JP2007124554A - Image converting apparatus and image converting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image converting apparatus which can perform optimal image conversions according to an image processing mode. <P>SOLUTION: The image converting apparatus 56 converts five color image data of an image forming apparatus 53 which forms an image by using a plurality of shade black color materials of distinct richness to four color image data corresponding to an image forming apparatus 52 which forms an image by using one black color material. The apparatus 56 is provided with an ink formation means 562 which controls ink generation rate when the five color image data is converted to the four color image data corresponding to image processing mode selected when the five color image data is formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention converts image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities into image data corresponding to an image forming apparatus that forms an image using a single black color material. Alternatively, an image conversion apparatus that converts image data of an image forming apparatus that forms an image using one black color material into image data of an image forming apparatus that forms an image using a plurality of dark and light black color materials having different densities, and The present invention relates to an image conversion method.

In recent years, in ink jet printers, a method using light ink has been used as a method for eliminating graininess such as photographic images. In this case, an image is reproduced using two light and dark inks having the same color, such as light cyan and magenta ink as well as light magenta. In particular, by using light ink in a low density region, the graininess is improved and a photographic image without roughness is realized.
For example, Patent Document 1 has a plurality of dark and light ink distribution tables having different densities, and when it is difficult to stably discharge at least one kind of ink, the remaining ink is selectively used by using the distribution table. An ink jet recording method and apparatus capable of continuing stable recording by performing recording using the above are disclosed.
Also in electrophotography, a configuration using a low density toner (hereinafter, light toner) and a high density toner (dark toner) based on the same concept is disclosed (see Patent Document 2).
Japanese Patent Laid-Open No. 06-199031 JP 2001-290319 A

By the way, in an office environment in which a plurality of image forming apparatuses are connected to a network, for example, when an image stored in an image forming apparatus capable of reproducing four colors is to be output by an image forming apparatus capable of reproducing five colors, or in five colors. In some cases, an image stored in a possible image forming apparatus may be output by an image forming apparatus capable of reproducing four colors. In such a case, it is necessary to convert the image signal to make it suitable for the image forming apparatus as the output destination. At the time of the conversion, it is desired to perform conversion so that the image quality capability of the output destination image forming apparatus can be utilized to the maximum.
Accordingly, the present invention has been made in view of the above-described points, and an object thereof is to provide an image conversion apparatus and an image conversion method capable of performing optimal image conversion according to an image processing mode.

In order to achieve the above object, according to the first aspect of the present invention, the first image data of an image forming apparatus for forming an image using a plurality of light and dark black color materials having different densities is used as an image using one black color material. The image conversion apparatus converts the image data into second image data corresponding to the image forming apparatus that forms the first image data according to the image processing mode selected when generating the first image data. Is provided with black generation means for controlling the black generation rate when converting the image data into the second image data.
According to a second aspect of the present invention, in the image conversion apparatus according to the first aspect, the black ink generating means includes a first mode in which the image processing mode emphasizes character image quality and a second mode in which image or photo image quality is emphasized. Of these, the black generation rate is controlled to be higher in the first mode than in the second mode.
According to a third aspect of the present invention, the first image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities is used as an image forming apparatus that forms an image using a single black color material. An image conversion apparatus for converting into corresponding second image data, wherein the first image data is converted into the second image data in accordance with a use amount and a use ratio of a light and dark black color material in the first image data. It is characterized by comprising black generating means for controlling the black generating rate when converting to.
According to a fourth aspect of the present invention, in the image conversion apparatus according to the third aspect, the black ink generating unit uses a large amount of a light black color material with respect to a use amount and a use ratio of the dark and light black color material in the first image data. In the image area, the black generation rate of the second image data is controlled to be lower than in the image area that uses less light black color material.

According to a fifth aspect of the present invention, the second image data of the image forming apparatus that forms an image using one black color material is used as the second image data of the image forming apparatus that forms an image using a plurality of dark and light black color materials having different densities. An image conversion apparatus that converts image data into a first image data, wherein the second image data is converted into the first image data according to an image processing mode selected when generating the second image data. In this case, there is provided a black generating means for controlling the use ratio of each of the dark and light black color materials.
According to a sixth aspect of the present invention, in the image conversion apparatus according to the fifth aspect, the black ink generating means includes a first mode in which the image processing mode places importance on character image quality and a second mode in which the image quality or picture quality is emphasized. Of these, when the second mode is selected, the usage ratio of the light black color material is controlled to be higher than that in the first mode.
According to a seventh aspect of the present invention, the second image data of the image forming apparatus that forms an image using one black color material is used as the second image data of the image forming apparatus that forms an image using a plurality of dark and light black color materials having different densities. An image conversion device for converting into first image data, wherein the second image data is converted into the first image according to the use amount and use ratio of the color color material and the black color material in the second image data. It is characterized by comprising black generating means for controlling the use ratio of each of the dark and light black color materials when converted into data.
According to an eighth aspect of the present invention, in the image conversion apparatus according to the seventh aspect, the black ink generating unit uses a black color material in which the usage amount and usage ratio of the color color material and the black color material in the second image data are the same. In the image area that uses less, the usage rate of the light black color material in the first image data is controlled to be higher than in the image area that uses much black color material.
According to a ninth aspect of the present invention, the first image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities is used as an image forming apparatus that forms an image using a single black color material. An image conversion method for converting into corresponding second image data, wherein the first image data is converted into the second image data according to an image processing mode selected when generating the first image data. It is characterized by controlling the black generation rate at the time of conversion.

According to a tenth aspect of the present invention, first image data of an image forming apparatus that forms an image using a plurality of dark and light black color materials having different densities is used as an image forming apparatus that forms an image using a single black color material. An image conversion method for converting into corresponding second image data, wherein the first image data is converted into the second image data in accordance with a use amount and a use ratio of a light and dark black color material in the first image data. It is characterized by controlling the black generation rate when converting to.
According to an eleventh aspect of the present invention, the second image data of the image forming apparatus that forms an image using one black color material is used as the second image data of the image forming apparatus that forms an image using a plurality of dark and light black color materials having different densities. An image conversion method for converting to first image data, wherein the second image data is converted to the first image data in accordance with an image processing mode selected when generating the second image data. In this case, the usage ratio of each of the dark and light black color materials is controlled.
According to a twelfth aspect of the present invention, the second image data of the image forming apparatus that forms an image using one black color material is used as the second image data of the image forming apparatus that forms an image using a plurality of dark and light black color materials having different densities. An image conversion method for converting into first image data, wherein the second image data is converted into the first image according to the use amount and use ratio of the color color material and the black color material in the second image data. It is characterized by controlling the usage ratio of each of the dark and light black color materials when converting to data.

The present invention is configured to control the black generation rate of the second image data to be converted according to the image processing mode selected when the first image data is generated, and thus according to the image processing mode. It is possible to perform optimal image conversion.
Further, the present invention is configured to control the black generation rate of the second image data converted according to the usage amount and usage ratio of the dark and black color material in the first image data, so that the image processing mode information is It is possible to perform optimal image conversion based on the result of determining whether the emphasis is on character or photo.
Further, the present invention is configured to control the use ratio of the dark and black color material in the converted first image data according to the image processing mode selected when generating the second image data. Optimal image conversion according to the image processing mode can be performed.
Further, the present invention is configured to control the use ratio of the light and dark black color material in the first image data converted according to the use amount and the use ratio of the color color material and the black color material in the second image data. Thus, even if there is no image processing mode information, it is possible to perform optimal image conversion based on the result of determining whether the emphasis is on text or photo.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration example of an image forming system using an image forming apparatus according to the present invention.
As shown in FIG. 1, a network 51 of the image forming system according to the present embodiment includes two image forming apparatuses 52 and 53, an image forming apparatus 52 capable of reproducing four colors and an image forming apparatus 53 capable of reproducing five colors. It is connected. These image forming apparatuses 52 and 53 are provided with HDDs (Hard Disk Drives) 54 and 55 which are storage means for storing images. The image forming apparatus 52 capable of reproducing four colors reproduces a color image with four colors of cyan, magenta, yellow, and black, and is a general color printer or color copier. On the other hand, the image forming apparatus 53 capable of reproducing five colors reproduces a color image with five colors obtained by adding light black (black toner having a low density) to the four colors described above. The present invention relates to an image forming apparatus having such a dark and light color material, and particularly to an image forming apparatus having a light and dark black color material.
As will be described later, each of the image forming apparatuses 52 and 53 has a configuration in which an image signal in the middle of image processing can be temporarily stored in a storage unit. This is because the stored image signal is taken out again and used for image reproduction when a plurality of copies are made or when it is output again later.

FIG. 2 is a schematic diagram of an image forming apparatus 53 capable of reproducing five colors according to the present invention.
A basic image forming operation of the image forming apparatus 53 will be described with reference to FIG.
The recording sheets 1 are separated and called one by one by the sheet feeding roller 2 and are conveyed to the conveying roller pair 3. Further, the transport roller pair 3 transports the recording paper 1 and transports it to the registration roller pair 4. The registration roller pair 4 is configured so that the rotation and stop of the roller can be freely controlled by a registration clutch (not shown), and the recording paper 1 is temporarily stopped by the registration roller pair 4 in order to wait for a series of image forming processes to be described later. Let
An image forming station 35 surrounded by a broken line is a cyan plate image forming station. A charging charger 6, an exposure beam 7, a developing device 8, a cleaning blade 9, and a primary transfer charger 10 are arranged around the photosensitive member 5. And performs a series of image forming operations. The surface of the photoconductor 5 uniformly charged by the charging charger 6 is irradiated with an exposure beam 7 from a writing unit (not shown), and a latent image is formed on the photoconductor. The developing device 8 develops cyan toner on the latent image and visualizes it as a toner image. Further, the toner image is transferred to the intermediate transfer belt 40 by the primary transfer charger 10. The toner remaining on the photoreceptor 5 is scraped off by the cleaning blade 9. Further, it is charged again by the charging charger 6 and thereafter the above-described image forming operation is repeated.
An image forming station 36 surrounded by a broken line is a magenta image forming station. Like the cyan plate, the charging charger 12, the exposure beam 13, the developing device 14, the cleaning blade 15, and the primary are arranged around the photosensitive member 11. A transfer charger 16 is disposed, and a magenta plate is formed by performing a series of image forming operations, and the toner image is transferred to the intermediate transfer belt 40.
Further, the image forming stations 37, 38, and 39 are yellow plate, dark black plate, and light black plate image forming stations, respectively. The image forming station 37 has a charging charger 18, an exposure beam 19, and a developer around the photosensitive member 17. 20, a cleaning blade 21 and a primary transfer charger 22 are disposed. Similarly, in the image forming station 38, the charging charger 24, the exposure beam 25, the developing unit 26, the cleaning blade 27, and the primary transfer charger 28 are arranged around the photosensitive member 23, and the image forming station 39 is charged around the photosensitive member 29. A charger 30, an exposure beam 31, a developing device 32, a cleaning blade 33, and a primary transfer charger 34 are arranged. Then, each toner image is transferred to the intermediate transfer belt 40.
After the toner images of all colors are transferred to the transfer belt 40, the recording paper 1 that has been temporarily stopped by the pair of registration rollers 4 is re-conveyed in time, and is transferred onto the recording paper by the secondary transfer charger 41. Transfer toner of all colors.
Next, the toner is conveyed to the fixing device 43, and unfixed toner is fixed on the recording paper by heat and pressure, and is output. The toner remaining on the intermediate transfer belt 40 is scraped off by bringing the intermediate transfer cleaner 42 into contact with the belt, and the intermediate transfer belt 40 is cleaned.

FIG. 3 is a diagram for explaining image processing of the image forming apparatus 53 capable of reproducing five colors.
FIG. 3 shows a configuration corresponding to both a copy output that outputs an image signal input from an image capturing unit such as a scanner and a print output that outputs image data input from a host computer. The system controller 100 performs overall operation control.
The digital color image signal input by the scanner 101 is converted from a linear reflectance signal into a linear density signal by the scanner γ correction means 102. Further, the input masking means 103 converts the signal dependent on the input device into a standard signal such as RGB independent of the device. Next, the filter processing unit 104 corrects the spatial frequency characteristics. Specifically, an image that requires sharpness such as characters is sharply corrected by an edge enhancement filter, and an image that requires smoothness such as a photograph is softly corrected by a smoothing filter. Do. The image signal corrected as described above is input to the color conversion means 106 via the selector 105. The color conversion means 106 converts the RGB signal, which is a standard signal, into a device-dependent signal corresponding to the color material of the output engine 110. Here, the output engine uses a total of five toners of cyan (c), magenta (m), yellow (y) color materials and dark black (bk), light black (lk) achromatic materials. Since the image is reproduced, the color conversion means performs color separation into five colors of C, M, Y, K, Bk, and Lk in accordance with this. The operation of the color conversion means 106 will be described in detail later.

The output from the color conversion unit 106 is temporarily stored in the storage unit 107. The accumulated image signal is read again, and after the γ characteristic is converted by table conversion by the printer γ correction unit 108, a predetermined dither process is performed by the halftone processing unit 109 and output to the output engine 110. Is done. As for printer data processing, data for printer output output from a personal computer (PC) (not shown) is input to the image expansion means 112 via the host I / F 111, and the image expansion means 112 uses RGB bits. Convert to a map image. The subsequent processing is the same as the flow of the image signal from the scanner.
Details of the color conversion means 106 will be described with reference to FIG.
The standard signal RGB input to the color conversion unit 106 is converted into a device-dependent CMY image signal by the color correction unit 1061. Various methods can be considered for the color correction processing. Here, it is assumed that the following masking operation is performed.
C = α11 × R + α12 × G + α13 × B + β1
M = α21 × R + α22 × G + α23 × B + β2
Y = α31 × R + α32 × G + α33 × B + β3
... (Formula 1)
However, α11 to α33 and β1 to β3 are predetermined color correction coefficients, and CMY also outputs 8-bit signals for RGB 8-bit (0-255) image signals.

Next, the image signal from the color correction unit 1061 is input to the black generation unit 1062, and the black generation unit 1062 generates a K signal. The generation of the K signal is obtained by (Equation 2), and when this is graphed, it is as shown in FIG.
K = Min (C, M, Y) (Formula 2)
Further, the UCR (under color removal) means 1063 converts the C ′, M ′, and Y ′ signals obtained by subtracting the black component from the C, M, and Y signals and the K signal generated by the black generation means 1062 as follows: Obtained by Equation 3.
C ′ = C−K
M ′ = M−K
Y '= YK
... (Formula 3)
Next, the K signal generated by the black generation means 1062 is decomposed into a Bk signal and an Lk signal by the Bk / Lk separation means 1064.
Here, two types of separation tables are shown. The separation table shown in FIG. 6 is a separation table that consumes a little amount of toner but places importance on graininess. Further, the color separation table shown in FIG. 7 is a color separation table in which the granularity is worse than the table shown in FIG.
In the image forming apparatus 53 capable of reproducing five colors according to the present embodiment, when the image processing mode giving priority to the photographic image quality is selected by the system controller 100 shown in FIG. 3, the color separation table shown in FIG. , Bk version is generated. On the contrary, when the image processing mode giving priority to the character image quality is selected, the separation table shown in FIG. 7 is used. This is because granularity is not so important for text images, and it is better to reduce the amount of toner used. For photographic images, graininess is important, so even if the amount of toner used is somewhat high, the graininess is excellent. This is because it is preferable to perform image reproduction.

FIG. 8 shows the granularity when the separation tables shown in FIGS. 6 and 7 are used. In any case, the granularity is obtained when a gray scale is reproduced using only Bk and Lk without using color toner.
The solid line shown in FIG. 8 is the granularity of FIG. 6, and the alternate long and short dash line is the granularity of FIG.
As can be seen from FIG. 8, it can be seen that the image shown in FIG. 6 is capable of smooth image reproduction with low granularity and less granularity. Further, in the toner use amount comparison between FIG. 6 and FIG. 7, the separation table of FIG. 6 consumes 1.2 times as much toner as FIG. It has been measured.
As described above, the reproduction method using the same light black (Lk) toner includes a control method in which granularity is emphasized and toner usage saving is emphasized, and these are selectively used in the character mode and the photo mode.
On the other hand, the operation of the image forming apparatus 52 capable of reproducing four colors will be described with reference to FIG.
The image forming apparatus 52 capable of reproducing four colors is almost the same as the apparatus capable of reproducing five colors, and differs from FIG. The color conversion means 106 in FIG. 9 is configured to convert RGB signals into signals of four colors C, M, Y, and Bk. Details of the color conversion means 106 in FIG. 9 will be described with reference to FIG. The standard signal RGB input to the color conversion unit 106 is converted into a device-dependent CMY image signal by the color correction unit 1061. Various methods are conceivable for the color correction process, and it is assumed that the same masking operation as shown in the above (Equation 1) is performed.

Next, the image signal from the color correction unit 1061 is input to the black generation unit 1062 to generate a K signal. The generation of the K signal is configured to be switched between a mode in which character image quality is emphasized and a mode in which photo quality is emphasized. In the mode in which character image quality is emphasized, black generation as shown in FIG. 11 is performed. When expressed by an equation, it is the same as (Equation 2) described above, and all achromatic components are K signals. On the other hand, black generation as shown in FIG. Expressed as an expression, it becomes as shown in (Expression 4).
When Min (C, M, Y) ≦ T, K = 0
When Min (C, M, Y)> T, K = Min (C, M, Y) × β4 + γ1
... (Formula 4)
However, β4 is a predetermined coefficient and a number less than 1. γ1 is an intercept constant in FIG.
After that, the UCR processing 1063 is performed in the UCR means 1063, which is the same as the above (Equation 3). That is, in the mode in which photographic image quality is emphasized, the black generation rate is lowered by conversion as shown in FIG. 12, and control is performed so that more C, M, and Y color toners are used to express the same gray component. Conversely, in a mode in which character image quality is emphasized, control is performed such that the black generation rate is increased by conversion as shown in FIG. 11 and Bk toner is positively used to express the gray component.
In general, it is known that it is better to reproduce gray using equal amounts of C, M, and Y toners than to reproduce gray with a single black color, and this is a well-known fact. However, when reproducing using C, M, and Y toners, many toners are used. Therefore, in the present embodiment, as described above, different ink generation is performed in the mode in which the photographic image quality is emphasized and the mode in which the character image quality is emphasized, thereby realizing a usage method suitable for each.

[First Embodiment]
Now, returning to FIG. 1, there is a case where it is desired to output the image data of the image forming apparatus 53 capable of reproducing five colors by the image forming apparatus 52 capable of reproducing four colors. For this purpose, it is necessary to convert the image data generated for the five-color image forming apparatus 53 shown in FIG. 13 into the four-color image forming apparatus 52.
In the present embodiment, five-color image data (first image data) (CMYBkLk) of C, M, Y, Bk, and Lk read from the HDD 55 of the image forming apparatus 53 is converted by the image conversion means (image conversion apparatus) 56. The image data is converted, converted into four-color image data (second image data) of C, M, Y, B, and K, and transferred to the HDD 54 of the image forming apparatus 52.
At this time, the image conversion unit 56 simultaneously reads out the image processing mode information stored in the HDD 55 of the image forming apparatus 53 and determines whether the image is processed with character priority or is processed with priority on photograph. It is configured so that the conversion method in the conversion means varies depending on the information. The image conversion means 56 may be provided in the image forming apparatus 53 capable of reproducing five colors, or may be provided in the image forming apparatus 52 capable of reproducing four colors. Moreover, you may exist in an intermediate position as another apparatus.

An example of image conversion in the image conversion means 56 will be described with reference to FIG. The image conversion means 56 receives the CMYBkLk 5-color signal and the image processing mode information mode, and outputs a converted 4-color image signal C′M′Y′Bk ′.
First, the Bk and Lk signals are synthesized by the synthesizing means 561, and a synthesized black signal KM is generated. This can be understood by examining beforehand the black density when the Bk value and the Lk value are combined, and is configured to output a Bk value that can represent the same density as this density. . In other words, a combination of five colors that can reproduce the same color as the input signal of five colors is obtained.
Next, the KM signal is controlled again by the re-ink generating means 562 so as to change the value of the black signal. At this time, if the mode signal is character priority (first mode), Bk ′ = KM, and if it is photograph priority (second mode), Bk ′ = KM × β5. Here, β5 is a constant less than 1.
That is, in the character priority mode, the granularity is not considered important, and importance is placed on reducing the toner consumption, and a four-color signal with a high ink setting is output. In other words, all black components expressed by Bk and Lk in the input signal are output as Bk ′ signals. Further, since the value of KM-Bk ′ output at the same time is zero, the addition result in the adding means 563 to 565 is equivalent to the input C, M, Y signal, that is, C ′ = C, M ′ = M, Y ′ = Y.
On the other hand, in the photo priority mode, Bk ′ is a value smaller than KM, that is, control is performed so as to reduce the amount of black color material to be used. Further, the KM-Bk ′ signal has a positive value, and the addition results in the adding means 563 to 565 are C ′ = C + (KM−Bk ′), M ′ = M + (KM−Bk ′), Y ′ = Y +. (KM-Bk ′), and reproduction is performed so that cyan, magenta, and yellow color materials are often used. As a result, although the amount of toner consumption increases, image reproduction with an emphasis on graininess is realized.
As described above, in the first embodiment, the five-color image data is converted into the four-color image data by the re-ink generation unit 562 of the image conversion unit 56 according to the image processing mode selected when generating the five-color image data. Since the ink generation rate at the time of conversion to is controlled, optimal image conversion according to the image processing mode can be performed.
Further, when the image processing mode is the first mode in which importance is attached to the character image quality, the ink generation rate is controlled to be higher than that in the second mode in which the image processing mode places importance on the picture (photograph) image quality. In a mode that emphasizes image quality, image reproduction with good graininess can be performed, and in a mode that emphasizes character image quality, image reproduction with a small amount of toner can be performed.

[Second Embodiment]
In the first embodiment described above, it is assumed that image processing mode information can be obtained for both image data, but there are image processing apparatuses that do not hold the image processing mode.
Therefore, in the second embodiment, even in such a case, it is determined from the image data whether the processing content is focused on characters or photos, and appropriate conversion from 5 colors to 4 colors is performed.
In the second embodiment, as shown in FIG. 15, data stored in the HDD 55 of the image forming apparatus 53 is read, and it is determined whether the processing content determination unit 57 emphasizes text or photo, and image conversion unit In 56, conversion is performed according to the determination result dpm, and the image is transferred to the HDD 54 of the image forming apparatus 52.
The configuration of the processing content determination unit 57 and the image conversion unit 56 will be described with reference to FIG.
In FIG. 16, the processing content determination means 57 receives the Bk signal and the Lk signal, the separation table determination means 571 determines whether a separation table with emphasis on characters or a photograph is used, and determines the determination result dpm. It is configured to output. The separation table determination unit 571 determines the value of the Bk signal value relative to the Lk signal value and the combination thereof.
FIGS. 17 and 18 show the separation tables in FIGS. 6 and 7 described above, in which the x-axis and y-axis are redrawn and the relationship between Lk and Bk is rewritten.
The Lk-Bk relationship diagram corresponding to the table of FIG. 6 focusing on photographs is FIG. 17, and the relationship diagram corresponding to the table of FIG. 7 focusing on characters is FIG.

FIG. 17 has a feature that a large amount of Lk (light color material) is used with respect to Bk (dark color material) (= use ratio of Lk is high), and FIG. 18 has a low ratio of use of Lk with respect to Bk. . In this way, there is a difference in the relationship between Lk and Bk between the two separation tables, and by analyzing this difference, it can be seen which separation table was used.
The determination result dpm of character priority or photo priority is input to the reink generation unit 562 of the image conversion unit 56. Since the operation of the image conversion means is the same as that described above, description thereof is omitted.
As described above, by analyzing the relationship between the data of Lk and Bk, it is possible to determine whether the emphasis is on text or on the photograph, and conversion to a four-color signal applying an appropriate black generation rate is possible. it can. Various types of Lk and Bk separation tables other than those shown in FIGS. 17 and 18 can be set. However, when the Lk usage ratio is set high, the graininess is improved and the Lk usage is improved. When the ratio is low, the tendency of the graininess to deteriorate does not change, so by analyzing the ratio it can be determined whether or not the graininess-oriented setting has been set, so even if another separation table is used, the judgment is Is possible.
As described above, in the second embodiment, four-color image data (second image data) converted according to the use amount and use ratio of the dark and light black color material in the five-color image data (first image data). Therefore, even if there is no image processing mode information, it is possible to perform optimal image conversion based on the result of determining whether the emphasis is on text or photo. Further, in the image area that uses a large amount of light color material with respect to the use amount and the use ratio of the dark and light black color material in the five-color image data, the black color of the converted four-color image data is larger than the image area that uses a relatively light color material. Since the generation rate is controlled to be low, image reproduction with good graininess can be performed in a mode that emphasizes photographic image quality, and image reproduction with a small amount of toner can be performed in a mode that emphasizes character image quality.

[Third Embodiment]
Next, the third embodiment aims to output data of the image forming apparatus 52 capable of reproducing four colors to the image forming apparatus 53 capable of reproducing five colors.
FIG. 19 shows a diagram for explaining the third embodiment.
In FIG. 19, the image signal and the image processing mode information mode are read from the image forming apparatus 52 capable of reproducing four colors and transferred to the image conversion unit 56. The image conversion means 56 performs appropriate image conversion based on the mode signal, that is, whether the image is generated with emphasis on character image quality or photographic image quality, and the image forming apparatus 53 capable of reproducing five colors. If reproduction is important, the image is converted so that the image has good graininess. If the character is important, the image is converted so that the amount of toner used is reduced and output. The converted five-color image data CMYBkLk is transferred to the HDD 55 and output from the image forming apparatus.
The configuration operation of the image conversion means 56 shown in FIG. 19 will be described with reference to FIG.

As shown in FIG. 20, C, M, Y, and Bk signals and a mode signal are input, and five color image signals of C ′, M ′, Y ′, Bk ′, and Lk ′ are output. First, each signal of CMYBk is input to the re-ink generation unit 566. The re-ink generating unit 566 is configured to extract the gray component KS included in the CMY, perform synthesis with the black signal Bk, and output a new black signal KN. This is expressed by the following formula.
KS = min (C, M, Y) (Formula 5)
KN = Bk + KS (Formula 6)
That is, all gray components (achromatic components) of the color image expressed in CMYK are extracted and output as KN. At the same time, KS, which is a gray component extracted from the C, M, and Y signals, needs to be subtracted from each of the C, M, and Y signals. Therefore, the subtraction circuits 567 to 569 perform subtraction. Expressed as a formula:
C '= C-KS
M '= M-KS
Y '= Y-KS
... (Formula 7)
It becomes. Further, the KN signal is decomposed into a Bk ′ signal and an Lk ′ signal by the color separation unit 572. Here, the color separation means 572 inputs a mode signal, and if it is a mode that emphasizes photography, it is converted so as to increase the usage ratio of the light black color material (Lk ′), and the mode that emphasizes characters is used. In such a case, the usage ratio of the light black color material is reduced. The conversion for increasing the use ratio of light black is conversion based on the ratio of the decomposition table as shown in FIG. 6, for example. The conversion for reducing the use ratio of light black is to perform conversion based on the ratio of the decomposition table as shown in FIG. By controlling in this way, it is possible to reproduce an image with excellent graininess using a light black color material positively for signals generated with emphasis on characters when generating four colors, and generated with emphasis on photography. For signals, it is possible to reproduce an image with a small amount of toner that actively uses a dark black color material.
As described above, according to the third embodiment, the five-color image data (first image) to be converted according to the image processing mode selected when generating the four-color image data (second image data). Since the usage ratio of the black color material for each of the data density is controlled, optimum image conversion according to the image processing mode can be performed.
Further, when the image processing mode is a mode in which image (photo) image quality is emphasized, the usage ratio of the light black color material is controlled to be higher than that in the case where the image processing mode is a mode in which character image quality is emphasized. Therefore, even if there is no image processing mode information, it is possible to perform optimum image conversion based on the result of determining whether the emphasis is on text or photo.

[Fourth Embodiment]
In the fourth embodiment, when there is no mode signal that is image processing mode information, the CMYBk four-color image signal is analyzed, optimally processed, and output. As shown in FIG. 21, the four-color image signal read from the image forming apparatus 52 capable of reproducing four colors is transferred to the processing content determination unit 57 and the image conversion unit 56. The processing content determination unit 57 determines the processing content and outputs the determination result dpm to the image conversion unit 56. The image conversion means 56 is configured to appropriately convert an image based on dpm and transfer the five-color image data CMYKBkLk to the HDD 55. The configuration and operation of the processing content determination unit 57 will be described with reference to FIG.
In FIG. 22, each input CMYBk signal is input to the black generation rate determination unit 573 in the processing content determination unit 57. The black generation rate determination unit 573 analyzes the C, M, Y, and Bk signals to determine whether the black processing is performed with emphasis on characters or the black processing is performed with emphasis on photos, and outputs a determination signal dpm. Expressed as an expression:
Black generation rate: KR = Bk / (Bk + KS)
If (KR <β6) dpm = photo priority else dpm = character priority KS = min (C, M, Y) (Equation 8)
β6 is a threshold value for determination.
KS is an achromatic component included in the C, M, and Y color signals. Based on this and the Bk signal generated for the black material, it is possible to determine how much the black generation rate KR was as shown in (Equation 8). When the value of KR is smaller than the predetermined determination threshold value β6, it is determined that the photograph is prioritized.
The determination result dpm is input to the image conversion means 56, and the separation method of Bk ′ and Lk ′ is controlled based on the determination result. Since the operation of the image conversion means 56 is the same as that described in the third embodiment, a description thereof will be omitted.

By configuring as described above, it is determined whether the emphasis is on the character or the photograph by analyzing the CMYBk signal, and the light black color material is positively applied to the signal generated with emphasis on the character when generating four colors. Therefore, it is possible to reproduce an image with a small amount of toner that actively uses a dark black color material for a signal generated with emphasis on photography.
According to the fourth embodiment, the five-color image data (first image data) to be converted is converted according to the use amount and the use ratio of the color color material and the black color material in the four-color image data (second image data). (1 image data) is used to control the usage ratio of each black and white color material, so that optimal image conversion can be performed based on the result of determining whether the emphasis is on text or photo without image processing mode information. It can be performed.
In addition, the usage amount and the usage ratio of the color color material and the black color material in the four-color image data are converted in the image area in which the black color material is used less than in the image area in which the black color material is relatively used. Since the usage rate of the light black color material in color image data is controlled to be high, it is possible to reproduce images with good graininess in a mode that emphasizes photographic image quality, and less toner is used in a mode that emphasizes character image quality. Image reproduction can be performed.

In the present embodiment described so far, as shown in FIG. 1, the image forming apparatus 52 capable of reproducing four colors and the image forming apparatus 53 capable of reproducing five colors are connected to the network 51 and output mutual data. In this case, the image conversion in this case has been described. However, the case where conversion from four colors to five colors or five colors to four colors is necessary is not limited to this example.
For example, although the image is generated and stored in the five-color reproduction mode, the light black toner of the image forming apparatus 53 may end, and reproduction with light black may not be performed. In such a case, based on the method described above, if the image conversion unit 56 converts the image data from the 5-color signal to the 4-color signal and outputs it, the same aim as when the initial image was generated, That is, it is possible to perform image conversion and reproduction while retaining the aim of emphasizing characters or photographs. The same applies when image data generated and stored in the five-color reproduction mode is converted to a four-color signal with high versatility when backing up. As described above, this method is effective at the time of conversion from four colors to five colors or from five colors to four colors even when not connected to the network or stored in the HDD.

1 is a diagram illustrating a configuration example of an image forming system using an image forming apparatus according to the present invention. 1 is a schematic diagram of an image forming apparatus capable of reproducing five colors according to the present invention. It is a diagram illustrating image processing of an image forming apparatus capable of reproducing five colors. It is a figure explaining the detail of the color conversion means shown in FIG. It is a graph figure of K signal. It is the figure which showed an example of the separation table. It is the figure which showed an example of the separation table. It is the figure which showed the granularity when using the separation table shown in FIG. 6 and FIG. It is a diagram illustrating image processing of an image forming apparatus capable of reproducing four colors. It is a figure explaining the detail of the color conversion means shown in FIG. FIG. 6 is a graph showing black generation in a mode in which character image quality is emphasized. It is the graph which showed the black ink generation in the mode which attaches importance to the picture quality. FIG. 3 is a diagram illustrating a first embodiment for outputting image data of an image forming apparatus capable of reproducing five colors by an image forming apparatus capable of reproducing four colors. It is a figure showing composition and operation of image conversion means of a 1st embodiment. FIG. 6 is a diagram illustrating a second embodiment for outputting image data of an image forming apparatus capable of reproducing five colors by an image forming apparatus capable of reproducing four colors. It is the figure which showed the structure and operation | movement of the image conversion means of 2nd Embodiment. It is the figure which showed the other example of the separation table. It is the figure which showed the other example of the separation table. FIG. 10 is a diagram illustrating a third embodiment for outputting image data of an image forming apparatus capable of reproducing four colors by an image forming apparatus capable of reproducing five colors. It is the figure which showed the structure and operation | movement of the image conversion means of 3rd Embodiment. FIG. 10 is a diagram illustrating a fourth embodiment for outputting image data of an image forming apparatus capable of reproducing four colors by an image forming apparatus capable of reproducing five colors. It is the figure which showed the structure and operation | movement of the image conversion means of 4th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Recording paper, 2 ... Paper feeding roller, 3 ... Conveying roller pair, 4 ... Registration roller pair, 5 ... Photoconductor, 6 ... Charger, 7 ... Exposure beam, 9 ... Cleaning blade, 10, 16, 22, 28 34, primary transfer charger 11, 17, 23, 29 ... photoconductor, 12, 18, 24, 30 ... charge charger 13, 19, 25, 31 ... exposure beam, 14, 20, 26, 32 ... development 15, 21, 27, 33 ... cleaning blade, 35, 36, 37, 38, 39 ... image forming station, 40 ... intermediate transfer belt, 41 ... secondary transfer charger, 42 ... intermediate transfer cleaner, 43 ... fixing device , 51 ... Network, 52, 53 ... Image forming apparatus, 54, 55 ... HDD, 56 ... Image conversion means, 57 ... Processing content determination means, 100 ... System controller, 101 ... Scan , 102 ... Correction means, 103 ... Input masking means, 104 ... Filter processing means, 105 ... Selector, 106 ... Color conversion means, 107 ... Storage means, 108 ... Correction means, 109 ... Halftone processing means, 110 ... Output engine, 111 ... Host I / F, 112 ... Image development means, 561 ... Composition means, 562 ... Re-ink generation means, 563 ... Addition means, 567 ... Re-ink generation means, 567 ... Subtraction circuit, 571 ... Separation table determination means, 572 ... Color separation means, 573 ... Black generation rate determination means, 1061 ... Color correction means, 1062 ... Black generation means, 1063 ... UCR means, 1064 ... Bk / Lk separation means

Claims (12)

First image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities is used as second image data corresponding to an image forming apparatus that forms an image using one black color material. An image conversion device for converting to
According to an image processing mode selected when generating the first image data, a black generation unit is provided for controlling a black generation rate when the first image data is converted into the second image data. An image conversion apparatus characterized by that.   The image conversion apparatus according to claim 1, wherein the black ink generating unit includes a first mode in which the image processing mode emphasizes character image quality and a second mode in which design or photo image quality is emphasized. If there is, the image conversion apparatus controls the black generation rate higher than that in the second mode. First image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities is used as second image data corresponding to an image forming apparatus that forms an image using one black color material. An image conversion device for converting to
There is provided black generation means for controlling a black generation rate when converting the first image data into the second image data in accordance with the usage amount and usage ratio of the dark and black color material in the first image data. An image conversion apparatus characterized by that.   4. The image conversion apparatus according to claim 3, wherein the black generating means uses a light black color material in an image area in which a large amount of light black color material is used, with respect to a usage amount and a usage ratio of the light and dark black color material in the first image data. An image conversion apparatus that controls the black generation rate of the second image data to be lower than an image area that uses less color material. Converting second image data of an image forming apparatus that forms an image using a single black color material into first image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities An image conversion device that
In accordance with the image processing mode selected when generating the second image data, when the second image data is converted into the first image data, the usage ratio of each of the dark and light black color materials is controlled. An image conversion apparatus comprising black generating means for performing the above.   6. The image conversion apparatus according to claim 5, wherein the black ink generating means is in the second mode among the first mode in which the image processing mode places importance on character image quality and the second mode in which image quality or picture quality is emphasized. If there is, the image conversion apparatus controls the use ratio of the light black color material to be higher than that in the first mode. Converting second image data of an image forming apparatus that forms an image using a single black color material into first image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities An image conversion device that
Depending on the usage amount and usage ratio of the color color material and the black color material in the second image data, the usage ratio of each of the light and dark black color materials when converting the second image data into the first image data An image conversion apparatus comprising black generation means for controlling the ink.   The image conversion device according to claim 7, wherein the black generation unit uses an amount and a use ratio of a color color material and a black color material in the second image data in an image region in which a small amount of the black color material is used. An image conversion apparatus characterized by controlling a usage rate of a light black color material in the first image data to be higher than that in an image region in which a large amount of black color material is used. First image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities is used as second image data corresponding to an image forming apparatus that forms an image using one black color material. An image conversion method for converting to
An image conversion characterized by controlling a black generation rate when converting the first image data into the second image data according to an image processing mode selected when generating the first image data. Method. First image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities is used as second image data corresponding to an image forming apparatus that forms an image using one black color material. An image conversion method for converting to
An image that controls a black generation rate when converting the first image data into the second image data in accordance with a use amount and a use ratio of the dark and black color material in the first image data. Conversion method. Converting second image data of an image forming apparatus that forms an image using a single black color material into first image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities An image conversion method for
In accordance with the image processing mode selected when generating the second image data, when the second image data is converted into the first image data, the usage ratio of each of the dark and light black color materials is controlled. An image conversion method characterized by: Converting second image data of an image forming apparatus that forms an image using a single black color material into first image data of an image forming apparatus that forms an image using a plurality of light and dark black color materials having different densities An image conversion method for
Depending on the usage amount and usage ratio of the color color material and the black color material in the second image data, the usage ratio of each of the light and dark black color materials when converting the second image data into the first image data The image conversion method characterized by controlling.

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