JPH10257334A - Color correction processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate the hue of image signal which expresses a color space, with simple circuit configuration. SOLUTION: Tow-dimensional(2D) circuits 11a and 11b convent 3D RGB signals into 2D data (x) and (y) and based on the 2D data (x) and (y) respectively converted by the 2D circuits 11a and 11b, a hue discrimination part 13 discriminates 8×8 hue areas. At the hue discrimination circuit 13, a 1st hue- discriminating part discriminates hue areas I-VIII on a color plane based on the 2D data (x) and (y), a hue rotational moving part rotates the hue areas I-VIII discriminated by the 1st hue discriminating part, and a 2nd hue- discriminating part discriminates the hue areas I-VIII, rotated by the hue rotational moving part, while further dividing them into fine hue areas S1-S8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a hue of color image data based on, for example, R (red), G (green), and B (blue) signals, and obtains C (cyan), M
The present invention relates to a color correction processing device suitable for converting color signals of (magenta), Y (yellow), and K (black).

[0002]

2. Description of the Related Art Conventionally, methods for detecting the hues of digital color image signals R, G, and B representing a color space include, for example, (1) Digital color representing a color space as disclosed in Japanese Patent Application Laid-Open No. 1-114267. There is known a method of performing a multiplication process according to a value of a signal having the largest value among image signals R, G, and B, and detecting a hue based on a result of the multiplication.

[0003] For example, (2)
As disclosed in Japanese Patent Laid-Open Publication No. 5 (1999) -2005, by determining a hue region to which a color indicated by an image signal belongs, selecting a predetermined set of parameters according to the determined region, and processing the image signal based on the selected parameters. There are known methods for performing color conversion and changing a hue area.

Here, an example of an image forming apparatus for performing color conversion will be described with reference to FIG. FIG. 1 is a block diagram illustrating an electrical configuration of an image forming apparatus according to a conventional example. In FIG. 1, the image forming apparatus is schematically composed of a reading control unit 101, an image processing unit 100, an image recording unit 108, a synchronization control unit 111, and a system control unit 112.

A reading control unit 101 is a unit for reading a document image, and includes a CCD 7 and an A / D converter 102.
And a shading correction unit 103. C
The CD 7 is provided for each of the three colors of RGB, and each CCD 7 r,
The output signals of 7g and 7b are A / D converters 102r and 102
The signals are converted into 8-bit digital signals by g and 102b, respectively, and input to the shading correction circuit 103.
The shading correction circuit 103 corrects unevenness in the sensitivity of the CCD reading optical system, variations in the sensitivity of the light receiving elements in each CCD and dark current, and outputs 10-bit read color gradation signals R, G, and B. I do.

The image processing unit 100 includes a γ correction circuit 1
04, a color correction circuit 105, a scaling processing circuit 106, and a dither processing circuit 107. The gamma correction circuit 104 performs logarithmic conversion on the input read color gradation signals R, G, and B, and performs console 300 conversion. , The tone characteristics are corrected in accordance with the instruction, and the read color density signals Dr, Dg, Db of R, G, B of 8 bits are output. Color correction circuit 105
Performs a masking process and outputs R, G, B input signals D
r, Dg and Db are signals corresponding to the recording colors of C, M, Y and Bk (corresponding to the recording density of each toner) Dc, Dm, Dy,
Convert to Dbk. In this conversion, basic color correction for correcting the amount of deviation of the recording characteristics of the apparatus from the ideal characteristics and arbitrary color correction based on instructions from the console board 300 are performed.

The 8-bit recording color density signals Dc, Dm, Dr and Dbk output from the color correction circuit 105 are:
It is applied to the scaling processing circuit 106. Magnification processing circuit 106
Performs a scaling process in the main scanning direction on each color signal in response to an instruction from the console board 300, and outputs 8-bit recording color density signals Dc ', Dm', Dr ', and Dbk'.
Is output. The magnification in the sub-scanning direction is changed by changing the moving speed of the first carriage on which the first mirror is mounted.

The signal output from the scaling processing circuit 106 is applied to a dither processing circuit 107. The dither processing circuit 107 dithers the recording color density signals Dc ′, Dm ′, Dr ′ and Dbk ′, and outputs recording color gradation signals C, M, Y and Bk of 3 bits each. In the dither processing, the correction of the non-linear characteristic on the gradation of the recording system is also performed.

The image recording unit 108 energizes the semiconductor lasers 43c, 43m, 43y and 43bk according to the recording color gradation signals C, M, Y and Bk output from the image processing unit 100. The signal of Bk is given to the laser driver 110bk as it is, but the signals Y,
M and C are buffer memories 109y and 109m, respectively.
After being held at 109c, they are read out after a predetermined delay time, respectively, and given to the laser drivers 110y, 110m and 110c.

The synchronization control unit 111 matches the timing of signal transmission / reception between the reading processing unit 101, the image processing unit 100, and the image recording unit 108, and between respective elements in each unit.

The system control unit 112 includes a CPU 1
13, ROM 114, RAM 115, I / O port 11
6, 117, 118, 119 and 120, and controls the entire copying machine. Further, the system control unit 112 performs display control of the console board 300 and detection of key input and adjustment instruction, and performs a predetermined operation according to the key input.

The color correction circuit 105 includes, for example, a hue region determination circuit, a black extraction circuit, a black removal circuit, and a masking circuit. The hue area determination circuit is a circuit that determines which of the plurality of preset areas the hue indicated by the input read color density signals Dr, Dg, and Db belongs to, and a result of the determination is a 3-bit hue determination signal. S
Output as area. The black extraction circuit generates a signal Dbk for determining the recording density of the black toner component from the input read color density signals Dr, Dg, Db, and the black removal circuit records based on the recording color density signal Dbk output by the black extraction circuit. The signals Dc, Dm, and Dy representing the recording densities of the respective cyan, magenta, and yellow toners are corrected. The masking circuit generates signals Dc, Dm and Dy representing the respective recording densities of the cyan, magenta and yellow toners of the recording color based on the recording color density signals Dc ', Dm', Dr 'and Dbk'. This masking circuit corrects an error based on the difference between the actual characteristics of the recording colors and the ideal characteristics. Further, color correction based on an instruction from the operator is also executed by this masking process.

FIG. 13 shows the details of the configuration of the hue region determination circuit. In the figure, the hue region determination circuit 121
It comprises a hue coding circuit 125, a boundary hue holding circuit 126, a hue comparison circuit 127 and a coding circuit 128. The hue encoding circuit 125 generates an 8-bit hue code corresponding to the hue indicated by the read color density signals Dr, Dg, and Db. The boundary hue holding circuit 126 has a function of holding and outputting eight 8-bit data. The data held by the boundary hue holding circuit 126 is set by the system control unit 112. Also, eight 8-bit data H1, H2, H3, H4, H5, H6, H7, H8 output by the boundary hue holding circuit 126 are output.
Are arranged in advance so as to satisfy the relationship of H1≥H2≥H3≥H4≥H5≥H6≥H7≥H8.

The hue comparison circuit 127 is a hue coding circuit 1
25 outputs the 8-bit code H to the boundary hue holding circuit 1
26 outputs the eight 8-bit data data H1, H
2, H3, H4, H5, H6, H7, and H8, and outputs eight binary signals indicating the magnitude relation of each. The coding circuit 128 outputs the eight 2
As shown in FIG. 13, a combination of the value signal states is output as a 3-bit signal Sarea. That is,
Since the eight 8-bit data H1, H2, H3, H4, H5, H6, H7, and H8 output from the boundary hue holding circuit 126 are arranged in descending order, a combination of the states of the eight signals output from the hue comparison circuit 127 is provided. Becomes nine kinds. Also,
The case where all the signals indicating the comparison results are L (ie, H> H1) and the case where all the signals are H (ie, H ≦ H8) can be regarded as the same hue region due to the hue periodicity. Therefore, the combination of signals output from the hue comparison circuit 127 is eight in total, and can be encoded into a 3-bit code.

Therefore, an image signal input by referring to the signal Sarea (combination of Dr, Dg, Db)
To which of the eight types of regions the color hue belongs.

[0016]

However, in the above prior art example (1), as a circuit for detecting a hue by multiplying an RGB signal representing a color space, a memory for outputting a hue using an 8-bit RGB signal as an address. In the case where is used, there is a problem that the circuit configuration becomes large. In addition, there is a problem in that the circuit for changing the hue area also becomes large.

Further, in the above-mentioned conventional example (2), since the hue is coded to determine the hue area as described above, a large amount of memory is required.

A first object of the present invention is to provide a color correction processing apparatus capable of determining a hue area of an image signal representing a color space with a simple circuit configuration. Is to provide.

It is a second object of the present invention to provide a color correction processing apparatus which can determine the hue of an image signal representing a color space with a simple circuit configuration.

[0020]

To achieve the above object, a first means is a color correction processing for detecting a hue of a color space represented by an RGB three-dimensional image signal and performing a desired color correction. Means for converting an RGB three-dimensional image signal representing the color space into a two-dimensional image signal representing a color plane; and a two-dimensional image signal converted by the means for converting the image signal into a two-dimensional image signal. Means for determining a hue region for extracting the hue of the three-dimensional image signal based on the hue.

The second means is a color correction processing device based on the same premise as the first means.
Means for converting a two-dimensional image signal into a two-dimensional image signal representing a color plane, and a hue of the three-dimensional image signal based on the two-dimensional image signal converted by the two-dimensional image signal And means for extracting

A third means is a color correction processing device based on the same premise as the first means, and is a color correction processing device for RGB representing the color space.
Means for converting a two-dimensional image signal into a two-dimensional image signal representing a color plane, and a hue of the three-dimensional image signal based on the two-dimensional image signal converted by the two-dimensional image signal Means for setting the hue area of the three-dimensional image signal based on the two-dimensional image signal converted by the two-dimensional image signal converted by the means for converting the two-dimensional image signal; Means for identifying which of the hue areas set by the means for setting the hue area contains the hue thus set.

According to a fourth aspect, in the first to third aspects, the hue is extracted through a plurality of processing steps.

The fifth means is characterized in that the plurality of processing steps in the fourth means include a hue rotational movement step.

The sixth means is characterized in that the means for converting into a two-dimensional image signal in the first to third means converts the image signal into a plane having an achromatic axis in a color space as an origin.

The seventh means is that the means for setting the hue area in the third means is a predetermined step, ie, nm, on a plane formed by a two-dimensional image signal representing a color plane.
The feature is that the boundaries of the hues at the stage (n ≧ m ≧ 1) [n and m are positive integers] are set at equal angular intervals with respect to a given point.

An eighth means is that, when the means for setting a hue region in the seventh means extracts the hue of the predetermined stage and then extracts the hue of the next stage of the predetermined stage, the two-dimensional image The signal is rotated around the arbitrary point to extract the hue of the next stage, in other words, b-1 (n ≧ n)
b> 1) [n and b are positive integers] After extracting the hue at the stage, when extracting the hue at the b stage, the two-dimensional image signal is rotated around the arbitrary point to b It is characterized by extracting the hue of the stage.

In this case, the means for judging the hue area in the first means is the same as the hue area judging section 12 in FIG.
The means for extracting the hue in the second means corresponds to the hue determination unit 13 in FIG. 7, and the means for extracting the hue in the third means corresponds to the hue determination unit 13 in FIG.
However, the means for setting the hue area corresponds to the hue area selection unit 2 in FIG. 1, and the means for identifying which hue area is included in the hue area corresponds to the hue area identification unit 3 in FIG.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

1. First Embodiment FIG. 1 is a block diagram showing one embodiment of a color correction processing device according to a first embodiment of the present invention, FIG. 2 is a block diagram showing a hue region identification unit in FIG. 1 in detail, and FIG. Is an explanatory diagram showing a relationship between a color space and a color plane, FIG. 4 is an explanatory diagram showing a two-dimensional hue region, FIG. 5 is a block diagram showing the hue determination unit in FIG. 2 in detail,
FIG. 6 is an explanatory diagram showing a hue area obtained by dividing the hue area of FIG. 4 into smaller smaller areas.

1.1 Schematic Configuration of Color Correction Processing Apparatus FIG. 1 is a block diagram showing a schematic configuration of a hue boundary setting means of the color correction processing apparatus and a hue division masking processing apparatus based on a hue area variable method during color conversion processing. . In the figure, a hue division masking processing device is a characteristic input device 1
a, an operation unit 1b, a hue region selection unit 2, a hue region identification unit 3, a masking coefficient calculation unit 4, and a color correction unit 5. The input characteristic device 1a is a device that indicates the characteristics of an image input device such as a scanner, and a user can perform a desired input by operating the operation unit 1b.
a and the output signal from the operation unit 1 b are input signals to the hue region selection unit 2. The hue area selection unit 2 sets a hue area for dividing the hue based on the input signal.
A hue area selection result is output, and this output is an input signal of the hue area identification unit 3. Further, the read densities R, G, and B in the color space as input image signals are also input to the hue area identification unit 3. The hue region identification unit 3 identifies a hue region of the input image signal based on these input signals.

1.2 Details of Hue Area Identifying Unit As shown in detail in FIG. 2, the hue area identifying unit 3 includes first and second two-dimensional conversion circuits 11a and 11b and a hue area shown in detail in FIG. And a determination unit 12. In this circuit, the hue region is identified. The two-dimensional circuit 11a,
In step 11b, the read densities R, G, and B are used as input signals to convert these three-dimensional data into two-dimensional data.
At this time, the output of the first two-dimensional conversion circuit 11a is set to x,
The output of the two-dimensional conversion circuit 11b becomes y. Here, the conversion equations in these two-dimensional circuits 11a and 11b are as follows: x = Xr.R + Xg.G + Xb.By = Yr.R + Yg.G + Yb.B (1) where coefficients Xr, Xg, Xb, Yr, Yg and Yb have a relationship of Xr + Xg + Xb = 0 Yr + Yg + Yb = 0 XrrYr or Xg ≠ Yg or Xb ≠ Yb.

1.2.1 Color Space and Color Plane The hue is, for example, as shown in FIG.
In a color space graph represented by three axes of G and B, a straight line R = G =
It can be identified by the direction 31 from B, and is converted into a plane such that the relationship of the direction 31 is not broken down by the above equation (1) and an achromatic color is set at the origin. The state of this conversion is shown in FIG. The data converted in this way is the input signal of the hue region determination unit 12 in FIG. 2, and the hue region determination unit 12 identifies the hue region on the plane converted to the read density in the color space.
The determination method here is, for example, as shown in FIG. 4, four straight lines represented by y = x y = 0 y = −x x = 0, in other words, eight straight lines drawn every 45 ° from the origin. The boundaries of the hue regions (the eight regions I to VIII) are set in advance by straight lines, and the hue regions are set by the hue region selection unit 2 by selecting the set boundaries. As a result, the input image signal Can be set.

1.2.2 Two-dimensional hue area The hue area is, for example, a hue area A in FIG. 4, hue I and hue II, and a hue area B in hue III, hue IV and hue V. , The hue area C is set as hue VI and hue VII. Then
The hue area A at this time is represented by y> 0, x> 0,
When there is an input image signal in this range, the hue area of the image signal is determined as hue area A.

Referring again to FIG. 1, the hue region selection unit 2
Is also an input signal of the masking coefficient calculating section 4, and the masking coefficient calculating section 4 to which this signal is input calculates the masking coefficient between the selected hue region and the one after the above. Hue identification result of output signal from hue region identification unit 3 and masking coefficient calculation unit 4
The masking coefficients for each hue region of the output signal and the read densities R, G, and B in the color space are input signals to the color correction unit 5, and the color correction unit 5 converts the input image signal based on these input signals. The recording image signals C, M, and Y are generated.

Thus, the hue area is set in the hue area selecting section 2
Thus, depending on the input signals of the input characteristic device 1a and the operation unit 1b, the boundaries of the hue regions can be easily set and changed according to the input conditions. Further, even if the input characteristic device 1a is replaced with an input device having a different characteristic such as a scanner, the input characteristic device 1a can arbitrarily and easily set or change it in the hue region selection unit 2.

1.2.3 Hue Judgment In the hue region, the boundaries of the hue regions are set in advance on the secondary plane as described above. In this setting, if a large number of boundaries are set in advance, the circuit It is inevitable that the size becomes large in the configuration, and the processing speed is affected. Therefore, the input image signal is roughly determined on the secondary plane in hue, and thereafter, is rotated and moved with the origin as a fulcrum, and the hue is determined at the moved position. At this time, when setting the boundary,
It is desirable to set them at equal angular intervals as much as possible.

FIG. 5 schematically shows a two-stage hue judging section and hue area judging section on a secondary plane. That is, in this process, first, the image data x and y subjected to the quadratic planarization are input to the first hue determination unit 21 as input signals. The first hue determination unit 21 determines the hue of the first-stage input image. Next, the image data x and y output from the first hue determination unit 21 are rotated and converted into X and Y in the hue rotation / movement unit 22. Then, a hue area in the area rotated and moved by the second hue determination unit 23 with respect to these X and Y is determined, and based on the two determination results of the first and second hue determination units 21 and 23, The hue of the input image is identified. From this result, the hue area determination unit 24 determines the hue area on the plane indicated by the first quadratic flattened input image. Also,
The hue region selection method in this case selects hues divided by a preset boundary on this plane. For example, assume that 64 hue boundaries are set on the secondary plane where the input image signal is converted. At this time, the boundary of the first hue determination unit 21 in FIG. 5 is set as shown in FIG. Further, the boundaries are set so that the hue I is substantially equal as shown in FIG. At this time, the hues divided at this boundary are represented by S1, S2, S3, S4, S5, S6, S
7, S8. The quadratic planarized data x, y is the first
It is assumed that the hue determination unit 21 has determined that the hue is II.
At that time, the hue rotation / movement unit 22 changes x,
Rotate y. In this case, X = x + y Y = −x + y (2) Here, mathematically, originally, X ′ = (x + y) / √2 Y ′ = (− x + y) / √2 (3), but in order to determine the hue, It suffices if it is on a straight line connecting the point (x, y) and the origin (0, 0). In other words, it is sufficient that the directional ratio of the straight line is not impaired. X = ax 'y = ay' where a Assuming that 変 換 0, X = aX ′ Y = aY ′ (4) is converted. Hue I is converted by such a conversion formula, and the second hue determination unit 23 further identifies the hue. Further, the hue area selection unit 2 in FIG. 1 selects the hue area A ′ as “from S1 of hue I to S4 of hue II” or the like to identify the hue area in the hue area determination unit 24 of FIG.

2. Second Embodiment FIGS. 7 to 11 are diagrams for explaining a color correction processing device according to a second embodiment. FIG. 7 is a block diagram showing the hue region identification unit of FIG. 1 in detail, and FIG. FIG. 9 is an explanatory diagram showing a two-dimensional hue region, FIG. 9 is a block diagram showing the hue judging unit in FIG. 7 in detail, and FIGS. 10 and 11 are explanatory diagrams showing an operation screen of the operation unit in FIG.

2.1 Schematic Configuration of Color Correction Apparatus The color correction processing apparatus in the second embodiment is equivalent to the color correction processing apparatus in the first embodiment shown in FIG. Are denoted by the same reference numerals, and overlapping description will be omitted as appropriate.

2.2 Details of Hue Region Identification Unit The hue region identification unit 3 in the second embodiment has two-dimensional circuits 11a and 11b and a hue determination unit shown in FIG. 9 as shown in detail in FIG. 13 and the hue region determination unit 12
Having. Here, the hue is, for example, R = G in a color space represented by three axes of RGB as shown in FIG.
= B because it can be identified by the direction 31
As shown in FIG. 3B, the two-dimensional conversion circuits 11a and 11b perform three-dimensional RG processing so that the relationship of the direction 31 does not collapse based on the above equation (1) and the achromatic color becomes the origin.
The B signal is converted into two-dimensional data x, y (illustration 32).

2.2.1 Color Space and Color Plane As shown in FIG. 8, the two-dimensional data shown in the above equation (1) has a boundary between y = xy = 0 and y = -xx = 0. Hue regions I to VIII.

As shown in detail in FIG. 9, the hue judging section 13 judges an 8 × 8 hue area based on the two-dimensional data x and y converted by the two-dimensional circuits 11a and 11b, respectively. First, the hue judging unit 21 outputs the two-dimensional circuit 11
a, two-dimensional data x converted by 11b,
Based on y and the following equation (5), as shown in FIG.
To VIII, y ≧ x: hue region II, III, IV, Vy ≧ 0: hue region I, II, III, IV y ≧ −x: hue region VIII, I, II, III x ≧ 0: Hue areas VII, VIII, I, II (5) The determination result is output to the hue area determination unit 12 as the upper 3 bits of the 6-bit determination data as follows.

000: Hue area I 001: Hue area II 010: Hue area III 011: Hue area IV 100: Hue area V 101: Hue area VI 110: Hue area VII 111: Hue area VIII For example, the input signal is changed to Hue I. If they belong, “false” is identified as “true” in equation (5), and the hue I =
This value is notified to the hue region determination unit 12 as 000. Then, for example, when it is determined that the hue area II is the hue area II, the hue rotation / movement unit 22 replaces the hue area II with the hue area I by the equation (2).
Rotate and move. Then, the above equation (4) and (5)
The rotation and movement of the hue regions I to VIII can be performed by the equations.

The hue determination section 23 determines small areas S1 to S8 obtained by further dividing the hue area I rotated and moved in this manner into eight parts, as shown in FIG. The data is coded as the lower three bits of the data as follows, and is output to the hue area determination unit 12.

000: S1 001: S2 010: S3 011: S4 100: S5 101: S6 110: S7 111: S8 Therefore, as an example, the code of the hue area IV-S5 is “011100”, and this 6-bit code is the hue. It is sent to the area determination unit 12. The hue area determination unit 12 finally determines the hue area based on the hue area determination code and the code from the hue area selection unit 2.

Next, a case where the user sets a hue area will be described. For example, when the hue area shown in FIG. 8 is used, the user selects a desired area and the number thereof while viewing the eight-part hue areas I to VIII on the two-dimensional screen shown in FIG. 10 via the operation unit 1b. , The upper 3 bits of the code described above are sent to the hue area selection unit 2. For example, hue area A
Are selected as 001 ≦ A ≦ 010. FIG.
, R, Y, G, C, B,
A screen in which the size of M can be selected in five steps is displayed, and when the user selects this, a small area S smaller than the hue areas I to VIII is displayed.
1 to S8 are selected, and the lower three bits of the code are sent to the hue area selector 2.

For example, as a result of the selection shown in FIG. 11, when the hue region R is such as the hue regions I-S1 to II-S3, the hue-region selection section 2 sets the 6-bit code "000".
000 ”to“ 001101 ”are determined as the hue region R, and are sent to the hue region determination unit 12 and the masking coefficient calculation unit 4.

Next, the hue area determination section 12 outputs the hue determination section 1
The hue area of the RGB signal in the color space is identified based on the hue determined in Step 3 and the hue area selected by the hue area selection unit 2 shown in FIG. At this time, if the result determined by the hue determination unit 13 is, for example, I-S7, the code indicated by the input image signals R, G, and B is "00011".
0 ", so that the hue region determination unit 12 determines the hue region R. Thus, the characteristic input device 1
The boundary of the hue area can be easily set and changed based on the input data a and the operation unit 1b.

The code signal is supplied to the color correction unit 5 shown in FIG.
The input image signal in this case becomes a recording image signal using the masking coefficient of the hue region R calculated by the masking coefficient calculation unit 4 in the color correction unit 5.

In addition, each unit not particularly described has the same configuration and functions as the first embodiment.

[0052]

As described above, according to the first aspect of the present invention, a means for converting an RGB three-dimensional image signal representing a color space into a two-dimensional image signal representing a color plane, and Converted by the means for converting the image signal into
Means for determining a hue region for extracting the hue of the three-dimensional image signal based on the three-dimensional image signal, so that when the hue indicated by the input image is extracted, the input image is a color space signal. By converting a certain thing into a plane signal, the hue area can be easily changed. In addition, this makes it possible to select an optimal hue region depending on the characteristics of the input unit.

According to the second aspect of the present invention, a three-dimensional image signal representing a color space is converted into a two-dimensional image signal representing a color plane, and a three-dimensional image signal is generated based on the two-dimensional image signal. Is extracted and determined, the hue of the image signal representing the color space can be determined with a simple circuit configuration.

According to the third aspect of the present invention, an RGB three-dimensional image signal representing a color space is converted into a two-dimensional image signal representing a color plane, and the three-dimensional image signal is converted based on the converted two-dimensional image signal. The hue of the three-dimensional image signal is extracted based on the two-dimensional image signal converted, and the hue region of the three-dimensional image signal is set based on the converted two-dimensional image signal. , It is possible to simplify the circuit configuration and easily change the hue region.

According to the fourth aspect of the present invention, when the hue is extracted, the hue is extracted in a plurality of stages, so that the circuit configuration for extracting the hue can be simplified. Further, in this way, the circuit configuration is simplified even if a large number of boundaries of the hue region are set in advance because the range in which the variable width of the hue region can be selected is widened.

According to the fifth aspect of the present invention, the hue of the input signal is roughly determined on the two-dimensional plane, and then the input signal is rotated, so that the circuit configuration can be further simplified.

According to the sixth aspect of the present invention, by converting the image signal into a plane having the achromatic axis as the origin, the hue area is expanded around the origin on the plane, thereby facilitating the setting of the hue area. Accordingly, the circuit configuration of the device can be simplified.

According to the seventh and eighth aspects of the present invention, when the hue is extracted, the hue is extracted in multiple stages.
The circuit configuration for extracting the hue can be simplified, and the same effect as in the fourth aspect can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a color correction processing device according to first and second embodiments of the present invention.

FIG. 2 is a block diagram showing in detail a hue region identification unit of FIG. 1;

FIG. 3 is an explanatory diagram showing a relationship between a color space and a color plane.

FIG. 4 is an explanatory diagram illustrating a two-dimensional hue region according to the first embodiment.

FIG. 5 is a block diagram illustrating a hue determination unit according to the first embodiment in detail.

FIG. 6 is an explanatory diagram showing a hue area obtained by dividing the hue area of FIG. 4 into smaller smaller areas.

FIG. 7 is a block diagram illustrating in detail a hue region identification unit according to a second embodiment.

FIG. 8 is an explanatory diagram illustrating a two-dimensional hue region according to a second embodiment.

FIG. 9 is a block diagram illustrating in detail a hue determination unit according to a third embodiment.

FIG. 10 is an explanatory diagram illustrating an operation screen of the operation unit in FIG. 1;

FIG. 11 is an explanatory diagram illustrating an operation screen of the operation unit in FIG. 1;

FIG. 12 is a block diagram illustrating an electrical configuration of an image forming apparatus that performs color conversion according to a conventional example.

13 is a block diagram showing a specific configuration of a hue area determination circuit in FIG.

[Explanation of symbols]

 1a Input characteristic device 1b Operation unit 2 Hue region selection unit 3 Hue region identification unit 4 Masking coefficient calculation unit 5 Color correction unit 11a, 11b Two-dimensional circuit 12 Hue region determination unit 13 Hue determination unit 21 First hue determination unit 22 Hue rotation moving unit 23 Second hue determination unit 24 Hue area determination unit

Claims (8)

[Claims] 1. A color correction processing device for detecting a hue of a color space represented by an RGB three-dimensional image signal and performing a desired color correction, wherein a color is obtained from the RGB three-dimensional image signal representing the color space. Means for converting the two-dimensional image signal into a two-dimensional image signal representing a plane; and hue for extracting the hue of the three-dimensional image signal based on the two-dimensional image signal converted by the two-dimensional image signal And a means for determining an area. 2. A color correction processing device for detecting a hue of a color space represented by an RGB three-dimensional image signal and performing a desired color correction, comprising the steps of: detecting a color from an RGB three-dimensional image signal representing the color space; Means for converting the two-dimensional image signal into a two-dimensional image signal representing a plane; means for extracting the hue of the three-dimensional image signal based on the two-dimensional image signal converted by the two-dimensional image signal; A color correction processing device comprising: 3. A color correction processing device for detecting a hue of a color space represented by an RGB three-dimensional image signal and performing a desired color correction, wherein a color is calculated from the RGB three-dimensional image signal representing the color space. Means for converting the two-dimensional image signal into a two-dimensional image signal representing a plane; means for extracting the hue of the three-dimensional image signal based on the two-dimensional image signal converted by the two-dimensional image signal; Means for setting the hue area of the three-dimensional image signal based on the two-dimensional image signal converted by the two-dimensional image signal converting means; and converting the hue extracted by the extracting means into the hue. Means for identifying which of the hue areas set by the area setting means is included in the hue area. 4. The color correction processing apparatus according to claim 1, wherein the extraction of the hue is performed through a plurality of processing steps. 5. The color correction processing circuit according to claim 4, wherein said plurality of processing steps include a hue rotational movement step. 6. The color as claimed in claim 1, wherein said means for converting into a two-dimensional image signal converts the image signal into a plane having an achromatic axis in a color space as an origin. Correction processing device. 7. The means for setting a hue area sets a hue boundary at a predetermined stage on a plane formed by a two-dimensional image signal representing a color plane at equal angular intervals with respect to an arbitrary point. 4. The color correction processing device according to claim 3, wherein: 8. The means for setting the hue region, wherein after extracting the hue of the predetermined stage, when extracting the hue of the next stage of the predetermined stage, the two-dimensional image signal is centered on the arbitrary point. The color correction processing device according to claim 7, wherein the color correction processing unit is rotated to extract the hue of the next stage.