a surface
sequential manner by considering spectral characteristics of
toners. A spatial frequency filter 107 makes edge enhancement,
smoothing or the like according to one's need and outputs a final
recording signal to a printer (not shown).
[0063] The color conversion unit 104 includes a coordinate
transformation (RGB-HSI transformation) section 108 for forming
three signals representing the hue (H (0 to 360.degree.)), the
saturation (S (0 to 255)) and the intensity (I (0 to 255)) of a
color by coordinate transformation of three colors signals R, G and
B look-up tables (LUT) 109 to 111 for converting the signals H, S
and I into H1, S1 and I1 different from the original by using
conversion tables previously set, and coordinate reverse
transformation (HSI-RGB transformation) section 112 for converting
H1, S1 and I1 into signals on the original RGB coordinate
system.
[0064] As mentioned above, when the start key is pressed after a
point of a color before conversion and a corresponding point of a
color after conversion have been designated, pre-scanning is
started to read three color signals R, G and B of the designated
two points from the image reading section 101. The colors before
and after conversion are extracted from the points and are
converted into coordinates on the HSI coordinate system by a CPU
(not shown) and data is written in the look-up tables 109 to 111 in
such a manner that the color after conversion is output when the
color before conversion is input. Thereafter, at the time of image
formation by main scanning, an image in which the color has been
converted by being passed through the LUTs is output.
[0065] FIGS. 3(a), 3(b) and 3(c) show an example of the content of
the LUT 109 shown in FIG. 1. In this example, only the hue H is
converted from green (120.degree.) to red (0.degree.), while the
saturation S and the intensity I are passed without being
processed.
[0066] If the hue before conversion is closer to 120.degree. (60 to
180.degree.), the hue of the color after conversion is closer to
0.degree.. At a position close to a boundary, the converted color
is close to the color before conversion. Therefore, there is no
possibility of occurrence of a color discontinuity even at the
color boundary, and it is possible to obtain an apparently natural
color-converted image. In this example, the width of the boundary
areas is set to .+-. 60.degree.. However, this value is variable
with respect to hues and is read out according to the designation
of the hue before conversion from a ROM (not shown) in which
boundary widths are previously written.
[0067] Needless to say, the content of the LUT is not limited to
the example shown in FIGS. 3(a) to 3(C) . In this embodiment, the
result of conversion calculation is previously written in the LUTs.
Alternatively, conversion can be made by calculations using an
operational circuit or operational processor.
[0068] <Second Embodiment>
[0069] FIG. 4 is a block diagram showing the configuration of color
conversion unit 104 in accordance with the second embodiment of the
present invention.
[0070] In the first embodiment, the hue H, the saturation S and the
intensity I are independently converted by the LUTs 109 to 111,
respectively. Alternatively, LUTs can be arranged in such a manner
that two or three of the three coordinates are correlated. In such
a case, in order to reduce the number of address bits of the LUTs,
the number of bits of a main signal in the three signals input to
the LUTs, e.g., signal H in the H conversion LUT, is maintained
while the numbers of bits of other signals, e.g., signals S and I
in the H conversion LUT, are reduced.
[0071] In this embodiment, 8 bits for a main signal and 3 bits for
other signals, i.e., 14 bits in total, are input to each of HLUT
401, SLUT 402 and ILUT 403, and an 8-bit signal after conversion is
output from each LUT.
[0072] If the three signals are converted by being correlated in
this manner, color conversion of higher accuracy is possible. For
example, if an operator wishes to convert a flesh color into a more
reddish color, a higher degree of conversion is set for a portion
of a slightly lower saturation in a main hue of the flesh color
while a lower degree of conversion is set for a portion closer to
orange (having a higher saturation). In this embodiment, the number
of bits of the signals other than the main signal is reducing by
using only upper bits. However, other various methods for reducing
the number of bits are possible. For example, the signals other
than the main signal may be converted into two-value signals by a
comparator to input 10 bits in total to each LUT.
[0073] <Third Embodiment>
[0074] In the first embodiment, if different kinds of processing
are respectively performed on different areas, area signals are
input for addressing in the LUTs, thereby facilitating
processing.
[0075] If the coordinate transformation section 108 and the
coordinate reverse transformation section 112 are arranged as
hardware, there is a possibility of occurrence of an error or bit
failure during calculation, which results in a deterioration in
image quality. Therefore, the signals R, G and B may be passes
through the reverse coordinate transformation section 108 and the
coordinate transformation section 112 without being processed if
the input and the output of each LUT are equal to each other,
thereby reducing deteriorations in image quality due to coordinate
transformation.
[0076] FIG. 5 shows the configuration of color conversion unit 104
in accordance with the third embodiment of the present invention. A
signal MODE 501 designating a conversion mode is supplied. Each of
comparators (CMP) 502 to 505 outputs 1 when inputs are equal to
each other, and outputs 0 when two inputs are not equal. An AND
gate 506, an OR gate 507 and a selector 508 are also provided.
[0077] The mode signal MODE is con rolled by a CPU (not shown) to
previously write in LUTs data on a color to be converted with
respect to modes, i.e., areas, and a color after conversion. It is
therefore possible to easily change the mode of conversion of
colors before and after conversion by changing the mode signal with
respect to areas.
[0078] On the other hand, in the comparators 502 to 504, the input
and output signals of each LUT are always compared. If the input
and output are equal to each other, "1" is output. If the input and
output are different from each other, "0" is output. The three
signals from the comparators 502 to 504 are supplied to the AND
gate 506, and "1" is output from the AND gate 506 if these three
signals are unchanged, that is, color conversion is not
effected.
[0079] The comparator 505 monitors to examine whether the mode
signal MODE has a predetermined value (representing a through
mode). If a through mode is designated, the output from the
comparator 505 is such that "1" is forcibly output from the OR gate
507.
[0080] The selector 508 is supplied with the signals R, G and B
before conversion and is also supplied with the signals R, G and B
which have undergone transformation/reverse transformation. The
selector 508 outputs the signals before conversion (through
signals) if the above-mentioned OR output becomes "1", and outputs
the converted signals if the OR output is "0".
[0081] In this manner, areas where color conversion is to be made
and areas where color conversion is not be made or the kinds of
conversion with respect to areas are changed. Also, it is possible
to obtain outputs without causing any deterioration with respect to
non-converted pixels or areas. Such areas are designated with a
pointing device (not shown) such as a digitizer, mouse or the
like.
[0082] In the first to third embodiments, as described above, input
color image signals formed of three color-decomposed signals are
converted into multivalued color tone signals having values
representing the hue, saturation and intensity the converted
multivalued color tone signals obtained are further converted into
previously-designated multivalued color tone signals by using at
least one function for obtaining a continuous output from a
continuous input, for example, as shown in FIGS. 3(a) to 3(c), and
the converted multivalued color tone signals are again changed into
three-color color-decomposed signals. It is therefore possible to
obtain a good color-converted image in which a signal-changed
boundary is unnoticeable.
[0083] Also, a determination is made as to whether the tone of a
converted color is changed. The input color image signals are
directly output as converted signals if it is determined that the
color tone is not changed, and the three-color color-decomposed
signals from the coordinate reverse transformation means are output
as converted signals if it is determined that the color tone is
changed. It is therefore possible to perform coordinate
transformation without unnecessarily deteriorating the image.
[0084] <Fourth Embodiment>
[0085] In the fourth embodiment, a function conversion table for
color conversion processing is rewritten to realize various kinds
of color conversion processing using a single hardware
arrangement.
[0086] FIG. 7 is a block diagram schematically showing the
configuration of the fourth embodiment of the present invention,
and FIG. 8 is a block diagram schematically showing functions of a
digital full-color copying machine in accordance with this
embodiment.
[0087] Referring first to FIG. 8, blocks representing functions of
a digital full-color copying machine to which this embodiment is
applied are illustrated with respect to the flow of processing. A
3-line CCD line sensor 1010 color-decomposes reflected light from
an original to convert the image light into electrical signals. An
A/D converter 1042 converts analog output signals R, G and B from
the line sensor 1010 into digital signals. A shading correction
circuit 1014 corrects an output non-uniformity with respect to each
color of the line sensor 1010 and the inclination of the quantity
of light from a light source. An input masking circuit 1016
corrects RGB spectroscopic characteristics of the sensor 1010 on a
standard RGB space
[0088] A color processing circuit 1018 makes various kinds of
conversion of colors. The color processing circuit 1018 has a
circuit configuration shown in FIG. 7. A color space compression
circuit 1020 compresses image signals distributed in the standard
RGB space into signals in a color space range such that the read
image can be reproduced by an output unit (printer). A light
quantity/density conversion circuit 1022 converts an RGB brightness
signal into density signals representing the densities of cyan (C),
magenta (M) and yellow (Y). An under color removal (UCR) and output
masking circuit 1024 corrects the three color density signals C, M
and Y according to spectral characteristics of toners, forms a
black signal Bk, and outputs the signals one by one in a surface
sequential manner in accordance with recording colors in the
printer.
[0089] An F value correction table 1026 corrects the density value
(F value) of each color in accordance with a density designation. A
magnification changing circuit 1028 changes the size of the
processed image. A spatial frequency filter 1030 processes the
image for edge enhancement or smoothing. A printer characteristic
correction table 1032 corrects the image signals (the output from
the spatial frequency filter 1030) to be output for printing
according to color tone characteristics of a connected printer
1034.
[0090] In the digital full-color copying machine, an original image
read by the line sensor 1010 undergoes various kinds of processing
shown as functional blocks in FIG. 8 and is thereafter output as a
print from the printer 1034.
[0091] The circuit shown in FIG. 7 is used as color processing
circuit 1018 shown in FIG. 8. A coordinate transformation circuit
1040 shown in FIG. 7 converts an RGB color space into an HSL color
space in terms of hue (H), saturation (S) and lightness (L), and
have output signals Hin, Sin and Lin with respect to input signals
Rin, Gin and Bin supplied from the input masking circuit 1016. A
selection circuit 1042 selects the outputs Hin, Sin and Lin from
the conversion circuit 1040 or HSL color space data on a CPU bus
1044 (CPU address bus).
[0092] A function conversion circuit 1048 converts color
components, i.e., the hue (H), the saturation (S) and the lightness
(L) from the selection circuit 1042, by functions f(H), f(S) and
f(L), respectively. The function conversion circuit 1046 is formed
of a RAM in which a function conversion table is stored. Inputs are
given as addresses in the RAM and outputs are obtained as table
values. The function conversion table is rewritten according to
color processing described below by using CPU data with CPU
addresses output from the CPU. A line CPUACC is set to high level
when the function conversion table is rewritten. When the level of
CPUACC is low, rewriting is not performed, and the outputs from the
coordinate transformation circuit 1040 are directly output to the
function conversion circuit 1046.
[0093] A selection circuit 1048 selects signals or data according
to the level of CPUACC. That is, the selection circuit 1048
directly outputs the outputs from the function conversion circuit
1046 when the level of CPUACC is low, and selects data on a CPU
data bus 1050 to write this data in the table of function
conversion circuit 1046 if the level of CPUACC is high. A
coordinate reverse transformation circuit 1052 returns the color
components in the HSL color space output from the selection circuit
1048 to the RGB color space. Outputs Rout, Gout and Bout from the
coordinate reverse transformation circuit 1052 are applied to the
color space compression circuit 1020 shown in FIG. 8.
[0094] FIG. 9 illustrates the HSL color space used for the
coordinate transformation circuit 1040 and the coordinate reverse
transformation circuit 1052. By well-known calculations, 8-bit
image signals R, G and B in the RGB color space are converted into
H (0 to 360.degree.), S (8 bits) and L (8 bits). The coordinate
transformation circuit 1040 and the coordinate reverse
transformation circuit 1052 can be set to pass the signals
therethrough without processing. The function conversion circuit
1046 can also be utilized to convert the RGB image.
[0095] Means for forming a monochromatic image in any selected
color with the circuit shown in FIG. 7 will be described with
respect to the following cases (1) and (2) by way of example
[0096] In a case where it is desirable to maintain the lightness L
and to fix the hue H and the saturation S at certain values.
[0097] In this case, color information (HO, SO, LO) on a desired
single color (designated color) is set by being sampled from a
orignal image during pre-scanning or by being selected from, and
the following values are written in the function conversion circuit
1046;
[0098] f(H) =HO (constant)
[0099] f(S) =SO (constant)
[0100] f(L) =L (through).
[0101] The input image consisting of Rin, Gin and Bin is input to
the function conversion circuit 46 through the circuits 1040 and
1042, and the hue H and the saturation S are fixed at constant
values HO and SO in the function conversion circuit 1046. The
outputs from the function conversion circuit 1046 are applied to
the coordinate reverse transformation circuit 1052 through the
selection circuit 1048 to be returned to the RGB space. The image
represented by the outputs Rout, Gout and Bout from the coordinate
reverse transformation circuit 1052 is such that the lightness of
the input is maintained while the hue and the saturation are fixed
at constant values.
[0102] In this conversion process, "black" in the original is still
"black" after conversion. Pixels having the same color as the
designated color are in the same color before and after
conversion.
[0103] (2) In a case where the lightness L is compressed with
"black" in the original related to a "designated color"
[0104] In this case,
[0105] f(H)=HO (constant),
[0106] f(S)=SO (constant), and
[0107] f(L)=(L.times.(255-LO)/225)+LO
[0108] are set in the function conversion circuit 1046. LO is a
constant which determines the lowest lightness after conversion and
the inclination of compression. In this example of conversion,
"black" in the original is converted into a designated color having
the lowest lightness.
[0109] Even if the value of hue H is constant, it is possible that
the resulting color will be seen as a different color due to a
printer characteristic, a deformation of the color space or other
causes. Functions f(H), f(S) and f(L) formed by considering
correction functions may be set in the function conversion circuit
1046.
[0110] In this embodiment, HSL posterization, for example, can
easily be realized by changing the functions f(H), f(S) and f(L)
set in the function conversion circuit 1046. In such a case, 1 f (
H ) = int ( H / 30 ) , f ( S ) = S0 ( constant ) ( when S = 0 ) =
int ( S / 128 ) ( S 0 ) , and f ( L ) = int ( L / 64 )
[0111] are set in the function conversion circuit 1046. Into is a
function for obtaining an integer, as is well known.
[0112] In the case of hue/saturation/contrast adjustment,
[0113] f(H)=H+.delta.H,
[0114] f(S)=S+.delta.S, and
[0115] f(L)=L+.delta.L
[0116] are set. .delta.H, .delta.S and .delta.L are bias or offset
values for adjustment. .delta.H, .delta.S and .delta.L may be set
constant values or may be varied with respect to the input hue,
saturation and lightness.
[0117] The combination of the kinds of processing described above
can be realized by using a composite function of the functions for
the processing. It is apparent that other kinds of processing can
be realized by suitably setting functions f(H), f(S) and f(L).
Further, posterization for reducing the gradations of each color in
the RGB space and solarization for inverting the gradations of each
color at an intermediate point can also be realized by setting the
coordinate transformation circuit 1040 and the coordinate reverse
transformation circuit 1052 in a through state.
[0118] The embodiment has been described with respect to an example
of coordinate transformation from an RGB color space to an HSL
color space. However, coordinate systems having three coordinates
of the hue, saturation and lightness are not limited to the
above-described example. For example, conversion from an L*a*B
space into a polar coodinate system can also be utilized.
[0119] To enable each of the above-described functions to be set
for an arbitrary area in one picture frame, the processing system
may be arranged so that the function for the desired conversion can
be selected with respect to each designated area. FIG. 10 is a
block diagram schematically showing an example of a circuit
configuration arranged for such a selecting function.
[0120] Referring to FIG. 10, a selection circuit 1060 selects an
area code signal AREA whi h is generated in synchronization with
the image signal input and which designates a place in one picture
frame where the presently-processed pixel exists, or a CPU address
(address bus) 1062 or CPU data (data bus) 1064 output from a CPU
such as that shown in FIG. 22. An area code RAM 1066 has a table
for generating a designation signal for designating a function used
in a function conversion circuit 1072 at a rear stage in accordance
with the signal AREA output from the selection circuit 1060.
[0121] Processing code data input through the CPU data bus 1064
with addresses designated through the CPU address bus 1062 are
previously written in the area code RAM 1066. The area code RAM
1066 is supplied with the signal AREA and selects and outputs, in
accordance with the signal AREA, a processing code which designates
a kind of processing performed by the function conversion circuit
1072. This processing code is input to upper bits in a function
conversion RAM used in the function conversion circuit 1072.
[0122] The area designation operation may be performed by the same
method as in the first embodiment.
[0123] A coordinate transformation circuit 1068 which is the same
as the coordinate transformation circuit 1040 is provided. A
selection circuit 1070 selects outputs Hin, Sin and Lin from the
coordinate transformation circuit 1068 and an output from the area
code RAM 1066, or HSL color space data on the CPU bus 1062 (CPU
address bus) and data in place of the output from the area code RAM
1066.
[0124] The function conversion circuit 1072 converts color
component data, i.e., the hue (H), the saturation (S) and the
lightness (L) by using functions f(H, AREA), f(S, AREA), f(L, AREA)
in accordance with the selection output from the selection circuit
1070 and the area code. A selection circuit 1074 selects outputs
from the function conversion circuit 1072 or data on the CPU bus
(data bus) 1064. A coordinate reverse transformation circuit 1076
returns to the RGB color space the color component signal in the
HSL color space output from the selection circuit 1074. Outputs
Rout, Gout and Bout from the coordinate reverse transformation
circuit 1076 are applied to the color space compression circuit
1020 of FIG. 8.
[0125] Function conversion data is previously written in the
function conversion circuit 1072. The desired function data input
through CPU data bus 1064 is written in the function conversion
circuit 1072 with addresses input through CPU address bus 1062.
This function data is determined by a user's input operation
through a panel (not shown) and is written in lower bits of the
function conversion RAM.
[0126] The area code signal AREA designates an area where the
present target pixel exist in synchronization with the image
signal. The area code signal AREA is input to the area code RAM
1066 through the selection circuit 1060. In the area code RAM 1066,
the codes designating various kinds of processing to be effected on
arbitrary designated areas are previously written. The output from
the RAM 1066 corresponds to upper bits of the function conversion
RAM used for the function conversion circuit 1072. By changing the
processing codes, the conversion functions used in the function
conversion circuit 1072 can be changed with respect to areas,
thereby enabling plural kinds of color processing to be performed
with respect to arbitrary areas in one picture frame. In other
respects, the operation of this circuit is the same as that of the
circuit shown in FIG. 7.
[0127] In the HSL coordinate system of the embodiment shown in FIG.
7, it is possible that a printed color will vary largely depending
upon values S and L even when one value of H is designated, because
of a characteristic of the system. FIG. 11 shows an example of the
relationship between L and the apparent hue. In this example, if a
user's color of H=200.degree. is set, the color is seen as if it is
changed closer to cyan under a dark (small lightness) condition
even though the color is selected as blue under a light (large
lightness) condition.
[0128] Therefore, in the case of converting H through the full
range of L (hue conversion and user's color), it is desirable to
utilize An conversion table as an H correction coefficient table so
that the characteristic of the coordinate system is corrected. FIG.
12 shows a circuit configuration of color processing circuit 1018
realizing this function.
[0129] Referring to FIG. 12, a selection circuit 1080 selects area
code signal AREA designating the area where the target pixel exists
or a CPU address (address bus) 1082 and an area code RAM 1086
outputs a selection signal for selecting a function used for
function conversion and 1-bit correction mode signal in accordance
with an output from the selection circuit 1080. Codes (address
signals) for desinating functions for function conversion to be
effected on each area and the correction mode signal designating
the existence/non-existence of correction on the designated area
are previously stored in the area code RAM 1086.
[0130] There are provided a coordinate transformation circuit 1088
which is the same as coordinate transformation circuit 1040, a
selection circuit 1090 which is the same as selection circuit 1070,
and a function conversion circuit 1092 which is the same as
function conversion circuit 1072. A selection circuit 1094 selects
outputs from the function conversion circuit 1092 or date on a CPU
bus (data bus) 1084, as in the case of selection circuit 1094.
[0131] A calculation circuit 1096 calculates H and L components in
selection outputs from the selection circuit 1094. A selection
circuit 1098 selects H component, S component and L component
outputs from the selection circuit 1094 or an output from the
calculation circuit 1096, an S component output from the selection
circuit 1090 and an L component output from the selection circuit
1090 according to the correction mode signal output from the area
code RAM 1086. A coordinate reverse transformation circuit 1100
returns the output of the selection circuit 1098 from the HSL color
space to the RGB color space, as in the case of coordinate reverse
transformation circuit 1076. Outputs Rout, Gout and Bout from the
coordinate reverse transformation circuit 1100 are applied to the
color space compression circuit 1020 of FIG. 8.
[0132] Processing in each of the circuits 1088, 1090, 1092 and 1094
is the same as that in the corresponding circuit shown in FIG. 10.
When an H correction mode is selected, the area code RAM 1086
outputs an address change signal such as to change the address of f
(L, AREA) in the function conversion circuit 1092 from the address
with which the L conversion table is stored to the H correction
coefficient table. The function conversion circuit 1092 thereby
outputs an L component output and an H correction coefficient
during the time in the H correction mode. The calculation circuit
1096 calculates the H component output from f (H, AREA) with the H
correction coefficient output from f(L, AREA) and outputs a
corrected H signal. The selection circuit 1098 selects the outputs
in accordance with the correction mode signal from the area code
RAM 1086 (1 bit in the output from the area code RAM 1086 (which is
1 in the correction mode)), that is, it selects both H and L
converted in th qrdinary manner at the time of calculation
involving L, that is, during the time other than the time in the
correction mode, and selects, during the time in the H correction
mode, L and S in the state before being input to the circuit 1092.
As a result, during the time in the correction mode, the selection
circuit 1098 outputs signals in which the S and L components are
not changed and only the hue has been corrected. Thus, the
variation in color depending upon the lightness can be reduced in
the case of setting the hue uniformly through the full lightness
range.
[0133] In the arrangement shown in FIG. 12, the L conversion table
and the H correction table are combined to reduce the circuit
scale. However, the hue correction means is not limited to this
arrangement. For example, a correction circuit may be provided
before the H conversion function to correct the lightness L and the
hue H and, if necessary, the saturation S before the function
conversion.
[0134] During the time for modes other than the H correction mode,
the selection circuit 1098 selects and outputs the H component
output, the S component output and the L component output from the
selection circuit 1094. In other respects, the operation and effect
are the same as those of the arrangement shown in FIG. 10.
[0135] In the case of processing, for example, for changing "red
into blue" in the embodiment shown in FIG. 7, conversion functions,
i.e., conversion tables, such as those shown in FIG. 13, are used
to convert all colors having hues close to red from "white" to
"black" into blue. On the other hand, there is a need for a color
processing function for "changing only very red into blue" by
limiting both the saturation and the brightness. To realize such a
function, the processing system may be arranged in such a manner
that the values of the signals H, S and L and the values of signals
representing a "particular color" are compared by a window
comparator, and color conversion is made only when each component
is within a certain range about the particular color.
[0136] FIG. 14 is a block diagram schematically showing the
configuration of an example of color processing circuit 1018
arranged in such a manner. The same components as those shown in
FIG. 7 are indicated by the same reference characters. Registers
1102 and 1104, 1106 and 1108, and 1110 and 1112 hold upper and
lower limit values of the hue H, upper and lower limit values of
the saturation S, and upper and lower limit values of the lightness
L. A decision circuit 1114 compares the values H, S and L output
from the coordinate transformation circuit 1040 with the
corresponding upper and lower limits values held by the registers
1102 to 1112 to determine whether or not each component is within
the designated range. The registers 1102 to 1112 and the decision
circuit 1114 constitute a window comparator.
[0137] A selection circuit 1116 selects RGB outputs from coordinate
reverse transformation circuit 1052 if the decision circuit 1114
determines that each of H, S and L is within the designated range.
The selection circuit 1116 selects inputs Rin, Gin and Bin if any
one of H, S and L is not within the corresponding designated range.
Outputs from the selection circuit 1116 are obtained as the outputs
Rout, Gout and Bout from color processing circuit 1018.
[0138] The decision circuit 1114 compares the value H output from
the coordinate transformation circuit 1040 with the upper and lower
limit values in the registers 1102 and 1104, the value S output
from the coordinate transformation circuit 1040 with the upper and
lower limit values in the registers 1106 and 1108, and the value S
output from the coordinate transformation circuit 1040 with the
upper and lower limit values in the registers 1110 and 1112. The
decision circuit 1114 outputs "1" when all the values H, S and L
are within the corresponding ranges limited by the upper and lower
limits, and outputs "0" if any of the values H, S and L is out of
the corresponding range. The selection circuit 1116 selects the RGB
outputs from the coordinate reverse transformation circuit 1052
when the output from the decision circuit is 4114 and selects
inputs Rin, Gin and Bin when the output from the decision circuit
1114 is "0".
[0139] It is possible to selectively realize, for example, a
function of erasing only red-penciled portions in a corrected
original (designating "red" and replacing the corresponding portion
with white) and a function of leaving only red-penciled portion
designating "red" and replacing the portion other than with white)
by converting the output from the decision circuit 1114 according
to one's need.
[0140] With respect to the case of detecting "red" and the case of
detecting "white" for color conversion, it is necessary to change
the upper and lower limit values of the registers 1102 to 1112.
[0141] For example, it is assumed here that in the case of
detection of "red (H=0, S=255, L=128)",
[0142] -10.ltoreq.H.ltoreq.10
[0143] 255-50 .ltoreq.S.ltoreq.255+50
[0144] 128-50 .ltoreq.L.ltoreq.128+50
[0145] have been set by the registers 1102 to 1112. If the
processing system is operated to detect "white (H=indefinite, S=0,
L=255)" under the same setting, then only "white" accidentally
recognized as a color having a hue value close to the set value
among "white", with which, intrinsically, no hue cannot be set (in
other words, any hue value can be set), resulting in a mottled
image. Moreover, even a portion having a substantially high
density, i.e., an L value of about 50, can be selected. To prevent
this problem, if a value close to "white" is selected as a
"particular color", the window setting may be changed so that
[0146] H=whole range (or no range designation)
[0147] -10 .ltoreq.S.ltoreq.10
[0148] 255-10.ltoreq.L.ltoreq.255+10.
[0149] The method of changing the window setting is not limited to
this. Colors vary in recognizability. For example, a change in a
light color can be recognized more easily than a corresponding
change in a dark color, and an apparent change in "blue" is smaller
than a corresponding change in "red". If the window setting values
are changed by considering these facts, the effect of
discrimination of a particular color by processing becomes closer
to the effect of discrimination with human eyes.
[0150] Actually, tables of "particular colors" and "window setting
values" are prepared for a CPU shown in FIG. 22 and described
below, and the CPU automatically selects window setting values,
i.e., the values held by the registers 1102 to 1112 according to
the designation of a "particular color" from a user
[0151] In a case where a particular color of a color halftone dot
original such as a printed matter is determined by the window, the
particular color is determined at dot-like areas in correspondence
with the halftone dots, as shown in FIG. 15, so that the color
after conversion is visually recognized as different from the
designated color. In such a situation, the resulting image may have
a certain roughness. Therefore, a smoothing circuit is provided for
processing before the coordinate transformation and color
determination is made after the values R, G and B, or H, S and L
have been smoothed, whereby the portions which are visually
recognized and the color portions determined by processing become
substantially equal to each other. FIG. 16 is a block diagram
schematically showing an example of a circuit configuration
realizing this effect. In the arrangement shown in FIG. 16, in
comparison with the arrangement shown in FIG. 14, a smoothing
circuit 1118 is provided at a stage after the coordinate
transformation circuit 1040. Also, a decision signal processing
circuit 1120 for processing the determination result from the
decision circuit 1114 is provided, and the selection circuit 1116
is controlled by the output from the decision signal processing
circuit 1120. The selection circuits 1043 and 1048 are removed
since they are unnecessary.
[0152] In this example, the resolution of an input image
represented by Rin, Gin and Bin is 400 dpi, and 5.times.5 smoothing
circuit 1118 smoothes dots formed at a density of 133 to 175 dpi,
which corresponds to the density of dot screen lines of ordinary
printed matters. The decision signal processing circuit 1120
thickens or thins image portions having decision result
non-uniformity at the boundaries between colors by majority
operation or the like. In other respects, the operation and effect
of this arrangement are the same as those of the arrangement shown
in FIG. 14.
[0153] In a portion of the smoothing circuit 1118 where the hue
signal H is processed, the hue signal H is rotated through
360.degree. one time. Therefore, a pre-processing circuit for
calculating the actual range of the signal value is provided at
this portion along with a common product/sum calculation circuit
for processing the signals S and L as well as the signal H.
[0154] In the arrangement shown in FIG. 16, non-color-processed
image signals are output with respect to pixels other than the
pixels corresponding to designated areas, thereby reducing the
unnecessary reduction in resolution due to smoothing by the
smoothing circuit 1118. Alternatively, the signals smoothed by the
smoothing circuit 1118 may be input only to the decision circuit
1114 in order to reduce the reduction in resolution due to
smoothing.
[0155] In the arrangement shown in FIG. 16, the HSL signals are
smoothed. However, the arrangement may alternatively be such that
input RGB signals Rin, Gin and Bin may be smoothed before being
converted into HSL signals and undergoing determination processing
in the decision circuit 1114.
[0156] It is apparent that the color space compression circuit 1020
shown in FIG. 8 can be integrally combined with the color
processing circuit 1018 arranged as described above. FIG. 17 shows
a color space in the case where the color space compression circuit
1020 is integrally combined with the color processing circuit 1018.
During pre-scanning, a signal value representing the maximum
saturation S in each of hues of 0.degree., (R), 60.degree. (Y),
120.degree. (G), 180.degree. (C), 240.degree. (B) and 300.degree.
(M) is sampled. This value is compared with the corresponding
maximum value of the printer reproducible color space. If the image
contains a value not reproducible by the printer, the saturation
component of the corresponding hue component is compressed so be
made reproducible.
[0157] When each color processing function is executed, the color
space compressing function obtained by pre-scanning and the
function for the processing are combined and written in RAMS of
conversion circuits 1046, 1072 and 1092.
[0158] In the fourth embodiment of the invention, as can be easily
understood from the above, RGB signals are converted into values in
a cylindrical coordinate system consisting of the hue, the
saturation and the lightness of colors and various kinds of
conversion processing are performed in this coordinate system,
thereby realizing a multiple functions with a single hardware
arrangement. Also, an operator can intuitively designate a color
advantageously effectively.
[0159] <Fifth Embodiment>
[0160] A color image processing apparatus in accordance with the
fifth embodiment of the present invention will be described which
has both a first adjustment function of adjusting a color by
designating a particular color to be converted and by setting a
degree of conversion, and a second adjustment function of setting
the entire surface as colors to be converted and changing the set
colors by equal amounts on the hue circle. This apparatus has the
same circuit configuration as that shown in FIG. 8.
[0161] An example of the operation for hue adjustment will be
described below. FIGS. 18(a) through 18(d) show examples of
displays on an operating unit. First, when a "color adjustment hard
key" (not shown) is operated, a graphic image such as that shown in
FIG. 18(a) is displayed. Then, "HUE ADJUSTMENT" 1201 is selected
and "OK" 1202 is operated. A graphic image such as that shown in
FIG. 18(b) is thereby displayed. A hue to be adjusted on an
original is selected from "RED", "YELLOW", "GREEN", "CYAN", "BLUE",
"MAGENTA" and "WHOLE" by operating corresponding selected color
keys 1203 to 1209 in the displayed graphic image. In the initial
state of setting through the graphic shown in FIG. 18(b), "WHOLE"
is selected and hue adjustment of all colors is set if the
selecting operation is omitted. If "WHOLE" 1209 is selected, all
the colors on the original are converted by equal amounts on the
hue circle according to an adjustment value designated by "FINE HUE
ADJUSTMENT KEYS" 1210 on the left-hand side of FIG. 18(b). If
"YELLOW" 1204 is selected and designated as a color to be adjusted,
a graphic image is displayed which contains "FINE HUE ADJUSTMENT
KEYS" 1211 for setting the direction and the number of steps of
adjustment of each selected color on the hue circle, as shown in
FIG. 18(c). In this embodiment, "FINE HUE ADJUSTMENT KEYS" 1211 are
operable to change the color three steps at the maximum from a
standard point in the direction of each of the adjacent hues, for
example, red and green if the selected color is yellow. After the
desired value has been designated by the "FINE HUE ADJUSTMENT KEYS"
1210 or 1211, "OK" 1202 is operated to complete setting, thereby
starting copying.
[0162] FIG. 19 is an H-f(H) graph showing a characteristic of
conversion between colors before and after conversion in the
function conversion circuit 1046 shown in FIG. 7 in a case where Y
is changed two steps in the direction G while C is changed one step
in the direction G. The hue is changed through ten degrees by one
step of the operating unit. In this example, the entire surface
offset=0, Y is changed by +2, C is changed by -1, and the other
hues are not changed. Accordingly, the value of change in each hue
is determined as shown in FIG. 19, and H between each adjacent pair
of hues is calculated by interpolation calculation. Simultaneously
with the start of copying, this content is set in the function
conversion circuit 1046, and the hues of read image data are
converted by the function conversion circuit 1046. Each of
saturation adjustment and contrast adjustment is executed by
rewriting the contents of f(S) and f(L) in the same manner.
[0163] FIG. 18(d) shows an example of an adjustment graphic image
in the case of saturation adjustment. Also in the case of
saturation adjustment, the entire original or selected colors are
designated with "SELECTED COLOR" keys 1203 to 1209, as in the case
of hue adjustment, and an adjustment degree is set with "FINE
SATURATION ADJUSTMENT KEYS" 1212, thereby enabling saturation
adjustment to be started. Lightness adjustment can also be
performed by selecting "LIGHTNESS ADJUSTMENT" 1199 and by
performing the same operation as saturation adjustment. The amount
of adjustment is not limited to that described above and may be an
amount of gain adjustment as represented by f(x)=.alpha.X, or an
amount expressed by any other function, as well as an offset
expressed by f(X)=X+.delta.X (X: H, S, L). Some of these kinds of
adjustment (for example, hue adjustment and saturation adjustment)
may be set in combination with each other.
[0164] As described above, hue adjustment, saturation adjustment
and lightness adjustment are possible with respect to any or all of
particular colors on an original. Further, since each adjustment
can be set by the function conversion circuit 1046, combined
adjustment can easily be performed by using a composite
function.
[0165] Consequently, color adjustment can be performed freely and
conveniently.
[0166] A case of changing color adjustment processing with respect
to arbitrary areas in an image frame using the circuit shown in
FIG. 10 will now be described. The area code signal AREA shown in
FIG. 10 is a signal which is synchronized with the image signal
input and which designates the area in the image frame where the
presently-processed pixel exists, as mentioned above. The signal
AREA is input to the area code RAM 66 through the selection circuit
1060. Codes designating processing performed on arbitrary
designated areas are previously stored in the RAM 1066. The output
from the RAM 1066 is input as upper bits in the function conversion
RAM used for the function conversion circuit 1072. It is possible
to change the conversion function used in the function conversion
circuit 1072 by changing the processing codes and to apply plural
kinds of color processing to arbitrary areas in one image
frame.
[0167] A case of designating two areas and performing hue
adjustment on the first area and saturation adjustment on the
second area will be described below by way of example. FIGS. 20(a)
through 20(d) show operating graphic images successively displayed
in a case where area designation is made.
[0168] First, an "area designation" hard key (not shown) is
operated to display the graphic image shown in FIG. 20(a) on the
operating unit. One or more areas, e.g., areas 1 and 2, where
colors are to be adjusted, are designated in a "WINDOW" 1222
corresponding to the surface of an original with a digitizer by
selecting "RECTANGLE" 1220 or "NON-RECTANGLE" 1221. The area 1 is
first input. When the designation of area 1 is completed and "OK"
key 1223 is displayed as shown in FIG. 20(b), "OK" key 1223 is
operated. Then, various kinds of processing from which one to be
performed on area 1 is selected are displayed in the graphic image
shown in FIG. 20(c), and "HUE ADJUSTMENT" key 1224 is selected in
this case (on the main unit side, by referring to this selection, a
functional code for "HUE ADJUSTMENT" is set with address 1
(representing area 1) in the area code RAM 1066).
[0169] Parameter setting at the time of hue adjustment is the same
as that described above with reference to FIGS. 18 and 19.
[0170] When the setting of area 1 is completed, the graphic image
shown in FIG. 20(d), for inputting the next area, is displayed.
Subsequently, area 2 is designated and saturation adjustment is
designated as processing to be performed on area 2 with "SATURATION
ADJUSTMENT" key 1225, followed by setting necessary parameters. If
the setting for the desired processing is completed, "OK" key 1226
is operated without inputting another area through the input image.
Area input operation is thereby terminated. Lightness adjustment
can also be performed by the designation operation with "LIGHTNESS
ADJUSTMENT" key 1227 in the same manner.
[0171] As described above, a plurality of areas can be set on the
input image, and various kinds of adjustment selected as desired
can be respectively performed on the areas. Thus, it is possible to
perform various kinds of adjustment on any areas.
[0172] As described above, this embodiment is provided with a
designation means for selecting one of a set of particular hue
components or a set of all hue components as a hue to be adjusted
and a setting means for setting a rate of change in a hue component
or a saturation component of an image signal corresponding to the
adjusted hue designated by, the designation means whereby color
adjustment can be performed freely and conveniently.
[0173] A particular one of colors of an original and the hues of
all the colors can be mixedly adjusted, for example, by designating
the particular color as a color to be adjusted, setting a rate of
change of a component to be changed, and thereafter
color-converting al the hues of the image on the hue circle by
equal amounts.
[0174] <Sixth Embodiment>
[0175] The sixth embodiment of the present invention will now be
described in which variable smoothing is performed for color
conversion of a halftone dot image to achieve high-accuracy color
conversion. The construction of the apparatus of this embodiment is
the same as that shown in FIG. 8.
[0176] FIG. 22 is a block diagram of a control unit 1213 usable in
the above-described embodiments and connected to the CPU buses (CPU
address bus, CPU data bus).
[0177] A microcomputer or a central processing unit (CPU) 1301
controls the overall image processing operation. A program for
operating the CPU 1301 is stored in a ROM 1302. A RAM 1303 is used
as a work area for executing various programs. An input/output port
(hereinafter referred to as I/O port) 1304 is connected to the CPU
1301. A liquid crystal display controller 1305 serves to control a
liquid crystal display device mounted on an operating unit 1214. A
VRAM 1306 stores data displayed on the liquid crystal display
device. The content of the VRAM 1306 can be rewritten by the CPU
1301 through the liquid crystal display controller 1305.
[0178] The operating unit 1214 connected to the control unit 1213
is used by a user to set an operating mode of a digital full-color
copying machine in accordance with the sixth embodiment. FIG. 21
illustrates the operating unit 1214 having a liquid crystal display
screen 2201, a ten key cluster 2202, a reset key 2203, a copy start
key 2204, a cassette selection key 2205, an actual size setting key
2207, a zoom key 2206, a color conversion key 2208, and an OK key
2209.
[0179] This embodiment has the same image processing circuit as
that illustrated in FIG. 16. Smoothing circuit 1118 of this
embodiment is arranged so as to be variable in smoothing effect by
a signal designated by a user through the operating unit 1214.
[0180] When the color conversion key 2208 of the operating unit
1214 shown in FIG. 21 is pressed, the graphic image on the liquid
crystal display is changed to an image such as illustrated in FIG.
23. A color to be converted is selected by designating a number
using the ten key cluster 2202. The number is selected by referring
to a color card in which colors and numbers are previously
correlated. When the OK key 1401 is pressed, an image such as that
shown in FIG. 24 is displayed, and a color after conversion is
selected in the same manner. Colors before and after conversion are
not selected exclusively from the color card. For example, a table
in which colors and numbers are correlated may be previously
written in a ROM (not shown). Such a table is displayed by an
instruction from the operating unit 1214 to enable the user to
select any one of the colors in the table.
[0181] If an adjustment key 1402 in the graphic image shown in FIG.
23 is operated, an image such as that shown in FIG. 25 is displayed
to enable the degree of smoothing to be changed. One of five
filters, e.g., those shown in FIG. 26, can be selected by moving a
cursor 1604 using "ADJUSTMENT KEYS" 1602 and 1603 to set the
desired degree of smoothing. If the OK key 1601 is operated, the
display is changed to the normal graphic image shown in FIG.
21.
[0182] If the filter is stronger, the image is unsharpened more
strongly. The coefficients of the filters are not limited to those
shown in FIG. 26 and may be variously determined by the CPU 1301.
The method of changing the filtering effect is not limited to the
above-described method of changing the coefficients for weighting
central and peripheral pixels. It is also possible to change the
degree of unsharpening of the image by changing the size of a
filter. Filters having both the size and weighting coefficients
varied may also be used.
[0183] The method of setting the selected filter in the smoothing
circuit 1118 will be described. The filter is determined by the CPU
in accordance with the designation from the operating unit 1214,
and is sent to the selection circuits 1042 and the 1048 via the CPU
bus shown in FIG. 22. The filter as an output from the CPU is
written in the smoothing circuit 1118 when writing it in the
smoothing circuit 1118 is instructed by the CPU through the CPUACC.
It is possible to obtain plural kinds of image data by changing the
setting of the above-described variable filter. It is therefore
possible to make color conversion in accordance with an operator's
preference. In the above-described example, the filter is set by a
user. However, the arrangement may alternatively be such that
pre-scanning is performed with line sensor 1010 shown in FIG. 8 and
CPU 1301 automatically determines the density of screen lines of a
halftone dot image and automatically selects an optimal filter
according to the result of determination. If the filter is
automatically changed in this manner, the colors of the original
halftone dot image can be accurately reproduced and it is therefore
possible to achieve accurate color identification and color
conversion. The decision signal processing circuit 1120 thickens or
thins image portions having decision result non-uniformity at the
boundaries between colors by majority operation or the like. In
other respects, the operation and effect of this arrangement are
the same as those of the arrangement shown in FIG. 16.
[0184] In a portion of the smoothing circuit 1118 where the hue
signal H is processed, the hue signal H is rotated through
360.degree. one time. Therefore, a pre-processing circuit for
calculating the actual range of the signal value is provided at
this portion along with a common product/sum calculation circuit
for processing the signals S and L as well as the signal H.
[0185] In this embodiment, various filters differing in weighting
or size are determined automatically or by user setting to perform
smoothing before color identification processing. However, it is
apparent that the same effect can also be achieved by changing the
window size or a constant of majority decision (in which a target
pixel an m x m window is recognized as a particular color when it
is determined that a number of pixels equal to or larger than a
predetermined number n among the pixels in the window has a
particular color).
[0186] In this embodiment, as described above, area processing
characteristics are set for area processing, and color
identification is made on the basis of image data processed in
accordance with the processing characteristics. It is therefore
possible to perform plural kinds of color identification by
changing the setting. Even if the image after color conversion made
by the operator is unsatisfactory, plural kinds of image after
color conversion can be obtained by changing the above-described
setting.
[0187] The area processing characteristics are controlled according
to the density of halftone dot lines of a halftone dot image. It is
therefore possible to accurately reproduce the color of the image
as well as to accurately identify the color regardless of the
density of halftone dot image lines.
[0188] 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 claims.
* * * * *