JP2017038222A - Image forming apparatus, control method of the same, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of accurately removing ground information from image data.SOLUTION: Characters are printed on a front surface, both surfaces of an original on a rear surface of which characters or patterns are not printed are read, information included in the front surface of the original and information included in the rear surface as ground information is acquired, and the ground information is removed from the information included in the front surface.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus, a control method for the image forming apparatus, and a program.

  Conventionally, for example, when reading a document on which characters are printed, the background color of the document (hereinafter referred to as “background information”) is replaced with white to remove the background information, and only the characters printed on the document are extracted. An image forming apparatus that executes background information removal processing is known (for example, Patent Document 1).

  There is also known an image forming apparatus that acquires background information by reading the back side of a recording sheet on which characters are printed only on the front side (for example, Patent Document 2). In the image forming apparatus disclosed in Patent Literature 2, when characters are printed on the back side of the recording paper after obtaining the background information, both sides of the recording paper are read to form image data corresponding to both sides of the recording paper. Background information removal processing for removing background information from each image data is executed.

  Usually, the background information removal processing for removing the background information from the read image data is specifically executed by the following procedure. First, for example, the image forming apparatus reads the surface of a document on which black characters are printed on a light gray background, forms image data 800 (FIG. 8A) on the surface, and configures the image data 800. A luminance histogram 810 indicating each luminance distribution is acquired (FIG. 8B). The luminance histogram 810 has a relatively large luminance value peak 811 and a relatively small luminance value peak 812. Since the background is light gray and the character is black, the luminance value of the background is larger than the luminance value of the character, and the peak 811 corresponds to the background and the peak 812 corresponds to the character. Therefore, by removing the peak 811 from the luminance histogram 810, a luminance histogram 830 (FIG. 8D) having only the peak 812 corresponding to the character is obtained. As a result, based on the luminance histogram 730, image data 820 (FIG. 8C) obtained by removing background information from the image data 800 is obtained. Note that when removing the peak 811 from the luminance histogram 810, it is necessary to sort the peak 811 and the peak 812, but a threshold is used for sorting.

JP 2003-60911 A Japanese Patent Laying-Open No. 2015-76832

  However, even if the background information removal processing method described above is executed, it may be difficult to remove only the background information. For example, when the background of the document is dark gray and the characters are black (FIG. 9A), the difference between the brightness values of dark gray and black is small, and thus a luminance histogram 910 obtained from the document (FIG. 9 ( In B)), the peak 911 corresponding to the background and the peak 912 corresponding to the character are close to each other. In this case, if a threshold value is set so as to accurately leave the peak 912, a part of the peak 911 may not be removed from the luminance histogram 910. That is, there is a problem that the background information cannot be accurately removed from the image data.

  An object of the present invention is to provide an image forming apparatus, an image forming apparatus control method, and a program capable of accurately removing background information from image data.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a reading unit that reads a front surface and a back surface of a document, and whether or not any one of the front and back surfaces of the read document is subjected to a printing process. Determining means for determining whether or not the printing process has been performed on either one of the front surface and the back surface of the read original, the first of the one surface on which the printing process has been performed. And acquisition means for acquiring the second information on the other surface not subjected to the printing process, and removal means for removing the second information from the acquired first information. It is characterized by that.

  According to the present invention, background information can be accurately removed from image data.

1 is a front view of an MFP as an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram used for explaining an internal configuration of the scanner in FIG. 1 and a document reading process executed by the scanner. FIG. 2 is a block diagram schematically showing an internal configuration of the MFP of FIG. 1. It is a flowchart which shows the procedure of the base information removal process performed by CPU which the controller in FIG. 3 has. It is a figure used in order to demonstrate the method by which the back surface information as base information is removed from surface information in step S407 of FIG. FIG. 6 is a diagram used for explaining a method of removing one peak when two peaks included in a luminance histogram obtained based on image data corresponding to the surface of the original in FIG. 5 are superimposed. It is a flowchart which shows the procedure of the modification of the base information removal process of FIG. It is a figure used in order to explain the luminance histogram which shows the distribution of each luminance which constitutes the image data corresponding to the manuscript where the black character was printed on the light gray background, and the image data. FIG. 5 is a diagram used for explaining image data corresponding to a document in which black characters are printed on a dark gray background, and a luminance histogram indicating distribution of each luminance constituting the image data.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a front view of MFP 100 as an image forming apparatus according to an embodiment of the present invention.

  1 includes a scanner 101 (reading unit), a printer 102, an operation display unit 103, and a controller 104. The scanner 101 includes a document feeder 105 and a tray 106. The printer 102 includes cassettes 107 to 109 and a paper discharge tray 110. Prepare.

  The scanner 101 reads the front and back surfaces of the document and generates image data corresponding to the read surface. For example, when a plurality of originals are set on the tray 106 and the user instructs reading of the originals set on the tray 106 via the operation display unit 103, the original feeder 105 reads the originals placed on the tray 106 one by one. Sheets are fed to the scanner 101 one by one. The scanner 101 starts reading the fed document. For example, the printer 102 prints image data generated by the scanner 101 on a recording sheet. Before the image data is printed, the recording paper is stored in the cassettes 107 to 109, and the recording paper on which the image data is printed is discharged to the paper discharge tray 110. The controller 104 controls the operation of the MFP 100.

  FIG. 2 is a diagram used to explain the internal configuration of the scanner 101 in FIG. 1 and the document reading process executed by the scanner 101.

  The scanner 101 in FIG. 2 includes an ADF 201 and an image reading unit 202. The ADF 201 includes a paper discharge tray 110, a paper feed roller 211, a separation roller 212, a drawing roller 213, a registration roller 214, a surface reading / conveying roller 215, a surface reading upstream roller 216, a surface reading downstream roller 217, and a counter member 218. In addition, the ADF 201 includes a back surface reading conveyance roller 219, a back surface reading upstream roller 220, a back surface reading downstream roller 221, a facing member 222, a paper discharge sensor 223, and a paper discharge roller 224. Further, the ADF 201 includes a document presence / absence detection sensor 226, a post-separation sensor 227, a registration sensor 228, a read sensor 229, a separation pad 230, double feed detection sensors 231 and 232, a document tray 233, a back side scanning glass 234, and an optical scanner unit 235. Prepare. The optical scanner unit 235 includes LEDs 236 and 237, mirrors 238, 239 and 240, and a back image reading sensor 241. The image reading unit 202 includes a surface flow reading glass 251, an optical scanner unit 252, and a document tray glass 253. The optical scanner unit 252 includes LEDs 261 and 262, mirrors 263, 264, 265, and a surface image reading sensor 266. .

  The document reading mode executed by the scanner 101 includes a fixed reading mode for reading a document placed on the document tray glass 253 and a flow reading mode for reading a document conveyed inside the ADF 201. In the fixed reading mode, the document placed on the document tray glass 253 is read by causing the optical scanner unit 252 to scan at a constant speed in the sub-scanning direction (the direction of the arrow in FIG. 2). On the other hand, in the flow-reading mode, first, in order to read the surface of the original by the optical scanner unit 252, the paper feed roller 211 drops on the original surface of the original bundle S stacked on the original tray 233 and rotates on the original surface. . When the paper feed roller 211 rotates on the original surface, the uppermost original of the original bundle S is conveyed into the ADF 201. At this time, when not only the uppermost document in the document bundle S but also a plurality of documents are conveyed, only the uppermost document is separated from the plurality of documents conveyed by the separation roller 212 and the separation pad 230. The double feed detection sensors 231 and 232 detect whether or not there is one document that has passed through the separation roller 212 and the separation pad 230. When it is detected that there are a plurality of documents, the operation display unit 103 displays a plurality of documents. Is displayed in the ADF 201.

  The uppermost document in the conveyed document bundle S passes through the post-separation sensor 227, the double feed detection sensors 231 and 232, the drawing roller 213, and the registration sensor 228 in order, and is temporarily stopped by the registration roller 214. Although the document may be skewed when being conveyed, the document is temporarily stopped by the registration roller 214 and bent in a loop shape, and the skew is eliminated when the bending is eliminated.

  Next, the document passes through the read sensor 229 and the front surface reading conveyance roller 215 in order, and the surface flow reading glass 251, which is a position for reading the surface of the document (hereinafter referred to as “front surface reading position”), and the facing member 218. It is conveyed to. When the document passes through the surface reading position, the surface of the document is irradiated by the LED light from the LEDs 261 and 262. The surface image reading sensor 266 detects the reflected light obtained by the irradiation of the LED light through the mirrors 263, 264, 265 and reads the surface of the document. The document that has passed the front side reading position is conveyed to the rear side reading conveyance roller 219.

  Thereafter, in order to read the back side of the document conveyed by the optical scanner unit 235 to the back surface reading and conveying roller 219, the document passes through the back surface reading upstream roller 220 to read the back side of the document (hereinafter referred to as "back surface reading position"). ") Is conveyed between the back-flow-reading glass 234 and the opposing member 222. When the document passes through the back surface reading position, the back surface of the document is irradiated by the LED light from the LEDs 236 and 237. The back side image reading sensor 241 reads the back side of the document by detecting the reflected light obtained by the irradiation of the LED light through the mirrors 238, 239 and 240. If single-sided scanning setting for reading only the front side of the document is set in MFP 100, the document passes through the back side scanning position without being scanned on the back side. The document that has passed through the back side reading position sequentially passes through the paper discharge sensor 223 and the paper discharge roller 224 and is conveyed to the paper discharge tray 110, and the reading of the document in the flow reading mode is completed.

  FIG. 3 is a block diagram schematically showing an internal configuration of MFP 100 in FIG.

  3 includes a scanner 101, a printer 102, an operation display unit 103, a controller 104, and a document feeder 105. The controller 104 includes a CPU 301 (determination unit, acquisition unit), a RAM 302, a ROM 303, a LAN controller 304, a local I / F 305, a modem 306, and an HDD 307. The controller 104 includes a printer I / F 308, a scanner I / F 309, an image rotation unit 310, an image compression / decompression unit 311, and an operation display unit I / F 312.

  CPU 301 controls communication of MFP 100 as a whole and various devices connected to MFP 100 and MFP 100 based on a control program or the like stored in ROM 303. The CPU 301 controls various processes executed in the controller 104 based on a control program stored in the ROM 303. A RAM 302 is a system work memory of the CPU 301. The RAM 302 temporarily stores image data, for example. The ROM 303 stores a boot program.

  The LAN controller 304 is connected to a client PC 314 as an external device via the LAN 313 and communicates image data and the like with the client PC 314. The local I / F 305 is an interface for connecting a USB cable 315, for example. When MFP 100 is connected to client PC 316 as an external device via USB cable 315, MFP 100 communicates image data and the like with client PC 316. The modem 306 is connected to the public line 317 and performs, for example, FAX communication with an external FAX apparatus. For example, the HDD 307 stores system software and image data for starting up or operating the MFP 100.

  A printer I / F 308 is connected to the printer 102 and executes image processing for printing image data. The printer 102 is connected to the CPU 351, RAM 352, and ROM 353, and the printer 102, CPU 351, RAM 352, and ROM 353 are connected to each other. The CPU 351 executes a program stored in the ROM 353 to control the printer 102. A RAM 352 is a work memory of the printer 102.

  A scanner I / F 309 is connected to the scanner 101, and the scanner 101 is connected to the document feeder 105. The scanner 101 is connected to the CPU 361, RAM 362, and ROM 363, and the scanner 101, CPU 361, RAM 362, and ROM 363 are connected to each other. The CPU 361 controls the printer 102 by executing a program stored in the ROM 363. A RAM 362 is a work memory of the scanner 101.

  For example, the image rotation unit 310 performs a rotation process for rotating the image data on the image data stored in the HDD 307. The image compression / decompression unit 311 compresses multi-valued, for example, image data expressed in an 8-bit format to JPEG and binary image data to JBIG, MMR, MH, etc., and decompresses the compressed image data. The operation display unit 103 is connected to the operation display unit I / F 312.

  FIG. 4 is a flowchart showing a background information removal processing procedure executed by the CPU 301 in FIG. In this embodiment, the front and back surfaces of the document are read, but it is assumed that characters are printed on the front surface (one surface) of the document (that is, the printing process has been completed).

  In FIG. 4, first, it is determined whether or not single-sided reading setting for reading only the surface of the document is set in the MFP 100 (step S401). As a result of the determination in step S401, when the single-sided reading setting is not set in the MFP 100, both sides of the original are read (step S402), and this process is terminated. On the other hand, when the single-sided reading setting is set in MFP 100, it is determined whether or not the background information removal setting for removing background information from the read image data is set in MFP 100 (step S403).

  If the background information removal setting is not set in the MFP 100 as a result of the determination in step S403, the front side of the document is read (step S404), and the process is terminated. On the other hand, when the background information removal setting is set in MFP 100, both sides of the document are read (step S405), and it is determined whether characters, figures, or the like are printed on the back side (the other side) of the document (step S405). S406). As a result of the determination in step S406, when characters, figures, or the like are not printed on the back side of the document, information on the back side of the document (hereinafter referred to as “back side information”) is extracted from the back side of the read document. The back side information thus made is used as background information. Next, information on the surface of the document (hereinafter referred to as “surface information”) is extracted from the surface of the read document, and back surface information as background information is removed from the extracted surface information (step S407). End the process.

  FIG. 5 is a diagram used to explain a method of removing back surface information as background information from front surface information in step S407 of FIG.

  For example, in the above-described step S405, the background on the front and back sides of the document is dark gray, only black characters are printed on the front side of the document, and no characters or figures are printed on the back side of the document. Both sides are read. As a result, image data 501 corresponding to the front side of the document and image data 502 corresponding to the back side of the document are obtained. Further, a luminance histogram 503 (first information) that is surface information is obtained based on the image data 501, and a luminance histogram 504 (second information) that is back surface information is obtained based on the image data 502.

  The luminance histogram 503 has a peak 503a (third information) and a peak 503b, and the luminance value indicated by the peak 503a is larger than the luminance value indicated by the peak 503b. Here, the surface information includes background information on the surface of the document (hereinafter referred to as “surface background information”) and information indicating characters printed on the surface of the document (hereinafter referred to as “surface character information”). . Therefore, the luminance histogram 503 that is the surface information includes a peak indicating the surface background information and a peak indicating the surface character information. Further, since the background is dark gray and the character is black on the surface of the document, the peak luminance value indicating the surface background information is larger than the peak luminance value indicating the surface character information. Therefore, in the luminance histogram 503, the peak 503a corresponds to the peak indicating the surface background information, and the peak 503b corresponds to the peak indicating the surface character information.

  The luminance histogram 504 has a peak 504a. The luminance histogram 504 is information on the back side of a document on which no characters, graphics, or the like are printed, and is nothing but background information on the document. Therefore, the peak 504a included in the luminance histogram 504 is a peak indicating background information.

  As described above, since the background on the front side and the back side of the document are both dark gray, the peak 503a indicating the surface background information coincides with the peak 504a indicating the background information on the back side of the document. Therefore, when the luminance histogram 504 (peak 504a) is removed from the luminance histogram 503, the peak 503a is removed from the luminance histogram 503, and the luminance histogram 505 having only the peak 503b corresponding to the surface character or the like is obtained.

  Further, when characters, graphics, or the like are printed on the back side of the document, the back side information includes background information on the back side of the document (hereinafter referred to as “back side ground information”) and information indicating the characters printed on the back side of the document. (Hereinafter referred to as “backside character information”). At this time, the luminance histogram which is the back surface information includes a peak indicating the back surface background information and a peak indicating the back surface character information. Therefore, when the luminance histogram which is the back surface information is removed from the luminance histogram which is the front surface information, not only the peak indicating the back surface background information but also the peak indicating the back surface character information is removed from the luminance histogram which is the surface information. As a result, only the peak indicating the surface character information cannot remain in the luminance histogram after removal. Correspondingly, in the processing of FIG. 4, when characters, graphics, or the like are printed on the back side of the document as a result of the determination in step S406, only the front side ground information is removed from the front side information, and the back side ground is removed from the back side information. Only the information is removed (step S408). Specifically, in order to remove the surface ground information from the surface information, the surface ground information and the surface character information are sorted using a threshold value, and the sorted surface ground information is removed from the surface information. Further, the back surface ground information is removed from the back surface information in the same manner as the front surface ground information is removed from the front surface information.

  According to the processing of FIG. 4, when characters, graphics, or the like are not printed on the back side of the document (YES in step S406), the brightness histogram 504, which is the back side information, is removed from the brightness histogram 503, which is the read front side information. (Step S407). Since the luminance histogram 504 that is back surface information is nothing but background information, the background information of the document can be removed from the image data on the surface of the document without using a threshold value by removing the luminance histogram 504 from the luminance histogram 503. it can. As a result, the background information can be accurately removed from the image data even if the peak of the brightness value corresponding to the characters printed on the surface of the document is close to the peak of the brightness value corresponding to the background of the document. .

  Further, according to the processing of FIG. 4, when characters, graphics, or the like are printed on the back side of the document (NO in step S406), only the front side ground information is removed from the front side information, and only the back side ground information is removed from the back side information. It is removed (step S408). That is, the back surface information is not used to remove the front surface information from the front surface information, and the front surface information is not used to remove the back surface information from the back surface information. If the back surface information is used when the front surface information is removed from the front surface information, it is necessary to extract the back surface ground information from the back surface information. Further, in order to use the surface information when removing the back surface ground information from the back surface information, it is necessary to extract the surface ground information from the surface information. On the other hand, if only the front surface information is removed from the front surface information or only the back surface information is removed from the back surface information, it is possible to save time and effort for extracting the back surface information and the front surface information. That is, it is possible to reduce labor in the background information removal process.

  Incidentally, the peaks 503a and 503b included in the luminance histogram 503 may partially overlap (FIG. 6A). In this case, even if the luminance histogram 504 is removed from the luminance histogram 503, the peak 503a cannot be accurately removed from the luminance histogram 503. Even if the luminance histogram 503 (surface information) is sorted into the luminance histogram 503a (surface background information) and the luminance histogram 503b (surface character information) using the threshold, the peak 503a can be accurately removed from the luminance histogram 503. Can not. Therefore, in this case, a portion of the luminance value larger than the luminance value indicated by the valley portion 601 formed by overlapping the peaks 503a and 503b among the luminances constituting the peak 503a (shaded portion in FIG. 6A). May be removed. Thereby, although the peak 503a cannot be accurately removed from the luminance histogram 503, most of the peak 503a can be removed. Further, even if most of the peak 503a is removed by removing a portion having a luminance value larger than the intersection 602 of the skirt of the peak 503b and the horizontal axis of the luminance histogram 503 (shaded portion in FIG. 6B). Good. In this case, partial omission of surface character information can be prevented.

  FIG. 7 is a flowchart showing the procedure of a modification of the background information removal process of FIG.

  The processing in steps S401 to S408 in FIG. 7 is the same as the processing in steps S401 to S408 in FIG. 4, and only differences from the processing in FIG. 4 will be described below. In the following modification, it is assumed that the background on the front side of the document and the background on the back side may not be the same color. Accordingly, the peak 503a (front surface background information) included in the luminance histogram 503 may not match the peak 504a (back surface background information) included in the luminance histogram 504. However, since both the peak 503a and the peak 504a are background information, the peak 503a and the peak 504a correspond to each other.

  In FIG. 7, when characters, graphics, or the like are not printed on the back side of the document (YES in step S406), the difference between the luminance value indicated by the peak 503a and the luminance value indicated by the peak 504a falls within a predetermined range. It is determined whether or not it is included (step S701).

  Here, as described above, the peak 504a corresponds to the back surface ground information, and the peak 503a corresponds to the front surface ground information. Therefore, when the difference value between the luminance value indicated by the peak 504a and the luminance value indicated by the peak 503a is not included in the predetermined range, the surface background information and the back surface information are significantly different, that is, the surface background. And the background color of the back surface are greatly different. In this case, when the peak 504a is removed from the luminance histogram 503, the back surface ground information that is significantly different from the front surface ground information is removed from the surface image data. As a result, the surface ground information cannot be appropriately removed from the surface image data. Correspondingly, in this modified example, when the difference between the luminance value indicated by the peak 504a and the luminance value indicated by the peak 503a is not included in the predetermined range, the peak 504a is removed from the luminance histogram 503. First, the peak 503a is removed. That is, surface character information is acquired using only surface information (surface ground information).

  Specifically, as a result of the determination in step S701, when the difference value between the luminance value indicated by the peak 503a and the luminance value indicated by the peak 504a is included in the predetermined range, the process proceeds to step S407. On the other hand, when the difference value between the luminance value indicated by the peak 503a and the luminance value indicated by the peak 504a is not included in the predetermined range, the process proceeds to step S408. The predetermined range is preferably 0 or more and 25 or less in order to avoid the use of back surface ground information that is significantly different from the front surface ground information.

  According to the processing of FIG. 7, when it is determined that the difference between the luminance value indicated by the peak 503a and the luminance value indicated by the peak 504a is not included in the predetermined range, the peak 503a is removed from the luminance histogram 503. Is done. As a result, the surface background information is removed from the image data of the front surface, and it is possible to prevent the back surface background information greatly different from the surface background information from being removed from the surface image data. As a result, background information can be appropriately removed from the image data.

  The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in the computer of the system or apparatus read and execute the program This process can be realized. The present invention can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

100 MFP
301 CPU
503, 504 Luminance histogram 503a, 503b, 504a Peak

Claims (7)

Reading means for reading the front and back sides of the document;
A discriminating means for discriminating whether or not any one of the front side and the back side of the read document has been subjected to a printing process;
When it is determined that the printing process has not been performed on either the front surface or the back surface of the read document, the first information on the one surface on which the printing process has been performed and the printing process are performed Obtaining means for obtaining second information of the other surface not applied;
An image forming apparatus comprising: a removing unit that removes the second information from the acquired first information.   The image forming apparatus according to claim 1, wherein the first information and the second information are luminance value distributions. The third information included in the first information and corresponding to the second information is acquired, the vertex of the luminance value distribution of the second information and the vertex of the luminance value distribution of the third information A determination means for determining whether or not the difference value is included in a predetermined range,
When the determination unit determines that the difference value between the vertex of the luminance value of the second information and the vertex of the luminance value of the third information is included in the predetermined range, the removal unit is acquired The image forming apparatus according to claim 2, wherein the third information is removed from the first information.   The image forming apparatus according to claim 3, wherein the predetermined range is 0 or more and 25 or less.   When it is determined that the printing process has been performed on both the front side and the back side of the read original, the acquisition unit acquires the information on the front side of the original and the information on the back side of the original and removes the information. The means uses only the information on the front side of the document when removing part of the information from the information on the front side of the document, and means for removing the information on the back side of the document when using the information on the back side of the document. The image forming apparatus according to claim 1, wherein only information on the back surface is used. A reading step for reading the front and back sides of the document;
A discriminating step for discriminating whether or not any one of the front side and the back side of the read original is subjected to a printing process;
When it is determined that the printing process has not been performed on either the front surface or the back surface of the read document, the first information on the one surface on which the printing process has been performed and the printing process are performed An acquisition step of acquiring second information of the other surface that has not been applied;
And a removing step of removing the second information from the acquired first information. A program for causing a computer to execute a control method of an image forming apparatus,
The control method of the image forming apparatus is:
A reading step for reading the front and back sides of the document;
A discriminating step for discriminating whether or not any one of the front side and the back side of the read original is subjected to a printing process;
When it is determined that the printing process has not been performed on either the front surface or the back surface of the read document, the first information on the one surface on which the printing process has been performed and the printing process are performed An acquisition step of acquiring second information of the other surface that has not been applied;
And a removal step of removing the second information from the acquired first information.