JP4528805B2 - Image forming apparatus, image processing method, and image processing program - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that converts an input full-color image in RGB format into an image having a desired single hue and outputs the image.

Conventionally, in an image forming apparatus such as a color printer, input RGB color image data is converted into corresponding CMYK format image data by using a predetermined color conversion table (LUT) and printed. I am trying to output.
Specifically, as shown in the block diagram of FIG. 19, RGB format image data input by the image information input unit 101a is converted into CMYK format image data via a color conversion processing unit 102a including a color conversion table. The image information is output by the image information output unit 105a through each process in the gamma correction unit 103a and the screen processing unit 104a.
Therefore, in the field of color image forming apparatuses, how to faithfully reproduce primary colors is a priority issue.
However, depending on the user's usage, there may be a case where the output image is not always faithful to the primary color but a monochrome color such as black and white is desired, and there is a case where higher speed is desired than reproduction accuracy.

For this reason, a color image processing method for converting RGB values belonging to a predetermined full color area into a single color value and a device for performing color adjustment for each hue axis have been proposed (for example, see Patent Documents 1 and 2).
Specifically, according to the color image processing method described in Patent Document 1, target image data (RGB data) is converted into XYZ values, which are further converted into xyY values. Then, it is determined whether the xyY value belongs to any region of black, blue, red, yellow, and white, and a single color corresponding to the determination result is output.
In addition, the color adjustment device described in Patent Document 2 divides the hue axis in the chromaticity diagram into a plurality of parts and adjusts the hue, brightness, and color saturation for each hue axis selected from the divided hue axes. Be able to.

JP 2002-290750 A JP 2004-64198 A

However, among the previously proposed documents as described above, the color image processing method of Patent Document 1 aims at faithful reproduction at the time of outputting an image of a monochromatic subject, and is therefore effective for reproducing primary colors. However, it is inefficient as a means of converting a full-color subject into a monochrome monochrome color. Therefore, if both speeding-up is required, it is necessary to modify hardware, expand the ASIC scale, etc., leading to an increase in cost.
Further, by either method of Patent Document 1 or Patent Document 2, it is possible to output a black and white image, but it is impossible to output a monochrome image in other single hues (for example, red, green, and blue). Therefore, there is no room for the user to select a desired hue, which is inconvenient.

  The present invention has been proposed in order to solve the problems of the conventional techniques as described above, and an input full-color image can be easily converted into a single-color image as necessary and output. It is an object of the present invention to provide an image forming apparatus in which the user can arbitrarily select the hue and can realize these with a simple hardware / software configuration.

In order to achieve the above object, an image forming apparatus of the present invention includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated with each other in advance, and RGB data is obtained by referring to the color conversion table. An image forming apparatus that converts CMYK data into an output, and outputs first RGB / HCB conversion means for converting input RGB data into HCB data, and HCB obtained through the first RGB / HCB conversion means. The data is converted into RGB data by means other than the reverse conversion of the conversion means in the first RGB / HCB conversion means, and the hue value included in the HCB data is converted to a single hue value designated in advance. First HCB / RGB conversion means and RGB data obtained through the first HCB / RGB conversion means are converted into the color conversion table. Color conversion means for converting the CMYK data monochromatic phased by reference to Le, a configuration equipped with.

According to the image forming apparatus of the present invention having such a configuration, RGB data such as a full-color image as a subject is once converted into HCB data and unified into a single hue (single hue), and then the RGB data is again obtained. Processing to return to the format is performed.
The RGB data obtained as a result of the processing is converted into CMYK data by referring to the color conversion table and output.
Therefore, it is possible to easily generate and output monochrome color image data as required by a normal full-color image forming apparatus.

The color conversion table indispensable for the implementation of the present invention is not limited to the standard color conversion table provided in the full-color image forming apparatus, and the image forming apparatus of the present invention can be used with a simple algorithm. Can be realized.
In particular, with respect to the HCB / RGB conversion performed in the present invention, it is not necessary to perform reverse conversion of RGB / HCB conversion, and since RGB data is directly calculated, simple arithmetic processing is possible.

Therefore, it is possible to realize an image forming apparatus having a simple configuration in both software and hardware.
In addition, since an arbitrary hue can be selected as the single hue image to be output, it is possible to realize an image forming apparatus excellent in convenience and expandability.

The image forming apparatus of the present invention includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated with each other in advance, and converts RGB data into CMYK data by referring to the color conversion table. An image forming apparatus that performs output, wherein RGB data constituting the color conversion table is extracted and converted to HCB data, and obtained via the second RGB / HCB conversion means. The second HCB / RGB which converts the HCB data thus obtained into RGB data by another means different from the inverse conversion of the conversion means in the second RGB / HCB conversion means, and converts it into a single hue value designated in advance. Refer to the color conversion table for the RGB data obtained through the conversion means and the second HCB / RGB conversion means. Thus, the first color conversion means for converting to CMYK data, and the color conversion for generating another color conversion table by associating the RGB data with the CMYK data obtained through the first color conversion means A table generation unit and a second color conversion unit that converts the input RGB data into CMYK data that has been converted into a single hue by referring to the other color conversion table.

According to the image forming apparatus of the present invention having such a configuration, monochrome color image data is output by referring to a color conversion table processed for a single hue for input data such as a full-color image to be a subject. It is like that.
For this reason, it is necessary to generate a color conversion table for a single hue in advance. This is achieved by converting the RGB data on the color conversion table provided in advance into a single hue and associating the CMYK data with the new data. This can be easily realized by generating a simple color conversion table.

Specifically, RGB data set on the color conversion table is taken out, and the data is temporarily converted into HCB data.
Then, the hue value included in the HCB data is converted to data in the RGB data format again while replacing the hue value with one hue value.
Next, CMYK data is obtained by referring to the color conversion table for the RGB data obtained through these processes, and a color conversion table for a single hue is generated by associating the original RGB data. can do.
By using the color conversion table generated in this way, it becomes possible to obtain an output image that has been made into a single hue.

For this reason, it is possible to easily output monochrome color image data as required without any particular modification to the conventional full-color image forming apparatus.
Further, the image forming apparatus of the present invention can be realized by using a simple algorithm.
In particular, with respect to the HCB / RGB conversion performed in the present invention, RGB data can be calculated without performing the inverse conversion of RGB / HCB conversion, so that simple arithmetic processing is possible.
Therefore, it is possible to realize an image forming apparatus having a simple configuration in both software and hardware.
In addition, since an arbitrary hue can be selected as the single hue image to be output, it is possible to realize an image forming apparatus excellent in convenience and expandability.

In the image forming apparatus of the present invention , the first or second HCB / RGB conversion means relates to RGB data (A {r, g, b}) at an arbitrary point A in the RGB three-dimensional space. Alternatively , a triangle WPK having the maximum saturation point P, the white point W, and the black point K at the hue value H included in the HCB data obtained via the second RGB / HCB conversion means is formed, and this triangle WPK is formed. And the area division ratio (Sp, Sw, Sk) of the three triangles (KAW, PAK, WAP) formed by two of the vertices from the point A, and the following equation: The RGB data (A after replacing the hue value H included in the HCB data obtained through the first or second RGB / HCB conversion means with one hue value H ′ specified in advance by calculation. '{R', g ', b'}) The image forming apparatus according to claim 1 or 2, characterized in that conversion.
A ′ {r ′, g ′, b ′} = Sp * P ′ {P′r, P′g, P′b} + Sw * W {1,1,1} + Sk * K {0, 0, 0} (However, P ′ {r ′, g ′, b ′} is the maximum saturation point corresponding to the hue value H ′.)

According to the image forming apparatus of the present invention having such a configuration, with respect to the HCB / RGB conversion, after the original RGB / HCB conversion is performed without reverse conversion of the original RGB / HCB conversion, RGB data can be acquired.
Specifically, RGB data can be easily and directly calculated by capturing a part of the RGB color space expressed in three dimensions two-dimensionally.
In particular, the RGB data (A ′ {r ′, g ′, b ′}) to be obtained can be obtained more easily by calculating the above formula using the area of the triangle using the maximum saturation point. It has become.
Therefore, in particular, it is possible to realize an image forming apparatus having a simple algorithm.

The image forming apparatus of the present invention, a color conversion table storing means for previously storing one or more other color conversion table generated by the color conversion table generating means, in response to the input operation, the predetermined color conversion A reference table selection unit that selects any one of the table or the one or more other color conversion tables, and the second color conversion unit selects the input image data as the selected image data. By referring to one reference table, it is converted to CMYK data that is made into a single hue.

According to the image forming apparatus of the present invention having such a configuration, a color conversion table for a plurality of single hues is prepared in advance in addition to a standard color conversion table, and a user's color conversion table is prepared from them. One color conversion table can be selected arbitrarily.
By referring to the color conversion table corresponding to the selection of the input image, it is possible to flexibly output a normal full-color image or a monochromatic image.
Therefore, it is possible to realize an image forming apparatus that is excellent in convenience and expandability.

The image processing method of the present invention includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated with each other in advance, and converts RGB data into CMYK data by referring to the color conversion table. An image processing method for outputting predetermined input image data in a single hue by an image forming apparatus that performs output, wherein the input RGB data is converted into HCB data; and The HCB data obtained through one step is converted into RGB data by another means different from the inverse conversion performed in the first step, and is converted to a single hue value specified in advance. The RGB data obtained through the second step and the second step are monochromatic by referring to the color conversion table. A third step of converting into MYK data and as a method having.
The image processing method of the present invention includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated with each other in advance, and converts RGB data into CMYK data by referring to the color conversion table. An image processing method in which predetermined input image data is converted into a single hue and output by an image forming apparatus that performs output, and RGB data constituting the color conversion table is extracted and converted into HCB data. The HCB data obtained through the first step and the first step are converted into RGB data by another means different from the inverse transformation of the conversion means performed in the first step, and designated in advance. A second step for making a single hue value into one hue value and the RGB data obtained through the second step are referred to the color conversion table. The fourth step of generating another color conversion table by associating the third step of converting to CMYK data with the RGB data and the CMYK data obtained through the third step And a fifth step of converting the input RGB data into CMYK data that is made into a single hue by referring to the other color conversion table.

Thus, the present invention can be realized not only as the device invention described above but also as a method invention.
Therefore, the present invention can be carried out without being limited by the hardware configuration, and thus can be provided as a method having excellent versatility and expandability, and the present invention can be realized in various forms.

The image processing program of the present invention includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated in advance, and converts RGB data into CMYK data by referring to the color conversion table. An image processing program for outputting predetermined input image data into a single hue by an image forming apparatus that performs output, and outputting the input RGB data to HCB data by a computer constituting the image forming apparatus. First RGB / HCB conversion means for converting, HCB data obtained via the first RGB / HCB conversion means is converted into RGB data by other means different from the reverse conversion of the conversion means in the first RGB / HCB conversion means. First HCB / RGB conversion means for converting to a single hue value in advance and The RGB data obtained through the first HCB / RGB conversion unit is a program for functioning as a color conversion means for converting the CMYK data monochromatic phased by reference to the color conversion table.
The image processing program of the present invention includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated in advance, and converts RGB data into CMYK data by referring to the color conversion table. An image processing program for outputting predetermined input image data in an arbitrary hue by an image forming apparatus that performs output, and outputting the RGB data that configures the color conversion table to the computer that configures the image forming apparatus The second RGB / HCB conversion means for extracting the HCB data and converting the HCB data obtained via the second RGB / HCB conversion means to the inverse conversion of the conversion means in the second RGB / HCB conversion means Convert to RGB data by other different means, and make a single hue into one specified hue value CB / RGB conversion means, first color conversion means for converting RGB data obtained via the second HCB / RGB conversion means into CMYK data by referring to the color conversion table, the RGB data and the By associating the CMYK data obtained through the first color conversion means, a color conversion table generation means for generating another color conversion table, and the input RGB data is referred to the other color conversion table. Thus, the program is made to function as second color conversion means for converting into monochromatic CMYK data.

Thus, the present invention can also be realized as a program.
As a result, the present invention can be realized by installing a program not only in a printer but also in various image forming apparatuses having a computer function, such as an image scanner and a copying machine, and has excellent versatility and expandability. It can be provided as a processing program.

  As described above, according to the image processing apparatus and the like of the present invention, it is possible to easily realize that a target full-color image is converted into a single hue and output.

A preferred embodiment of the present invention will be described below with reference to FIGS.
Here, the image forming apparatus of the present embodiment described below is realized by processing, means, and functions executed by a computer according to instructions of a program (software). The program sends a command to each component of the computer to perform predetermined processing and functions as shown below. That is, each process / means in the image forming apparatus of the present embodiment is realized by specific means in which a program and a computer cooperate.
Note that all or part of the program is provided by, for example, a magnetic disk, optical disk, semiconductor memory, or any other computer-readable recording medium, and the program read from the recording medium is installed in the computer and executed. The The program can also be loaded and executed directly on a computer through a communication line without using a recording medium.

[First embodiment]
FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus according to the first embodiment of the present invention.
As shown in FIG. 1, the image forming apparatus according to the present embodiment includes an image information input unit 101, a monochromatic processing unit 500, a color conversion processing unit 102, a gamma correction unit 103, a screen processing unit 104, and an image information output unit 105. Composed.
Hereinafter, each part constituting the image forming apparatus of the present embodiment will be described in detail.

The image information input unit 101 inputs image data such as a full-color image. Specifically, the image information input unit 101 constitutes an interface for inputting RGB format image data from an external host computer or the like.
The single hue conversion processing unit 500 converts the image data input by the image information input unit 101 into a desired hue and delivers the data to the color conversion processing unit 102 described later.
Specifically, the first RGB / HCB conversion means and the first HCB / RGB conversion means of the present invention are used.

The first RGB / HCB conversion means converts the input RGB data into HCB format image data, whereby each data of hue value (H), saturation value (C), and lightness value (B) is obtained. Can be requested.
The first HCB / RGB conversion means replaces the hue value (H) included in the HCB data acquired by the first RGB / HCB conversion means with an arbitrary hue (H ′) designated by the user to make a single hue. At the same time, the HCB data (H′CB) is converted into the data format (RGB data) of the original image.
In particular, in the present embodiment, the RGB data is acquired by another arithmetic expression without using the method of inversely converting the conversion method used in the first RGB / HCB conversion means.
The specific method of the RGB data to HCB data conversion method (first RGB / HCB conversion means) and the HCB data to RGB data conversion method (first HCB / RGB conversion means) will be described in detail later. To do.

The color conversion processing unit 102 converts image data obtained through the processing of the single hue conversion processing unit 500 into image data in an output format, and constitutes color conversion means of the present invention.
Specifically, the RGB data acquired via the first HCB / RGB conversion means is converted into CMYK data.
The gamma correction unit 103 corrects a predetermined gamma characteristic for the CMYK data acquired via the color conversion processing unit 102, and the screen processing unit 104 prevents the CMYK data from causing interference. The gradation level is adjusted.

Here, the monochromatic process in the image forming apparatus of the present embodiment having the above-described configuration will be described in detail with reference to the drawings.
FIG. 2 is a flowchart for explaining the monochromatic processing in the monochromatic processing section 500 of the image forming apparatus according to the present embodiment.
As shown in FIG. 2 and the above, the monochromatic processing unit 500 starts by inputting RGB data as an original image from an external host computer or the like (A501).
The RGB data of the input original image is subjected to RGB / HCB conversion by the first RGB / HCB conversion means of the present invention (A502), and HCB data is generated (A503).

Here, a specific method of the RGB / HCB conversion (first RGB / HCB conversion means) will be described in detail with reference to FIGS.
FIG. 3 is an explanatory diagram that three-dimensionally represents the RGB space, in which the line segment W-K is a straight line L (r = g = b).
FIG. 4 is an explanatory diagram showing the RGB space shown in FIG. 3 rotated so that the straight line L is vertical. Further, FIG. 5 is a diagram when these diagrams are viewed from the diagonal W point direction. It is explanatory drawing. Thus, by representing the RGB data and the CMYK data in a ring shape, the hue can be indicated by an angle (hue angle) in the range of 0 ° to 360 °.

Here, as shown in FIG. 6, when there is an arbitrary point A {r, g, b} in the RGB space, the coordinate value of the point E when the foot of the perpendicular to the straight line L is the point E Calculate using the following formula.
E = {(r + g + b) / 3, (r + g + b) / 3, (r + g + b) / 3}}
Since the saturation corresponding to an arbitrary RGB value corresponds to the length of the line segment EA, the saturation value C can be calculated by the following calculation.
C = (EA × EA) ^0.5 = | EA |
However, EA = {r− (r + g + b) / 3, g− (r + g + b) / 3, b− (r + g + b) / 3}.

  Next, in calculating the hue value H corresponding to an arbitrary RGB value, it is necessary to set a reference hue direction in advance. The hue direction can be arbitrarily set. Here, for example, as shown in FIGS. 6 and 7, the red point (R) is a point F, and the hue direction, that is, the point F {1, 0, 0} direction is set to a hue angle of 0 °, and a perpendicular foot drawn from the point F to the straight line L is defined as a point Z. Vectors EA and ZF are obtained, and hues corresponding to angles formed by these vectors (hue angles) The value H is calculated.

Specifically, the hue value (hue angle) H can be obtained by the following calculation on a program (for example, C language).
H = ArcCos [(EA.ZF) / ((EA.EA) ^. 5) x ((ZF.ZF) ^. 5)] * (sign)
However, F = {1,0,0}, Z = {1 / 3,1 / 3,1 / 3}, ZF = {2/3, -1 / 3, -1 / 3}, and sign is Use the sign when calculating the inner product of the outer product of the vector EA and the vector ZF and the direction vector {1, 1, 1} of the straight line L, for example, set to +1 if positive and -1 if negative Or vice versa. The sign EA is multiplied by ArcCos [(EA.ZF) / ((EA.EA) ^. 5) x ((ZF.ZF) ^. 5)] This is because even if the angle is advanced in the clockwise direction with respect to the vector ZF, the same value is generated even if the angle is delayed by the same amount in the counterclockwise direction. This is to define it.

Instead of the sign function, unit vectors may be obtained at the time of obtaining the vectors EA and ZF, then these outer products may be obtained, the inner product S with the direction vector of the straight line L may be calculated, and the result may be multiplied.
That is, S = {(EA * ZF) / | (EA * ZF) |}. {WK / | WK |}
H = Cos-1 {(EA.ZF) / (| EA | x | ZF |)} xS
The hue angle may be obtained by (where a * b means the outer product of the vectors a and b, a.b means the inner product of the vectors a and b, and | a | is the magnitude of the vector a) Means).
When an arbitrary point is located on the straight line L, a predetermined hue value that is provisionally determined may be assigned temporarily.

Next, in calculating the lightness value B corresponding to an arbitrary RGB value, the length of the line segment IE when the black point (K) is the point I {0, 0, 0} corresponds to the lightness value. Specifically, the brightness value B can be calculated by the following calculation.
B = EI.EI ^ (. 5) = | EI |
As described above, HCB data corresponding to arbitrary RGB data can be calculated.

On the other hand, returning to the main flow of FIG. 2, the user selects a desired hue and designates in advance one hue value (H ′) for making a single hue (A504).
Specifically, as shown in FIG. 8, a desired color selection unit 801 and a desired hue value calculation unit 802 perform the following processes, respectively.
The desired color selection unit 801 displays a hue circle, a predetermined patch image, and the like on which a hue gradually changes and all hues are displayed as shown in FIG. Select by pointing device. The hue circle shown in FIG. 9 is a monochrome display, but is actually shown as a chromatic full-color display.
Further, unlike the above, the RGB values may be read by the user directly inputting the desired RGB values.
Then, the desired hue value calculation unit 802 converts the RGB values into HCB data by means similar to the step A502 (first RGB / HCB conversion means), so that a desired hue value (H ′) is obtained. Can be extracted.

Next, the hue value (H) included in the HCB value of the original image obtained in step A503 is replaced with the desired hue value (H ′) (A505), and the other HCB data (H′CB) is replaced. Obtain (A506).
Then, HCB / RGB conversion is performed on the image data (H′CB) obtained in step A506 (A507), so that the data format (RGB data) is the same as that of the original image and is made into a single hue. Image data (R′G′B ′) is obtained (A508).
That is, by performing Step A504 to Step A508, the first HCB / RGB conversion means of the present invention is executed.

Here, the HCB / RGB conversion performed in step A507 of the present embodiment is not simply an inverse conversion of RGB / HCB conversion, but based on a special technique, and will be described in detail below.
First, as shown in FIG. 10, each RGB value (RGB value of point A in the example of FIG. 10) constituting the original image and the RGB value of the maximum saturation point P in the same hue are extracted, and the HCB value is obtained. Calculate in advance.
FIG. 10 is an explanatory view showing a maximum saturation point (point P) of a hue including an arbitrary point A and a hue plane (triangle) composed of the points P, W and K on the RGB three-dimensional space. FIG. 11 is an explanatory diagram showing FIG. 10 so that the line segment KW (straight line L) is vertical.

Note that the RGB value of the maximum saturation point P in the same hue as the arbitrary point A {r, g, b} can be obtained by the following calculation formula.
P = (A−Min [A]) / Max [(A−Min [A])]
(However, Min [A] is the smallest value in {r, g, b}, Max [A] is the largest value in {r, g, b}, and A-Min [A] is , Meaning Min [A] is subtracted from each element of point A)

Next, at the four points of maximum saturation point P, white point W, black point K, and point A thus determined, the line segments AW, AK, AP and triangles are obtained using the CB values after the HCB conversion. A small triangle formed by each side of the WPK is set, and a ratio (Sp, Sw, Sk) by which each small triangle divides the triangle WPK in terms of area is obtained.
Specifically, as shown in FIG. 12, after setting the hue plane (triangle WPK) including the point A, only the triangle WPK is extracted as shown in FIG. 13, and then, as shown in FIG. Small triangles KAW, PAK, and WAP that constitute the WPK are set.
Then, the area ratios Sp, Sw, Sk when the area values of the set triangles are ΔWPK, ΔKAW, ΔPAK, ΔWAP are obtained by the following equations.
Sp = △ KAW / △ WPK
Sw = △ PAK / △ WPK
Sk = △ WAP / △ WPK

As a method for calculating ΔKAW, ΔPAK, ΔWAP, for example, a vector AW, a vector AP, and a vector AK with a point A as a fulcrum are obtained, and then a formula for the area of a triangle in a two-dimensional plane is applied Can be sought.
For example, the area S of the triangle OAB when the vector OA {a, b} and the vector OB {c, d} are assumed on the two-dimensional plane can be obtained by the following calculation formula.
S = (1/2) | ad-bc |
(Where | a | means the absolute value of vector a)
In addition, since the hue value H is the same, the calculation result can be easily obtained because it is only necessary to calculate in consideration of the CB value.
On the other hand, ΔWPK may be calculated by the same method as described above, or may be obtained by obtaining the sum of ΔKAW, ΔPAK, and ΔWAP.

Next, RGB data that has been converted into a single hue to an arbitrary hue value (H ′) can be obtained by the following equation using the area ratio.
A ′ {r ′, g ′, b ′} = Sp * P ′ {P′r, P′g, P′b} + Sw * W {1,1,1} + Sk * K {0, 0, 0} (However, the point P ′ is the maximum saturation point corresponding to the hue value H ′.)

  The RGB data (A ′ {r ′, g ′, b ′}) thus obtained is converted into CMYK data by the color conversion processing unit 102 and printed by the image information output unit 105 as described above. It will be output.

  As described above, according to the image forming apparatus of the present embodiment, the single hue conversion processing unit 500 temporarily converts the input RGB data into HCB data, of which the hue value (H) is an arbitrary hue value (H ′ ) And reverse conversion to RGB data, and by referring to the color conversion table for the RGB data (R′G′B ′), it is possible to output monochromatic CMYK data. .

For this reason, not only can a full-color image be output, but also a single-colored image can be acquired as necessary, and the convenience of the image forming apparatus can be improved.
In addition, since a color conversion processing unit (color conversion table) that is provided as a standard in conventional full-color image forming apparatuses can be used as it is, no special modification is required, and simple program changes can be used. The present invention can be realized.
Therefore, it is possible to provide the image forming apparatus of the present invention easily and at low cost.
Furthermore, since the user can specify an arbitrary hue value, it is possible to further improve convenience and provide an image forming apparatus with excellent expandability.

[Second Embodiment]
Next, an image forming apparatus according to a second embodiment of the present invention will be described with reference to FIGS. 15 and 16.
FIG. 15 is a block diagram showing a schematic configuration of an image forming apparatus according to the second embodiment of the present invention.
As shown in FIG. 15, the image forming apparatus of the present embodiment has substantially the same configuration as that of the first embodiment described above, but a color conversion processing unit 102 (color conversion table) processed in advance for a single hue. It is characterized by having.
For this reason, the input RGB image data can be processed simultaneously with the single hue conversion processing and the conversion processing into CMYK data by referring to the color conversion table for single hue.

  Here, the color conversion processing unit 102 includes second RGB / HCB conversion means, second HCB / RGB conversion means, first color conversion means, and color conversion table generation means of the present invention. By referring to the color conversion table generated by the color conversion table generating means, it is possible to output monochromatic image data.

The second RGB / HCB conversion means extracts input side data (RGB data) on a color conversion table (not shown) provided as a standard in the image forming apparatus, and converts the data into HCB format image data. Is. Thereby, each data of hue value (H), saturation value (C), and lightness value (B) can be acquired.
The specific method of the second RGB / HCB conversion means is substantially the same as that of the first RGB / HCB conversion means of the present invention, and a detailed description thereof will be omitted.

The second HCB / RGB conversion means replaces the hue value (H) included in the HCB data acquired by the second RGB / HCB conversion means with an arbitrary hue (H ′) designated by the user to make a single hue. At the same time, the HCB data (H′CB) is converted into the data format (RGB data) of the original image.
In particular, the second HCB / RGB conversion means is characterized in that the RGB data is obtained by another arithmetic expression without using the inverse conversion of the second RGB / HCB conversion means described above. Since it is the same as one HCB / RGB conversion means, detailed description is omitted.

The first color conversion means converts the RGB data acquired via the second HCB / RGB conversion means into CMYK data by referring to a standard color conversion table.
The color conversion table generation unit generates a new color conversion table by associating the CMYK data obtained through the first color conversion unit with the original RGB data.
Then, by referring to the generated color conversion table, the input image data (RGB) is converted into monochromatic CMYK data (second color conversion means of the present invention).
Since the gamma correction unit 103 and the screen processing unit 104 are the same as those in the first embodiment described above, detailed description thereof is omitted.

Here, the monochromatic process in the image forming apparatus of the present embodiment having the above-described configuration will be described in detail with reference to the drawings.
FIG. 16 is a flowchart for explaining the monochromatic processing in the color conversion processing unit 102 of the image forming apparatus according to the present embodiment.
As shown in FIG. 16, the processing of the color conversion processing unit 102 according to the present embodiment is substantially the same procedure as in the first embodiment described above, but in this embodiment, a standard for a full-color image forming apparatus. (B501), which starts from extracting input data (RGB data) at grid points on the three-dimensional color conversion table provided in (B501).
The extracted RGB data is subjected to RGB / HCB conversion by the second RGB / HCB conversion means (B502), and HCB data is generated (B503).
Next, the user selects a desired hue, specifically calculates the hue value, and designates in advance one hue (H ′) for making a single hue (B504).

Thus, the hue value (H) of the HCB value obtained in step B503 is replaced with the desired hue value (H ′) (B505), and other HCB data (H′CB) is acquired ( B506).
Further, by performing HCB / RGB conversion on the image data (H′CB) obtained in step B506 (B507), the data format (RGB data) is the same as that of the original image and is made into a single hue. Image data (R′G′B ′) can be obtained (B508).
That is, the second HCB / RGB conversion means of the present invention is executed by performing Step B504 to Step B508.
For details on the second HCB / RGB conversion means, refer to the description in the first embodiment.

The image data (R′G′B ′) obtained through step B508 is converted into output format CMYK data by referring to a standard color conversion table (B509). ), Monochromatic CMYK data is acquired (B510).
Next, a new color conversion table is generated by associating the CMYK data obtained in step B510 with the RGB data (B511).

  In this way, by using the color conversion table that is standardly provided in the full-color image forming apparatus, it is possible to generate another color conversion table that has been converted into a single hue, and the input RGB image data is By referring to this color conversion table, the image data is output as image data converted to a predetermined output format while being converted to a single hue.

As described above, according to the image forming apparatus of the present embodiment, the input RGB image data is not converted into a single hue as in the first embodiment, but a color conversion table converted into a single hue is provided in advance. By referring to the color conversion table, a monochrome color image can be output.
Therefore, not only can the same effect as the first embodiment described above be exhibited, but also output processing can be speeded up, and a more convenient image forming apparatus can be realized.

[Third embodiment]
Next, an image forming apparatus according to a third embodiment of the present invention will be described with reference to FIG.
FIG. 17 is a block diagram showing a schematic configuration of an image forming apparatus according to the third embodiment of the present invention.
As shown in FIG. 17, the image forming apparatus according to the present embodiment has substantially the same configuration as that of the second embodiment described above. However, the color conversion processing unit 102a provided as a standard in the full-color image forming apparatus and Separately, the color conversion processing unit 102 for single hue is stored in advance by the color conversion table storage means of the present invention.
In addition, a changeover switch 201 is provided, and each color conversion processing unit (color conversion table) referred to for color conversion processing of input image data can be arbitrarily selected to constitute the reference table selection means of the present invention. This is also characteristic.

  For this reason, the user can freely select the color conversion table, and can output data of a full-color image or a single-color image according to the usage mode.

  As described above, according to the image forming apparatus of the present embodiment, not only the same effects as those of the second embodiment are exhibited, but also the color conversion processing unit 102a for full color and the color conversion processing unit for single hue. 102 and the changeover switch 201, the output image can be switched as necessary, and the convenience can be further improved.

[Fourth embodiment]
Next, an image forming apparatus according to a fourth embodiment of the present invention will be described with reference to FIG.
FIG. 18 is a block diagram showing a schematic configuration of an image forming apparatus according to the fourth embodiment of the present invention.
As shown in FIG. 18, the image forming apparatus according to the present embodiment has substantially the same configuration as that of the third embodiment described above. It is different in that an arbitrary color conversion table can be downloaded.

  Specifically, the color conversion processing unit 102a provided as a standard is set as an initial setting, and one color conversion table is downloaded from the color table group 202 stored in advance by the color conversion table storage means of the present invention. Thus, a color conversion processing unit 102 that can flexibly perform a single hue process is provided. One of these color conversion tables can be switched by the changeover switch 201 by the reference table selection means of the present invention.

  For this reason, the user can output a normal full-color image, and if necessary, selects an arbitrary color conversion table from a plurality of color conversion tables converted into a single hue, and obtains a desired monochrome image. Can be output.

  As described above, according to the image forming apparatus of the present embodiment, not only the same effects as those of the above-described embodiments are exhibited, but also a plurality of hue variations of the single-hue image data to be output can be owned. Therefore, it is possible to realize an image forming apparatus that is more convenient and expandable.

The image forming apparatus according to the present invention has been described with reference to the preferred embodiment. However, the image forming apparatus according to the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. It goes without saying that implementation is possible.
For example, in the image forming apparatus of the present invention, the first data conversion means converts RGB data into a data format other than HCB data (for example, HSV, HSL, HLS, HSI, etc.), and reverse conversion thereof. The structure to utilize may be sufficient.
Thereby, the scope of the embodiment is further expanded, and the expandability can be further improved.

  The present invention can be suitably used for an image forming apparatus including a color conversion unit that performs color conversion by referring to a color conversion table.

1 is a block diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 4 is a flowchart for explaining a monochromatic process in the image forming apparatus according to the first embodiment. It is explanatory drawing for demonstrating the RGB space used logically in the image forming apparatus which concerns on 1st embodiment. It is the figure which rotated and expressed the RGB space shown in FIG. 3 so that the straight line L which consists of line segment WK might become vertical. It is a figure at the time of seeing the RGB space shown in FIG. 3 from the W point direction of the straight line L. FIG. It is explanatory drawing for demonstrating the saturation and the lightness in the arbitrary points A on RGB space shown in FIG. FIG. 7 is a diagram when an arbitrary point A in the RGB space shown in FIG. 6 is viewed from the direction of the W point of the straight line L. FIG. 5 is an explanatory diagram for describing a method for extracting a desired hue in the image forming apparatus according to the first embodiment. FIG. 3 is an explanatory diagram illustrating an example of a desired hue selection image in the image forming apparatus according to the first embodiment. FIG. 4 is an explanatory view showing a maximum saturation point (point P) of a hue including an arbitrary point A and a hue plane (triangle) including points P, W and K on the RGB space shown in FIG. 3. It is explanatory drawing which represented the arbitrary points A in RGB space shown in FIG. 10 so that the straight line L might become perpendicular | vertical. It is explanatory drawing which represented the hue surface (triangle) which consists of the point A in RGB space shown in FIG. 10, the maximum saturation point P, the point W, and the point K so that the straight line L might become perpendicular | vertical. It is explanatory drawing at the time of taking out the hue surface (triangle) which consists of the maximum saturation point P, the point W, and the point K from the RGB space shown in FIG. It is explanatory drawing showing the small triangles KAW, PAK, and WAP which comprise the triangle WPK shown in FIG. 13, and the triangle WPK. It is a block diagram which shows schematic structure of the image forming apparatus which concerns on 2nd embodiment. 10 is a flowchart for explaining a monochromatic process of the image forming apparatus according to the second embodiment. It is a block diagram which shows schematic structure of the image forming apparatus which concerns on 3rd embodiment. It is a block diagram which shows schematic structure of the image forming apparatus which concerns on 4th embodiment. It is a block diagram which shows schematic structure of the conventional image forming apparatus.

Explanation of symbols

101 Image information input unit 102 Color conversion processing unit (single hue)
102a Color conversion processor (full color)
105 Image information output unit 500 Monochromatic processing unit 201 Changeover switch 202 Color table group

Claims (7)

An image forming apparatus that includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated in advance, converts RGB data into CMYK data by referring to the color conversion table, and outputs the converted data.
First RGB / HCB conversion means for converting input RGB data into HCB data;
The HCB data obtained via the first RGB / HCB conversion means is converted into RGB data by means other than the reverse conversion of the conversion means in the first RGB / HCB conversion means, and is included in the HCB data. First HCB / RGB conversion means for converting the hue value to be a single hue into a predetermined hue value;
Color conversion means for converting RGB data obtained via the first HCB / RGB conversion means into CMYK data that is made into a single hue by referring to the color conversion table ;
The first HCB / RGB conversion means includes:
The maximum saturation in the hue value H included in the HCB data obtained through the first RGB / HCB conversion means for the RGB data (A {r, g, b}) at an arbitrary point A in the RGB three-dimensional space. A triangle WPK having points P, white points W, and black points K as vertices is formed, and three triangles (KAW, PAK) formed by the triangle WPK and the point A and two of the vertices are formed. , WAP) and calculating the following expression after calculating the area division ratio (Sp, Sw, Sk), and included in the HCB data obtained through the first RGB / HCB conversion means the hue value H, 'as well as replacing the predetermined RGB data (a' pre-specified one hue value H {r ', g', b '}) the image forming apparatus characterized that you convert.
A ′ {r ′, g ′, b ′} = Sp * P ′ {P′r, P′g, P′b} + Sw * W {1,1,1} + Sk * K {0, 0, 0} (However, P ′ {P′r, P′g, P′b} is the maximum saturation point corresponding to the hue value H ′.) An image forming apparatus that includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated in advance, converts RGB data into CMYK data by referring to the color conversion table, and outputs the converted data.
Second RGB / HCB data conversion means for extracting RGB data constituting the color conversion table and converting the RGB data into HCB data;
The HCB data obtained via the second RGB / HCB conversion means is converted into RGB data by means other than the reverse conversion of the conversion means in the second RGB / HCB conversion means, A second HCB / RGB conversion means for converting the hue value into a single hue;
First color conversion means for converting RGB data obtained via the second HCB / RGB conversion means into CMYK data by referring to the color conversion table;
Color conversion table generation means for generating another color conversion table by associating the RGB data with the CMYK data obtained via the first color conversion means;
Second color conversion means for converting the input RGB data into CMYK data that has been made into a single hue by referring to the other color conversion table ;
The second HCB / RGB conversion means includes:
The maximum saturation in the hue value H included in the HCB data obtained through the second RGB / HCB conversion means for the RGB data (A {r, g, b}) at an arbitrary point A in the RGB three-dimensional space A triangle WPK having points P, white points W, and black points K as vertices is formed, and three triangles (KAW, PAK) formed by the triangle WPK and the point A and two of the vertices are formed. , WAP) and calculating the following expression after calculating the area division ratio (Sp, Sw, Sk), and included in the HCB data obtained through the second RGB / HCB conversion means the hue value H, 'as well as replacing the predetermined RGB data (a' pre-specified one hue value H {r ', g', b '}) the image forming apparatus characterized that you convert.
A ′ {r ′, g ′, b ′} = Sp * P ′ {P′r, P′g, P′b} + Sw * W {1,1,1} + Sk * K {0, 0, 0} (However, P ′ {P′r, P′g, P′b} is the maximum saturation point corresponding to the hue value H ′.) Color conversion table storage means for storing in advance one or more other color conversion tables generated by the color conversion table generation means;
Reference table selecting means for selecting any one of the predetermined color conversion table or the one or more other color conversion tables according to an input operation, and
The second color conversion means includes
The input image data, by referring to the one of the reference table selected, the image forming apparatus according to claim 2, wherein the converting the CMYK data into a single color of. An image forming apparatus that includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated with each other in advance and converts RGB data into CMYK data by referring to the color conversion table. An image processing method for converting input image data into an arbitrary hue and outputting it,
A first step of converting the input RGB data into HCB data;
The HCB data obtained through the first step is converted into RGB data by another means different from the inverse conversion performed in the first step, and the single hue value is converted into one predetermined hue value. The second step
The RGB data obtained through the second step, have a, a third step of converting the CMYK data monochromatic phased by reference to the color conversion table,
In the second step,
With respect to RGB data (A {r, g, b}) at an arbitrary point A in the RGB three-dimensional space, the maximum saturation point P and the white point at the hue value H included in the HCB data obtained in the first step. A triangle WPK having W and a black point K as vertices is formed, and this triangle WPK and three triangles (KAW, PAK, WAP) formed by the point A and two of the vertices After calculating the area-wise division ratios (Sp, Sw, Sk), the hue value H included in the HCB data obtained in the first step is calculated by calculating the following equation. 'while replacing the predetermined RGB data (a' hue value H {r ', g', b '}) an image processing method that converts into.
A ′ {r ′, g ′, b ′} = Sp * P ′ {P′r, P′g, P′b} + Sw * W {1,1,1} + Sk * K {0, 0, 0} (However, P ′ {P′r, P′g, P′b} is the maximum saturation point corresponding to the hue value H ′.) An image forming apparatus that includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated with each other in advance and converts RGB data into CMYK data by referring to the color conversion table. An image processing method for converting input image data into an arbitrary hue and outputting it,
A first step of extracting RGB data constituting the color conversion table and converting it into HCB data;
The HCB data obtained through the first step is converted into RGB data by another means different from the inverse conversion performed in the first step, and the single color value is converted into one predetermined hue value. A second step to phase,
A third step of converting the RGB data obtained through the second step into CMYK data by referring to the color conversion table;
A fourth step of generating another color conversion table by associating the RGB data with the CMYK data obtained through the third step;
The RGB data inputted, by referring to the other color conversion table, it possesses a fifth step of converting the CMYK data into a single color of, a,
In the second step,
With respect to RGB data (A {r, g, b}) at an arbitrary point A in the RGB three-dimensional space, the maximum saturation point P and the white point at the hue value H included in the HCB data obtained in the first step. A triangle WPK having W and a black point K as vertices is formed, and the triangle WPK and three triangles (KAW, PAK, WAP) formed by the point A and two of the vertices are formed. After calculating the area-wise division ratios (Sp, Sw, Sk), the hue value H included in the HCB data obtained in the first step is calculated by calculating the following equation. 'while replacing the predetermined RGB data (a' hue value H {r ', g', b '}) an image processing method that converts into.
A ′ {r ′, g ′, b ′} = Sp * P ′ {P′r, P′g, P′b} + Sw * W {1,1,1} + Sk * K {0, 0, 0} (However, P ′ {P′r, P′g, P′b} is the maximum saturation point corresponding to the hue value H ′.) An image forming apparatus that includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated with each other in advance and converts RGB data into CMYK data by referring to the color conversion table. An image processing program for converting input image data into a single hue and outputting it,
A computer constituting the image forming apparatus;
First RGB / HCB conversion means for converting input RGB data into HCB data;
The HCB data obtained via the first RGB / HCB conversion means is converted into RGB data by means other than the reverse conversion of the conversion means in the first RGB / HCB conversion means, First HCB / RGB conversion means for converting the hue value into a single hue;
The RGB data obtained via the first HCB / RGB conversion means functions as color conversion means for converting the data into monochromatic CMYK data by referring to the color conversion table ,
The first HCB / RGB conversion means is
The maximum saturation in the hue value H included in the HCB data obtained through the first RGB / HCB conversion means for the RGB data (A {r, g, b}) at an arbitrary point A in the RGB three-dimensional space. A triangle WPK having points P, white points W, and black points K as vertices is formed, and three triangles (KAW, PAK) formed by the triangle WPK and the point A and two of the vertices are formed. , WAP) and calculating the following expression after calculating the area division ratio (Sp, Sw, Sk), and included in the HCB data obtained through the first RGB / HCB conversion means An image processing program for replacing a hue value H with a predetermined hue value H ′ and functioning as a means for converting into predetermined RGB data (A ′ {r ′, g ′, b ′}) .
A ′ {r ′, g ′, b ′} = Sp * P ′ {P′r, P′g, P′b} + Sw * W {1,1,1} + Sk * K {0, 0, 0} (However, P ′ {P′r, P′g, P′b} is the maximum saturation point corresponding to the hue value H ′.) An image forming apparatus that includes a three-dimensional color conversion table in which input RGB data and output CMYK data are associated with each other in advance and converts RGB data into CMYK data by referring to the color conversion table. An image processing program for converting input image data into a single hue and outputting it,
A computer constituting the image forming apparatus;
Second RGB / HCB conversion means for extracting RGB data constituting the color conversion table and converting it into HCB data;
The HCB data obtained via the second RGB / HCB conversion means is converted into RGB data by means other than the reverse conversion of the conversion means in the second RGB / HCB conversion means, A second HCB / RGB conversion means for converting the hue value into a single hue;
First color conversion means for converting RGB data obtained via the second HCB / RGB conversion means into CMYK data by referring to the color conversion table;
Color conversion table generating means for generating another color conversion table by associating the RGB data with the CMYK data obtained through the first color conversion means;
The input RGB data is made to function as a second color conversion unit that converts the input RGB data into CMYK data that is made into a single hue by referring to the other color conversion table .
The second HCB / RGB conversion means,
The maximum saturation in the hue value H included in the HCB data obtained through the second RGB / HCB conversion means for the RGB data (A {r, g, b}) at an arbitrary point A in the RGB three-dimensional space A triangle WPK having points P, white points W, and black points K as vertices is formed, and three triangles (KAW, PAK) formed by the triangle WPK and the point A and two of the vertices are formed. , WAP) and calculating the following expression after calculating the area division ratio (Sp, Sw, Sk), and included in the HCB data obtained through the second RGB / HCB conversion means An image processing program for replacing a hue value H with a predetermined hue value H ′ and functioning as a means for converting into predetermined RGB data (A ′ {r ′, g ′, b ′}) .
A ′ {r ′, g ′, b ′} = Sp * P ′ {P′r, P′g, P′b} + Sw * W {1,1,1} + Sk * K {0, 0, 0} (However, P ′ {P′r, P′g, P′b} is the maximum saturation point corresponding to the hue value H ′.)