JP5904024B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that reads a document. More specifically, the present invention relates to a technique for performing image processing on image data of a read original when the bound original such as a book is read in a spread state.

  2. Description of the Related Art Conventionally, as disclosed in Patent Document 1, for example, when a document placed on a document placement table is read, an edge portion that is a portion having a large density difference is extracted from the read image data. It has been known. In this document, even if only a part of the four edges can be extracted, the image area of the document can be estimated based on the extracted edge portion.

  Also, when the image reading device reads a book that has been bound into a book or the like (hereinafter referred to as a “page spread document”), the read image data connects the right page and the left page. The binding portion may be a black region. If there is a large black area in the center of the image, it will not look good. On the other hand, a technique is also known in which a black area corresponding to the binding portion of the document is specified, and image data in the specified area is converted to white. For example, there is a technique in which a black area boundary corresponding to a binding portion is specified by the technique for extracting the edge portion described above, and the black area is processed based on the specified boundary.

JP 2008-35173 A

  However, the conventional technique described above has the following problems. That is, depending on the manuscript, information such as characters is recorded up to the vicinity of the binding portion. On the other hand, the size of the black area of the binding portion changes depending on how the user holds the document. Therefore, depending on how the user holds down the document, information near the binding portion may be included in the binding portion. Since the information included in the binding portion is lost by image processing, a part of the information included in the document is missing in the image data after reading. Therefore, it is difficult for the user to grasp the contents of the manuscript.

  The present invention has been made to solve the above-described problems of the prior art. That is, an object of the present invention is to provide an image reading apparatus that suppresses information loss in image data after reading a spread original.

  In order to solve this problem, an image reading apparatus includes a reading unit that reads an image of a document, and extracts a document region from the image data read by the reading unit with respect to the value of the density gradient in each pixel. From a first threshold value to be used as a boundary, a first generation unit that generates a first edge image composed of pixels having a first value and pixels having a second value, and image data read by the reading unit, A first value pixel and a second value pixel are defined with a second threshold value, which is a value whose density gradient is gentler than the first threshold value with respect to the density gradient value of the pixel. A second generation unit that generates a two-edge image; a document range determination unit that determines, from the first edge image, a region continuously surrounded by pixels having the first value as a range of a document region; From the two-edge image, the document range determination A specific range determining unit that determines a region having the largest area as a range of the specific region among the regions constituted by pixels of the second value in the original region determined by the copy unit, the original region and the specific region And an image processing unit that performs image processing on the image data of the document area using the area.

  An image reading apparatus disclosed in this specification has a reading unit that reads an image of a document. The original read by the reading unit may be a sheet-like original or a spread original. The image reading apparatus further includes a first generation unit that generates a first edge image and a second generation unit that generates a second edge image. The first generation unit and the second generation unit binarize the density gradient value of each pixel with different thresholds as boundaries, and generate respective edge images. The value of the density gradient is a value indicating the density difference with respect to neighboring pixels in each pixel, and is simply referred to as “density difference value” below. The density difference value is obtained for each pixel by, for example, filtering the read image data. Alternatively, the density difference value may simply be the difference between the density value of each pixel and the density value of an adjacent pixel.

  The first threshold value used in the first generation unit is a value suitable for use in extracting a document area from image data read by the reading unit. The first threshold is preferably a threshold for extracting a line generated by the outer periphery of the document page, and a value that does not extract a density difference due to unevenness on the paper surface. On the other hand, the second threshold value used in the second generation unit is a value that can extract a gentler gradient than the first threshold value. The second threshold is preferably a value that also extracts a density difference due to unevenness on the paper surface. The first value pixel with the threshold as the boundary is a pixel whose density difference value is larger than the threshold value, and the second value pixel is a pixel whose density difference value is equal to or less than the threshold value.

  Further, the image reading apparatus has a document range determination unit and a specific range determination unit. The document range determination unit sets the range of the document region as a region that is continuously surrounded by pixels having the first value of the first edge image, that is, pixels having a density difference value larger than the first threshold value. For example, if the original is a two-page original, an area including two pages of images is determined as the original area. The entire area acquired as image data by reflected light from the original may be used as the original area. Alternatively, an area obtained by excluding an area appearing as a dark portion on both sides of a page due to overlapping of edge portions of other pages from the entire area of the original may be used as the original area. If the original is a sheet, an area corresponding to the entire sheet is determined as the original area.

  The specific range determination unit has an area of the second region of the original region, that is, a region constituted by a series of pixels having a density difference equal to or smaller than the second threshold value in the second edge image. The largest area is determined as the range of the specific area. A pixel having a density difference equal to or smaller than the second threshold corresponds to a pixel having a very small density difference from the neighborhood. For example, in a region where the binding portion of a spread document is read in black, the density gradually changes near the boundary of the edge, but there is almost no density difference from the adjacent pixels in the central portion where the shadow is reflected. On the other hand, in the area where the document surface is read, a minute density difference is generated due to the unevenness of the document surface, so that the density difference value of most pixels is larger than the second threshold value. Therefore, the specific range determining unit determines only the center portion of the binding portion as the specific region when the spread original is read. As a result, the vicinity of the boundary of the binding portion can be outside the range of the specific area.

  Furthermore, the image reading apparatus has an image processing unit. The image processing unit processes image data within the range of the document area using the document area determined by the document range determination unit and the specific area determined by the specific range determination unit. As the image processing, for example, the image processing unit performs a process of extracting image data in a range other than the specific area in the document area. Alternatively, the image processing unit may perform processing for converting an image within the specific area into white or a base color. Since the specific area determined by the specific range determination unit does not include the vicinity of the binding portion boundary, the image processing unit does not process the image data near the binding portion boundary. Therefore, the possibility that the document information is lost is lower than in the case where the entire binding portion including the vicinity of the boundary of the binding portion is subjected to image processing.

  Further, the image reading device disclosed in the present specification includes an extraction region determination unit that determines an extraction region to be extracted from the document region from the document region and the specific region, and the image processing unit May perform a process of extracting an area corresponding to the extraction area from the image data read by the reading unit.

  The extraction area determination unit determines an extraction area in the image data using the determined document area and the specific area. For example, the extraction area determination unit sets a range included in the document area and not included in the specific area in the image data as the extraction area. In a spread document, only the central portion of the binding portion is determined as the specific region. Thus, image data in a range excluding the central portion of the binding portion in the original region is obtained. Further, in the spread document, the document area is divided by the specific area, so that image data of each page may be extracted. In this way, since the peripheral portion is deleted while leaving the image data corresponding to the range of the document, compact image data of only the required portion can be obtained. Therefore, it is possible to extract an image with a low possibility of character loss or the like regardless of the type of document and the orientation of the document set by the user.

  The image reading device disclosed in the present specification includes a presence determination unit that determines whether or not a region corresponding to the specific region exists in the second edge image, and the extraction region determination unit includes: When the presence determination unit determines that there is no area corresponding to the specific area, the document area may be determined as the extraction area.

  For example, when the area of the specific region determined by the specific range determination unit is equal to or less than a predetermined limit area, the presence determination unit determines that the specific region does not exist. Alternatively, the presence determination unit determines that the specific region does not exist when the ratio of the area of the specific region determined by the specific range determination unit is equal to or less than a predetermined limit ratio. May be. For example, the presence determination unit determines that there is no region corresponding to the specific region if there is no region in the image data where many pixels having a density difference value equal to or smaller than the second threshold are gathered. When there is no area corresponding to the specific area, it is preferable that the processing range of the image processing unit is equal to the range of the document area.

  The image reading apparatus disclosed in the present specification further includes a position determination unit that determines whether or not an area corresponding to the specific area is located in the center of the document area, and the extraction area determination unit includes When the position determination unit determines that the area corresponding to the specific area is not located at the center of the document area, the document area may be determined as the extraction area. If the area corresponding to the specific area is not located at the center of the document area, there is a possibility that the specific area is not a binding portion and the document is not a spread document. If it is not a double-page spread document, it is preferable to determine the document area as an extraction area as it is.

  Further, the image reading device disclosed in the present specification includes a document table having a reading area where the reading unit can read the placed document, and the specific area constituting a part of the boundary of the reading area. A boundary determination unit that determines whether or not the extraction region determination unit determines that the region corresponding to the specific region is not located in the center of the document region by the position determination unit; and When the boundary determination unit determines that the specific area constitutes a part of the boundary of the reading area, a range other than the specific area in the document area may be determined as the extraction area.

  Even if the area corresponding to the specific area is not located at the center of the original area, if the specific area constitutes a part of the boundary of the reading area, there is a possibility that it is one page of the spread original. For example, when the user places only one page on the document table, the longitudinal direction of the specific area may be arranged along the boundary of the reading area. Therefore, when the boundary determination unit determines that the specific area constitutes a part of the boundary of the reading area, it is less likely that the document information is lost by performing an extraction process taking the specific area into account. Is preferable.

  Further, the image reading apparatus disclosed in the present specification causes the reading unit to read a document at a predetermined resolution, and causes the reading unit to read a document at a lower resolution than the first reading mode. A switching unit that switches between the second reading mode, the reading unit reads the document in the first reading mode after reading the document in the second reading mode, and the first generation unit includes the reading unit; Generates the first edge image from the image data read in the second reading mode, and the second generation unit generates the second edge image from the image data read by the reading unit in the second reading mode. The image processing unit may perform the image processing on the image data read by the reading unit in the first reading mode. By separately generating and processing each edge image, the processing load at the same time can be reduced.

  The second threshold value may be a value for detecting a value of density gradient due to unevenness on the surface of the document. In this way, the second edge image includes the background portion of the document. Therefore, it is possible to appropriately extract only the dark part due to the light not reaching like the binding part.

  Further, the image reading apparatus disclosed in the present specification is configured such that the first edge image includes an edge in which pixels having the first value are continuous within a predetermined width from one side to the inside of the document area. When there is a line, the range of the document area may be changed to a range constituted by the innermost edge line. If an edge line appears in a range within a predetermined width from one side to the inside of the document area and substantially parallel to that side, it can be determined that the edge line is due to the edge of another page. That is, it may be determined that the portion where the edge line appears does not include document information. Therefore, the innermost edge line can be used as the boundary of the document area.

  According to the present invention, an image reading apparatus that suppresses information loss in image data after reading a spread original is realized.

FIG. 2 is a perspective view showing an external appearance of the MFP according to the embodiment with a cover opened. FIG. 2 is a block diagram showing an electrical configuration of the MFP shown in FIG. 1. It is a flowchart which shows the procedure of an image reading process. It is a flowchart which shows the procedure of an image reading process. 5A is an explanatory diagram illustrating an example of an image of a reading result, FIG. 5B is an explanatory diagram illustrating an example of an image density value of one line in FIG. 5A, and FIG. It is explanatory drawing which shows the example of a 1st edge image. It is explanatory drawing which shows the example of a 2nd edge image. It is explanatory drawing which shows the example of a document area | region. It is explanatory drawing which shows the example of a document area | region. It is explanatory drawing which shows the example of the image data which read one side of the facing original. It is explanatory drawing which shows the example of the 1st edge image of FIG. It is explanatory drawing which shows the example of the 2nd edge image of FIG.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying an image reading apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a multi-function peripheral (MFP) having an image reading function and an image forming function.

[MFP configuration]
An appearance of the MFP 100 according to this embodiment is shown in FIG. MFP 100 includes an image forming unit 1 that prints an image on a sheet, and an image reading unit 2 (an example of a reading unit) that reads an image of a document. Although not shown in the drawing, the image forming unit 1 is provided at the lower part of the main body 10 of the image reading unit 2. The image forming method of the image forming unit 1 may be an electrophotographic method or an ink jet method. Further, even if a color image can be formed, it may be dedicated to a monochrome image.

  As shown in FIG. 1, the image reading unit 2 includes a main body unit 10 that reads an image and a cover 20. The cover 20 is positioned above the main body 10 and has one side connected to the main body 10 so as to be rotatable with respect to the main body 10. The cover 20 may include an automatic document feeder (ADF: Auto Document Feeder).

  The main body 10 includes a contact glass 11 (an example of a document table) on the upper surface thereof. When reading a document, the user places the document on the contact glass 11 with the reading surface facing downward. The reading area that can be read by the image reading unit 2 is within the range of the contact glass 11 and within the movable range of the image sensor 15 described later. Alternatively, an unreadable region may be provided along the outer periphery of the contact glass 11. In that case, the area inside the unreadable area is the reading area.

  Further, an image sensor 15 that reads an image of a document is provided inside the main body 10 and below the contact glass 11. The image sensor 15 has optical elements arranged in a line in the main scanning direction, and is provided so as to be movable in the sub scanning direction. The image sensor 15 emits light toward the document placed on the contact glass 11, converts the reflected light from the document into an electrical signal, and outputs it. As the image sensor 15, for example, a contact-image-sensor (CIS) or a charge-coupled device (CCD) is applicable.

  The MFP 100 further includes, on the front side thereof, an operation panel 40 including a button group 41 including various buttons (for example, buttons for a start key, a stop key, and a numeric keypad) and a display unit 42 including a liquid crystal display. ing. The button group 41 and the display unit 42 allow the operation status to be displayed and the operation input by the user to be performed.

[Electric configuration of MFP]
Next, the electrical configuration of the MFP 100 will be described. As illustrated in FIG. 2, the MFP 100 includes a control unit 30 that includes a CPU 31, a ROM 32, a RAM 33, and an NVRAM (Non Volatile RAM) 34. The control unit 30 is electrically connected to the image forming unit 1, the image reading unit 2, the operation panel 40, the network interface 37, and the USB interface 38.

  The ROM 32 stores various control programs and image processing programs for controlling the MFP 100, various settings, initial values, and the like. Further, the ROM 32 has an area for storing a threshold value for generating a first edge image and a second edge image, which will be described later, and stores a first threshold value 45 and a second threshold value 46. The first threshold 45 and the second threshold 46 are determined and stored in advance based on the performance of the image reading unit 2 of the MFP 100, the type of filter for calculating the density difference value, and the like. The ROM 32 also stores a limit area 47 that is a threshold for determining a specific area.

  The RAM 33 is used as a work area from which various control programs are read, or as a storage area for temporarily storing image data of a document read by the image reading unit 2 and image data sent via the network interface 37. The The RAM 33 is also used as a storage area for temporarily storing a first edge image and a second edge image, which will be described later. The NVRAM 34 is a non-volatile storage means and is used as a storage area for storing various settings.

  CPU 31 (an example of a first generation unit, a second generation unit, a document range determination unit, a specific range determination unit, an image processing unit, an extraction region determination unit, a presence determination unit, a position determination unit, a boundary determination unit, and a switching unit) Calculations for realizing various functions such as an image reading function and an image forming function in the MFP 100 are executed and become the center of control. The CPU 31 controls each component of the MFP 100 according to the control program read from the ROM 32 while storing the processing result in the RAM 33 or the NVRAM 34.

  Further, the CPU 31 performs image processing on the image data read by the image reading unit 2 in accordance with, for example, an image processing program read from the ROM 32. Further, the CPU 31 switches the reading resolution of the image reading unit 2. The image reading mode by the image reading unit 2 includes a main scan and a pre-scan as two types of scans having different reading resolutions. The main scan is a scan at a resolution designated by the user. The main scan corresponds to the first reading mode. The pre-scan is a scan at a lower resolution than the main scan and corresponds to the second reading mode. The CPU 31 selects either pre-scan or main scan and operates the image reading unit 2.

  The network interface 37 is connected to the network. The MFP 100 can perform data communication with another information processing apparatus (not shown, for example, a computer) via the network interface 37. The USB interface 38 is connected to a peripheral device (not shown, for example, a flash memory) capable of USB connection. The MFP 100 can perform data communication with an external peripheral device or the like via the USB interface 38.

[Book Scan Mode]
Next, the book scan mode of the MFP 100 will be described with reference to the flowcharts of FIGS. In the book scan mode, an image of a spread original is read by the image reading unit 2, a range including document information is determined from image data read by the image reading unit 2, and an image for each page is formed. Mode. Further, MFP 100 outputs the formed image in accordance with a user instruction.

  When instructing execution of the book scan mode, the user opens the cover 20 and sets it on the contact glass 11 with the reading surface of the spread original facing downward. Further, the user presses a button instructing to start reading in the book scan mode in the button group 41 while pressing the document. Pressing this button serves as an instruction to start execution of the book scan mode.

  Hereinafter, a book scan reading process executed by the CPU 31 when an instruction to start execution of the book scan mode is received will be described. When receiving an instruction to execute the book scan mode, the CPU 31 first causes the image reading unit 2 to perform prescan (S101 in FIG. 3). That is, in S101, the CPU 31 causes the image reading unit 2 to read at a lower resolution than the scan resolution instructed by the user. Further, the CPU 31 stores the image data acquired in S101 in the RAM 33.

  The image data obtained by the pre-scan has a smaller data amount than the image data obtained by the main scan, that is, reading at the scan resolution specified by the user. Therefore, by performing the process described later using image data obtained by pre-scanning, the time required for the process is shortened compared to the case of using the main scan data.

  FIG. 5A shows an example of image data when a facing document is read. The image data 51 obtained in S101 includes page areas 53 and 54 for two pages, a dark portion 55 between them, and dark portions 56 and 57 due to the ends of other pages formed outside both pages. However, at this stage, the boundary between the page area 53 and the dark part 55 and the boundary between the page area 54 and the dark part 55 are not clear. Note that the image data 51 may further include a dark portion or the like on the outer peripheral side from the range shown in FIG. 5A depending on the size of the document and the placement position of the document on the contact glass 11.

  In the example shown in FIG. 5, the image density of the pixel in the target column indicated by the alternate long and short dash line in FIG. 5A in the image data 51 has a shape as shown in FIG. 5B, for example. In FIG. 5 (b), the pixels with a larger amount of light received by the image sensor 15 are plotted higher. That is, in FIG. 5B, the upper pixel is a higher density pixel, and the lower pixel is a lower density pixel. That is, the pixels that read the paper surface between the printed characters are pixels that are generally white and have a high density, and pixels that are dark and have a low density appear at the printed characters. However, the values of the image data vary considerably because there are irregularities on the surface of the document in the background portion and the print portion of the document.

  Subsequently, the CPU 31 performs a filtering process on the image data 51 read in S101 to obtain a density difference value of each pixel (S102 in FIG. 3). In S102, the CPU 31 calculates a sum of squares for each pixel by applying a filter that weights the image density of the surrounding pixels according to the directionality. The density difference value of each pixel obtained as a result of S102 is a value indicating the gradient of density from the surrounding pixels, and a pixel having a steeper gradient has a larger value.

  For example, among the results of filtering the image data of FIG. 5A, the density difference value of each pixel in the target column is as shown in FIG. 5C. In FIG. 5C, the horizontal axis is a pixel having a density difference value of 0, and is a pixel having no density difference from neighboring pixels. The pixel at the boundary between the printed character and the background has a large density difference from the neighborhood, and thus appears as a protruding value in FIG. On the other hand, the density difference value of the background portion of the document is not as large as the pixel at the boundary described above, but is a value larger than 0, and varies within a certain range as indicated by a range D in FIG. Value.

  The dark portion 55 resulting from the binding portion of the document is a shadow image with almost no color unevenness and almost no variation as shown in FIG. That is, in the dark part 55, the density difference with the neighboring pixels is extremely small. For this reason, the density difference value of the pixels included in the dark portion 55 is almost 0 as shown in FIG. In the document area, pixels with extremely small density difference values are rarely gathered at locations other than the dark portion 55.

  Next, the CPU 31 reads the first threshold value 45 and the second threshold value 46 (see FIG. 2) from the ROM 32 (S103 in FIG. 3). The first threshold value 45 and the second threshold value 46 are threshold values for binarizing the density difference value (for example, FIG. 5C) calculated by the CPU 31 in S102 of FIG. The first threshold 45 and the second threshold 46 are determined in advance before shipment of the MFP 100 and are stored in the ROM 32.

  As shown in FIG. 5C, the first threshold 45 is a value larger than the upper limit of the range D that is the density difference value of the background portion. Therefore, the CPU 31 can use the first threshold value 45 to extract a line corresponding to the outer periphery of the document and an outer frame of characters. On the other hand, the second threshold value 46 is a value smaller than the first threshold value 45. As shown in FIG. 5C, the second threshold value 46 is a value that is equal to or less than the lower limit of the range D that is the density difference value of the background portion. The CPU 31 may execute S103 before S101, may be executed between S101 and S102, or may be executed in parallel with S101 and S102.

  Next, the CPU 31 generates a first edge image by binarizing the density difference value obtained in S102 using the first threshold value 45 read in S103 of FIG. 3 (S105). An example of the first edge image 61 of the image data 51 is shown in FIG. FIG. 6 shows an edge line represented by a broken line due to successive appearance of pixels having density difference values larger than the first threshold 45. However, small capital letters in the figure are shown as solid lines for ease of viewing. Here, the CPU 31 functions as a first generation unit.

  As shown in FIG. 5C, the first threshold 45 is a value larger than the upper limit of the range D. Therefore, as shown in FIG. 6, the first edge image 61 obtained in S <b> 105 of FIG. 3 is an image obtained by extracting a page frame and a character outline frame as edge lines from the image data 51. On the other hand, in a portion where the density gradually changes, such as a dark portion 55 (see FIG. 5A) between pages, the density difference from neighboring pixels is medium, and the density difference value is the first. May fall below threshold 45. In the example shown in FIG. 6, only the edge line that largely includes the range of the dark part 55 is extracted. After S105, the CPU 31 stores the generated first edge image 61 in the RAM 33 (S106).

  The CPU 31 also generates a second edge image in parallel with S105 to S106 in FIG. That is, the CPU 31 generates the second edge image 63 by binarizing the density difference value obtained in S102 using the second threshold value 46 read in S103 (S108). An example of the second edge image 63 of the image data 51 is shown in FIG. FIG. 7 shows pixels whose density difference value is larger than the second threshold value 46 in black. Here, the CPU 31 functions as a second generation unit.

  As shown in FIG. 5C, the second threshold value 46 is a value equal to or lower than the lower limit of the range D. Accordingly, the density difference value of most pixels including the background portion is larger than the second threshold value 46. Therefore, as shown in FIG. 7, in the second edge image 63 obtained in S108 of FIG. 3, most pixels are represented in black. In FIG. 7, white portions appear only in the portions of the image data 51 where there is almost no density difference from neighboring pixels.

  That is, the range that appears white in the second edge image 63 is only the range in which there is almost no density difference in the central portion of the dark portion 55. In the background portion, pixels with density difference values below the range D may appear slightly, but they do not appear together. Pixels whose density difference values are below the range D are indicated by white squares in FIG. After S108, the CPU 31 stores the second edge image 63 in the RAM 33 (S109).

  After S106 and S109 in FIG. 3 are completed, the CPU 31 determines the range of the document area based on the edge line of the first edge image 61 (S111). Specifically, as shown in FIG. 8, the CPU 31 determines the document area 66 as the outermost area among the areas surrounded by the edge lines appearing in the first edge image 61. The document area 66 includes the entire range of image data generated by receiving reflected light from the document.

  Further, when the edge line parallel to one side forming the boundary is within the predetermined width from the boundary, the CPU 31 sets the document area 66 as the innermost edge of the parallel edge lines. You may make it the range comprised with a line. For example, the range constituted by the innermost edge lines among the parallel edge lines is determined as the document area 66, or the outermost area among the areas surrounded by the edge lines appearing in the first edge image 61 is set as the parallel Or change to a range constituted by the innermost edge line.

  The parallel edge line is an edge line that extends from one side of two sides that intersect at least a part of one side forming the boundary of the document region 66 to the other side. As a result, the document area 66 is changed to the range shown in FIG. Note that the document area is an area of the document where characters and images that the user can visually recognize.

  The document area 66 determined in S111 is a minimum rectangular area including both the page areas 53 and 54 of the pages on both sides. The document area 66 includes page areas 53 and 54 of the image data 51 and a dark portion 55 between them. Here, the CPU 31 functions as a document range determination unit.

  Next, the CPU 31 determines a specific area based on the second edge image 63 in the document area 66 determined in S111 of FIG. 3 (S113). In the second edge image 63, the CPU 31 determines a region having the largest area as a range of the specific region among regions formed by successive pixels with small density differences. In the example of FIG. 7, the CPU 31 determines the range of the white area at the center of the dark part 55 as the specific area 64. Here, the CPU 31 functions as a specific range determining unit.

  However, the CPU 31 does not determine a region whose area is too small as the range of the specific region. In other words, if the area of the region where pixels having a small density difference are continuous is smaller than the limit area 47 stored in the ROM 32, the CPU 31 determines that the specific region does not exist. For example, when the document is not a spread document but a simple sheet, there is no binding portion. Therefore, in order to avoid determining the white square portion in the page area as the specific area, the area having an area that is too small is excluded from the determination target of the specific area. When the CPU 31 determines that the specific area does not exist, the CPU 31 inputs information indicating that the specific area does not exist in the area where the specific area 64 is stored.

  Then, the CPU 31 performs image processing of the image data 51 based on the document area 66 determined in S111 of FIG. 3 and the specific area 64 determined in S113 (S115). Details of the image processing will be described later.

  After S115 in FIG. 3, the CPU 31 outputs the image data after the image processing based on a user instruction (S117). For example, the CPU 31 causes the image forming unit 1 to print image data. Alternatively, the CPU 31 may convert the image data into a file and send it to the target device in accordance with a user instruction. The CPU 31 causes the image data to be transmitted to another information processing apparatus via the network interface 37, for example. Alternatively, the CPU 31 may store image data in storage means such as a flash memory (not shown) connected via the USB interface 38. This completes the book scan reading process.

[Image processing]
Next, the contents of the image processing executed in S115 of FIG. 3 during the book scan reading process will be described with reference to the flowchart of FIG.

  First, the CPU 31 determines whether or not a specific area has been determined in S113 of FIG. 3 (S201 of FIG. 4). When the specific area 64 is not determined in S113 of FIG. 3, information indicating that the specific area does not exist is input to the area storing the specific area 64 of the RAM 33. If the information indicating that the specific area does not exist is input to the RAM 33, the CPU 31 determines that the image data 51 does not have the specific area (S201: No). Otherwise, the CPU 31 determines that the specific area 64 has been determined (S201: Yes).

  When there is no specific area (S201: No), for example, the original is not a spread original but a sheet-like original. When the document is in a sheet form, the binding portion does not exist, and the entire document area 66 in the image data 51 is the range of the image data to be output. Therefore, the CPU 31 determines the extraction area to be extracted as the document area 66 (S203). Here, the CPU 31 functions as an extraction region determination unit.

  Next, the CPU 31 causes the image reading unit 2 to perform a main scan (S205). Then, the CPU 31 extracts image data in a range corresponding to the extraction area determined in S203 from the image data obtained by the main scan, and stores it in the RAM 33 as output image data (S206). After S206, the CPU 31 ends the image processing, returns to FIG. 3, and proceeds to S117.

  On the other hand, returning to the description of S201 in FIG. 4, if the CPU 31 determines that the second edge image 63 has a specific area (S201: Yes), it determines whether the specific area 64 can be regarded as a binding portion. . Therefore, the CPU 31 determines whether or not the specific area 64 is near the center of the document area 66 (S210). Here, the CPU 31 functions as a position determination unit.

  In S210 of FIG. 4, the CPU 31 determines whether or not a part of the specific area 64 is included within a predetermined size range including a pixel corresponding to the center of the document area 66, for example. Alternatively, the CPU 31 may also determine whether or not the specific area 64 is arranged to divide the document area 66 into two. That is, when it can be considered that the arrangement of the specific area 64 corresponds to the binding portion of the document area 66, the CPU 31 determines that the range excluding the specific area 64 from the document area 66 is an image range including information.

  Therefore, when the CPU 31 determines in S210 of FIG. 4 that the specific area 64 is the center of the document area 66 (S210: Yes), the CPU 31 regards the specific area 64 as a binding portion. When the specific area 64 is regarded as the binding portion, the CPU 31 determines the extraction area as a range excluding the specific area 64 in the document area 66 (S213). Here, the CPU 31 functions as an extraction region determination unit.

  Next, the CPU 31 causes the image reading unit 2 to perform a main scan (S215 in FIG. 4). Then, the CPU 31 extracts image data in a range corresponding to the extraction area determined in S213 from the image data obtained by the main scan, and stores it in the RAM 33 as output image data (S216).

  The extraction area extracted in S213 of FIG. 4 is a range obtained by excluding the specific area 64 shown in FIG. 7 from the document area 66 shown in FIG. That is, the extraction area is an area corresponding to two pages in which the document area 66 is divided into two by the specific area 64. Therefore, the CPU 31 can handle these two areas as different image data. Specifically, the CPU 31 extracts two image data corresponding to each page.

  As described above, the specific region 64 includes only a very dark portion at the center of the dark portion. Therefore, for example, as indicated by the letter “J” in FIG. 6, even if information exists at the boundary between the dark part and the page area, the information is not lost. After S216, the CPU 31 ends the image processing, returns to FIG. 3, and proceeds to S117.

  On the other hand, returning to the description of S210 in FIG. 4, when the CPU 31 determines that the specific area 64 is not the central portion of the document area 66 (S210: No), the arrangement of the specific area 64 is confirmed in more detail. . Specifically, the CPU 31 determines whether or not the specific area 64 is on a reading frame that is a boundary of a readable range of the image reading unit 2. That is, the CPU 31 determines whether or not the specific area 64 includes a part of the outermost pixel in the image data 51 (S220). Here, the CPU 31 functions as a boundary determination unit.

  In this embodiment, the readable range of the image reading unit 2 is the range of the contact glass 11. When the user sets the original so that only one page of the two-page spread original is read, a binding portion may be arranged along the edge of the contact glass 11. When the binding portion is arranged along the edge of the contact glass 11, image data as shown in FIG. 10 is obtained. An example of the first edge image generated based on the image data of FIG. 10 is shown in FIG. Further, FIG. 12 shows an example of the second edge image generated based on the image data of FIG.

  In the example shown in FIGS. 10 to 12, although the specific area 64 is not the central portion of the document area 66, the CPU 31 determines that the specific area 64 is a binding portion and removes it. Therefore, if it is desirable to determine and remove the specific area 64 as a binding portion, for example, the CPU 31 may confirm whether or not the longitudinal direction of the specific area 64 is along the edge of the reading frame. Then, the CPU 31 determines whether or not to determine the specific area 64 as a binding portion based on the shape and arrangement of the specific area 64.

  When the CPU 31 determines that the specific area 64 is in the reading frame in S220 of FIG. 4 (S220: Yes), the CPU 31 excludes the specific area 64 from the original area 66. The range is determined (S223). Here, the CPU 31 functions as an extraction region determination unit.

  Next, the CPU 31 causes the image reading unit 2 to perform a main scan (S225). Then, the CPU 31 extracts image data in a range corresponding to the extraction area determined in S223 from the image data obtained by the main scan, and stores it in the RAM 33 as output image data (S226). After S226, the CPU 31 ends the image processing, returns to FIG. 3, and proceeds to S117.

  If the CPU 31 determines in S220 in FIG. 4 that the specific area 64 is not on the reading frame (S220: No), the CPU 31 selects the extraction area as the specific area as in the case where there is no specific area (S201: No). The entire range of the document area 66 including 64 is determined (S203). When the specific area 64 is not on the reading frame, the possibility that the specific area 64 is a part of the image is high. Therefore, the CPU 31 determines that the entire document area 66 of the image data 51 is within the range of image data to be output. Therefore, the above-described S205 and S206 are executed to finish the image processing, and the process returns to FIG. 3 and proceeds to S117.

  As described above in detail, in MFP 100 of this embodiment, CPU 31 generates two types of edge images from image data obtained by reading a document using two types of threshold values. Further, the CPU 31 determines a document area and a specific area based on the two types of generated edge images, and performs image processing on the image data based on the determined area. Since the second threshold value is a value that can extract a gentler density gradient than the first threshold value, only the pixels having almost no density difference from neighboring pixels are extracted from the second edge image based on the second threshold value. . That is, the specific area 64 determined based on the second edge image hardly includes pixels including document information. Therefore, an image reading apparatus that suppresses information loss in image data after reading a spread original is realized.

Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the present invention is not limited to the MFP, and can be applied to any apparatus having an image reading function such as a copying machine, a scanner, and a FAX.

  Further, for example, in the above-described embodiment, the document region 66 is first changed from the outermost range of the edge line to the inner edge line, but may not be changed. That is, the outermost range that is continuously surrounded by the pixels having the first value in the first edge image may be the document area 66. In this way, the document area 66 is a range that includes the entire range of image data read by the reflected light from the document. Alternatively, the innermost range from the beginning may be determined as the document region 66 without going through a changing procedure.

  Further, for example, in the above-described embodiment, when a two-page spread document including information for two pages is read in the book scan mode, the image processing is extracted as separate image data for each page area. However, image processing is not limited to this, and image data obtained by changing the color of the dark portion at the center including the areas of both pages may be used. For example, the image data of pixels other than the range selected as the extraction area may be changed from the main scanned image data. The color after the change can be selected from, for example, the same color as the background portion of the document, white, the color of adjacent pixels, and the like.

  Further, for example, the processing of the present invention may be performed not only in the book scan mode but also when an instruction to read a document that outputs one image data is given. That is, the user's instruction may not be a book scan, but the first edge image and the second edge image may be generated from the read image data. Then, the image processing of this embodiment may be performed according to the presence or absence of the specific area.

  In this embodiment, the processes of S105 to S106 and the processes of S108 to S109 are performed in parallel. However, the present invention is not limited to this, and one may be performed first and the other may be performed later. In this embodiment, the limit area 47 is a fixed value. However, the present invention is not limited to this, and the limit area 47 may be variable according to the document size.

  In each of the above-described embodiments, the edge image is generated based on the image data obtained by performing the pre-scan. However, the present invention is not limited to this. For example, if the image reading apparatus has sufficient processing capability, the main scan may be performed from the beginning. Further, image data corresponding to pre-scan may be generated from image data obtained by the main scan. In the above flowchart, the main scan is performed after the document area and the specific area are determined. However, the execution timing of the main scan is not limited to this. It may be done at an earlier stage.

  The processing disclosed in the embodiments may be executed by a single CPU, a plurality of CPUs, hardware such as an ASIC, or a combination thereof. Further, the processing disclosed in the embodiment can be realized in various modes such as a recording medium or a method recording a program for executing the processing.

2 Image reading unit 11 Contact glass 31 CPU
51 Image Data 45 First Threshold 46 Second Threshold 61 First Edge Image 63 Second Edge Image 64 Specific Area 66 Document Area

Claims (8)

A reading unit for reading an image of a document;
A density gradient value at each pixel is used as a density difference value, which is a value used to extract a document area from image data read by the reading unit and is larger than the upper limit of the density difference value of the background portion of the document. A pixel having a density difference value larger than the first threshold value is a pixel having a first steep gradient value, and a pixel having a density difference value not greater than the first threshold value is a pixel having a first gentle gradient value. A first generator for generating a first edge image composed of pixels having a steep gradient value and pixels having the first gentle gradient value ;
From the image data the reading unit has read, density difference value than the second threshold value or less value lower limit of the density difference values of the ground portion of the gradients of concentration than the first threshold value is the original it gentle Nedea is The pixel having the second steep gradient value is defined as a pixel having a large steep gradient value and the pixel having a density difference value not greater than the second threshold value is defined as a pixel having the second gentle gradient value. A second generation unit that generates a second edge image composed of pixels of two gentle gradient values ;
A document range determination unit that determines a region continuously surrounded by pixels of the first steep slope value from the first edge image as a range of a document region;
From the second edge image, a region having the largest area among the regions composed of pixels of the second gentle gradient value in the document region determined by the document range determination unit is determined as the range of the specific region. A specific range determination unit to perform,
An image processing unit that performs image processing on image data in the document area using the document area and the specific area;
An image reading apparatus comprising: The image reading apparatus according to claim 1,
An extraction area determination unit that determines an extraction area to be extracted from the original area from the original area and the specific area;
The image processing apparatus, wherein the image processing unit performs a process of extracting an area corresponding to the extraction area from the image data read by the reading unit. The image reading apparatus according to claim 2,
A presence determination unit that determines whether or not an area corresponding to the specific area exists in the second edge image;
The image reading apparatus, wherein the extraction area determination unit determines the document area as the extraction area when the existence determination unit determines that there is no area corresponding to the specific area. In the image reading apparatus according to claim 2 or 3,
A position determination unit that determines whether or not an area corresponding to the specific area is located in the center of the document area;
The extraction area determination unit determines the document area as the extraction area when the position determination unit determines that the area corresponding to the specific area is not located in the center of the document area. An image reading apparatus. The image reading apparatus according to claim 4,
A document table having a reading area where the reading unit can read the placed document;
A boundary determination unit for determining whether or not the specific area constitutes a part of the boundary of the reading area;
The extraction area determination unit determines that the position determination unit determines that the area corresponding to the specific area is not located in the center of the document area, and the boundary determination unit determines a part of the boundary of the reading area. An image reading apparatus characterized in that, when it is determined that the specific area is configured, a range other than the specific area in the document area is determined as the extraction area. In the image reading apparatus according to any one of claims 1 to 5,
A switching unit that switches between a first reading mode in which the reading unit reads a document at a predetermined resolution and a second reading mode in which the reading unit reads a document at a lower resolution than the first reading mode;
The reading unit reads the document in the first reading mode after reading the document in the second reading mode,
The first generation unit generates the first edge image from image data read by the reading unit in the second reading mode,
The second generation unit generates the second edge image from image data read by the reading unit in the second reading mode,
The image reading apparatus, wherein the image processing unit performs the image processing on image data read by the reading unit in the first reading mode. In the image reading device according to any one of claims 1 to 6,
2. The image reading apparatus according to claim 1, wherein the second threshold value is a value for detecting a value of a density gradient due to unevenness on the surface of the document. In the image reading apparatus according to any one of claims 1 to 7,
In the first edge image, when there is an edge line in which pixels having the first steep slope value are continuous within a predetermined width from one side to the inside of the document area, the range of the document area is the largest. An image reading apparatus that changes to a range constituted by the inner edge lines.

Images