JP2019208290A - Image reading apparatus, control method of the same, and program - Google Patents

Abstract

To provide a mechanism for correcting a distortion of a read image due to a change in a current inclination due to transportation and forming it suitably.SOLUTION: The image reading apparatus is configured to: create a gamma curve from a density distribution of image data obtained by reading an image from a document; extract a polygon indicating a contour of an image indicated by the image data using the gamma curve; divide the extracted polygon into a plurality of squares; and transform each of the divided squares into a rectangles and join them.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image reading apparatus that reads an image from a document, a control method thereof, a program, and an image reading system.

  The image reading apparatus includes a flat bed type scanner and a sheet feed type scanner. In order to read a sheet-like document with an image sensor and convert it into digital data, a flatbed scanner moves the line-shaped image sensor from end to end while the document is placed on a flat floor. Take an image. On the other hand, the sheet feed type scanner has a paper feed table on which one or a plurality of documents are set and a document transport mechanism, and images a document by arranging a line-shaped image sensor in the middle of the transport path. In either method, the document to be imaged may not be parallel to the image sensor, and as a result of imaging, an image as if the document is tilted is obtained. If the image of the document is tilted, the visibility is deteriorated and the processing such as optical character recognition is adversely affected. Therefore, it is desirable to remove the tilt of the document as much as possible. For this reason, many have an inclination correction process for converting an original image into an upright state by detecting the inclination angle of the original document recorded in the image and rotating the entire image in the opposite direction of the inclination angle. Examples of tilt detection techniques include Patent Document 1 and Patent Document 2.

Japanese Patent Laid-Open No. 03-198178 Japanese Patent Laid-Open No. 02-193267

  However, the above prior art has the following problems. In the case of a sheet feed type scanner, a configuration in which the vicinity of the center of the front end of a document set on a paper feed tray is sandwiched between a pair of rollers and the roller is rotated to convey the document to the position of the image sensor. However, if the original is biased to the left or right and is set on the paper feed stand and the force to convey the original is not equal to the left or right, the original will be tilted immediately after the start of conveyance, The slope may increase rapidly. In this way, when the inclination of the document greatly changes during document transportation, the document image read by the scanner is not a simple rotation of the rectangle, but an image in which distortion occurs in the intermediate portion as shown in FIG. Become. However, the conventional tilt correction process only rotates the entire image uniformly, and when distortion occurs in the middle of the original image, it cannot be corrected and corrected to an upright rectangle. It was.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a mechanism that corrects a distortion of a read image due to a change in the current inclination due to conveyance and forms the image appropriately.

  The present invention is, for example, an image reading apparatus using a reading unit that reads an image from a document, a gamma curve generating unit that generates a gamma curve from a density distribution of image data read by the reading unit, and the gamma curve. A polygon extracting means for extracting a polygon indicating the contour of the image indicated by the image data; a dividing means for dividing the polygon extracted by the polygon extracting means into a plurality of quadrangles; and the dividing means for dividing the polygon. Each of the plurality of quadrilaterals is provided with a deforming unit that transforms the rectangle into a rectangle, and a coupling unit that joins the plurality of rectangles deformed by the deforming unit.

  The present invention also provides an image reading system including an image reading device that reads an image from a document and an image processing device that processes image data read by the image reading device. Reading means for reading an image; creating means for creating a gamma curve from a density distribution of image data read by the reading means; image data read by the reading means; and gamma curve created by the creating means for the image processing Transmitting means for transmitting to the apparatus, wherein the image processing apparatus uses the gamma curve to extract a polygon indicating the contour of the image indicated by the image data, and the polygon extracting means. Dividing means for dividing the extracted polygon into a plurality of quadrilaterals, and a plurality of quadrilaterals divided by the dividing means, respectively , Characterized in that it comprises a deforming means for deforming the rectangular, and coupling means for coupling a plurality of rectangular deformed by said deforming means.

  According to the present invention, it is possible to correct the distortion of the read image due to the change in the current inclination due to the conveyance, and it is possible to suitably form the image.

External view of the scanner. The internal block diagram of a scanner. 1 is an overall configuration diagram of an image system. The figure which shows the read image of a document. The figure which shows the polygon which comprises the outline of a document. The figure which shows the polygon by which the point which becomes a pair of a vertex was added. The figure which shows the square obtained by dividing | segmenting a polygon. The figure which shows the rectangle deform | transformed from the square. The figure which shows the image of the original document by which distortion was correct | amended. The figure which shows the mapping from a rectangle to a rectangle. The figure which shows density distribution of the opposing surface of an image sensor. The figure which shows a gamma curve. The figure which shows the image of the original document which applied the gamma curve. The flowchart of distortion correction. 6 is a flowchart for obtaining a document image. The figure which shows the method of calculating | requiring the point on the opposite side of a vertex.

  An embodiment of the present invention is shown below. The individual embodiments described below will help to understand various concepts, such as superordinate concepts, intermediate concepts and subordinate concepts of the present invention. Further, the technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments.

<Configuration of image reading apparatus>
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. First, a configuration example of the image reading apparatus according to the present embodiment will be described with reference to FIGS. 1 and 2. The image reading apparatus according to the present embodiment is a sheet feed type scanner. Note that the present invention is not limited to this, and is an apparatus that reads an image from an original, and can be applied to any apparatus that can read an image while the original is tilted by the mechanism and the read image may be distorted. can do.

  The scanner 1 includes a paper feed tray 101 on which a document 205 is set, a paper discharge tray 102 on which a scanned document is discharged, a roller 201 that transports the document from the paper feed tray 101 to the paper discharge tray 102, and the document as image data. The image sensor 202 is input. Further, the scanner 1 connects a paper discharge sensor (not shown) that detects that a document has been discharged, a memory that stores a program and image data, a CPU board 203 equipped with a CPU that controls the program, and the scanner 1 to a computer. An external interface 204 is provided. As the external interface 204, a known communication interface such as SCSI, USB, Bluetooth (registered trademark), Ethernet (registered trademark), or wireless LAN is used. The surface facing the image sensor 202 may have high or low reflectance.

<Image reading system configuration>
Next, a configuration example of an image reading system including a sheet feed type scanner will be described with reference to FIG. The scanner 1 is connected to the image processing apparatus 302 by an interface cable. The image processing apparatus 302 includes a CPU that is a program processing unit (not shown) and a storage unit that stores programs and image data. A display 301 serving as a display unit and a keyboard 303 serving as an input unit are connected to the image processing apparatus 302. The input unit may be a mouse, a touch panel, etc. in addition to the keyboard.

<Image reading process>
Next, with reference to FIG. 15, a processing procedure when reading an image of an original with the scanner 1 in the present embodiment will be described. The process described below is realized by the CPU of the scanner 1 or the image processing apparatus 302 executing a control program stored in the memory.

  First, in step S <b> 1501, the CPU of the scanner 1 acquires an image on the opposite surface of the image sensor 202 using the image sensor 202. Subsequently, in S1502, the CPU of the scanner 1 obtains the density distribution of the image on the opposite surface. An example of the density distribution is shown in FIG. In FIG. 11, the horizontal axis indicates the concentration, and the vertical axis indicates the frequency. In S1502, a histogram as shown in FIG. 11 is acquired.

  Next, in S1503, the CPU of the scanner 1 functions as a gamma curve creating unit, and creates a gamma curve in which the vertex P of the density distribution shown in FIG. 11 is the darkest and becomes brighter as the distance from the vertex P increases. An example of the gamma curve created in this way is shown in FIG. Note that the gamma curve may be such that the vertex P of the density distribution is brightest and becomes darker as the distance from the vertex P increases. FIG. 12 shows input on the horizontal axis and output on the vertical axis.

  In step S <b> 1504, the CPU of the scanner 1 determines whether a document is present on the paper feed tray 101 by using a document detection sensor. If there is no document on the paper feed tray 101, the process is terminated. On the other hand, if there is a document, the process advances to step S1505. In step S <b> 1505, the CPU of the scanner 1 conveys one document out of the documents stacked on the sheet feeding table 101 to the position of the image sensor 202 by the roller 201. In step S <b> 1506, the CPU of the scanner 1 acquires an image of a document using the image sensor 202 and transmits the image to the image processing apparatus 302 using an interface cable. Further, the CPU of the scanner 1 also transmits information on the gamma curve created in S1503 to the image processing apparatus 302. An example of a read image of a document is shown in FIG. The read image shown in FIG. 4 shows a state in which the original conveyed by the roller 201 is skewed due to skew.

  In step S1507, the CPU of the image processing apparatus 302 performs image processing such as distortion correction and brightness correction. Details of the distortion correction will be described later. In step S1508, the CPU of the image processing apparatus 302 displays the image of the document on the display 301 and saves it in the storage unit, and then returns to step S1504 to process the next document. If there is no document on the paper feed tray 101, the process is terminated.

<Distortion correction processing>
Next, a distortion correction processing procedure in the image processing in S1507 will be described with reference to FIG. The process described below is realized by the CPU of the image processing apparatus 302 executing a control program stored in the memory.

  In S1401, the CPU of the image processing apparatus 302 applies the gamma curve created in S1504 to the read image of the document, so that only an area having a density equivalent to the opposite surface of the image sensor 202 is darkened. Get. The image obtained in S1401 is shown in FIG. Contour data is detected from the image of FIG. 13 by a known contour detection process, and a polygon is obtained from the contour data by a known vectorization process. Here, the CPU of the image processing apparatus 302 functions as polygon extraction means. The obtained polygon 500 is shown in FIG. As shown in FIG. 5, a polygon 500 indicating the outline of the read image is not a rectangle due to distortion, unlike a document. Although the process of extracting contour data using a gamma curve has been described here, the paper size and the inclination angle of the paper can also be detected using the gamma curve.

  Next, in S1402, the CPU of the image processing apparatus 302 functions as a side extracting unit, and among the sides constituting the polygon 500, the side having the inclination angle close to the horizontal and existing at the uppermost side is the side. The longest is the top side. Further, the CPU of the image processing apparatus 302 uses the side having the longest side length among the sides forming the polygon 500 and having the inclination angle close to the horizontal and existing at the bottom as the lower side. . That is, here, the CPU of the image processing apparatus 302 extracts the upper side and the lower side from the polygon 500.

  In step S1403, the CPU of the image processing apparatus 302 determines whether the difference between the lengths of the upper side and the lower side exceeds a predetermined threshold value. That is, it is determined whether or not the lengths of the upper side and the lower side are substantially the same. If the lengths of the upper and lower sides are significantly different, the process ends in error. On the other hand, if the upper side and the lower side are substantially the same length, that is, if the difference in length between the upper side and the lower side does not exceed the threshold value, the process proceeds to S1404.

  In step S <b> 1404, the CPU of the image processing apparatus 302 functions as a vertex creation unit and obtains a vertex pair. For example, the positions of points on opposite sides of the vertex 501 constituting the left side (one side) and the vertex 502 constituting the right side (the other side) are obtained. Here, with reference to FIG. 16, a method for obtaining the opposite point will be described in detail. Let P be the target vertex. Furthermore, let apexes adjacent to P be A and B, respectively. At this time, a straight line PQ that perpendicularly intersects the straight line AB is drawn. An intersection R between the straight line PQ and the opposite side is defined as a point on the opposite side of the vertex P. Similarly, the position of the point on the opposite side is obtained for each vertex constituting the right side. An example of vertices including the points newly obtained in this way is shown in FIG. When obtained by the method described with reference to FIG. 16, the positions of the points on the sides opposite to the vertices 501 and 502 shown in FIG. 5 are the vertices 601 and 602, respectively, as shown in FIG.

  Returning to the description of FIG. When the position of the point on the opposite side is obtained, in S1405, the CPU of the image processing apparatus 302 connects the point constituting the left side and the point constituting the right side obtained in S1404 by a straight line in order from the upper side. Divide into a plurality of squares with each point as a vertex. FIG. 7 shows a plurality of divided quadrangles. Here, the length of the left side of each square is hLn, the length of the right side is hRn, the length of the upper side of the uppermost square is wT, and the length of the lower side of the lowermost square is wB.

  In S1406, the CPU of the image processing apparatus 302 determines the width w and height hn when the plurality of quadrangles divided in S1405 are transformed into rectangles, and obtains the area. This is shown in FIG. For example, the longer side, the shorter side, or the average length of the upper side length wT and the lower side length wB is defined as the lateral width w of the rectangle. Further, the longer side, the shorter side, or the average length of the left side length hLn and the right side length hRn is defined as the height hn of the rectangle. Next, as shown in FIG. 9, if the width and height of the document after correcting the distortion are W and H, respectively, W is equal to w, and H is the total value of the heights hn of the respective rectangles. Σhn.

  In S1407, the CPU of the image processing apparatus 302 transforms each quadrangle into a rectangle. Here, a deformation method from the rectangle A′B′C′D ′ to the rectangle ABCD will be described with reference to FIG. When an arbitrary point existing inside the rectangle ABCD is P, an intersection E with the side AB is obtained by drawing a perpendicular line of the side AB passing through the point P. By the same operation, an intersection point F with the side BC, an intersection point G with the side CD, and an intersection point H with the side DA are obtained. Next, for the square A′B′C′D ′ before deformation, a point E ′ on the side A′B ′ such that AE: EB = A′E ′: E′B ′ is obtained. By the same operation, a point F ′ on the side B′C ′, a point G ′ on the side C′D ′, and a point H ′ on the side D′ A ′ are obtained. An intersection P ′ between the straight lines E′G ′ and F′H ′ is a point corresponding to the point P. In this manner, the square is transformed into a rectangle by associating an arbitrary point inside the rectangle ABCD with a point inside the rectangle A′B′C′D ′ on a one-to-one basis. In S1408, the CPU of the image processing apparatus 302 combines the transformed rectangles to obtain the final image shown in FIG.

  As described above, the image reading apparatus according to the present embodiment creates a gamma curve from the density distribution of image data obtained by reading an image from a document, and uses the gamma curve to contour the image indicated by the image data. Is extracted, the polygon is divided into a plurality of rectangles, and each of the divided rectangles is transformed into a rectangle and combined. As a result, it is possible to correct the distortion of the read image due to the document being inclined during conveyance.

  Also, instead of determining the width w of the rectangle based on the length of the upper side of the uppermost rectangle and the length of the lower side of the lowermost rectangle, the length of the upper side and the length of the lower side of the other rectangles You may take this into account. For example, the average value of the length of the upper side and the length of the lower side of each quadrangle may be w.

  Also, after having obtained a list of known standardized paper sizes (standard sizes) and obtaining the width W and height H of the original whose distortion has been corrected in S1406, W and H are compared with the list of paper sizes. Select a paper size that is close enough. Further, a correction coefficient such that W and H become the selected paper size may be obtained, and in the rectangular deformation processing in S1407, the size of the rectangle after the deformation may be the width and height multiplied by the correction coefficient. .

  In the above embodiment, the gamma curve of FIG. 12 is obtained by creating a density distribution based on the image of the opposite surface of the image sensor 202 in S1501, but the image of the opposite surface of the image sensor 202 is unique to the apparatus. It's a thing and it doesn't change much. Therefore, a gamma curve may be created at regular time intervals or when scanning is performed for the first time. Alternatively, the gamma curve data may be built in in advance, and the acquisition of the image of the opposite surface of the image sensor 202 and the creation of the density distribution may not be performed.

  In the above-described embodiment, the configuration in which the image processing apparatus 302 includes the image processing unit and the image processing apparatus 302 corrects the image distortion of the document acquired by the scanner 1 in S1507 has been described. It is good also as a structure with a process part. In this configuration, after the image of the original is acquired by the image sensor 202, the image processing unit of the scanner 1 corrects the distortion of the original image according to the flowchart of FIG.

<Other embodiments>
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

  The present invention is not limited to the above-described embodiment, and includes, for example, a conveyance path that conveys a sheet and an image reading unit that reads an image of the sheet conveyed through the conveyance path. In an image processing apparatus that reads an image (or an image processing system that is realized by cooperation between an image reading apparatus and a computer, or an image reading apparatus or computer, or an image processing program that realizes such cooperation), the orientation of a sheet is It is characterized by having a distortion correction means for correcting distortion of a sheet image caused by a change during conveyance. For example, the outline of the document recorded in the image is detected, the outline is approximated to a polygon, the polygon is divided into a plurality of rectangles, each rectangle is transformed into a rectangle, and the obtained rectangles are combined. To do. In the case of such a configuration, it is possible to correct the distortion of the original caused by the change in the inclination of the original in the middle of conveyance and transform the original into an upright rectangle.

  In the case of such a configuration, for example, the distortion correction unit includes a contour detection unit that detects the contour of the sheet recorded in the image information, and a polygon detection that converts the contour detected by the contour detection unit into a polygon. Means, a contour dividing means for dividing the polygon detected by the polygon detecting means into one or more quadrangles, a quadrangle deforming means for transforming each of the quadrilaterals divided by the contour dividing means into rectangles, and a quadrilateral deforming means It is preferable to have a rectangular combination means for combining a plurality of rectangles deformed by 1 into one rectangle.

  Furthermore, the distortion correction means has, for example, a plurality of paper size information, and a paper size selection means for selecting a paper size closest to the size of the rectangle combined by the rectangular combination means, and the rectangular combination means The quadrangle deforming means transforms each of the quadrilaterals divided by the contour dividing means into rectangles at an appropriate ratio so that the size of the rectangles combined by the sheet size selecting means becomes the size selected by the paper size selecting means. It is good to do.

  In addition, the distortion correction unit may not correct the distortion when, for example, the length of the upper side and the lower side of the polygon detected by the polygon detection unit are significantly different.

  For example, the distortion correction unit may be provided in the image reading apparatus, or may be provided in a computer (including an information processing terminal such as a smartphone or a tablet) connected to the image reading apparatus, or the image reading apparatus and the computer. Each of these may be divided into functions, or may be provided in a system in which the image reading apparatus and the computer are integrated.

  In the case of an image processing system according to the present invention, a density distribution unit that creates a density distribution of an image, a gamma curve creation unit that creates a gamma curve based on the density distribution, and a gamma that applies the gamma curve to an image. A processing unit, and an image reading unit reads an image on the opposite surface of the image reading unit, a density distribution creating unit creates a density distribution of the image on the opposite surface of the image reading unit, and a gamma curve creating unit It is preferable that a gamma curve is created based on the density distribution, the gamma processing unit applies the gamma curve to the sheet image read by the image reading unit, and then the contour is detected by the contour detection unit.

The present invention relates to an image reading apparatus for reading an image from a document, to a control method thereof, and program.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a mechanism that corrects a distortion of a read image due to a change in the inclination of a document due to conveyance and forms the image appropriately.

The present invention includes, for example, a polygon extracting unit that extracts a polygon from contour data obtained from a density distribution of an image read by the image reading unit, and an upper side and a lower side of the polygon extracted by the polygon extracting unit. Creating a vertex included in the other side to be paired with a vertex on one side constituting one side connecting the upper side and the lower side included in the polygon; Vertex creating means for creating a vertex included in one side that is paired with respect to the other vertex constituting the other side connecting the upper side and the lower side included in the polygon, and the polygon extraction Dividing means for dividing the polygon extracted by the means into a plurality of quadrilaterals, deforming means for transforming each of the plurality of quadrilaterals divided by the dividing means into rectangles, and deforming by the deforming means Combining means for combining a number of rectangles, wherein the dividing means is a quadrilateral having the upper side and a vertex closest to the upper side among the vertices of the polygon extracted by the polygon extracting means; A quadrangle in which a vertex included in the other side that is paired with respect to the vertex on the one side and a vertex that constitutes one side that is paired with respect to the other side of the vertex is a vertical angle; An image reading apparatus, wherein the image reading apparatus is divided into quadrilaterals having the lower side and a vertex closest to the lower side among the vertexes of the polygon extracted by the polygon extracting means. It is characterized by that.

According to the present invention, the distortion of the read image due to the change in the inclination of the document due to the conveyance can be corrected and the image can be suitably formed.

Claims (12)

An image reading device,
Reading means for reading an image from a document;
Gamma curve creating means for creating a gamma curve from the density distribution of the image data read by the reading means;
Using the gamma curve, a polygon extracting means for extracting a polygon indicating the contour of the image indicated by the image data;
Dividing means for dividing the polygon extracted by the polygon extracting means into a plurality of quadrilaterals;
Deformation means for transforming each of the plurality of quadrilaterals divided by the dividing means into rectangles;
An image reading apparatus comprising: a combining unit configured to combine a plurality of rectangles deformed by the deforming unit. The dividing means includes
Edge extracting means for extracting the upper and lower sides of the polygon extracted by the polygon extracting means;
Among the side edges connecting the upper side and the lower side, a vertex included in the other side that is paired with the vertex included in one side is created, and the pair is paired with the vertex included in the other side. Vertices creating means for creating vertices included on one side of
2. A plurality of rectangles surrounded by polygon vertices extracted by the polygon extraction means and the created vertices are divided so that the respective rectangles do not overlap with other rectangles. The image reading apparatus described in 1. The dividing means includes
The vertex contained in the said one side and the vertex contained in the said other side are divided | segmented into these squares according to the straight line formed by connecting in an order from the upper side. Image reading apparatus. The deformation means includes
In each of the plurality of quadrilaterals divided by the dividing means, comprising a determining means for determining the length of each side after being transformed into a rectangle,
4. The image reading apparatus according to claim 2, wherein the plurality of quadrangles are transformed into rectangles according to the length of each side determined by the determining unit. The determining means includes a plurality of squares divided by the dividing means.
Of the upper side and the lower side, the length of the longer side, the length of the shorter side, or the average side length is determined as the length of the upper side and the lower side after deformation,
Of the one side and the other side, the length of the longer side, the length of the shorter side, or the length of the average side is calculated by changing the length of one side and the other side after deformation. The image reading apparatus according to claim 4, wherein the length of the side is determined. The deformation means includes
The standard size closest to the size of the polygon extracted by the polygon extraction unit is selected from the list of standard sizes of the original, and when combined by the combining unit, the selected standard size is selected. The image reading apparatus according to claim 1, wherein a plurality of quadrangles are deformed.   The creation means creates a histogram showing the density distribution of the image data read by the reading means, and creates a gamma curve in which the vertex of the density distribution is the darkest and becomes brighter as the distance from the vertex increases. Item 7. The image reading apparatus according to any one of Items 1 to 6.   The creation means creates a histogram showing the density distribution of the image data read by the reading means, and creates a gamma curve in which the vertex of the density distribution is brightest and becomes darker as the distance from the vertex increases. Item 7. The image reading apparatus according to any one of Items 1 to 6. The apparatus further comprises conveying means for conveying the document,
The image reading apparatus according to claim 1, wherein the reading unit reads an image of a document conveyed by the conveying unit. An image reading system including an image reading device that reads an image from a document and an image processing device that processes image data read by the image reading device,
The image reading device includes:
Reading means for reading an image from a document;
Creating means for creating a gamma curve from the density distribution of the image data read by the reading means;
Image data read by the reading means, and a transmission means for transmitting the gamma curve created by the creating means to the image processing apparatus,
The image processing apparatus includes:
Using the gamma curve, a polygon extracting means for extracting a polygon indicating the contour of the image indicated by the image data;
Dividing means for dividing the polygon extracted by the polygon extracting means into a plurality of quadrilaterals;
Deformation means for transforming each of the plurality of quadrilaterals divided by the dividing means into rectangles;
An image reading system comprising: a combining unit configured to combine a plurality of rectangles deformed by the deforming unit. A method for controlling an image reading apparatus, comprising:
A reading process for reading an image from a document;
A gamma curve creating step of creating a gamma curve from the density distribution of the image data read in the reading step;
Using the gamma curve, a polygon extraction step of extracting a polygon indicating the contour of the image indicated by the image data;
A dividing step of dividing the polygon extracted in the polygon extracting step into a plurality of quadrilaterals;
A deformation step of deforming each of the plurality of quadrangles divided in the division step into a rectangle,
And a combining step of combining a plurality of rectangles deformed in the deformation step.   A computer-readable program for causing a computer to function as the image reading apparatus according to claim 1.