JP2003309732A - Image processing apparatus, image forming apparatus, image processing method, computer program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus, an image forming apparatus and an image processing method realizing application of proper image processing corresponding to fluorescent color ink to input image data, and to provide a computer program and a recording medium. <P>SOLUTION: An original type discrimination section 13 obtains saturation information from CMY data subjected to complementary color inversion, counts the number of pixels whose saturation is a predetermined saturation or over, and calculates a ratio of the pixels to the total number of pixels. When the ratio of the pixels to the total number of pixels is greater than a predetermined threshold value, the discrimination section 13 outputs a fluorescent light discrimination signal Sd denoting the use of fluorescent color ink to a color correction section 16. The color correction section 16 discriminates whether or not the saturation of each pixel is the predetermined threshold value or over, when the saturation of the pixel is the threshold value or over, the color correction section 16 outputs a pixel saturation discrimination signal Sc to an output conversion section 21. The output conversion section 21 converts output image data in response to the arrangement of ink jet heads 22 of an image output apparatus 4 being a printer of the ink jet recording system. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image processing for extracting color information such as saturation from input image data and determining whether or not to form an image using fluorescent color ink based on the extraction result. The present invention relates to an apparatus, an image forming apparatus, an image processing method, a computer program, and a recording medium.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer for forming an image on an image forming sheet based on image data of an original, an ink jet for ejecting ink from a nozzle of an ink jet printer for printing. There is a recording system. The ink jet recording type image forming apparatus is characterized in that it is light in weight, generates little noise, and can perform high-speed image formation without requiring special fixing on plain paper. Further, in recent years, digitalization of OA equipment has rapidly progressed, and the demand for color image output has increased, so that low-cost color inkjet printers have become widespread as digital color copying machines and color printers. Therefore, various types of inkjet printers have been actively studied. One of such inkjet printers uses a fluorescent color ink.

Japanese Unexamined Patent Publication No. 9-131860 discloses an ink jet printer having a fluorescent color head and using fluorescent color ink. The fluorescent color image data for forming the fluorescent color image is created by the application of the host computer and stored in the fluorescent color memory area of the printer driver. Then, the fluorescent color image data is transferred to the printer together with the other color data. This data is decomposed into data for each color by the data analysis unit of the printer, and the fluorescent color image data is stored in the fluorescent color memory area. The fluorescent color head is driven based on this data, and an image is formed with fluorescent color ink. In this way, a specific part of an image can be printed with fluorescent color ink by using the fluorescent color ink, and printing can be performed in a place where the amount of light is small, or by changing the type of the light to be emitted Different printing can be performed.

Further, Japanese Patent Application Laid-Open No. 10-130558 discloses that the characteristic of fluorescent color ink is that it is possible to express a color tone having a higher saturation than that of ordinary ink. This makes it possible to express colors outside the normal color gamut by applying fluorescent color ink to areas where saturation is saturated with normal ink,
The image quality can be improved.

[0005]

However, JP-A-9-1
In Japanese Patent No. 31860, fluorescent color ink is used only for forming an image having a fluorescent effect such that it shines in a place where the amount of light is small. Therefore, there is a problem that the image quality cannot be improved. Further, in the printing system disclosed in Japanese Patent Laid-Open No. 9-131860, fluorescent color data is created independently, or an arbitrary portion of image data is copied and converted into an image for fluorescent color to obtain an original image. Fluorescent color ink is used for all image data of a predetermined area regardless of the image data. Therefore, for example, when the black character area or the black line drawing portion is included in the area using the fluorescent color ink, the fluorescent color ink is also used for the black character area and the black line drawing portion. At this time, if a color shift occurs in the black character area and the black line drawing portion, the fluorescent ink is highly saturated, which makes it more noticeable and rather deteriorates the image quality.

The present invention has been made in view of the above problems, and an object of the present invention is to decide whether or not to use the fluorescent color ink based on a judgment criterion utilizing the characteristics of the fluorescent color ink as described above, and to input the input image. An object of the present invention is to provide an image processing apparatus, an image forming apparatus, an image processing method, a computer program, and a recording medium, which are capable of performing an appropriate image processing corresponding to fluorescent color ink on data.

[0007]

An image processing apparatus according to the present invention applies image processing to input image data to obtain output image data, and outputs the output image data to an image output means having a plurality of color inks including fluorescent color inks. In the image processing device for outputting, the extraction means for extracting the feature amount from the input image data, and the use or non-use of the fluorescent color ink is determined based on the extraction result, and the determination result is output as a fluorescence determination signal. And a document type determination unit for performing the image processing based on the fluorescence determination signal.

In the image processing apparatus according to the present invention, the feature amount is saturation data, and when the ratio of pixels having a predetermined saturation or more to all pixels in the input image data is larger than a predetermined threshold value, The fluorescence determination signal is a signal indicating that the fluorescent color ink is used.

In the image processing apparatus according to the present invention, output conversion for converting the input image data into output image data including data relating to use or non-use of the fluorescent color ink based on the fluorescence determination signal and outputting the output image data. It is characterized by comprising means.

In the image processing apparatus according to the present invention, color information is extracted from the input image data, and the fluorescent color ink is used or not used in correspondence with each pixel of the input image data based on the color information. Is provided and a color correction means for outputting the determination result as a pixel fluorescence control signal is provided, and the image processing is performed based on the pixel fluorescence control signal.

In the image processing apparatus according to the present invention, the color information is saturation data, and the color correction means uses pixel fluorescent control in which the fluorescent color ink is used in correspondence with pixels having a predetermined saturation or higher. It is characterized in that it is configured to output a signal.

In the image processing apparatus according to the present invention, the color information is memory color data, and the color correction means uses the fluorescent color ink corresponding to the pixels within the range of the memory color data. It is characterized in that it is configured to output a pixel fluorescence control signal.

In the image processing apparatus according to the present invention, the color correction means determines whether or not the fluorescent color ink is used for the pixel based on an image type determination signal for determining the image type of the pixel. It is characterized as being configured.

An image forming apparatus according to the present invention comprises the image processing apparatus according to the present invention, and forms an image by outputting the output image data processed by the image processing apparatus to the image output means. It is characterized by

An image processing method according to the present invention is an image processing method for subjecting input image data to image processing to obtain output image data, and outputting the output image data to an image output means provided with a plurality of color inks including fluorescent color inks. In, the characteristic amount is extracted from the input image data, the result of determining the use or non-use of the fluorescent color ink based on the extraction result is used as a fluorescence determination signal, and the image processing is performed based on the fluorescence determination signal. It is characterized by

In the image processing method according to the present invention, color information is extracted from the input image data, and the use or non-use of the fluorescent color ink for each pixel of the input image data is determined based on the color information. The result is used as a pixel fluorescence control signal, and the image processing is performed based on the pixel fluorescence control signal.

A computer program according to the present invention is
In a computer program for causing a computer to perform an image processing method of obtaining output image data by performing image processing on input image data, and outputting the output image data to an image output unit having a plurality of color inks including fluorescent color ink, A step of causing a computer to extract a characteristic amount from the input image data; a step of causing the computer to determine whether or not to use the fluorescent color ink based on the extraction result; and a step of causing the computer to determine the determination result as a fluorescence determination signal. Is output.

A computer program according to the present invention is
In a computer program for causing a computer to execute image processing for outputting the output image data to image output means having a plurality of color inks including fluorescent color inks, the image processing is performed on the input image data as output image data A step of extracting color information from the input image data, a step of causing a computer to determine the use or non-use of the fluorescent color ink for each pixel of the input image data based on the color information,
Causing the computer to output the determination result as a pixel fluorescence control signal.

The recording medium according to the present invention is an image processing method for subjecting input image data to image processing to obtain output image data, and outputting the output image data to an image output means provided with a plurality of color inks including fluorescent color inks. A computer-readable recording medium in which a computer program for execution by a computer is recorded, the step of causing the computer to extract a characteristic amount from the input image data, and the computer based on the extraction result. And a computer program for causing a computer to execute a step of determining whether or not the fluorescent color ink is used or not, and a step of causing the computer to output the determination result as a fluorescence determination signal.

The recording medium according to the present invention processes an input image data into output image data, and outputs an image processing method for outputting the output image data to an image output means provided with a plurality of color inks including fluorescent color inks. A computer-readable recording medium having a computer program recorded thereon for causing the computer to extract the color information from the input image data, and the computer based on the color information. Recording a computer program for executing a step of determining whether or not the fluorescent color ink is used for each pixel of the input image data, and a step of causing the computer to output the determination result as a pixel fluorescence control signal. It is characterized by being.

In the image processing apparatus according to the present invention, the extraction means for extracting the characteristic amount indicating the predetermined image characteristic from the input image data, and the fluorescence for judging whether or not the fluorescent color ink is used based on the extraction result. Since the document type determining unit that outputs a determination signal is provided, the characteristics of the fluorescent color ink can be selected by selecting the feature amount that indicates the feature of the image without relying on the determination depending on the experience of the user of the image processing apparatus or the individual difference. Whether or not to use the fluorescent color ink can be determined based on a judgment criterion that makes use of the above.

In the image processing apparatus according to the present invention, since the fluorescent color ink is used when the ratio of the pixels having the predetermined saturation or more to all the pixels is larger than the preset threshold value, the saturation of the entire original document is high. It is possible to select a document and use the fluorescent color ink only for the selected document, and it is possible to improve the image quality of the image formed by the image forming apparatus.

In the image processing apparatus according to the present invention, when the input image data is converted into the output image data, the image conversion apparatus is provided with the output conversion means for outputting the data including the data regarding the use or non-use of the fluorescent color ink. Upon receiving a fluorescence determination signal indicating whether or not to use the fluorescent color ink output by the document type determination means, for example, for image data having a predetermined saturation or higher, it is converted into image data using the fluorescent color ink. Can be output. That is, since the fluorescent color ink can be selectively used according to the saturation of each area of the document, the image quality of an image to be formed can be improved and wasteful use of the fluorescent color ink can be suppressed. .

In the image processing apparatus according to the present invention, after determining whether or not the fluorescent color ink should be used, the color correcting means uses the color information such as the saturation and the memory color to obtain the color correction means from the input image data. Since the pixel fluorescence control signal for selectively using the fluorescent color ink is output only to the portion (pixel), the output image data can be converted using the pixel fluorescence control signal, and the minimum unit of the image can be used. The fluorescent color ink can be applied to each pixel, and output image data capable of forming a finer image can be obtained. Further, by using the memory color data, it is possible to perform color correction that emphasizes the memory color rather than the original color reproduction, and it is possible to perform preferable image reproduction.

In the image processing apparatus according to the present invention, fluorescent color ink is applied to an image type, for example, a photographic area determined by the area separation processing, or a specific image such as a printed photographic original or a photographic paper photographic original. By applying it, it is possible to avoid the use of fluorescent color ink in the black character and black line drawing areas, and it is possible to obtain output image data that can suppress color fringing that may occur in the black character and black line drawing areas.

In the image forming apparatus according to the present invention, it is possible to provide an image forming apparatus capable of forming an image excellent in color reproducibility by utilizing the characteristics of fluorescent color ink.

In the image processing method according to the present invention, a feature amount indicating a predetermined image feature is selected from the input image data, it is determined whether or not the fluorescent color ink is used based on the selected result, and the determination is made. Since the document type determining means for outputting the result as the fluorescence determining signal is provided, the fluorescent color ink can be selected by selecting the feature amount that indicates the feature of the image without relying on the determination depending on the experience of the user of the image processing apparatus or the individual difference. Whether or not to use the fluorescent color ink can be determined based on the judgment criteria that makes use of the characteristics of.

In the image processing method according to the present invention, after determining whether or not to use the fluorescent color ink for the original,
The pixel fluorescence control signal is output by using the color information such as the saturation and the memory color to output the pixel fluorescence control signal that selectively uses the fluorescent color ink only in a necessary portion (pixel) of the input image data. An image processing method for obtaining output image data capable of performing finer image formation by enabling conversion of output image data using can do.

In the computer program according to the present invention, if incorporated in a computer, image processing for extracting a characteristic amount from input image data and determining whether or not to record using fluorescent color ink based on the extraction result. The method can be read and executed by a computer, and the image processing method can be general-purpose.

In the computer program according to the present invention, if incorporated in a computer, the fluorescent color ink is selectively used only in a necessary portion (pixel) of the input image data by using the color information of the input image data. The computer can read and execute an image processing method capable of applying the fluorescent color ink for each pixel, which is the minimum unit of the image, and the image processing method can be general-purpose.

The recording medium according to the present invention makes it possible to easily provide the computer program according to the present invention.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus including an image processing apparatus according to the present invention. In the figure, 1 is an image forming apparatus, for example, a digital color copying machine. Image forming apparatus 1
Is connected to the image processing device 2 and the image processing device 2 and is connected to the image input device 3 and the image processing device 2 as an image input device for inputting input image data to the image processing device 2 and output from the image processing device 2. An image output device 4 as an image output means for receiving image data and forming an image on an image forming medium,
An operation panel 5 for performing various operations is provided.

The image processing apparatus 2 serves as an A / D conversion unit 11, a shading correction unit 12, a document type determination unit 13 which is a document type determination unit, an input gradation correction unit 14, an area separation processing unit 15, and a color correction unit. Color correction unit 16, black generation undercolor removal unit 17, spatial filter processing unit 18, output tone correction unit 1
9, a gradation reproduction processing unit 20, and an output conversion unit 21 as an output conversion unit.

The image input device 3 is, for example, a CCD (Charge Coupled Dev) as an image reading means.
ice) is composed of a scanner unit equipped with a solid-state image pickup device, and a reflected light image from a document is converted into RGB (R: red, G: green,
The analog image signal of (B: blue) is read by the CCD and input to the image processing device 2.

The analog image signal read by the image input device 3 is input to the image processing device 2 as input image data, and inside the image processing device 2, the A / D conversion part 11, the shading correction part 12, the document type. Judgment unit 1
3, input tone correction unit 14, area separation processing unit 15, color correction unit 16, black generation undercolor removal unit 17, spatial filter processing unit 1
8, the output gradation correction unit 19, the gradation reproduction processing unit 20, and the output conversion unit 21 are sent in this order, and predetermined image processing is performed in each unit. Eventually CMYK and LC, LM
(C: cyan, M: magenta, Y: yellow, K: black,
It is output to the color image output device 4 as a digital image signal of LC: light cyan, LM: light magenta and a fluorescent digital image signal of Cf, Mf, Yf (Cf: fluorescent cyan, Mf: fluorescent magenta, Yf: fluorescent yellow). It

The A / D converter 11 performs analog / digital conversion of RGB analog image signals into RGB digital signals. The shading correction unit 12 is the A / D conversion unit 1.
The R, G, and B digital signals sent from No. 1 are subjected to processing for removing various distortions generated in the illumination system, the imaging system, and the imaging system of the image input device 3.

In the original type determining section 13, the RGB signal (the RGB reflectance signal) from which various distortions have been removed by the shading correcting section 12 is complement-color-inverted into a CMY signal, and the density signal etc. The signal is converted into a signal that can be easily handled by the adopted image processing system (hereinafter, simply referred to as image data, and may also be referred to as input image data or output image data). At the same time, in the manuscript type determination unit 13, the manuscript corresponding to the input image data is a character manuscript, a photographic manuscript (printed photograph / photographic paper photograph), or a character / photograph manuscript combining them. Is automatically determined. The determination as to whether or not to print using the fluorescent color ink on the input image data is also performed by the document type determination unit 13, and the determination result is output to the color correction unit 16 as a fluorescence determination signal Sd. To do.

The input tone correction unit 14 adjusts the color balance of the image data and, at the same time, performs image quality adjustment processing such as background density removal and contrast on the image data based on the determination result of the document type determination unit 13.

The area separation processing section 15 separates each pixel into a character area, a halftone dot area, or a photographic area based on the CMY signal (image data) of each pixel. Based on the separation result, the region separation processing unit 15 outputs the region identification signal Sr as an image type determination signal indicating which region the pixel belongs to, the color correction unit 16, the black generation undercolor removal unit 17, the spatial filter processing. The input image data output from the input tone correction unit 14 is directly output to the color correction unit 16 in the subsequent stage while being output to the unit 18 and the tone reproduction processing unit 20.

The color correction section 16 carries out a process for removing color turbidity based on the spectral characteristics of the CMY color materials containing unnecessary absorption components in order to realize faithful color reproduction. The color correction unit 16 extracts color information such as saturation and memory color of the input image data, and based on that, which part (pixel) of the input image data is extracted.
The pixel saturation determination signal Sc as a pixel fluorescence control signal for determining whether to use fluorescent color ink for the output conversion unit 2
Output to 1.

The black generation and undercolor removal section 17 is used for the CM after color correction.
Black generation for generating black (K) image data from image data of three colors of Y, and subtraction of K image data for black generation from original CMY image data to generate new CMY image data. Perform processing. In the black generation undercolor removal unit 17, the CMY three-color image data is converted into CMYK four-color image data.

As an example of black generation processing, a method of generating black by skeleton black is known as a general method. In this method, the input / output characteristic of the skeleton curve is y = f (x), the input data is C, M, Y, the output data is C ', M', Y ', K', and UCR (Un
der Color Removal rate is α (0 <α
If <1), the black generation and undercolor removal processing is expressed by the following equation (1). K ′ = f {min (C, M, Y)}, C ′ = C−αK ′, M ′ = M−αK ′, Y ′ = Y−αK ′ (1) That is, formula (1) C ′, M ′, Y ′ calculated by
K ′ becomes output image data (CMYK output image data).

The spatial filter processing unit 18 performs a spatial filter process by a digital filter on the CMYK image data input from the black generation and undercolor removal unit 17 based on the region identification signal Sr to correct the spatial frequency characteristic. By doing so, processing is performed so as to prevent blurring and deterioration of graininess of the output image. The tone reproduction processing unit 20 also includes the spatial filter processing unit 1.
Similar to step 8, predetermined processing is performed on the CMYK image data based on the area identification signal Sr.

For example, the areas separated as "characters" in the area separation processing unit 15 are processed by the spatial filter processing unit 18 in order to improve the reproducibility of black characters or color characters in particular. That is, the area separated as a character has a high frequency emphasis amount increased by the sharpness emphasis process of the spatial filter process. At the same time, the gradation reproduction processing unit 20 selects the binarization or multi-value conversion processing on a high resolution screen suitable for reproduction of high frequency.

Further, the area separated as the halftone dots by the area separation processing section 15 is subjected to the low-pass filter processing for removing the input halftone dot component in the spatial filter processing section 18. Then, the output gradation correction unit 19 performs an output gradation correction process for converting image data such as a density signal into a halftone dot area ratio which is a characteristic value of the image output device 4. After that, the gradation reproduction processing unit 20 performs gradation reproduction processing (halftone generation) for finally separating the image into pixels and processing so that each gradation can be reproduced.

Further, with respect to the area separated as a photograph by the area separation processing section 15, the gradation reproduction processing section 20 performs binarization or multi-value conversion processing on the screen with emphasis on gradation reproducibility.

The output converter 21 converts the output image data in accordance with the arrangement of the inkjet heads 22 (see FIGS. 2 and 3) in the inkjet recording type printer as the image output device 4, for example. Therefore, in the output conversion unit 21, the CMY transmitted from the gradation reproduction processing unit 20.
Depending on the arrangement of the inkjet heads 22, the image data of K is, for example, K, LC, LM, C, M, Y, Cf, M.
It is converted into image data of f and Yf (see FIG. 3). In addition, the output conversion unit 21 determines which image data to use the fluorescent color ink based on the pixel saturation determination signal Sc output from the color correction unit 16, and sets the corresponding image data to the fluorescent color image. Convert to data.

The image data (output image data) subjected to each of the above-described image processing is temporarily stored in the storage means, read at a predetermined timing, and input to the image output device 4. The image output device 4 outputs (prints) image data onto an image forming medium (for example, image forming paper). The image output device 4 is not limited to a printer, and a copying machine, a multi-function peripheral, or the like can be applied as long as it uses fluorescent color ink.

The operation panel 5 is composed of a display unit such as a liquid crystal display and a decision button (not shown), and the user can operate the image forming apparatus 1 via the operation panel 5. .

FIG. 2 is a perspective view showing a main structure of an ink jet recording type printer which is an example of an image output device. The inkjet recording type printer is roughly composed of an inkjet head 22, a carriage 23, a conveyance roller 24, a guide shaft 25, a holding means 26, and a motor 2.
7, a drive belt 28, and a maintenance unit 29. The carriage 23 has the inkjet head 22 mounted thereon, and has an arrow mark X with respect to the image forming medium PS.
It is relatively movable in the main scanning directions of the 1 and X2 directions. Then, while the image forming medium PS is fed from a sheet feeding unit (not shown) in the sub-scanning direction of arrow Y, image formation is performed by the inkjet head 22 that moves in the directions of arrow X1 and X2. The image forming mediums PS provided in the sheet feeding section (not shown) are fed one by one by a sheet feeding roller (not shown), and the inkjet head 22 is fed by a feeding roller 24 which is a feeding unit for feeding the image forming medium PS.
Supplied in parts. Image forming medium P on which image formation is completed
S is discharged to a paper discharge unit (not shown).

The ink jet head 22 is slidably supported on a guide shaft 25 and a holding means 26 extending in the main scanning direction (arrows X1, X2 directions), and its position with respect to the image forming medium PS is determined. Further, a drive belt 28 driven by a motor 27, which is a drive unit, is stretched in parallel with the guide shaft 25, and the inkjet head 22 is driven to be displaced by the drive belt 28. The maintenance unit 29 is a part where maintenance such as cleaning of the inkjet head 22 is performed.

FIG. 3 is a perspective view showing the structure of the main part of the ink jet head. The ink jet head 22 is a general multi-color ink, for example, C, M, Y, K, LC, L.
Ink tanks 22t for 6 color inks consisting of M and C
Three-color fluorescent ink tank 22 composed of f, Mf, and Yf
f and. These ink tanks 22f and 22t are connected to the image forming medium PS from the nozzle 22n according to the image data.
Ink is ejected on top.

A method of determining whether or not printing (image formation) is performed by using the fluorescent color ink, which is performed in the document type determining section 13, will be described with reference to FIGS. 4, 5 and 6. FIG. 4 is a block diagram showing a main part of a document type determination unit in the image processing apparatus according to the present invention, and FIG. 5 is a flowchart of image processing in the document type determination unit in the image processing apparatus according to the present invention. FIG. 6 is a graph showing an example of a saturation histogram created by the histogram creation unit in the image processing apparatus according to the present invention.

As shown in FIG. 4, the document type determining section 13
Is a histogram creation unit 31, a counting unit 32, a determination unit 3
3, the threshold value setting unit 33a is included, and the image processing for determining whether or not to use the fluorescent color ink is performed according to the flowchart of FIG.

The input image data sent from the shading correction section 12 is first subjected to complementary color inversion, converted into CMY data, and input to the saturation data calculation section 30. The saturation data calculating unit 30 determines the maximum density (m of the density values of C, M, and Y in the complementary CMY image data of CMY) (m
ax (C, M, Y)) and the one with the minimum concentration (min (C,
M, Y)) is selected and the difference is calculated (step S1). max (C, M, Y) and min (C, M, Y)
The difference is called as saturation data (max (C, M, Y) -min (C, M, Y)) because it is an index indicating the saturation of the image. That is, the saturation data is also one of the feature amounts of the image data. The saturation data calculated for each pixel is
Next, it is sent to the histogram creation unit 31. The histogram creation unit 31 creates a saturation histogram for the saturation data (step S2). The saturation data calculation unit 30 that performs the process of step S1 corresponds to an extraction unit that extracts the feature amount of the image.

Subsequently, the counting section 32 counts the number of pixels having a predetermined saturation or more, and calculates the ratio to the total number of pixels (step S3). After that, the determination unit 33 compares the ratio of the number of pixels having a predetermined saturation or more, which is obtained by the counting unit 32, with a threshold value preset in the threshold value setting unit 33a (step S4), and the ratio is larger than the preset threshold value. If (YES in step S4), the fluorescence determination signal Sd that the fluorescent color ink is used is output to the color correction unit 16 (step S5). If the above ratio is less than or equal to the preset threshold value (NO in S4), the process ends (END).

In FIG. 6, the horizontal axis represents the saturation of the saturation data,
The vertical axis represents the number of pixels. When the maximum density in the image processing apparatus 2 is set to 255, for example, the saturation value takes any value within the range of 0 to 255. FIG. 6A shows an example in which the ratio of the number of pixels having a predetermined saturation or higher is larger than a threshold value set in advance, and FIG. 6B shows the ratio of the number of pixels having a predetermined saturation or higher set in advance. This is an example of a case where the threshold is less than That is, the image of the original showing the saturation histogram as shown in FIG. 6A has a high saturation as a whole, and the image of the original having the saturation histogram as shown in FIG. 6B has a high saturation as a whole. Low. For the document shown in FIG. 6B, the saturation of the entire image is low, and the color tone changes when fluorescent color ink is used, which is not preferable.

Therefore, the fluorescence determination signal Sd for selectively using the fluorescent color ink is selectively output only in the case of the document (image data) showing the saturation histogram as shown in FIG. 6A. As a result, whether or not to use the fluorescent color ink is appropriately determined according to the saturation of the document without depending on the experience of the user himself or the determination depending on the individual difference. That is, it is possible to use the characteristics of the fluorescent color ink.

A method of determining which portion (which pixel) of the image data uses the fluorescent color ink will be described with reference to FIGS.
Will be explained. FIG. 7 is a block diagram showing a main part of a color correction unit in the image processing apparatus according to the present invention.
6 is a flowchart showing a pixel saturation determination process in a saturation determination unit in the image processing apparatus according to the present invention.

Fluorescence determination signal that fluorescent color ink is used
When the signal Sd is input to the color correction unit 16, the color correction unit
16, the input image is based on the color information of the input image data.
Whether to use fluorescent color ink for each pixel of data
Is determined. In this embodiment, the CMY signal is used.
The image data represented is L^*a^*b^*Convert it to data
Rani L^*a^*b^*Data is L^*C^*Converted to H data,
Above L^*C^*Saturation represented by H data is used as color information
To use. Note that L^*a^*b^*Data is CIE
(Commission International
e de l'Eclairage: International Commission on Illumination)
CIE1976L, which is a uniform color space defined by^*a^*b^*
Color space data, L^*Is the brightness, a^*b^*Is the chromaticity
It L^*a ^*b^*Data is L^*C^*Convert to H data
The method will be described later.

As shown in FIG. 7, the color correction unit 16 includes a saturation processing unit 40, and the saturation processing unit 40 includes a first color coordinate conversion unit 41, a saturation determination unit 42, and a second color coordinate conversion unit. 43, and the determination of pixel saturation in the saturation determination unit 42
This is performed according to the flowchart of FIG.

The input image data composed of CMY signals is first input to the first coordinate conversion section 41. First coordinate conversion unit 4
1 converts CMY image data into L ^* a ^* b ^* data (step S11). As a conversion method, a large number of color patches are created, L ^* a ^* b ^* values are colorimetrically measured, which is read into an image input device to obtain RGB input image data, and complementary color inversion is performed to obtain a CMY signal. . A transformation matrix or neural network that represents the correspondence of this image data,
By creating an LUT (look-up table: table reference), it becomes possible to convert input image data (complementary color-inverted CMY signals) into L ^* a ^* b ^* .
After that, the saturation C ^* and the hue angle H are calculated from the chromaticity a ^* b ^* from the following equation (2), and the L ^* a ^* b ^* data is converted into the L ^* C ^* H data (step S12). C ^* = √ (a * ² + b * ² ), H = tan ^-1 (b ^* / a ^* ) (2)

Next, the saturation determination unit 42 determines the saturation. First, it is determined whether or not the pixel saturation C ^* (saturation C ^* ) of one pixel is equal to or greater than a preset threshold value (step S13). If the pixel saturation C ^* is greater than or equal to the preset threshold value (YES in step S13), the pixel saturation determination signal Sc is output to the output conversion unit 21 (step S14). When the pixel saturation C ^* is smaller than a preset threshold value (NO in step S13), or after the pixel saturation determination signal Sc is output, it is determined whether the processing is completed for all pixels (step S15). If the processing has not been completed for all pixels (N in step S15)
O), the processing from step S13 to step S15 is repeatedly performed again, and when the processing is completed for all pixels (YES in step S15), the processing is ended (END).

It should be noted that the pixel saturation C ^{*, which} is the reference for saturation determination,
However, the threshold value set in advance may be set for each value of the hue angle H. For example, when the value of the hue angle H is 90 ° (yellow), the preset threshold value of the pixel saturation C ^* is 90.
It is preferable that Further, the value of the hue angle H is 330
In the case of ° (magenta), the preset threshold value of the pixel saturation C ^* is preferably 70.

When the processing shown in FIG. 8 is completed, the second color coordinate
By the conversion unit 43, L^*C^*Image data of H is color correction processing
It is converted into the processed CMY image data. How to convert
The method is a color patch CM output from the image output device 4.
Y data and L measured color^*C ^*Find the correspondence with the value of H
Therefore, similarly to the above-mentioned first color coordinate conversion unit, the conversion matrix,
Convert using local network, LUT, etc.

Pixel saturation determination signal S from the saturation determination section 42
c is input to the output conversion unit 21, and the image data of the corresponding pixel is converted into fluorescent color image data. This allows
Among the pixels of the original, fluorescent color ink is used for a portion (pixel) with high saturation, and it is possible to express a color gamut that cannot be produced by normal ink, and thus image quality can be improved. Further, since the fluorescent color ink is not used for the low-saturation portion of the document, printing can be performed without being given a change in color tone due to the fluorescent color ink.

In the present embodiment, the color correction unit 16 determines which portion (pixel) of the image data the fluorescent color ink is used for. This determination is the original type determination. It may be performed by the unit 13. In this case, for the pixels having a predetermined saturation or higher as shown in FIG. 6A, the document type determination unit 13 transfers the image data to the output conversion unit 21 so that the output conversion unit 21 converts the image data into fluorescent color image data. Fluorescence determination signal S (corresponding to pixel saturation determination signal Sc)
It is preferable that d is output. According to this, it is possible to improve the image quality by performing the printing using the fluorescent color ink in the highly saturated area of the input image data without performing the determination of the saturation in the color correction unit 16.

The fluorescent color ink is used in the area separation processing unit 1.
It is preferable to apply to the area determined as the halftone dot area and the photographic paper photograph area according to 5. That is, based on the area identification signal Sr output from the area separation processing unit 15,
In the color correction unit 16, it is preferable to perform the saturation determination only for the areas determined to be the halftone dot area and the photographic paper photograph area. According to this, it is possible to avoid a situation in which the color misregistration that may occur in the black character and the black line drawing portion of the character area becomes conspicuous due to the use of the fluorescent color ink.

As a method of separating the input image data into the character, halftone dot, and photographic areas in the area separation processing unit 15, for example, “Research Report of the Institute of Image Electronics Engineers of Japan, 90-06-0” is used.
4 ”can be used. The details will be described below. M × N (M, N
Is a natural number) Within the block of pixels, the following (1) to (3)
And the region identification signal S of the pixel of interest.
Let r.

(1) The average value (Dave) of the image data levels is calculated for the central 9 pixels in the block, and each pixel in the block is binarized using the average value. Further, the maximum pixel data level (Dmax) and the minimum pixel data level (Dmin) are also obtained at the same time.

(2) In the halftone dot area, the halftone dot area is identified by utilizing the large fluctuation of the image data in the small area and the high density compared to the background. The number of change points from 0 to 1 and the number of change points from 1 to 0 in the main scanning direction and the sub-scanning direction are obtained for the binarized data, and K is obtained respectively.
h and Kv. The above Kh and Kv are respectively compared with preset threshold values Th and Tv, and when both of them exceed the threshold value, a halftone dot area is set. In addition, in order to prevent erroneous determination of the background, the difference (Dmax-Dav) between the maximum pixel data level (Dmax) and the average value (Dave) of the image data levels.
e), and the average value of the image data levels (Dave)
Difference (Dave) between the minimum pixel data level (Dmin) and
-Dmin) is compared with preset threshold values B1 and B2, respectively. Then, Dmax-Dave> B1, Dav
If all of e-Dmin> B2, Kh> Th, and Kv> Tv are satisfied, it is determined to be a halftone dot region, and otherwise, it is determined to be a non-halftone dot region.

(3) Since it is considered that the difference between the maximum pixel data level and the minimum pixel data level is large and the density is high in the character area, the character area is identified as follows. The previously obtained maximum and minimum pixel data levels in the non-dot area and their difference (Dsub) are compared with preset thresholds Pa, Pb, and Pc, and Dmax> Pa, Dmin <Pb, or Dsub> Pc. In any of the above cases, it is determined to be the character area, and in the cases other than the above conditions, it is determined to be the photographic paper photograph area. In the above algorithm, the background area is also determined as the photographic paper photograph area, so the background area is detected and distinguished in advance. As this method, for example, the respective data levels of the data of the target pixel (complementary color-inverted CMY image data) are set to Dr, Dg, and Db, and the preset threshold is THbac.
If k, Dr <THback, Dg <THbac
When both k and Db <THback are satisfied, it is determined to be the base region.

It is also possible to select the image mode (image type determination signal) from the operation panel 5 and use the fluorescent color ink in the print photograph mode and the photographic paper photograph mode.

As another embodiment of the present invention, the stored color can be used as color information for determining whether or not the fluorescent color ink is used for each pixel.
The memory color refers to a color that a person has in memory of things that are familiar to him, such as the sky and leaves. That is, the memory color is a color that a person imagines with respect to a certain target object, and if the memory color is used for a familiar target object when reproducing an image of a document, visually preferable color reproduction can be realized. . The memorized color is determined by selecting from the Munsell color chart the color to be imaged for the above-mentioned familiar objects. Memory colors selected by this method are often more saturated than actual colors.

Therefore, for the image data of the color of the object that is present in the familiar environment in which the memory color is more saturated than the actual color, the saturation is represented by using the fluorescent color ink. Is increased, and visually preferable color reproduction is possible. That is, the use of the memory color (memory color data) as the color information means that the range of image data determined as the memory color (memory color data) is set in advance for the image data composed of CMY signals. For image data existing within the range, it means that fluorescent color ink is used as a memory color. For example, when the density is expressed in the range of 0 to 255, the input image data composed of CMY signals is 105 ≦ C ≦ 145, 65 ≦ M ≦ 105,0.
Those in the range of ≦ Y ≦ 55 are preferably represented as a memory color as a color representing sky blue, and fluorescent color ink is used. Also, the input image data composed of CMY signals is 165 ≦ C ≦ 205, 85 ≦ M ≦ 135,
Those in the range of 195 ≦ Y ≦ 235 are preferably represented as a memory color as a color representing the green color of the leaves of the tree, and fluorescent color ink is used. However, with respect to the skin color, the saturation of the memory color is generally lower than that of the actual color, and thus it is not preferable to use the fluorescent color ink as the memory color of the skin color.

It is to be noted that the central processing unit CPU (not shown) determines whether or not the input image data is within the predetermined range as described above, and the output conversion unit 2
A pixel fluorescence control signal that prompts the use of fluorescent color ink is output for the pixels corresponding to 1. In this case, the color correction unit 1
Unlike the configuration shown in FIG. 7, it is preferable that the configuration of 6 is composed of a member for which the direct conversion method using the LUT and the three-dimensional interpolation method are performed.

Further, in the present invention, a program capable of executing the image processing method according to the present invention is created, and the program is stored in a recording medium such as a hard disk, a floppy (registered trademark) disk or a CD-ROM. May be. With this configuration, it is possible to easily supply the recording medium to a computer or the like, and it is possible to cause the computer to easily execute the image processing method according to the present invention.

The program according to the present invention may be applied to a computer as software, for example, or a printer driver incorporating the program according to the present invention may be provided in the computer. Such an example will be described with reference to FIG.

FIG. 9 is a block diagram showing an example in which the image processing method according to the present invention is realized by a computer. More specifically, image processing in which fluorescent color ink is used for a portion (pixel) with high saturation is FIG. 3 is a block diagram showing a configuration of a printer driver included in the computer for performing the operation.

In the figure, the computer 51 comprises a printer driver 52, a communication port driver 57, and a communication port 58. The printer driver 52 includes a color correction unit 53, a gradation reproduction processing unit 54, an output conversion unit 55,
It comprises a printer language translation unit 56. Further, the computer 51 is an inkjet recording type printer (image output device) including fluorescent color ink via a communication port driver 57 such as RS232C, LAN, etc., and a communication port 58.
59 is connected.

The image data generated by executing various application programs in the computer 51 is expanded into image data and sent to the color correction section 53 in the printer driver 52. Although not shown, the computer 51 incorporates a program for performing the same process as the process performed by the document type determination unit 13 described above as software, and the color correction unit 53 stores the fluorescent color ink. A fluorescence determination signal Sd indicating whether or not to use is sent. In the color correction unit 53, the same processing as the color correction unit 16 included in the image processing apparatus 2 described above is performed on the image data, and the pixel saturation determination signal Sc is output to the output conversion unit 55.
Send to. Further, the color correction unit 53 also performs the processing in the black generation undercolor removal unit 17 in the image processing device 2. Color correction unit 5
The image data output from the image reproduction unit 3 is next processed by the tone reproduction processing unit 5
4, and gradation reproduction processing is performed. Subsequently, the image data is sent to the output conversion unit 55, and the image data is converted according to the arrangement of the inkjet head 22 (see FIGS. 2 and 3) of the printer 59. In this conversion, based on the pixel saturation determination signal Sc, the image data of the pixel for which the fluorescent color ink is to be used is converted so as to be output from the fluorescent color ink nozzle. The image data processed by the output conversion unit 55 is the printer language translation unit 56.
Sent to the printer for interpretation of the printer language.

The image data output from the printer language translation unit 56 includes the communication port driver 57 and the communication port 58.
And is input to the image output device 59, which is a printer. The image output device 59 outputs the input image data to an image forming medium such as an image forming sheet.

The program and recording medium according to the present invention can be additionally provided in the existing computer and printer as software and printer driver as described above. According to this, it becomes possible to easily implement the image processing method of the present invention.

In the present embodiment, a digital color copying machine is used as the image forming apparatus and a printer is used as the image output apparatus. However, the image forming apparatus is not limited to the digital function having a printer function, a copy function and a fax function. It may be a multifunction machine.

[0085]

As described in detail above, in the image processing apparatus according to the present invention, the image quality of the formed image in the image forming apparatus can be improved. In other words, the fluorescent color ink can express a color tone with high saturation compared to normal ink,
By applying the fluorescent color ink to the image data whose saturation is saturated with the normal ink, it is possible to reliably reproduce a color tone closer to the original image.

In the image processing apparatus according to the present invention, it is possible to select a highly saturated image as an image and use the fluorescent color ink only for the selected image. The image quality of can be improved.

In the image processing apparatus according to the present invention, the fluorescent color ink can be selectively used according to the saturation of each area of the input image, and the image quality of the formed image in the image forming apparatus can be improved. Further, since the data regarding the use or non-use of the fluorescent color ink is reflected in the output image data, the fluorescent color ink is not wastefully used.

The image processing apparatus according to the present invention can realize an image forming apparatus using fluorescent color ink for each pixel, which is the minimum unit of an image, and can improve the image quality of a formed image in the image forming apparatus. In addition, by adopting the memory color data as the determination target for using the fluorescent color, it is possible to perform color correction that emphasizes the memory color rather than the original color reproduction, and it is possible to perform preferable image reproduction.

In the image processing apparatus according to the present invention, an image type, for example, a photographic area determined by the area separation processing, or a fluorescent color for a specific image such as a printed photographic original or a photographic paper photographic original. By applying the ink, it is possible to avoid the use of fluorescent color ink in the black character, black line drawing area, it is possible to obtain output image data that can suppress the color fringing that may occur in the black character, black line drawing area, Since the proper image is formed, the image quality of the formed image in the image forming apparatus can be improved.

In the image forming apparatus according to the present invention, it is possible to form an image excellent in color reproducibility by utilizing the characteristics of fluorescent color ink. That is, since the fluorescent color ink can be selectively used only in the portion where the characteristics of the fluorescent color ink can be utilized, the fluorescent color ink is not wastefully used, and an image forming apparatus with low running cost can be realized. .

In the image processing method according to the present invention, the fluorescent color ink is applied to the image data of the original document whose saturation is saturated with the normal ink, thereby reliably reproducing the color tone closer to the original image. it can. Further, an image processing method using fluorescent color ink for each pixel, which is the minimum unit of an image, can be realized, and the image quality of a formed image in image formation can be improved.

The computer program according to the present invention is incorporated into a computer to extract a characteristic amount from input image data, and based on the extraction result, it is determined whether or not recording is performed using fluorescent color ink. The image processing method according to the present invention can be read and executed by a computer, and the image processing method according to the present invention can be general-purpose. Further, in the computer program according to the present invention, the fluorescent color ink can be selectively used only in a necessary portion (pixel) of the input image data by using the color information of the input image data. The computer can read and execute the image processing method according to the present invention in which the fluorescent color ink can be applied to each pixel, which is the minimum unit of, and the image processing method according to the present invention can be general-purpose. .

The recording medium according to the present invention can easily provide the computer program according to the present invention.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus including an image processing apparatus according to the present invention.

FIG. 2 is a perspective view showing a main configuration of an inkjet recording type printer which is an example of an image output device.

FIG. 3 is a perspective view showing a main configuration of an inkjet head.

FIG. 4 is a block diagram showing a main part of a document type determination unit in the image processing apparatus according to the present invention.

FIG. 5 is a flowchart of image processing in a document type determination unit in the image processing apparatus according to the present invention.

FIG. 6 is a graph showing an example of a saturation histogram created by a histogram creation unit in the image processing apparatus according to the present invention.

FIG. 7 is a block diagram showing a main part of a color correction unit in the image processing apparatus according to the present invention.

FIG. 8 is a flowchart showing a pixel saturation determination process in a saturation determination unit in the image processing apparatus according to the present invention.

FIG. 9 is a block diagram showing an example in which an image processing method according to the present invention is realized by a computer.

[Explanation of symbols]

1 Image forming device 2 Image processing device 3 Image input device 4 Image output device 5 Operation panel 11 A / D converter 12 Shading correction section 13 Document type determination unit 14 Input tone correction section 15 Area separation processing unit 16 color correction section 17 Black generation undercolor removal unit 18 Spatial filter processing unit 19 Output tone correction section 20 gradation reproduction processing section 21 Output converter 30 Saturation data calculator 31 Histogram creation section 32 counter 33 Judgment section 33a Threshold setting section 40 Saturation processor 41 First color coordinate conversion unit 42 Saturation determination unit 43 Second color coordinate conversion unit 51 computer Sd fluorescence determination signal Sc pixel saturation determination signal Sr area identification signal

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/46 B41J 3/04 101Z 5L096 F term (reference) 2C056 EA04 EA05 EA24 EB58 EB59 EC65 EE18 FA02 FA10 5B057 AA11 BA02 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CE17 CE18 DA17 DB02 DB06 DB09 DC19 DC25 DC36 5C074 BB16 DD24 DD26 DD27 FF15 GG09 5C077 LL20 MP08 PP28 PP33 PP51 PQ08 PQ12 PQ12 PQ12 PQ12 TT05 5C079 HA17 5A07A02 AQA15A02

Claims (14)

[Claims] 1. An image processing apparatus for subjecting input image data to image processing to output image data, and outputting the output image data to an image output means provided with a plurality of color inks including fluorescent color inks. The fluorescence determination signal is provided with extraction means for extracting a characteristic amount, and a document type determination means for determining the use or non-use of the fluorescent color ink based on the extraction result and outputting the determination result as a fluorescence determination signal. An image processing apparatus, wherein the image processing is performed based on the above. 2. The feature amount is saturation data, and when the ratio of pixels having a predetermined saturation or more to all pixels in the input image data is larger than a predetermined threshold value, the fluorescence determination signal is the fluorescent color. The image processing apparatus according to claim 1, wherein the signal is a signal indicating that ink is used. 3. An output conversion means for converting the input image data into output image data including data regarding use or non-use of the fluorescent color ink based on the fluorescence determination signal and outputting the output image data. The image processing apparatus according to claim 1. 4. Color information is extracted from the input image data, the use or non-use of the fluorescent color ink is determined corresponding to each pixel of the input image data based on the color information, and the determination result is displayed. The color correction means for outputting as a pixel fluorescence control signal is provided, and the image processing is performed based on the pixel fluorescence control signal.
The image processing device according to any one of 1 to 3. 5. The color information is saturation data, and the color correction means outputs a pixel fluorescence control signal for using the fluorescent color ink corresponding to a pixel having a predetermined saturation or more. The image processing apparatus according to claim 4, wherein 6. The configuration in which the color information is memory color data, and the color correction means outputs a pixel fluorescence control signal for using the fluorescent color ink corresponding to a pixel within the range of the memory color data. The image processing apparatus according to claim 4, wherein: 7. The color correction means is configured to determine whether or not the fluorescent color ink is used for the pixel based on an image type determination signal for determining an image type of the pixel. The image processing apparatus according to claim 4. 8. A configuration comprising the image processing device according to claim 1, wherein an image is formed by outputting output image data processed by the image processing device to the image output means. An image forming apparatus characterized by the following. 9. An image processing method, wherein image processing is performed on input image data to obtain output image data, and the output image data is output to an image output unit having a plurality of color inks including fluorescent color inks. An image processing characterized by extracting a characteristic amount, determining the use or non-use of the fluorescent color ink based on the extraction result as a fluorescence determination signal, and performing the image processing based on the fluorescence determination signal. Method. 10. The pixel fluorescence control signal is a result of extracting color information from the input image data and determining whether or not the fluorescent color ink is used for each pixel of the input image data based on the color information, The image processing method according to claim 9, wherein the image processing is performed based on the pixel fluorescence control signal. 11. An image processing method for causing a computer to execute image processing of input image data to obtain output image data, and outputting the output image data to an image output means provided with a plurality of color inks including fluorescent color inks. In the computer program, a step of causing a computer to extract a characteristic amount from the input image data, a step of causing the computer to determine whether or not to use the fluorescent color ink based on the extraction result, and a determination result of the computer. Is output as a fluorescence determination signal, and the computer program is executed. 12. An image processing method for causing a computer to execute image processing of input image data to obtain output image data, and outputting the output image data to an image output means provided with a plurality of color inks including fluorescent color inks. In a computer program, causing a computer to extract color information from the input image data, and causing the computer to determine whether or not to use the fluorescent color ink for each pixel of the input image data based on the color information. And a step of causing a computer to output the determination result as a pixel fluorescence control signal. 13. An image processing method for causing a computer to execute image processing of input image data to obtain output image data, and outputting the output image data to an image output means having a plurality of color inks including fluorescent color inks. A computer-readable recording medium in which a computer program is recorded, the step of causing a computer to extract a characteristic amount from the input image data, and causing the computer to extract the fluorescent color ink based on the extraction result. A computer-readable record characterized by recording a computer program for causing the computer to execute a step of determining whether to use or not to use and a step of causing the computer to output the determination result as a fluorescence determination signal. Medium. 14. A computer for causing a computer to execute an image processing method for processing input image data into output image data, and outputting the output image data to an image output means having a plurality of color inks including fluorescent color inks. A computer-readable recording medium in which a program is recorded, the method comprising causing a computer to extract color information from the input image data, and causing the computer to extract each of the input image data based on the color information. A computer program for causing a computer to execute a step of determining whether or not the fluorescent color ink is used for a pixel and a step of causing a computer to output the determination result as a pixel fluorescence control signal is recorded. A computer-readable recording medium.