JP5287349B2 - Image forming apparatus and color conversion apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus and a color conversion apparatus.

  In an electrophotographic image forming apparatus, an image is formed using a color toner that is a colored color material and a clear toner that is a transparent color material, and when the clear toner is used, the total amount of the color toner and the clear toner is determined. Some are configured to perform toner amount reduction control so as not to exceed the total toner amount limit value. Specifically, for example, there is a control that limits the clear toner amount based on the color toner amount and the total toner amount limit value (see, for example, Patent Document 1). In addition, when the clear toner is placed, there is a method using a color conversion parameter that uniformly reduces the amount of color toner as compared with the case where the clear toner is not placed (see, for example, Patent Document 2). Furthermore, the amount of color toner is different between the portion where the clear toner is placed and the portion where the clear toner is not placed, and the portion where the clear toner is placed is reduced by using a total toner amount limiting function (see FIG. For example, see Patent Document 2.)

JP 2007-11028 A JP 2007-155963 A

  The present invention provides an image forming apparatus and a color conversion apparatus that can suppress deterioration in color reproducibility in both the clear toner application portion and the non-application portion, and can also provide a visual effect when the clear toner is placed. The purpose is to provide.

According to a first aspect of the present invention, there is provided image forming means for forming an image using a transparent color material and a colored color material, and color material amount control for adjusting an amount of the colored color material used for image formation by the image forming means. The color material amount control means, when the transparent color material is the first amount, the first color conversion unit that specifies the amount of the color material corresponding to the first amount, and the transparent When the color material is a second amount different from the first amount, a plurality of color conversion units including a second color conversion unit that specifies the amount of the colored color material corresponding to the second amount, and the image When an amount of the transparent color material to be used by the forming unit is set, an interpolator that specifies the amount of the colored color material corresponding to the set amount by interpolating from the correspondence relationship of the plurality of color conversion units; An image forming apparatus including the image forming apparatus.
According to a second aspect of the present invention, the color material amount control unit includes a transparent color material amount adjusting unit that limits the set amount of the transparent color material to be used by the image forming unit and sets a new set amount. The image forming apparatus according to claim 1.
The invention according to claim 3 is characterized in that the plurality of color conversion units use a color difference minimum method for color gamut compression conversion for specifying the amount of the colored material. 2. The image forming apparatus according to 2.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second or third aspect, the color material amount control means is constituted by a direct look-up table.
According to a fifth aspect of the present invention, there is provided an information input means for inputting information relating to the amounts of the transparent color material and the colored color material used for image formation, and the transparent color material and the colored color material according to input information from the information input means. When the amount of color is specified, the amount of the color material is converted into a new amount so that the total amount of these combined does not exceed the color material total amount limit value, and the conversion mode is changed to the amount of the transparent color material. The color conversion device includes: a color conversion unit that makes a difference according to the information; and an information output unit that outputs information about the amount of the transparent color material and the converted color material.
The invention according to claim 6 is characterized in that the color conversion means specifies the amount of the color material corresponding to the first amount when the transparent color material is the first amount; and When the transparent color material is a second amount different from the first amount, a plurality of color conversion units including a second color conversion unit that specifies the amount of the colored color material corresponding to the second amount; and When the amount of the transparent color material is specified by the input information in the information input means, an interpolation for specifying the amount of the color material corresponding to the specified amount by interpolating from the correspondence relationship by the plurality of color conversion units The color conversion device according to claim 6, further comprising:
The invention according to claim 7 further comprises a transparent color material amount adjustment unit that limits the amount of the transparent color material specified by the input information in the information input means to make a new amount. Item 8. The color conversion device according to Item 6 or 7.
The invention according to claim 8 is characterized in that the plurality of color conversion units use a color difference minimum method for color gamut compression conversion for specifying the amount of the colored material. The color conversion device according to 7 or 8.

According to the inventions according to claims 1, 5 and 6, it is possible to suppress the occurrence of a color difference between the reduced portion and the non-reduced portion of the colored color material as compared with the case where the present configuration is not provided. And the visual effect by a transparent color material is acquired.
According to the second and seventh aspects of the invention, compared with the case where the present configuration is not provided, for example, in a region where there is a large amount of the color material that causes a problem of color reproducibility deterioration, the set amount of the transparent color material is set. It becomes possible to suppress the amount of the transparent color material by adding a restriction.
According to the third and eighth aspects of the invention, it is more effective in suppressing the color difference between the reduced portion and the non-reduced portion of the colored material compared to the case where the present configuration is not provided.
According to the fourth aspect of the present invention, the configuration of the image forming apparatus can be simplified as compared with the case where the present configuration is not provided.

1 is an explanatory diagram illustrating an example of a schematic configuration of an image forming apparatus. It is explanatory drawing which shows the other example of schematic structure of an image forming apparatus. It is explanatory drawing which shows an example of schematic structure of the color converter which concerns on this invention. It is explanatory drawing which shows the other example of schematic structure of the color converter which concerns on this invention. It is explanatory drawing which shows the outline | summary of the color gamut compression conversion by the color difference minimum method. FIG. 5 is an explanatory diagram specifically showing an outline of toner amount restriction performed by a clear toner adjustment unit. It is explanatory drawing which shows the outline | summary of the interpolation process which an interpolator performs concretely. 3 is an explanatory diagram specifically illustrating an outline of image formation in an image output apparatus based on a toner amount after color conversion. FIG.

  Hereinafter, an image forming apparatus and a color conversion apparatus according to the present invention will be described with reference to the drawings.

[Configuration example of image forming apparatus]
First, an image forming apparatus according to the present invention will be described.
The image forming apparatus described here outputs an image on a recording medium by an electrophotographic method, and is specifically used as a copying machine, a printer apparatus, or the like. Examples of the recording medium on which an image is output include printing paper such as plain paper or recycled paper, and an OHP sheet. However, there is no particular limitation on the type of the recording medium. Will be explained.

FIG. 1 is an explanatory diagram illustrating an example of a schematic configuration of an image forming apparatus.
The illustrated image forming apparatus includes an image forming unit 10 a and a control unit 20.

The image forming unit 10 a includes a plurality of (specifically, five) image forming units 11 to 15, an intermediate belt 16 as an image holding member, a secondary transfer device 17, and a fixing device 18. It is configured. That is, the image forming unit 10a in the illustrated example is a so-called “tandem method” in which five image forming units 11 to 15 are arranged in a line.
Each of the image forming units 11 to 15 forms an image through each process of charging → exposure → development → transfer. For this purpose, each of the image forming units 11 to 15 includes a photosensitive drum as an image carrier that is rotationally driven, a charger that uniformly charges the surface of the photosensitive drum, and a surface on the surface of the photosensitive drum. An exposure device that forms an electrostatic latent image, a developing device that develops an electrostatic latent image on the photosensitive drum to form a toner image, and a primary transfer that transfers the toner image on the photosensitive drum onto the intermediate belt 16 And a cleaning device for removing foreign matters such as residual toner on the photosensitive drum. However, each of the image forming units 11 to 15 performs image formation using a different color material (toner). Specifically, among the image forming units 11 to 15 arranged in a line, the image forming unit 11 at one end thereof (for example, the upstream end in the belt conveyance direction) uses clear toner that is a transparent color material. Then, image formation is performed. The other four image forming units 12 to 15 excluding the image forming unit 11 are colored color materials corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) ( An image is formed using a color toner. That is, each of the image forming units 11 to 15 functions as an image forming unit that forms an image using clear toner that is a transparent color material and color toner that is a color material.
The intermediate belt 16 is formed in an endless belt shape, and is circulated and driven at the same speed so as to pass through the primary transfer device in each of the image forming units 11 to 15, and is formed by each of the image forming units 11 to 15. The transferred toner images are transferred and overlaid. The intermediate belt 16 may be provided with a cleaning device that removes foreign matters such as residual toner and paper dust on the intermediate belt 16.
The secondary transfer device 17 transfers the toner image on the intermediate belt 16 that is an image holding member onto a sheet that is a recording medium.
The fixing device 18 executes a fixing process in the electrophotographic system, that is, performs a fixing process by heat and pressure on the paper after the toner image is transferred by the secondary transfer device 17, and performs the fixing process on the paper. The transferred image is fixed.
Since these constituent elements 11 to 18 are publicly known, explanations on details (for example, forming materials and operating principles) are omitted here.

The control unit 20 includes a CPU (Central Processing Unit) that functions as a microcomputer, and controls the operation of each of the constituent elements 11 to 18 in the above-described image forming unit 10a to control the image on the sheet. Processing such as output is performed.
Examples of the operation control performed by the control unit 20 include the following.
The control unit 20 adjusts the amounts of clear toner and color toner used for image formation in the image forming units 11 to 15 in the image output processing in the image forming unit 10a. That is, the control unit 20 functions as a color material amount control unit that controls the amount of toner used by each of the image forming units 11 to 15.
Of course, the control unit 20 can also perform other operation control without giving specific examples.

FIG. 2 is an explanatory diagram illustrating another example of the schematic configuration of the image forming apparatus.
In the illustrated image forming apparatus, the configuration of the image forming unit 10b is different from that of the above-described configuration example (see FIG. 1). That is, the image forming unit 10b in the image forming apparatus shown in the figure is of a so-called “rotary type” in which one image forming unit 19 is disposed.
The image forming unit 19 includes a plurality of developing units 19CT, 19Y, 19M, 19C, and 19K for one photosensitive drum 19D in order to support color images. Each of the developing devices 19CT, 19Y, 19M, 19C, and 19K performs image formation using a clear toner that is a transparent color material in addition to the color toner that is a color material. It is included. In other words, the image forming unit 19 includes a developing unit 19Y that develops a Y-color toner image, a developing unit 19M that develops an M-color toner image, a developing unit 19C that develops a C-color toner image, and a K-color toner image. A developing unit 19K for developing and a developing unit 19CT for developing a clear toner image are provided, and these are configured to selectively develop the latent image on the photosensitive drum 19D.
Note that other components in the image forming unit 19, such as a charger, an exposure device, a primary transfer device, and a cleaning device, are well known, and thus the description thereof is omitted here.
Further, the intermediate belt 16, the secondary transfer device 17, and the fixing device 18, which are components other than the image forming unit 19 in the image forming unit 10b, are the same as those in the above-described configuration example (see FIG. 1). .

  The control unit 20 that controls the operation of each of the components 16 to 19 in the image forming unit 10b is the same as in the configuration example described above (see FIG. 1). That is, the control unit 20 adjusts the amounts of clear toner and color toner used for image formation in the image forming unit 19 in image output processing in the image forming unit 10b.

[Configuration example of color conversion device]
Next, the control unit 20 that performs operation control on the image forming units 10a and 10b will be described in more detail.

  As described above, one of the control processes performed by the control unit 20 is toner amount control. The control unit 20 performs this toner amount control as described below. That is, when information related to the toner amount such as CMYK image information is input, the control unit 20 converts the input information into information related to a new toner amount while considering a preset total toner amount limit value. Thus, control adjustment is performed on the amount of toner used for image formation. That is, the control unit 20 functions as a color conversion device that converts information relating to the toner amount into information relating to a new toner amount.

FIG. 3 is an explanatory diagram showing an example of a schematic configuration of the color conversion apparatus according to the present invention.
In the illustrated example, the color conversion device corresponds to the control unit 20 or a part of the control unit 20 described above. Therefore, the same reference numerals as those of the control unit 20 are given to the color conversion device, and the following description will be given.

  The color conversion device 20 includes an information input terminal unit 21, an information output terminal unit 22, a first color conversion unit 23, a second color conversion unit 24, interpolators 25C, 25M, 25Y, and 25K, and clear. And a toner adjusting unit 26.

The information input terminal unit 21 is connected to the image input device 31 and receives information regarding the toner amount from the image input device 31.
Specific examples of the image input device 31 include a scanner device and a personal computer device, but are not particularly limited.
Examples of the toner amount information include image information for specifying the amount of toner of each color of CMYK and information for specifying the amount of clear toner, but the data format is not particularly limited.
That is, the information input terminal unit 21 functions as information input means for inputting information regarding the amounts of clear toner and color toner used for image formation.

The information output terminal unit 22 is connected to the image output device 32 and outputs information related to the toner amount after color conversion to the image output device 32.
The image output device 32 corresponds to the above-described image forming units 10a and 10b.
That is, the information output terminal unit 22 functions as information output means for outputting information about the amount of clear toner and the amount after color toner conversion.

In both the first color conversion unit 23 and the second color conversion unit 24, when the amounts of clear toner and color toner are specified by the input information at the information input terminal unit 21, the total amount of these is added in advance. The amount of the color toner is converted to a new amount so as not to exceed the set total toner amount limit value. That is, the first color conversion unit 23 and the second color conversion unit 24 function as part of the color conversion unit. Such first color conversion unit 23 and second color conversion unit 24 may be configured using, for example, a direct lookup table (hereinafter abbreviated as “DLUT”).
Among these, the first color conversion unit 23 specifies the amount of color toner corresponding to the first amount when the clear toner is the first amount. Examples of the first amount include a minimum value in the range of the assumed clear toner amount. That is, when the clear toner amount is 0%, the first color conversion unit 23 specifies the new color toner amount of each color so that the total amount of color toner of each color does not exceed the toner total amount limit value. It has become. More specifically, since the clear toner amount is 0%, the color conversion is performed so that the total color toner amount becomes the toner total amount limit value. From this, it can be said that the first color conversion unit 23 is designed to perform color conversion in a mode suitable for the case where the clear toner amount is 0%. Here, the mode of color conversion refers to an element that embodies the characteristics of the color conversion, such as the conditions for color conversion and the conversion result, and specifically, the color used for color conversion. The one specified by the conversion parameter.
On the other hand, the second color conversion unit 24 specifies the amount of color toner corresponding to the second amount when the clear toner is the second amount. Examples of the second amount include a maximum value in the range of the assumed clear toner amount. That is, when the clear toner amount is 100%, the second color conversion unit 24 sets the new color toner amount of each color so that the total amount of the clear toner and the color toner of each color does not exceed the toner total amount limit value. Is to identify. More specifically, since the clear toner amount is 100%, the color conversion is performed so that the total color toner amount becomes an amount obtained by subtracting the clear toner amount from the total toner amount limit value. From this, it can be said that the second color conversion unit 24 is designed to perform color conversion in a mode suitable for a case where the clear toner amount is 100%. That is, color conversion is performed in a manner different from that of the first color conversion unit 23.
Here, the case where the first color conversion unit 23 and the second color conversion unit 24 are provided is described as an example, but the color conversion device 20 includes a plurality of color conversion units including these. If it is. Therefore, it is conceivable to provide a third color conversion unit that performs color conversion in a manner different from the first color conversion unit 23 and the second color conversion unit 24.

  When the clear toner amount is specified by the input information at the information input terminal unit 21, the interpolators 25C, 25M, 25Y, and 25K convert the color toner amount corresponding to the specified amount to the first color conversion unit 23 and This is specified by interpolation from the correspondence relationship by the second color conversion unit 24. Therefore, for example, if the clear toner amount according to the input information is 50%, the conversion result in the first color conversion unit 23 corresponding to the case where the clear toner amount is 0% and the clear toner amount are 100%. Based on the conversion result in the second color conversion unit 24 corresponding to the case, the conversion result corresponding to the case where the clear toner amount is 50% is interpolated to obtain. In other words, the interpolators 25C, 25M, 25Y, and 25K use the plurality of color conversion units 23 and 24 to change the color conversion mode according to the clear toner amount based on the input information. Similar to the first color conversion unit 23 and the second color conversion unit 24, it functions as part of the color conversion means. The interpolation processing performed by the interpolators 25C, 25M, 25Y, and 25K may be performed using a known technique as will be described in detail later.

  When the clear toner amount is specified by the input information at the information input terminal unit 21, the clear toner adjusting unit 26 limits the specified amount to a new amount. The process for limiting the amount of clear toner may be performed according to a preset rule, as will be described in detail later. Note that when the clear toner adjustment unit 26 performs the clear toner amount restriction process, the clear toner amount after the restriction is used for the interpolation process by the interpolators 25C, 25M, 25Y, and 25K.

FIG. 4 is an explanatory diagram showing another example of the schematic configuration of the color conversion apparatus according to the present invention.
The color conversion device 20 ′ shown in the figure includes an information input terminal unit 21, an information output terminal unit 22, a clear toner adjustment unit 26, and a multidimensional LUT 27. The information input terminal unit 21, the information output terminal unit 22, and the clear toner adjustment unit 26 are the same as those in the configuration example described above (see FIG. 3), and thus the description thereof is omitted here.

  When the amounts of clear toner and color toner are specified by the input information at the information input terminal unit 21, the multi-dimensional LUT 27 is configured so that the total amount of the clear toner and the color toner does not exceed a preset total toner amount limit value. The amount of color toner is converted to a new amount, and the conversion mode is changed according to the amount of clear toner. Specifically, the functions of the first color conversion unit 23, the second color conversion unit 24, and the interpolators 25C, 25M, 25Y, and 25K in the above-described configuration example (see FIG. 3) are performed by one LUT. It has been realized. That is, the multidimensional LUT 27 functions as a color conversion unit. As the multidimensional LUT 27, a 5-input 4-output 5-dimensional LUT can be used. For a specific configuration method of the multidimensional LUT, for example, hypercube interpolation (see, for example, Japanese Patent Application Laid-Open No. 11-146218) or supertetrahedral. A known technique such as body interpolation (for example, see JP-A-6-141172) can be used.

[Example of processing operation of color conversion device]
Next, an example of processing operation in the color conversion devices 20 and 20 ′ will be described.
Here, the processing operation in the color conversion apparatus 20 will be described as an example with reference to FIG. However, the same applies to the processing operation example in the color conversion device 20 ′.

  For the color conversion device 20, pixel value data C, M, Y, K for each color of CMYK as information for specifying the color toner amount and the clear toner amount for each pixel of the formed image in the image output device 32 Is input to the information input terminal unit 21 from the image input device 31. At this time, the data C, M, Y, K, and CT are input to the information input terminal unit 21 in a range that does not exceed the maximum value set for each, that is, a value in the range of 0 to 100%. The

  When the data C, M, Y, K, and CT are input to the information input terminal unit 21, the first color conversion unit 23 creates new colors for each color based on the data C, M, Y, and K. Color conversion to data C1, M1, Y1, K1 for specifying the toner amount is performed. At this time, the first color conversion unit 23 uses a color conversion parameter suitable for the case where the clear toner amount is 0%, and sets the total amount of color toner (for example, a total of CMYK colors of up to 400%) in advance. The color conversion is performed so that the toner total amount limit value (for example, 250%) is reached. The color conversion results C1, M1, Y1, and K1 in the first color conversion unit 23 are sent to the interpolators 25C, 25M, 25Y, and 25K, respectively.

  When the data C, M, Y, K, and CT are input to the information input terminal unit 21, the second color conversion unit 24 selects the second data based on the data C, M, Y, and K. In addition to the color conversion results C1, M1, Y1, and K1 in the color conversion unit 24, color conversion to data C2, M2, Y2, and K2 for specifying the color toner amount of each new color is performed. At this time, the second color conversion unit 24 uses the color conversion parameter suitable for the case where the clear toner amount is 100%, and the total amount of color toner (for example, 400% of the total of CMYK colors at the maximum) is the total amount of toner. Color conversion is performed so that the amount (for example, 150%) obtained by subtracting the limit value (for example, 250%) and the clear toner amount (for example, 100%) is obtained. The color conversion results C2, M2, Y2, and K2 in the second color conversion unit 24 are sent to the interpolators 25C, 25M, 25Y, and 25K, respectively.

In the color conversion in the first color conversion unit 23 and the second color conversion unit 24, the color gamut is narrowed by limiting the total amount of color toner, and a color difference from the input target color occurs. In order to make it perceptually preferable, color gamut compression conversion processing called so-called gamut compression may be performed.
When the color difference from the input color is minimized, it is conceivable to use the color difference minimum method for the color gamut compression conversion process.

FIG. 5 is an explanatory diagram showing an outline of color gamut compression conversion by the color difference minimum method.
Lowering the toner total amount limit value narrows the lower hemisphere of the color gamut. Therefore, in general lightness / hue difference minimum compression (that is, color gamut compression while maintaining lightness and hue), color difference minimum compression (that is, color gamut compression that minimizes the color difference from the target color). However, the color difference from the target outside the gamut deteriorates. Therefore, for a target color outside the color gamut, color conversion parameters are determined after performing color difference minimum compression.
The color conversion parameter determination method can be determined by applying a known method (for example, see Japanese Patent Application Laid-Open No. 2001-169131) that ensures colorimetric color reproduction.

  In FIG. 3, when each data C, M, Y, K, CT is input to the information input terminal unit 21, the clear toner adjusting unit 26 applies a restriction to the data CT and newly clears the data CT. Data CT ′ regarding the toner amount is used.

FIG. 6 is an explanatory diagram specifically showing an outline of toner amount restriction performed by the clear toner adjustment unit.
As shown in FIG. 6A, the clear toner adjustment unit 26 includes a total toner amount calculation unit 26a, a clear toner amount maximum value LUT 26b, and a minimum value selection unit 26c. When the data C, M, Y, K, and CT are input to the information input terminal unit 21, first, the total toner amount calculating unit 26a is based on the data C, M, Y, and K, and the total color toner amount. (In other words, the total amount of each color of CMYK is 400% at the maximum.) Is calculated.
On the other hand, in the maximum clear toner amount value LUT26b, as shown in FIG. 6B, the correspondence relationship between the total color toner amount and the maximum clear toner amount allowable is set in advance.
Accordingly, when the total toner amount calculation unit 26a calculates the total color toner amount, as shown in FIG. 6A, the maximum value of the clear toner amount corresponding to the calculation result of the total color toner amount is obtained from the maximum clear toner amount value LUT26b. CTmax is output.
When the maximum value CTmax of the clear toner amount is output from the maximum clear toner amount value LUT26b, the minimum value selection unit 26c thereafter calculates the maximum value CTmax and the clear toner amount CT input to the information input terminal unit 21. In comparison, the smaller one is selected, and the selection result is sent as a new clear toner amount CT ′ to the interpolators 25C, 25M, 25Y, 25K and the information output terminal unit 22.
Through such a series of processing, the clear toner adjustment unit 26 sets a rule set in advance with respect to the clear toner amount, for example, to suppress the clear toner amount when the total amount of color toner is large. Restrictions will be added according to

  In FIG. 3, the color conversion results C1, M1, Y1, K1, C2, M2, Y2, and K2 are sent from the first color conversion unit 23 and the second color conversion unit 24, respectively, and from the clear toner adjustment unit 26. When the clear toner amount CT ′ is sent out, the interpolators 25C, 25M, 25Y, and 25K change the color toner amounts C ′, M ′, Y ′, and K ′ corresponding to the clear toner amount CT ′ to the first. It is specified by interpolation from the correspondence relationship between the color conversion unit 23 and the second color conversion unit 24.

FIG. 7 is an explanatory diagram specifically showing an outline of the interpolation processing performed by the interpolator.
In the illustrated example, an interpolator 25C that performs an interpolation process for C color is shown. However, it is assumed that exactly the same interpolation processing is performed in the interpolators 25M, 25Y, and 25K of other colors.
The interpolator 25C receives the C color toner amounts C1 and C2 from the first color conversion unit 23 and the second color conversion unit 24, respectively. Further, a clear toner amount CT ′ is input from the clear toner adjusting unit 26.
When these are input, the interpolator 25C performs linear interpolation, for example, and calculates a color toner amount C ′ satisfying C2 ≦ C ′ ≦ C1 from the clear toner amount CT ′. Specifically, the color toner amount C ′ is calculated using a preset arithmetic expression C ′ = C1− (C1−C2) × CT ′ / 100 (where 0% ≦ CT ′ ≦ 100%). It is possible. However, the interpolation processing for calculating the color toner amount C ′ may be performed by other known techniques such as spline interpolation.

  When the interpolators 25C, 25M, 25Y, and 25K calculate the color toner amounts C ′, M ′, Y ′, and K ′, as shown in FIG. 3, the calculation result is the clear toner amount from the clear toner adjustment unit 26. Together with CT ′, the data is output to the image output device 32 via the information output terminal unit 22.

FIG. 8 is an explanatory diagram specifically showing an outline of image formation in the image output apparatus based on the toner amount after color conversion. In the example, the toner total amount limit value is set to 250%.
As shown in FIG. 8A, when the total toner amount limit value is 250%, in the image portion in which the clear toner amount is designated as 0% from the image input device 31, the color conversion devices 20, 20 ' Through the color conversion processing, the color toner amounts C ′, M ′, Y ′, and K ′ of the respective colors become 100%, 100%, 20%, and 30%, respectively. This is the result of color conversion using a color conversion parameter suitable for the case where the clear toner amount is 0%.
Further, when the total toner amount limit value is 250%, an image portion in which the clear toner amount is designated as 100% from the image input device 31 is subjected to color conversion processing by the color conversion devices 20 and 20 ′. The color toner amounts C ′, M ′, Y ′, and K ′ of the respective colors are 33%, 60%, 0%, and 57%, respectively. This is the result of color conversion using color conversion parameters suitable for a clear toner amount of 100%.
Further, although not shown, for example, in the image portion in which the clear toner amount is designated as 50% from the image input device 31, the above-described color conversion results when the clear toner amount is 0% and 100% are obtained. By interpolation, the color toner amounts C ′, M ′, Y ′, and K ′ of the respective colors become 67%, 80%, 10%, and 43%, respectively. This corresponds to color conversion using color conversion parameters suitable for a clear toner amount of 50%.
That is, for the toner image formed by the image input device 31, according to the clear toner amount put on the toner image, that is, according to the clear toner amount and the color toner reduction amount based on the total toner amount limit value, respectively. In this case, color conversion is performed by a conversion mode suitable for the above case.
Therefore, as shown in FIG. 8B, according to the configuration described in the present embodiment, compared with the conventional configuration in which a uniform reference is applied to change the color in the same manner, the color toner The color difference between the reduced portion and the non-reduced portion is suppressed. In addition, since the clear toner amount is not necessarily reduced, a visual effect by the clear toner can be obtained. Furthermore, the total amount of the clear toner and the color toner is also suppressed within the toner total amount limit value.

In the above-described embodiments, preferred specific examples of the present invention have been described. However, the present invention is not limited to the contents.
For example, in the present embodiment, the case where a color image is formed and output using YMCK color toners has been described as an example. However, the present invention is not limited to this. That is, the present invention can be applied to not only a color compatible machine but also a monochrome compatible machine.
In addition, the functional blocks 21 to 26 of the color conversion apparatuses 20 and 20 ′ according to the present embodiment are realized by cooperation of hardware resources and software in one aspect. Specifically, the function of each functional block is realized by reading a program recorded on a recording medium into a main storage device (main memory) and executing it by a central processing unit (CPU). The The program can be provided by being recorded on a computer-readable recording medium such as a CD-ROM, or can be provided by communication as a data signal. However, each functional block may be realized only by hardware.
That is, the present invention is not limited to the contents described in each of the above-described embodiments, and may be appropriately changed without departing from the gist thereof.

  10a, 10b ... image forming unit, 11, 12, 13, 14, 15, 19 ... image forming unit, 20, 20 '... color conversion device (control unit), 21 ... information input terminal unit, 22 ... information output terminal unit , 23 ... first color conversion unit, 24 ... second color conversion unit, 25C, 25M, 25Y, 25K ... interpolator, 26 ... clear toner adjustment unit, 27 ... multidimensional LUT, 31 ... image input device, 32 ... Image output device

Claims (7)

Image forming means for forming an image using a transparent color material and a color material;
A color material amount control means for adjusting the amount of the color material used for image formation in the image forming means,
The color material amount control means includes
When the transparent color material is a first amount, a first color conversion unit that specifies an amount of the colored color material corresponding to the first amount and a second amount in which the transparent color material is different from the first amount A plurality of color conversion units including a second color conversion unit for specifying the amount of the colored material corresponding to the second amount,
When an amount of the transparent color material to be used by the image forming unit is set, an interpolator that specifies the amount of the color material corresponding to the set amount by interpolating from the correspondence relationship of the plurality of color conversion units. And an image forming apparatus. The color material amount control unit includes a transparent color material amount adjustment unit that limits a set amount of the transparent color material to be used by the image forming unit and sets a new set amount. Image forming apparatus. The image forming apparatus according to claim 1, wherein the plurality of color conversion units use a color difference minimum method for color gamut compression conversion for specifying the amount of the color material. The image forming apparatus according to claim 1, wherein the color material amount control unit is configured by a direct look-up table. Information input means for inputting information relating to the amount of transparent color material and colored color material used for image formation;
When the amount of the transparent color material and the color material is specified by the input information in the information input means, the amount of the color material is newly set so that the total amount of these combined color materials does not exceed the color material total amount limit value. Color conversion means that converts the amount of the conversion into a different amount according to the amount of the transparent color material,
An information output means for outputting information about the amount of the transparent color material and the amount after conversion of the color material;
Have
The color conversion means includes
When the transparent color material is a first amount, a first color conversion unit that specifies an amount of the colored color material corresponding to the first amount and a second amount in which the transparent color material is different from the first amount A plurality of color conversion units including a second color conversion unit for specifying the amount of the colored material corresponding to the second amount,
When the amount of the transparent color material is specified by the input information from the information input means, the amount of the colored color material corresponding to the specified amount is specified by interpolating from the correspondence relationship by the plurality of color conversion units. A color conversion device comprising an interpolator . The color conversion apparatus according to claim 5, further comprising: a transparent color material amount adjusting unit that limits the amount of the transparent color material specified by the input information in the information input unit and sets a new amount. The color conversion apparatus according to claim 5 or 6, wherein the plurality of color conversion units use a color difference minimum method for color gamut compression conversion for specifying the amount of the colored color material.

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