JP2013118670A - Image processor, image processing method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that it is difficult to discriminate a document printed on white paper from a blank document with a ground color since a data size after compression becomes large when the document has the ground color such as colored paper in a case when a read image is compressed and a blank determination is performed by using the data amount thereof.SOLUTION: An image processor includes: edge data generating means which detects an edge from image data and generates data showing a result of the detection; acquisition means which acquires a degree of dispersion of the edge data generated by the edge data generating means; and determining means which determines whether the image data has printing information or not in accordance with the degree of dispersion of the edge data acquired by the acquisition means.

Description

  The present invention relates to an image processing apparatus for determining whether read image data is image data having print information or blank image data having no print information.

In a copying machine equipped with an automatic document reader, even if a document printed on both sides and a document printed on one side are mixedly loaded, both sides are read.
However, with this method, the blank sheet on the back side of the document printed on one side is also read, and as a result, unnecessary data is processed, resulting in a slow process.
Further, when outputting the document read in this way, a blank paper surface without printing is also printed, and paper resources are wasted.
For example, in Japanese Patent Application Laid-Open No. 2004-228620, a blank page determination is performed in which a compression process is performed on image data acquired from a read original and the read original is determined to be blank using the data amount of the compressed data. A method has been proposed.
On the other hand, for example, Patent Document 2 proposes a blank page determination method for detecting an edge portion of image data acquired from a read document and determining whether the read document is a blank page using the detected edge amount. ing.

JP 2004-147193 A JP 2009-021681 A

  When distinguishing white paper (including colored colored paper originals) with no print information from originals with print information, the print information is not affected by the paper type or background color of the original. It is important to determine whether or not there is.

  The technique described in Patent Document 1 uses a method of compressing image data read from a document and determining whether the data is blank from the data size of the compressed data.

  In general, when a document is read using a scanner, noise occurs during reading due to the nature of the scanner and the paper quality of the document. This noise occurs when any kind of document is read.

However, when a white document is read, the read value in the absence of noise is already 255, which is the upper limit of the dynamic range (when the signal value is image data consisting of 8 bits for each of RGB). On top of this, the reading value fluctuates due to noise, and when the reading value exceeds 255, the reading value is clipped to 255. Therefore, all fluctuations due to noise do not affect the reading value. For this reason, the influence of noise is not so conspicuous on a blank original.
On the other hand, when a colored document is read, the read value without noise is not close to 255. Therefore, even if the reading value fluctuates due to noise on this, the value does not exceed 255 and is not clipped to 255. Therefore, all fluctuations due to noise affect the reading value.

  Therefore, when reading a colored document or the like, the compression ratio may be reduced due to the influence of the noise, and the data size may be increased.

  For this reason, in Japanese Patent Application Laid-Open No. 2004-228688, compared to reading a blank paper document, the data size after compression of image data obtained from the document becomes large when reading a colored paper document. Originally, since the data size when a white document having print information is compressed is larger than the data size when a colored document without print information is compressed, the two documents should be easily distinguished. However, due to the noise described above, there is a problem that it is difficult to distinguish between the two documents because the data size when the two originals are compressed is slightly different.

  Further, the technique described in Patent Document 2 picks up noise generated due to, for example, impurities contained in recycled paper as an edge, and when there is little print information on a white document, white having print information In some cases, there is no difference between the edge amount of impurities contained in the original document and recycled paper. For this reason, it is difficult to determine whether the detected edge is due to print information or due to noise generated due to impurities, and it is difficult to make a blank page determination using this edge amount.

  The present invention has been made to solve the above problems. An object of the present invention is to provide an image processing apparatus capable of improving the accuracy of blank page determination in a process of performing blank page determination for determining image data (document) having no print information.

  In order to solve the above-described problems, an image processing apparatus according to the present invention detects an edge from image data, creates edge data creating means for creating data indicating a result of the detection, and the edge data created by the edge data creating means. The image processing apparatus includes an acquisition unit that acquires a degree of dispersion, and a determination unit that determines whether the image data has print information according to the degree of dispersion of edge data acquired by the acquisition unit.

  It is possible to reduce the influence on the blank page misjudgment caused by the paper type of the document and the background color of the document, and it is possible to improve the accuracy when determining whether the captured document is a blank sheet having print information.

Overview of digital multi-function peripheral suitable for applying the present invention Scanner configuration diagram of a digital multi-function peripheral suitable for applying the present invention Control system configuration diagram of a digital multi-function peripheral suitable for applying the present invention Input image processing unit according to the first embodiment of the present invention Blank sheet determination processing unit suitable for applying the present invention Operation unit of a digital multi-function peripheral suitable for applying the present invention Example of the function operation screen for the blank page skip function An example of the threshold level operation screen in the blank page skip function It represents the flow of processing of Embodiment 1 in the present invention. Input image processing unit according to the second embodiment of the present invention It represents the flow of processing of Embodiment 2 in the present invention. (A) An example of threshold setting in the present invention, (b) An example of threshold setting in the present invention Input image processing unit according to the third embodiment of the present invention Example of the paper type registration operation screen in the blank page skip function An example of threshold setting according to the fourth embodiment of the present invention It explains the definition of blank paper in the present invention.

The best mode for carrying out the present invention will be described below with reference to the drawings.
Further, as shown in FIG. 16A, the blank paper refers to a document without print information. If there is no print information, a colored document such as colored paper or a recycled paper document is also handled as a blank sheet. Also, the image data when these are read is also called blank paper. On the other hand, as shown in FIG. 16B, a document on which minute characters such as page numbers are described is not blank.

(Embodiment 1)
FIG. 1 is a diagram showing a configuration of a digital multi-function peripheral 1 having an input device and an image processing system suitable for applying this embodiment.

<Image input unit (scanner)>
FIG. 2 shows details of the scanner 200 that is the image input device in FIG.
In FIG. 2, reference numeral 211 denotes a scanner unit, which includes a document illumination lamp 212, scanning mirrors 213 to 215, and the like.

  The scanner unit 211 causes reflected light from the original to enter a CCD sensor 217 including a sensor via scanning mirrors 213 to 215 and a lens 216.

  Next, the CCD sensor 217 converts it into an electrical signal representing image data.

  The original paper is set on the tray 202 of the original feeder 201, and the reading operation is started when the user gives a reading start instruction from the operation unit 400 of FIG. Specifically, the CPU 103 in FIG. 3 gives an instruction to the scanner 200. As a result, the feeder 201 feeds original sheets one by one and performs an original image reading operation.

  There are two types of apparatuses for reading a document from a feeder, a reverse double-sided type that scans one side of a document and reverses it to read the back side, and a one-pass double-sided type that simultaneously reads the front and back side by one operation.

<Image output unit (printer)>
In FIG. 1, a printer 300, which is an image output device, is a part that prints image data for which an output instruction has been issued on an image on paper.
The image data is image data obtained by reading a document with the scanner. This image data is output on paper by the following printing method.

  The printing method includes an electrophotographic method in which toner is fixed to paper using a photosensitive drum or a photosensitive belt, and an ink jet method in which ink is ejected from a minute nozzle array to directly print an image on the paper. The printing method is not particularly limited.

  Activation of the printing operation is started by an instruction from the controller CPU 103. The printer 300 has a plurality of paper feed stages so that different paper sizes or different paper orientations can be selected, and paper cassettes 302, 303, 304, and 305 corresponding to the paper feed stages are mounted. A paper discharge tray 306 receives paper that has been printed.

<Digital MFP control system configuration>
FIG. 3 shows a control system configuration of the digital multi-function peripheral 1 suitable for applying this embodiment.
The controller unit 100 is a controller for inputting / outputting image data and device information by being connected to a scanner 200 as an image input device and a printer 300 as an image output device, and connected to a LAN 800 or a telephone line 900. is there.

  The CPU 103 functions as a controller that controls the entire digital multi-function peripheral 1.

  The storage unit 107 stores image data and compressed data, and includes a system work memory for the CPU 103 to operate.

The operation unit I / F 104 is an interface unit with the operation unit 400 and outputs image data to be displayed on the operation unit 400 to the operation unit 400. Also, it plays a role of transmitting information input by the user from the operation unit 400 to the CPU 103.
A network I / F 105 is connected to the LAN 800 and inputs / outputs information. The modem 106 is connected to the public line 900 and performs modulation / demodulation processing for data transmission / reception.

  The above configuration is arranged on the system bus 101.

  The image bus I / F 108 is a bus bridge that connects the system bus 101 and the image bus 102 that transfers image data at high speed, and converts the data structure.

  The image bus 102 is a high-speed bus such as a PCI bus or IEEE1394.

  The device I / F unit 110 connects the scanner 200 and the printer 300, which are image input / output devices, to the controller 100, and performs synchronous / asynchronous conversion of image data.

  The compression / decompression processing unit 109 compresses image data and edge data described later by a predetermined compression method.

  The input image processing unit 500 corrects, processes, and edits image data read by the scanner 200, and performs processing suitable for subsequent print output or image transmission.

  The blank page determination processing unit 600 determines whether the image data input by the scanner 200 is blank based on the compressed data rate of the edge image compressed by the compression / decompression processing unit 109.

  The output image processing unit 700 performs correction, resolution conversion, and the like according to the printer on the print output image data.

  FIG. 4 is a block diagram showing a detailed configuration of the input image processing unit 500 of the image processing apparatus according to the first embodiment of the present invention.

  Reference numeral 501 denotes a sub-scanning color misregistration correction unit that corrects color misregistration in the sub-scanning direction of input image data. For example, a process of performing a 1 × 5 size filter operation for each color of image data is performed.

  Reference numeral 502 denotes a main scanning color misregistration correction unit that corrects color misregistration in the main scanning direction of input image data. For example, processing for performing a 5 × 1 size filter operation for each color of image data is performed.

  Reference numeral 503 denotes an image area determination unit for identifying the image type in the input image data. For example, the image area determination unit configures each image type such as a photograph part / character part, chromatic part / achromatic part, etc. in the input image. Identify the pixel to be used. Then, the image area determination unit 503 generates attribute flag data indicating the type for each pixel.

  Reference numeral 504 denotes a filter processing unit that arbitrarily corrects the spatial frequency of the input image data. For example, processing for performing a 9 × 9 size filter operation is performed.

  Reference numeral 505 denotes a histogram processing unit that samples and counts image signal data in the input image data. For example, the histogram processing unit 505 determines whether the input image data is a color image or a monochrome image, The background level is determined.

  Reference numeral 506 denotes an input color correction unit that corrects the color of the input image data, and performs processing such as converting the color space of the input image into an arbitrary color space, for example.

  Reference numeral 507 denotes an edge extraction unit that extracts, from the input image data, a portion having a large density change present in the input image data as an edge, and creates edge data to be described later. The edge extraction unit 507 performs, for example, 9 × 9 filter calculation to create edge data.

  The processing in the input image processing unit 500 is not limited to the processing using all of the above-described 501 to 506, and other image processing modules may be added or deleted. Furthermore, the processing order of 501 to 506 is not limited to this.

  FIG. 5 is a block diagram showing the structure of the blank page determination processing unit of the image processing apparatus according to the embodiment of the present invention.

  Reference numeral 601 denotes a compressed data rate calculation unit that calculates the compressed data rate of the compressed edge data. Here, it is only necessary to obtain a variance value of data, not limited to compression. A blank page determination unit 602 performs blank page determination processing based on the compressed data rate (dispersion value) calculated by the compressed data rate calculation unit (dispersion value acquisition unit) 601. If the compressed data rate (dispersion value) is smaller than the threshold value, it is determined that there is blank paper. If the compressed data rate (dispersion value) is greater than the threshold value, it is determined that there is print information. (Details of this determination method will be described later.) 603 is a blank page data erasing unit that erases image data determined to be blank by the blank page determination unit 602. The erased blank paper data will be described later.

<Operation unit>
FIG. 6 shows an example of an operation unit 400 of a digital multi-function peripheral suitable for applying the present embodiment.
The liquid crystal operation panel 401 is a combination of a liquid crystal and a touch panel, and displays setting contents, soft keys, and the like. A start key 402 is a hard key for instructing start of a copying operation and the like, and green and red LEDs are incorporated therein. The green LED is lit when the start is possible and the red LED is lit when the start is impossible. A stop key 403 is a hard key used to stop the operation. The hard key group 404 is provided with a numeric keypad, a clear key, a reset key, a guide key, and a user mode key.

<Blank skip function setting>
FIG. 7 is an example of an operation screen 800 for setting ON / OFF of the blank page skip function described above.

  A blank page skip ON button 803, a blank page skip OFF button 804, an OK button 801, and a cancel button 802 are arranged in the blank page skip function ON / OFF setting screen.

  The user designates whether or not to perform the blank page skip function by operating the blank page skip function by operating the ON button 803 and the OFF button 804.

  When the ON button 803 is pressed, a transition is made to the level adjustment screen 810 for the blank page skip function shown in FIG.

  When the OK button 801 is pressed, the setting content of ON / OFF of the blank page skip function displayed immediately before is held, and this operation screen is closed. When a cancel button 802 is pressed, the setting content of ON / OFF of the blank page skip function immediately before opening this operation screen is held, and this operation screen is closed.

FIG. 8 shows an example of an operation screen 810 for the user to set a threshold value used for the blank page skip function. In this embodiment, when the blank page skip function is set to ON, the “edge data compression amount (dispersion value)” is used when determining whether the image data is blank. (The details will be described later.)
A blank page skip function level adjustment bar 813, an OK button 811, and a cancel button 812 are arranged in the blank page skip function level adjustment setting screen. The user can change the threshold value related to the compression amount (dispersion value) of edge data used for blank sheet determination by operating the level adjustment bar 813. When the user operates the level adjustment bar 813 to “strong”, the read image data is easily determined to be blank.

  When the OK button 811 is pressed, the level adjustment setting content displayed immediately before is held, and this operation screen is closed. When the cancel button 812 is pressed, the setting contents immediately before opening the operation screen are held, and the operation screen is closed.

  Hereinafter, the image processing in the present embodiment will be described with reference to FIGS.

  When the image data is read from the scanner 200, the CPU 103 transmits the image data to the input image processing unit 500. As shown in FIG. 4, the input image processing unit 500 performs image processing 501 to 506 on the received image data.

  Simultaneously with the image processing, the input image processing unit 500 performs filtering processing for edge enhancement on the image data received by the edge extraction unit 507, and calculates edge strength in the image data.

  Next, the edge extraction unit 507 performs threshold processing on the calculated edge strength. If this edge strength value is greater than or equal to a threshold value, there is an edge, and if it is less than or equal to the threshold value, there is no edge. For example, this threshold is generally set to 128. If the edge strength is 128 or more, there is an edge, and if the edge strength is 128 or less, there is no edge. This threshold value can be set in advance by the user.

  Using this result, the presence / absence of an edge in each pixel constituting the image data is indicated in 1-bit units to create data. In this specification, this data is referred to as edge data.

  A general filter such as a Laplacian filter is used for the filtering process, but the present invention is not particularly limited to this method.

  Next, the image data processed by the input image processing unit 500 and the edge data generated by the edge extraction unit 507 are processed by the compression / decompression processing unit 109, for example, JPEG compression processing is performed on the image data. On the other hand, JBIG compression processing is performed.

  The compression method is not limited to these methods, and a compression method suitable for multi-value data may be used for image data. For the edge data, a compression method may be used in which the data amount is small for data having a small variance value and the data amount is large for data having a large variance value.

  Further, the compression of edge data is not limited to the compression method, and it is only necessary to obtain a dispersion value indicating the degree of dispersion of edge data.

  The CPU 103 writes the image data and edge data compressed by the compression / decompression processing unit 109 into the storage unit 107.

  Hereinafter, the flow of blank sheet determination processing in the present embodiment will be described with reference to FIG.

  FIG. 9 is a diagram illustrating a processing flow of blank sheet determination processing in the present embodiment.

  The procedure shown in the following flowchart is stored in any storage means (not shown) such as RAM, ROM, or HDD, and is executed by the CPU 103 in FIG.

  If the blank page skip function is set to ON, the CPU 103 reads out image data and edge data written in the storage unit 107 in units of pages in S1101.

  In step S1102, the compressed data calculation (distributed value acquisition) unit 601 calculates a compressed data rate (distributed value) from the edge data read in step S1101. The CPU 103 transmits the compressed data rate to the blank page determination unit 602.

In step S <b> 1103, the blank page determination unit 602 compares the received edge data compression data rate (dispersion value) with the threshold set on the blank page skip function level adjustment setting screen 800.
Here, this threshold value will be described.

For example, when edge detection is performed as described above from an original without print information (whether the background is colored or white) and the edge data is compressed using the result, the compression data rate (data amount after compression / data before compression) Amount) is about 3.0 × 10 ⁻⁵ %.

On the other hand, when the edge data is compressed using a white document having minute print information in which only the page number is printed, the compression data rate is about 7.0 × 10 ⁻⁵ %.

In order to distinguish two types of originals having such a compression data rate and to determine that an original without print information is blank, the threshold value of the compression data rate of edge data is set to “5.0 × 10 ⁻⁵ %”. . This threshold value varies depending on the threshold value for edge detection and the device used. The user may set in advance.

  When the compressed data rate of the edge image is smaller than the threshold value (when the variance value is small), it is determined as blank paper in S1104. If the compressed data rate is larger than the threshold value as a result of comparison (if the variance value is large), it is determined in S1105 that there is print information. Here, when the compressed data rate of the edge data is large (when the variance value is large), it indicates that there are many pixels in the image data whose density changes rapidly. That is, it can be determined that there is some print information in the image.

  When the compressed data rate is small (when the variance value is small), the density in the image data becomes uniform, and it can be determined that there is no print information.

  For example, even if JPEG compression is performed on the read image data, a tendency about the presence or absence of print information in the read image data can be obtained. However, as described above, the amount of data after compression of image data when reading a white document having minute print information and the data after compression of image data when reading a colored document without print information The amount is slightly different due to the influence of reading noise. Therefore, it is difficult to distinguish whether or not the sheet is blank using both. On the other hand, in this embodiment, by using the compressed data rate of edge data for blank sheet determination, the influence of the reading noise can be reduced, and a white document having printing information and a colored document having no printing information can be distinguished. it can.

  Note that this reading noise is noise that could not be removed by the noise removal filter at the time of reading.

  When the blank page determination unit 602 determines that the read image data is a blank page, the blank page data deletion unit 603 deletes the image data in step S1106.

  At this time, the CPU 103 may notify the user of the page of the image data determined to be blank by the blank page determination unit using a display unit (not shown). Further, when notified, the user may instruct to change the determination result, and control may be performed so as not to delete the image data determined to be blank by the blank page determination unit.

  Next, in step S1107, it is determined whether or not the blank page determination process has been completed for all pages of the image data input in step S1101. If it is determined that all the pages have not been completed, the process returns to S1101, and the next page is processed.

  If it is determined in step S1107 that all pages have been completed, the processing of the blank page determination processing unit 600 ends.

  Next, the compression / decompression processing unit 109 performs decompression on the image data of the page determined to have print information by the blank sheet determination processing unit 600.

  Further, the image data erased in S1106 may not be actually erased, but may be stored in the storage unit with a flag indicating that it is not decompressed while being compressed. Good.

  Next, the CPU 103 transmits the image data to the output image processing unit 700, and the output image processing unit 700 performs correction and resolution conversion according to the printer 300.

  Next, the CPU 103 transmits image data to the printer 300 and executes print processing. When performing FAX or transmission processing, image data may be transmitted through the LAN 800 or the public line 900 without being decompressed by the compression / decompression processing unit 109.

  In the present embodiment, the influence of reading noise can be reduced by creating edge data from the read image data and performing blank page determination based on the compressed data rate of the edge data. This makes it possible to distinguish between a white document having minute print information and a colored document having no print information.

(Embodiment 2)
Here, a method of performing blank page determination from the compressed data rate of edge data and the edge ratio of edge data in the blank page skip function will be described.

  In the first embodiment, it has been described that by using the compressed data rate of edge data, it is possible to distinguish between a white document having print information and a colored document having no print information such as colored paper.

  However, for example, in the case of a document (recycled paper document) in which many impurities are mixed, such as recycled paper, the impurities may be extracted as edges. That is, edge data resulting from random noise is extracted from the entire surface of the document, so that the compressed data rate of the edge data increases even if there is no print information on the document. On the other hand, the compressed data rate of edge data in a white document with minute print information is small.

  Whether or not the image data has print information determines the significance of the image data. However, in this case, it is desired to determine that image data without print information is blank. Therefore, a recycled paper document without the above print information should be determined as “blank”, and a white document with print information should be determined as “not blank”.

  However, the determination of only the compressed data rate of edge data requires that the threshold value of the compressed data rate of edge data be increased in order to determine that a recycled paper document having no print information is blank. Therefore, a white document having minute print information in which the compressed data rate of edge data is smaller than that of recycled paper is also determined as a blank paper.

  Therefore, in this embodiment, in addition to the compressed data rate of edge data used in the first embodiment, the edge ratio of edge data is also used for blank page determination.

  FIG. 12A shows the relationship between the edge ratio (number of edge pixels / total number of pixels) (%) and the compressed data rate (data amount after compression / data amount before compression) on a two-dimensional plane. is there. The x-axis shows the edge ratio (number of edge pixels / total number of pixels) (%), and the y-axis shows the compression ratio (data amount after compression / data amount before compression) (%). It is the figure which plotted the value obtained from the manuscript from which a color differs.

  As shown in FIG. 12A, even if the edge ratio in the edge data of the recycled paper original (a) having no print information and the white original (b) having minute print information is substantially the same, The compression rate of the edge data of a recycled paper document having no print information increases for the above reason. On the other hand, a white document having minute print information has a reduced edge data compression data rate.

  As described above, if only the edge compression data rate is used as a reference for blank page determination, it is not possible to determine only a recycled paper document having no print information as a blank sheet. Therefore, as shown in FIG. 12A, a threshold value using a linear function is provided.

For example, when creating edge data using the above edge threshold,
The coordinates (c) indicating blank paper data are (x, y) = (2.5 × 10 ⁻⁶ , 3.0 × 10 ⁻⁵ ), and the coordinates (a) indicating recycled paper data are (x, y). = (3.0 × 10 ⁻⁶ , y = 5.81 × 10 ⁻⁴ ) is plotted.

In addition, the coordinates (b) indicating the data of the page number which is the white background paper + the minute content are plotted as (x, y) = (7.6 × 10 ⁻⁵ , y = 6.7 × 10 ⁻⁵ ). The

  Among these, a white paper having no printing information and a recycled paper original having no printing information are determined to be blank. Then, it determines that a white background document with minute content such as a page number or a recycled paper document with minute content is not a blank sheet. For this purpose, the threshold value is set to y = ax + b (a: 6.5, b: −0.0001). Further, when the edge ratio and the compressed data rate both reach a certain value, the threshold value is not a linear function but takes a constant value for both the x-axis and the y-axis.

For example, on the x-axis, when the value reaches 1.0 × 10 ⁻⁴ , the threshold takes a constant value (x = 1.0 × 10 ⁻⁴ ). Similarly, on the y axis, when the value reaches 1.0 × 10 ⁻³ , the threshold value is a constant value (y = 1.0 × 10 ⁻³ ).

  By separating the area in the figure by this linear function and a straight line parallel to the x-axis and y-axis, an original having a value in the area (A) in the figure is replaced with a blank original having no print information, and the area (B). A document having a value can be separated from a document having printing information.

  Therefore, as shown in FIG. 12A, by providing a threshold value as a linear function, it is possible to determine that a recycled paper document without print information is a blank sheet, and a white background document with minute print information is not a blank sheet. .

  In addition, as the threshold value in the present embodiment, a linear threshold value may be used as shown in FIG. 12A, or a curved threshold value may be used as shown in FIG. Further, an experimentally obtained value is used as this threshold value. Further, a and b which are coefficients of the above formula also vary depending on device conditions and the like. This value may also be set in advance by the user.

  Hereinafter, the image processing in this embodiment will be described with reference to FIG.

  FIG. 10 shows the configuration of the input image processing unit 500 when performing blank page determination from the compressed data rate and edge ratio of edge data.

  Here, since 501 to 507 are the same as those in the first embodiment, description thereof is omitted. An edge ratio calculation unit 508 calculates an edge ratio from the edge data created by the edge extraction unit 507. Here, the edge ratio is a value obtained by counting the number of pixels in which there is a value in the edge data generated by the edge extraction unit 507 and dividing by the total number of pixels.

  Here, the edge ratio calculation unit 508 is not limited to being configured in the input image processing unit 500, and may be incorporated in the blank page determination processing unit 600.

  The blank page determination unit 602 performs blank page determination using the compressed data rate of the edge data calculated by the compressed data rate calculation unit 601 and the edge ratio calculated by the edge ratio calculation unit 508.

  Further, similarly to the first embodiment, not only the compressed data rate but also a dispersion value may be acquired.

  For example, processing from acquiring image data by reading a document from the scanner 200 and extracting an edge by the edge extraction unit 507 in the input image processing unit 500 is the same as that in the first embodiment, and thus description thereof is omitted.

  Next, an edge ratio calculation unit 508 in the input image processing unit 500 calculates an edge ratio included in the image data from the edge data generated by the edge extraction unit 507. The CPU 103 transmits the calculated edge ratio to the blank sheet determination processing unit 600.

  Hereinafter, the blank page determination process in the present embodiment will be described with reference to the flowchart of FIG.

  The procedure shown in the following flowchart is stored in any storage means (not shown) such as RAM, ROM, or HDD, and is executed by the CPU 103 in FIG.

  The image data and edge data processed by the input image processing unit 500 are compressed by the compression / decompression processing unit 109 and stored in the storage unit 107 as in the first embodiment.

  When the blank page skip function is set to ON, the CPU 103 transmits the image data and edge data stored in the storage unit 107 to the blank page determination processing unit 600. The blank page determination processing unit 600 receives image data and edge data in units of pages (S1201).

  In step S1202, the edge ratio of the received edge image is compared with a preset threshold value. If the edge ratio is smaller than the threshold value, the process proceeds to step S1203. If it is larger than the threshold value, it is determined in S1207 that there is print information. This is to speed up the processing without assuming that there is print information if it has an edge ratio of a certain level or more, and not performing subsequent blank page determination processing.

  In step S1203, the compressed data calculation unit calculates the compressed data rate (dispersion value) of the edge data from the edge data received in step S1201.

  In step S1204, the compressed data rate is compared with a preset threshold value. If the compressed data rate is smaller than the threshold value in the comparison result, the compressed data rate of the edge data is transmitted to the blank page determination unit 602, and the process proceeds to S1205. If the compressed data rate is greater than the threshold, it is determined in S1207 that there is print information. This is also for speeding up the processing, as in S1202, and all data may be determined in S1205 without providing S1202 and S1204.

  In step S1205, the blank page determination unit 602 compares the received compressed data rate and edge ratio of the edge data with the threshold value shown in FIG. 12 to determine whether the page is blank or print information.

  As a determination method, a method obtained by calculation may be used, or a LUT (Look Up Table) may be created in advance and the determination may be performed using this.

  Hereinafter, the processing from S1206 to S1209 after the blank page determination, the subsequent processing up to printer output, and the data transmission processing using the LAN 800 and the public line 900 are the same as those in the first embodiment, and thus description thereof is omitted.

  In this embodiment, by performing the blank page determination using the edge ratio of the edge data and the compressed data ratio, a document including impurities such as a recycled paper document but having no print information and a white document having minute print information are used. A distinction can be made.

(Embodiment 3)
Here, a case will be described in which the image area determination unit 503 is used as a method of performing edge extraction in blank page determination in the blank page skip function.

  In this embodiment, in the blank page determination process, the attribute flag data extracted by the image area determination unit 503 is used as edge data.

  Here, the attribute flag data is data indicating respective image types such as a photograph part / character part, a chromatic part / achromatic part, and the like. This attribute flag data is used as edge data in this embodiment. The attribute flag data is 1-bit image data composed of values “1” and “0” indicating a photograph part / character part.

  At the time of edge extraction, in the case of an edge extraction method such as a Laplacian filter, an edge of image data printed with halftone dots is also detected. Therefore, depending on the original, halftone dots are detected like noise during reading, and there is a possibility that the compressed data rate and edge ratio are the same as those of a recycled paper original without print information. Therefore, if the edge of the image data printed with halftone dots is used, there is a possibility that the paper will be blank as in the case of a recycled paper original having no print information although there is print information.

  In contrast to halftone dots where edges occur periodically in this way, edges do not occur periodically in character portions. Therefore, the image area determination unit 503 can separate a halftone dot and a character part. By assigning the attribute flag “0” with the halftone dots other than the photo portion / character portion, the image area flag data “1” is not generated for the halftone dots. Therefore, edge detection is increased by detecting halftone dots, and as a result, it is possible to reduce false detections that determine image data having print information as blank paper.

  FIG. 13 shows the configuration of the input image processing unit 500 when the image area determination unit 503 is used as an edge extraction method.

  Since the details of each part are the same as those in the first and second embodiments, the description thereof is omitted. However, the image area determination unit 503 transmits image data to the filter processing unit 504 and transmits attribute flag data to the edge ratio calculation unit 508.

  The edge ratio calculation unit 508 counts the effective pixels of the attribute flag data generated by the image area determination unit 503, and calculates a value obtained by dividing by the total number of pixels. Here, the effective pixel means a pixel in which “1” is stored in 1-bit data of the attribute flag data.

  Since the processing flow for blank page determination and the processing flow after blank page determination are the same as those in the first and second embodiments, description thereof will be omitted.

  However, the blank page determination unit 602 performs blank page determination using the compressed data rate of the attribute flag data generated by the image area determination unit 503. Also, it is possible to perform blank page determination from the compressed data rate and the edge ratio of the attribute flag data.

  In this embodiment, by using the attribute flag data extracted by the image area determination unit 503 as edge data, it is possible to reduce erroneous determination of blank paper due to detection of halftone dots. Further, it is not necessary to separately provide a dedicated edge extraction unit, and blank sheet determination processing can be performed using the current configuration of the digital multi-function peripheral. Further, since data calculated from a normal processing flow is used, the processing time can be greatly shortened.

(Embodiment 4)
Here, a method for changing the threshold according to the paper type of the document to be read in the blank page skip function will be described.

  For example, in recycled paper, the mixing ratio of impurities varies depending on the type.

In the case of recycled paper in which more impurities are mixed (noise-recycled recycled paper), the coordinates (x, y) = (1.4 × 10 ⁻⁴ , 9.2 ×) of the point (c) in FIG. 10 ⁻⁴ ). On the other hand, a document having minute print information on recycled paper (recycled paper in noise) has a value of coordinates (x, y) = (1.6 × 10 ⁻⁴ , 6.3 × 10 ⁻⁴ ) of the point (d). Take. Therefore, when the threshold value described in the second embodiment is used, there is a possibility that the point (c) and the point (d) belong to the same region. Therefore, it is difficult to determine that this noisy recycled paper original is a white paper without print information.

  Therefore, in the present embodiment, by changing the threshold value depending on the paper type, a recycled paper (a strong noise recycled paper) in which a large amount of impurities is mixed and a document having minute print information on the recycled paper (in the noise) are distinguished. .

  FIG. 14 shows an example of a paper type setting screen 820 for registering paper types.

  In the paper type setting screen for the blank page skip function, a low noise recycled paper button 823, a medium noise recycled paper button 824, a strong noise recycled paper button 825, an OK button 821, and a cancel button 822 are arranged. The user can change the threshold used for blank sheet determination according to the paper type by operating the low noise recycled paper button 823, the recycled paper button 824, and the strong noise recycled paper button 825.

  When the OK button 821 is pressed, the setting content of the paper type displayed immediately before is held, and this operation screen is closed. When the cancel button 822 is pressed, the setting contents immediately before opening the operation screen are held, and the operation screen is closed.

  The paper type setting screen of FIG. 14 is provided with a transition button on the level adjustment screen 810 of the blank page skip function shown in FIG. 8, or the low noise noise recycled paper button 823, the recycled paper button 824, on the level adjustment screen 810 of the blank page skip function. A strong noise recycled paper button 825 may be provided.

  In the present embodiment, a low noise recycled paper button 823, a medium noise recycled paper button 824, and a strong noise recycled paper button 825 are provided. Of these, at least one other than the recycled paper button 824 may be provided and added. It may be.

  FIG. 15 shows threshold values in this embodiment, and the threshold values are changed as indicated by arrows C or D based on the values set on the paper type setting screen 820.

  In the paper type setting screen 820 of FIG. 14, for example, when recycled paper 824 having medium noise is set, a document having a value in the area (B) outside the blank standard of “recycled paper (b)” in FIG. It is determined that the document is not blank paper and has printing information.

On the other hand, in FIG. 14, the document to be determined is set as a noisy recycled paper 825 containing a large amount of impurities. The compressed data rate of the recycled paper document is larger than that of the recycled paper document having a medium noise level, and it may be determined that the printed information is included even if there is no printed information. Therefore, if it is set to use a noisy recycled paper document, the area to be determined as blank paper is enlarged. Specifically, the threshold value parallel to the y axis is moved in the direction of arrow C in FIG. For example, the threshold value where x = 1.0 × 10 ⁻⁴ is set to about 1.5 × 10 ⁻⁴ . Then, among the points (c) and (d), the noise intensity having a value of the coordinates (x, y) = (1.4 × 10 ⁻⁴ , 9.2 × 10 ⁻⁴ ) of the point (c) A recycled paper document can belong to the blank area (A), and can be determined as a blank sheet without print information.

On the other hand, the point (a) indicated by the data of the recycled paper original with few impurities is coordinates (x, y) = (6.9 ×× 10 ⁻⁵ , 2.8 × 10 ⁻⁴ ). Even if printing information is added to the recycled paper document, this coordinate belongs to the blank area (A). Therefore, in this case, in order to make it easy to determine that the recycled paper document with a small amount of impurities is a blank sheet, the area to be determined as a blank sheet is reduced. Specifically, the threshold value parallel to the y-axis is moved in the direction D in FIG. For example, the threshold value where x = 1.0 × 10 ⁻⁴ is set to about 8.0 × 10 ⁻⁵ . Then, since the low noise recycled paper having print information belongs to the area (B) where the print information exists, it is possible to determine that only the recycled paper original (a) having no print information is a blank paper.

  Thus, in the blank page determination process, the CPU 103 changes the threshold value by calling a threshold value corresponding to the paper type set on the paper type setting screen 820, and the blank page determination unit 602 performs blank page determination.

  Since the processing flow of the blank page determination process is the same as in the second and third embodiments, description thereof is omitted.

  In the present embodiment, by changing the threshold value according to the paper type of the document, it is possible to distinguish between a document having print information and a blank sheet having no print information even when the mixing ratio of impurities contained in the paper is not constant. .

(Other embodiments)
The processing method for storing the program for operating the configuration of the above-described embodiment so as to realize the function of the above-described embodiment in a storage medium, reading the program stored in the storage medium as a code, and executing the program on the computer is also described above. It is included in the category of the embodiment. In addition to the storage medium storing the above program, the program itself is included in the above embodiment.

  As such a storage medium, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, and a ROM can be used.

  In addition, the processing is not limited to the single program stored in the above-described storage medium, but operates on the OS in cooperation with other software and expansion board functions to execute the operations of the above-described embodiments. This is also included in the category of the embodiment described above.

In order to solve the above problems, an image processing apparatus according to the present invention provides:
Detecting an edge from the image data, the edge data generating means for generating data indicating the result of said detection,
An acquisition unit that acquires a degree of dispersion of edge data created by the edge data generation unit, and whether or not the image data has print information according to the degree of dispersion of edge data acquired by the acquisition unit. Determining means for determining.

Claims (13)

Edge data creating means for detecting edges from image data and creating data indicating the detection results;
Obtaining means for obtaining the degree of dispersion of the edge data created by the edge data creating means;
An image processing apparatus comprising: a determination unit that determines whether the image data has print information according to a degree of dispersion of the edge data acquired by the acquisition unit. The determination unit further obtains the relationship between the dispersion value of the edge data and the edge ratio detected from the edge data on a two-dimensional plane when the recycled paper document is read on the two-dimensional plane. A setting means for setting a threshold value indicated by a linear function determined to distinguish image data and image data acquired when reading a white background document having minute print information;
When the variance value is larger than the threshold value set by the setting means, the image data is determined as no print information, and when the variance value is smaller than the threshold value, the image data is printed. The image processing apparatus according to claim 1, wherein it is determined that there is information.   The image processing apparatus according to claim 1, wherein attribute flag data obtained by determining an image area of the image data is used as the edge data. The image data is image data acquired by reading a document, and setting means for setting data relating to the paper type of the document;
A threshold value changing means for changing the threshold value of the edge ratio from the data relating to the set paper type;
The image processing apparatus according to claim 2, further comprising:   The image processing apparatus according to claim 1, wherein the variance value acquisition unit acquires a variance value of the edge data by obtaining a compressed data rate of the edge data created by the edge data creation unit. .   6. The image processing apparatus according to claim 1, wherein when the image data is determined to be image data having no print information by the determination unit, the image data having no print information is determined to be a blank document. . An edge data creation step of detecting an edge from image data and creating data indicating a result of the detection;
An obtaining step for obtaining a degree of dispersion of the edge data created in the edge data creating step;
A control method for an image processing apparatus, comprising: a determination step of determining whether or not the image data has print information in accordance with a degree of dispersion of edge data acquired in the acquisition step. The determination step is further obtained when the relationship between the variance value of the edge data and the edge ratio detected from the edge data is shown on a two-dimensional plane, and when a recycled paper document is read on the two-dimensional plane. A setting step for setting a threshold value indicated by a linear function determined to distinguish image data to be acquired from image data acquired when a white background document having minute print information is read,
If the variance value is larger than the threshold value set in the setting step, the image data is determined as no print information, and if the variance value is smaller than the threshold value, the image data is printed. 8. The method of controlling an image processing apparatus according to claim 7, wherein it is determined that there is information.   9. The method according to claim 7, wherein attribute flag data obtained by determining an image area of the image data is used as the edge data. The image data is image data obtained by reading a document; a setting step for setting data relating to a paper type of the document;
A threshold value changing step for changing the threshold value of the edge ratio from the data relating to the set paper type;
A control method for an image processing apparatus according to claim 8 or 9.   The image processing apparatus according to claim 7, wherein the dispersion value obtaining step obtains a dispersion value of the edge data by obtaining a compression data rate of the edge data created in the edge data creation step. Control method.   12. The image processing apparatus according to claim 7, wherein when the image data is determined to be image data having no print information in the determination step, the image data having no print information is determined to be a blank document. Control method.   A program for causing a computer to execute the method according to any one of claims 7 to 12.

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