JP2003198846A - Image reader and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader for changing gradation of image data obtained by reading in accordance with a histogram of a density obtained from an automatically read original. <P>SOLUTION: A ratio of frequency K=(W+B)/M is obtained, where a value W is obtained by integrating the frequency by each gradation toward a thinner side from a prescribed density da, a value B is obtained by integrating the frequency by each gradation toward a denser side from a prescribed density db, and a value M is obtained by integrating the frequency by each gradation from the prescribed density da to the prescribed density db and the image quality mode is set according to the ratio K of the frequency. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for reading an image from an original, and more particularly, to an image reading apparatus which is a text original, a photographic original, or a mixed photograph and text original. The present invention relates to an image reading device that changes the gradation of image data obtained by reading.

[0002]

2. Description of the Related Art At present, in a copying machine, which is one of image reading apparatuses, is a read document a character document composed of binary images such as characters so that a high quality document is printed out. , Or a photographic manuscript composed of high-definition images such as photographs, or a mixed manuscript composed of mixed characters and photographs, the gradation of the image data obtained by scanning the manuscript change.

In such a copying machine, in the character mode for reading a character original, a binarization process for clarifying the contrast of black and white is performed. Also, when the photo mode for reading a photo original or the mixed mode for reading a mixed original is used,
Halftone processing is performed to express the halftone. Further, in the mixed mode and the photograph mode, the gradation of the image data is changed so as to have higher definition in the photograph mode.

[0004]

As described above, in the image reading apparatus typified by the copying machine, the image quality mode is changed to the character mode, the photographic mode, and the mixed mode depending on the type of the original to read the image. However, it is necessary for the user to change the image quality modes each time the document is placed on the copying machine. Therefore, when there are multiple originals, the originals are read using the DF (Document Feeder).
It is necessary to place it on F, which is troublesome for the user.

Further, Japanese Laid-Open Patent Publication No. 7-38745 proposes an image forming apparatus capable of changing the image quality according to the image information of a document by using a neural network. However, when such a neural network is used, the system becomes large and uniform results cannot be obtained.

In view of such a problem, the present invention is an image reading apparatus capable of changing the gradation of image data obtained by reading according to a density histogram obtained from an automatically read document. The purpose is to provide.

[0007]

In order to achieve the above object, an image reading apparatus according to a first aspect of the present invention has a reading unit for reading an original to obtain image data, and
Based on the set image mode, one image quality mode is set from a plurality of image quality modes in which the image quality is changed by changing the gradation of image data with respect to the image drawn on the document read by the reading unit. In the image reading apparatus for processing the image data, one image quality mode is set from the plurality of image quality modes according to the shape of the histogram of the density distribution of the document obtained from the image data.

In such an image reading apparatus, as described in claim 2, in the histogram of the density distribution, the integrated value W of the frequency with respect to the density lower than the first density and the density higher than the second density. After obtaining the integral value B of the frequency with respect to the concentration and the integral value M of the frequency with respect to the concentration between the first and second concentrations, the ratio of the frequencies K = (B + W) /
The image quality mode may be set according to the value of M. That is, the image quality mode is set based on the proportion of the distribution of the intermediate density between the first and second densities.

At this time, further, as described in claim 3, the plurality of image quality modes are a character mode when a document in which many low gradation images such as characters are read is read.
A photograph mode when a document occupying a large number of high-gradation images such as photographs is read, and a mixed mode when a document having each of the low-gradation image and the high-gradation image is read. When the frequency ratio K is higher than a predetermined value Ka, the character mode is set. When the frequency ratio K is lower than a predetermined value Kb (Kb <Ka), the photo mode is set and the frequency ratio K is set. When is a value between the predetermined values Ka and Kb, the mixed mode may be set.

Further, as described in claim 4, in the density distribution histogram, the image quality mode may be set according to an intermediate density range having a predetermined width and a predetermined frequency. That is, in the distribution of the intermediate density, the image quality mode is set according to the width of the range having a predetermined frequency.

At this time, further, as described in claim 5, the plurality of image quality modes are a character mode at the time of reading an original document in which low gradation images such as characters occupy a large amount.
A photo mode when reading a manuscript occupying a large number of high-tone images such as photographs, and a mixed mode when reading a manuscript having each of the low-gradation image and the high-gradation image, When the intermediate density range Ra that is lower than the frequency threshold Ta is wider than the predetermined value Rx, the character mode is set, the intermediate density range Ra is narrower than the predetermined value Rx, and the frequency threshold Tb (Tb> Ta). When the lower intermediate density range Rb is narrower than the predetermined value Ry, the photograph mode is set, and the intermediate density range Ra is narrower than the predetermined value Rx and the intermediate density range Rb is wider than the predetermined value Ry. May be set to the mixed mode.

An image reading apparatus according to a sixth aspect is the image reading apparatus according to any one of the first to fifth aspects, further comprising a memory for temporarily recording the image data obtained by the reading unit, A memory control unit that controls reading and writing of the image data with respect to the memory;
A histogram of the density distribution of the original is formed from the image data read from the memory by the memory control unit, an image quality mode is set according to the shape of the histogram of the density distribution, and image data is set according to the set image quality mode. And an image processing unit that performs image processing on the.

An image reading apparatus according to a seventh aspect is the image reading apparatus according to any one of the first to fifth aspects, wherein the density distribution of the original is determined from the image data obtained by the reading unit. And a first image processing unit that sets the image quality mode according to the shape of the histogram of the density distribution, and the image data provided through the first image processing unit is temporarily recorded together with the set image quality mode. A memory, a memory control unit that controls reading and writing of the image data from and to the memory, and an image quality mode that is also read from the memory with respect to the image data read from the memory by the memory control unit. And a second image processing unit that performs image processing according to the above.

In the image reading apparatus according to claim 6 or 7, as described in claim 8, such as a copying machine provided with an image reproducing section for reproducing the image data subjected to the image processing. It may be an image forming apparatus.
Further, as described in claim 9, an image transmission device such as a network scanner or a facsimile device provided with an interface for transmitting the image data subjected to the image processing to the outside may be used. Further, as described in claim 10, an image recording apparatus such as a network scanner provided with a recording medium for recording the image data subjected to the image processing may be used.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. First, the configuration of an image reading apparatus common to the following embodiments will be described. FIG. 1 is a block diagram showing an internal configuration of a copying machine which is an image reading device. In each of the following embodiments, a copying machine will be taken as an example of the image reading apparatus.

The copying machine shown in FIG. 1 is a CCD which reads an image from a document and generates image data by performing a photoelectric conversion operation.
Reading unit 1 composed of (Charge Coupled Device)
An A / D conversion unit 2 for converting the image data read by the reading unit 1 into digital data, and an input side image for performing shading correction and gamma correction on the image data given from the A / D conversion unit 2. The processing unit 3, the memory control unit 4 for writing the image data given from the input side image processing unit 3 into the memory 5, and the memory 5 for writing and reading the image data by the memory control unit 4.
An output side image processing section 6 for performing various image processing such as edge enhancement on the image data read out from the memory 5 by the memory control section 4, and an optical print according to the image data given by the output side image processing section 6. The scanning circuit 7 for driving each light emitting element of the head 8 and the optical print head 8 in which the provided light emitting elements are ON / OFF controlled by the scanning circuit 7.

The outline of the operation of the copying machine having such a configuration will be briefly described. In the reading unit 1, reflected light from a document illuminated by a fluorescent lamp or the like is incident on the CCD, and image data which is an electric signal obtained by photoelectrically converting the incident light is A / D conversion unit. At 2, it is converted to digital data. When the image data to be the digital data is supplied to the input side image processing unit 3, shading correction for correcting the characteristic of the fluorescent lamp is performed, and then gamma correction for correcting the gamma characteristic is performed. The image data thus obtained is formed as BITMAP data having data for each point.

Then, this image data is stored in the memory controller 4
Is temporarily stored in the memory 5. After that, the image data temporarily stored in the memory 5 is read by the memory control unit 4 and given to the output side image processing unit 6. The output-side image processing unit 6 performs either binarization processing or halftone processing on the supplied image data. That is, when the processing is performed in the character mode, the image data is subjected to binarization processing such as edge enhancement processing, binary coding processing, and isolated point removal processing.
Further, when the processing is performed in the photo mode or the mixed mode, halftone processing by the error diffusion method or the dither matrix method is performed.

As described above, the scanning circuit 7 scans the optical print head 8 based on the image data subjected to the various image processings in the output side image processing section 6. That is, ON / OFF of the light emitting element provided in the optical print head 8 is controlled for each line according to the image data to print and reproduce the image on the recording paper. Note that the electrostatic reproduction method is used for the print reproduction, but a thermal method or an inkjet method may be used in which the ON / OFF of the current applied to the thermal resistance is controlled to perform the print reproduction on the thermal paper or the recording paper.

Each embodiment having the above-mentioned configuration and the general operation in common will be described below. In each of the following embodiments, since the setting processing method for setting the character mode, the photograph mode, and the mixed mode and the block for performing the setting processing are different from the placed document, the setting processing method and the setting processing are performed. The explanation will focus on blocks. Therefore, the description of the points that are the same as the above-described general operation will be omitted.

<First Embodiment> A first embodiment of the present invention will be described below. In the present embodiment, in the copying machine of FIG. 1 that operates as described above, the output side image processing unit 6 performs the setting process of setting the character mode, the photo mode, and the mixed mode.

As described above, the image data of one original read by the reading unit 1 is converted into digital data by the A / D conversion unit 2 and then given to the input side image processing unit 3 for each pixel. , Shading correction and gamma correction are performed, and stored in the memory 5 by the memory control unit 4. The image data of one original document thus stored in the memory 5 is read by the memory control unit 4 and given to the output side image processing unit 6. The image data stored in the memory 5 becomes image data for each pixel of the CCD provided in the reading unit 1.

In this way, the output side image processing unit 6 is provided with the memory 5
When the image data stored in the image data is given, the density of each pixel on the document is sequentially confirmed for each pixel from the data amount of the image data. In this way, when the density of each pixel is confirmed, the number of pixels for each density is counted, and the appearance frequency for each density is obtained to create a density histogram for one original as shown in FIG. To be done. That is, a histogram is created by calculating the appearance frequency of digital image data for each gradation of the data amount.

In this way, when the density histogram for one document as shown in FIG. 2 is created, the predetermined density d is obtained.
By integrating the frequency for each gradation with respect to the side lighter than a, the area W of the histogram on the white side becomes a predetermined density db (db
The area B of the histogram on the black side is determined to be the predetermined density da by integrating the frequency for each gradation on the darker side than> da).
To the predetermined density db, the area M of the histogram in the halftone is obtained by integrating the frequency for each gradation.

Areas W, B, M of such a histogram
When obtaining each, the data amount of the image data and the data amount corresponding to the predetermined densities da and db are compared for each pixel. Then, when the image data of pixels that become darker than the density da is input to the output-side image processing unit 6, the area W of the histogram is counted, and the image data of pixels that become darker than the density db is input to the output-side image processing unit 6. Then, the area B of the histogram is counted, and when the image data of pixels that are darker than the density da and thinner than the density db are input to the output side image processing unit 6, the area M of the histogram is counted. In this way, the areas W, B, M of each histogram are obtained.

By providing the values of the areas W, B, and M of each histogram obtained in this way to the following equation, the ratio K of the frequency of the white side and the frequency of the black side with respect to the frequency of the halftone can be obtained. K = (W + B) / M

Therefore, when the histogram as shown in FIG. 3A is formed and the frequency ratio K becomes larger than the predetermined value Ka, it is considered that a character document having a high frequency on the white side and a frequency on the black side are read. The character mode is set to perform image processing. Further, when a histogram as shown in FIG. 3B is formed and the frequency ratio K becomes smaller than a predetermined value Kb (Kb <Ka), it is considered that a photographic document having a high frequency of halftones has been read. The mode is set to perform image processing. Further, when the histogram as shown in FIG. 3C is formed and the frequency ratio K is between Kb and Ka, the image processing is performed as a mixed mode in which a mixed document in which characters and photographs are mixed is read. Set.

By thus setting each image quality mode, the image processing unit 6 on the output side performs image processing on the image data read from the memory 5 according to each image quality mode. That is, in the output-side image processing unit 6, for the image data read from the memory 5, the binarization processing is performed when the character mode is set, and the half tone with a low gradation is set when the mixed mode is set. When the tone processing is set to the photo mode, halftone processing with high gradation is performed.

In this way, the output side image processing unit 6 automatically sets each image quality mode, performs image processing according to each image quality mode, and then supplies the image data subjected to the image processing to the scanning circuit 7. Then, the operation of the optical print head 8 is controlled to print and reproduce the image on the recording paper.

<Second Embodiment> A second embodiment of the present invention will be described below. In the present embodiment, in the copying machine of FIG. 1 that operates as described above, the input side image processing unit 3 performs the setting process of setting the character mode, the photo mode, and the mixed mode. In the present embodiment,
The same determination processing as the output side image processing unit 6 in the copying machine of the first embodiment is performed. Therefore, the detailed description of the detailed processing operation of the setting operation will be omitted.

As described above, the image data of one original read by the reading unit 1 is converted into digital data by the A / D conversion unit 2 and then given to the input side image processing unit 3 for each pixel. , Shading correction and gamma correction are performed. The image data thus subjected to the shading correction and the gamma correction is given to the memory control unit 4 and stored in the memory 5, and the appearance frequency is obtained for each gradation of the data amount of the image data, and the appearance frequency of FIG. A histogram like this is created.

From the histogram thus created,
Similar to the first embodiment, the histogram areas W, B,
After each M is obtained, the ratio K of the frequency of the white side and the frequency of the black side to the frequency of the halftone is calculated. Then the ratio K of this frequency
And the predetermined values Ka and Kb are compared to set one of the character mode, the photo mode, and the mixed mode. Then, after the set image quality mode is given to the memory control unit 4, it is stored together with the image data stored in the memory 5 by the memory control unit 4. At this time, when each of the areas W, B, and M of the histogram is obtained, it is obtained by counting the image data in each density range, as in the first embodiment.

Thereafter, the image data stored in the memory 5 and the image quality mode set and stored together in the memory 5 are read by the memory control unit 4 and then given to the output side image processing unit 6. . Then, the output side image processing unit 6
In, the given image data is similarly subjected to image processing according to the read image quality mode. That is, binarization processing is performed when the image data is stored in the memory 5 so as to be processed in the character mode, and gradation processing is performed when the image data is stored in the memory 5 so that the image data is processed in the mixed mode. Low halftone processing of high gradation is performed when the image data is stored in the memory 5 so as to be processed in the photographic mode.

As described above, after the image quality modes are automatically set in the input side image processing section 3, the image data is stored in the memory 5 together with the image quality modes set. Then, according to the image quality mode stored in the memory 5,
After performing image processing on the image data stored in
The image data subjected to the image processing is given to the scanning circuit 7, and the operation of the optical print head 8 is controlled, whereby the image is printed and reproduced on the recording paper. Therefore, unlike the first embodiment, since the image quality mode is set before the image data is stored in the memory 5, it is not necessary to set the image quality mode at the time of output, and the time taken at the time of output is reduced. be able to.

<Third Embodiment> A third embodiment of the present invention will be described below. In the present embodiment, in the copying machine of FIG. 1 that operates as described above, as in the second embodiment, the input side image processing unit 3 performs the setting process for setting the character mode, the photo mode, and the mixed mode. Be seen.

As described above, as in the second embodiment,
The image data of one original read by the reading unit 1 is A
After being converted into digital data by the / D conversion unit 2, the data is given to the input side image processing unit 3 for each pixel and subjected to shading correction and gamma correction. When the shading correction and the gamma correction are performed, the image data is given to the memory control unit 4 and stored in the memory 5, and
Each image quality mode is set by performing the operation process according to the flowchart of FIG.

The setting of each image quality mode is performed by first determining the appearance frequency for each gradation of the data amount of the image data as in the first embodiment, and determining the density of one original as shown in FIG. A histogram is created (STEP 1). At this time, a histogram as shown in FIG. 5 is created by counting each gradation in order from the image data that has been subjected to gamma correction. When the histogram as shown in FIG. 5 is generated in this way, the frequency of each gradation and the threshold value Ta are compared in order from the intermediate gradation of the density between the predetermined densities dc and dd, and the intermediate value becomes lower than the threshold value Ta. It is confirmed whether or not the concentration range Ra is wider than the predetermined value Rx (STEP
2).

At this time, when the range Ra of the intermediate density is wider than the predetermined value Rx as shown in FIG. 6A, (Ye
s), since it is considered that a text original having a high frequency on the white side and the black side is read, image processing is set as a character mode (STEP 3). When the range Ra is narrower than the predetermined value Rx (No), the frequency of each gradation and the threshold Tb (Tb> Ta) are compared in order between the predetermined densities dc and dd, and the threshold Tb is obtained. It is confirmed whether or not the lower intermediate density range Rb is wider than the predetermined value Ry (STEP 4).

In STEP 4, as shown in FIG. 6B, when the intermediate density range Rb is narrower than the predetermined value Ry (No), it is considered that a photographic document having a high frequency of halftones has been read. The photo mode is set to perform image processing (STEP 5). Conversely, FIG. 6 (c)
When the intermediate density range Rb becomes wider than the predetermined value Ry (Yes), the image processing is set to be performed as a mixed mode in which a mixed document in which characters and photographs are mixed is read (STEP 6). .

STEP 3, STEP 5, and STEP 6
When each image quality mode is set by any of the above, the set image quality mode is given to the memory control unit 4 and then stored together with the image data stored in the memory 5 by the memory control unit 4. Then, as in the second embodiment, the memory 5
The image data stored in and the image quality mode set and stored in the memory 5 are read by the memory control unit 4 and then given to the output side image processing unit 6. Then, in the output side image processing unit 6, the given image data is subjected to image processing according to the image quality mode which is similarly read out.

As described above, after the image quality mode is automatically set in the input side image processing unit 3, the image data is stored together with the image quality mode set in the memory 5, and then the image quality mode stored in the memory 5 is stored. In accordance with, the image processing is performed on the image data. Therefore, similarly to the second embodiment, the image quality mode is set before the image data is stored in the memory 5, so that it is not necessary to set the image quality mode at the time of output, and the time taken at the time of output is reduced. be able to.

In the first to third embodiments, when the density histogram is formed, the data amount of the image data is 1
The number of pixels is counted for each gradation, and the appearance frequency is calculated for each gradation. However, the number of pixels is counted for each gradation of the data amount, and the appearance frequency is calculated for each gradation. It may be formed by asking for. Further, although the image reading apparatus in each of the above-described embodiments is an image forming apparatus such as a copying machine, it may be a facsimile apparatus or a network scanner that is provided with an interface instead of the scanning circuit and can communicate with an external network. Any image transmission device may be used, or an image recording device that records image data on a recording medium such as a hard disk may be used. Furthermore, in the case of an image transmitting device or an image recording device, the output side image processing unit may compress the image data.

[0043]

According to the present invention, since the image quality mode can be automatically set from the histogram showing the density distribution of the read image data, the image quality can be set every time the user places a document as in the conventional case. It is not necessary to set the mode, and the operation can be simplified. Therefore, D
For scanning multiple documents using F etc.,
No user setting is required and operation becomes easy. or,
Since the image quality mode is set before the image data is recorded in the memory, it is not necessary to set the image quality mode at the time of outputting the image data, so that the time taken at the time of outputting the image data can be reduced. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an internal configuration of an image reading apparatus of the present invention.

FIG. 2 is a diagram for explaining an image quality mode setting operation in the first and second embodiments.

FIG. 3 is a diagram showing an example of a histogram when each image quality mode is set in the first and second embodiments.

FIG. 4 is a flowchart showing an image quality mode setting operation in the third embodiment.

FIG. 5 is a diagram for explaining an image quality mode setting operation in the third embodiment.

FIG. 6 is a diagram showing an example of a histogram when each image quality mode is set in the third embodiment.

[Explanation of symbols]

1 Reader 2 A / D converter 3 Input side image processing unit 4 Memory control unit 5 memory section 6 Output side image processing unit 7 scanning circuit 8 optical print heads

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Claims (10)

[Claims] 1. A plurality of reading units, each having a reading unit for reading image data to obtain image data, and having a plurality of image quality changed by changing a gradation of image data with respect to an image drawn on the document read by the reading unit. In an image reading apparatus that sets one image quality mode from image quality modes and processes the image data based on the set image quality mode, in accordance with the shape of the histogram of the density distribution of the document obtained from the image data, An image reading apparatus characterized in that one image quality mode is set from among the image quality modes. 2. In the histogram of the density distribution,
An integrated value W of the frequency with respect to a density lower than the first density,
An integrated value B of the frequency with respect to the darker density than the second density,
The integrated value M of the frequency with respect to the concentration between the first and second concentrations
The image reading apparatus according to claim 1, wherein the image quality mode is set according to the value of the frequency ratio K = (B + W) / M after obtaining 3. A plurality of image quality modes, a character mode when a document occupying a large amount of low gradation images such as characters is read, and a character mode when a document occupying a large amount of high gradation images such as a photograph is read. And a mixed mode when a document having each of the low-gradation image and the high-gradation image is read, and when the frequency ratio K is higher than a predetermined value Ka, the character mode When the frequency ratio K is lower than a predetermined value Kb (Kb <Ka), the mode is set to the photo mode, and when the frequency ratio K is a value between the predetermined values Ka and Kb, it is mixed. The image reading apparatus according to claim 2, wherein the image reading apparatus is set to a mode. 4. In the histogram of the density distribution,
The image reading apparatus according to claim 1, wherein the image quality mode is set according to a range of intermediate density having a predetermined width and a predetermined frequency. 5. The character mode when a plurality of low-gradation images such as characters are read in the plurality of image quality modes, and when the original in which a lot of high-tone images such as photographs is read is read in the character mode. And a mixed mode when an original having each of the low-gradation image and the high-gradation image is read, and the intermediate density range Ra lower than the frequency threshold Ta is a predetermined value Rx. When the value is wider than the predetermined value, the character mode is set, and the intermediate density range Ra is narrower than the predetermined value Rx and lower than the frequency threshold value Tb (Tb> Ta).
When is smaller than the predetermined value Ry, the mode is set to the photo mode. When the range Ra of the intermediate density is narrower than the predetermined value Rx and when the range Rb of the intermediate density is wider than the predetermined value Ry, the mixed mode is set. The image reading device according to claim 4. 6. A memory for temporarily recording the image data obtained by the reading unit, a memory control unit for controlling reading and writing of the image data with respect to the memory, and a memory control unit for reading from the memory. An image processing for forming a histogram of the density distribution of the document from the output image data, setting an image quality mode according to the shape of the histogram of the density distribution, and performing image processing on the image data according to the set image quality mode. An image reading apparatus according to any one of claims 1 to 5, further comprising: 7. A first image processing unit that forms a histogram of the density distribution of the original from the image data obtained by the reading unit and sets an image quality mode according to the shape of the histogram of the density distribution; Image data given through 1 image processing unit,
A memory for temporarily recording with the set image quality mode, a memory control unit for controlling reading and writing of the image data from and to the memory, and image data read from the memory by the memory control unit, The image reading apparatus according to any one of claims 1 to 5, further comprising: a second image processing unit that performs image processing according to the image quality mode read from the memory. 8. An image forming apparatus, comprising: the image reading apparatus according to claim 6 or 7; and an image reproducing section that reproduces an image of the image data subjected to the image processing. 9. The image reading apparatus according to claim 6, further comprising an interface for transmitting the image data subjected to the image processing to the outside. 10. The image reading apparatus according to claim 6, further comprising a recording medium for recording the image data subjected to the image processing.