JP2018116644A - Image processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a table area in an original image.SOLUTION: A reduction processing part 21 determines one direction of a horizontal direction and a vertical direction as a reduction direction, does not reduce an original image in a direction perpendicular to the reduction direction, but reduces the original image in the reduction direction at a predetermined reduction ratio to create a reduction image. A connected pixel group detection part 22 detects connected pixel groups that continuously extend in the reduction direction, and a ruled line specification part 23 specifies positions of ruled lines in the original image from positions of the connected pixel groups detected in the reduction image on the basis of the reduction ratio. A table area specification part 24 specifies one or a plurality of continuous rectangles formed by the ruled lines specified by the ruled line specification part 23, specifies a circumscribed rectangle for the specified one or the plurality of continuous rectangles, and when the number of at least one of ruled lines in the horizontal direction and ruled lines in the vertical direction present in the circumscribed rectangle is equal to or larger than a predetermined value, specifies the circumscribed rectangle as a table area.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image processing apparatus.

  In a ruled line detection method, a reduced image is generated from an original image, and a black pixel corresponding to a ruled line in the original image is detected in the generated reduced image to detect a ruled line in the original image. The table area is detected based on the detected ruled line (see, for example, Patent Documents 1 and 2).

JP-A-6-4704 JP 2003-317107 A

  When the original image is reduced, the original image is generally reduced simultaneously in the horizontal direction and the vertical direction, and the pixel value of the pixel in the window of a predetermined size (for example, 2 pixels × 2 pixels) in the original image is used. One pixel is determined.

  For example, the average value of the pixel values of the pixels in the window in the original image is set as one pixel of the reduced image. For example, when the original image is a binary image, the logical sum of the pixel values of the pixels in the window in the original image is set as one pixel of the reduced image.

  When the average value of the pixel values in the window in the original image is set as one pixel pixel in the reduced image, the density of connected pixels in the reduced image corresponding to a ruled line that is a thin line having a width of one pixel in the original image. Becomes lower (the luminance value becomes higher), the connected pixels in the reduced image are not accurately detected, and as a result, the ruled lines in the original image may not be detected accurately.

  In addition, when the logical sum of the pixel values of the pixels in the window in the original image is set as one pixel of the reduced image, a pattern such as a pattern that is not a ruled line in the original image appears as a connected pixel in the reduced image. May be erroneously detected as a ruled line in the original image.

  Therefore, there is a possibility that a table area in the original image is not accurately detected, or a pattern in the original image is erroneously detected as a table area.

  The present invention has been made in view of the above problems, and an object thereof is to obtain an image processing apparatus that accurately detects a table area in an original image.

  The image processing apparatus according to the present invention uses one of a horizontal direction and a vertical direction as a reduction direction, and does not reduce the original image along the reduction direction without reducing the image along the direction perpendicular to the reduction direction. A reduction processing unit that generates a reduced image by reducing at a predetermined reduction rate, a connected pixel group detection unit that detects a connected pixel group that continuously extends in the reduction direction in the reduced image, and the reduction rate Based on the position of the connected pixel group detected in the reduced image, a ruled line specifying unit that specifies the position of the ruled line in the original image, and (a) a ruled line specified by the ruled line specifying unit 1 Alternatively, a plurality of continuous rectangles are specified, (b) a circumscribed rectangle for the specified one or a plurality of continuous rectangles is specified, and (c) a horizontal ruled line and a vertical ruled line existing in the circumscribed rectangle (D) when at least one of a horizontal ruled line and a vertical ruled line existing in the circumscribed rectangle is greater than or equal to a predetermined value, the circumscribed rectangle A table area specifying unit for specifying as a table area.

  According to the present invention, the surface area in the original image is accurately detected.

  These and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to an embodiment of the present invention. FIG. 2 is a diagram for explaining detection of horizontal ruled lines in the original image in the image processing apparatus shown in FIG. FIG. 3 is a diagram for explaining detection of vertical ruled lines in the original image in the image processing apparatus shown in FIG. FIG. 4 is a diagram for explaining the detection of broken ruled lines in the original image in the image processing apparatus shown in FIG. FIG. 5 is a diagram showing an example of a table area specified by the table area specifying unit 24 in the image processing apparatus shown in FIG.

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

  FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to an embodiment of the present invention. The image processing apparatus shown in FIG. 1 includes an image reading device 1, a storage device 2, a communication device 3, a printing device 4, and an arithmetic processing device 5.

  The image reading device 1 is an internal device that optically reads a document image from a document and generates image data of the document image (here, RGB data).

  The storage device 2 is a device capable of storing various data and programs. As the storage device 2, a nonvolatile mass storage medium such as a nonvolatile memory or a hard disk drive is used. For example, image data of a document image can be stored in the storage device 2.

  The communication device 3 is a device that performs data communication with an external device. As the communication device 3, a network interface that performs network communication, a modem that performs facsimile communication, or the like is used.

  Further, the printing apparatus 4 executes printing of a document image based on image data of a document image that has been subjected to image processing for printing such as color conversion and halftone processing.

  The arithmetic processing unit 5 is a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and loads a program from the ROM or the storage device 2 to the RAM. Various processing units are realized by executing the program by the CPU. In this embodiment, the read processing unit 11 and the table detection unit 12 are realized in the arithmetic processing unit 5.

  The reading processing unit 11 controls the image reading device 1 to acquire a document image, and stores image data of the document image in the storage device 2, RAM, or the like.

  The front detection unit 12 detects ruled lines in the document image (original image). Here, the ruled line to be detected is a thin line having a width of one pixel.

  The table detection unit 12 includes a reduction processing unit 21, a connected pixel group detection unit 22, a ruled line specification unit 23, and a table region specification unit 24.

  The reduction processing unit 21 sets one of the horizontal direction (main scanning direction) and the vertical direction (sub-scanning direction) as the reduction direction, and does not reduce the reduction along the direction perpendicular to the reduction direction. A reduced image is generated by reducing the original image at a predetermined reduction rate along the direction.

  At that time, the reduction processing unit 21 converts a plurality of pixels in the original image into one pixel in the reduced image, and calculates an average value of pixel values of the plurality of pixels in the original image as one pixel in the reduced image. Pixel value. For example, when converting two consecutive pixels in the original image into one pixel in the reduced image, the average value of the pixel values of the two pixels in the original image is the pixel value of one pixel in the reduced image. Is done.

  The above-described reduction rate is set corresponding to the interval between the line segments in the broken line of the broken line to be detected in the original image. The broken line has a plurality of line segments at a predetermined interval. The reciprocal of the number larger than the number of pixels in the interval between the line segments is set as the reduction ratio. By doing so, the broken line to be detected appears as a continuous connected pixel group in the reduced image.

  The connected pixel group detection unit 22 detects a connected pixel group that continuously extends along the reduction direction in the reduced image generated by the reduction processing unit 21. For example, the connected pixel group detection unit 22 detects a connected pixel group by existing edge extraction processing, labeling processing, or the like.

  Here, the connected pixel group is a plurality of pixels having a density equal to or higher than a predetermined threshold and continuous in a straight line. Here, since the ruled line to be detected is a thin line having a width of 1 pixel, the connected pixel group is also 1 pixel wide.

  The ruled line specifying unit 23 determines the ruled line corresponding to the connected pixel group in the original image from the position of the connected pixel group detected in the reduced image (for example, the pixel coordinate value of the two end points) based on the reduction ratio. Is specified (for example, the pixel coordinate value of the two end points). Since the correspondence between the pixels in the original image and the pixels in the reduced image is determined by the reduction ratio, the pixels in the original image corresponding to the pixels in the reduced image are specified based on the reduction ratio.

  The table area specifying unit 24 specifies (a) one or a plurality of continuous rectangles configured by the ruled lines specified by the ruled line specifying unit 23, and (b) a circumscribed rectangle for the specified one or a plurality of continuous rectangles. (C) determine whether at least one of a horizontal ruled line and a vertical ruled line existing in the circumscribed rectangle is greater than or equal to a predetermined value, and (d) a horizontal existing in the circumscribed rectangle. When at least one of a directional ruled line and a vertical ruled line is greater than or equal to a predetermined value, the circumscribed rectangle is specified as a table area.

  Further, the table area specifying unit 24 determines, for each of the horizontal ruled lines and the vertical ruled lines existing in the circumscribed rectangle, whether each ruled line is a broken line ruled line or a solid line ruled line. If at least one of the solid line ruled line arrangement and the broken line ruled line arrangement satisfies a specific condition, even if at least one of the horizontal ruled line and the vertical ruled line existing in the circumscribed rectangle is greater than or equal to a predetermined value, The circumscribed rectangle may not be specified as the table area (that is, such circumscribed rectangle may be excluded from the table area). For example, when all the dots in the ruled line are continuous, it is determined that the ruled line is a solid ruled line, and when the dots in the ruled line are intermittently continuous, the ruled line is a dashed ruled line. It is determined that

  For example, when all ruled lines corresponding to the four sides of the circumscribed rectangle are broken line ruled lines, the circumscribed rectangle may not be specified as the table region. Further, for example, when a part of the ruled lines corresponding to the four sides of the circumscribed rectangle is a broken line ruled line and the remaining of the ruled lines corresponding to the four sides of the circumscribed rectangle is a solid line ruled line, the circumscribed rectangle is displayed. It may not be specified as a region.

  Next, the operation of the image processing apparatus will be described.

  (A) Detection of horizontal ruled lines

  FIG. 2 is a diagram for explaining detection of horizontal ruled lines in the original image in the image processing apparatus shown in FIG.

  When detecting a horizontal ruled line in the original image, the reduction processing unit 21 sets the horizontal direction as the reduction direction, and reduces the original image at a predetermined reduction rate along the horizontal direction without reducing along the vertical direction. To generate a reduced image. As a result, for example, as shown in FIG. 2, horizontal ruled lines with a density of 100% in the original image appear as a group of connected pixels in the horizontal direction with a density of 100% in the reduced image.

  The connected pixel group detection unit 22 sequentially refers to the pixel values along the horizontal direction at each pixel position in the vertical direction in the reduced image, detects a connected pixel group that continuously extends along the horizontal direction, The detected position information of the connected pixel group is stored in a memory or the like. Thereafter, the ruled line specifying unit 23 specifies the position of the horizontal ruled line corresponding to the connected pixel group in the original image from the detected position of the connected pixel group. In the example shown in FIG. 2, two ruled lines in the horizontal direction in the original image are specified.

  (B) Detection of vertical ruled lines

  FIG. 3 is a diagram for explaining detection of vertical ruled lines in the original image in the image processing apparatus shown in FIG.

  When detecting a vertical ruled line in the original image, the reduction processing unit 21 sets the vertical direction as the reduction direction, and reduces the original image along the vertical direction at a predetermined reduction rate without reducing along the horizontal direction. To generate a reduced image. As a result, for example, as shown in FIG. 3, vertical ruled lines having a density of 100% in the original image appear as connected pixel groups in the vertical direction having a density of 100% in the reduced image.

  The connected pixel group detection unit 22 sequentially refers to the pixel values along the vertical direction at each pixel position in the horizontal direction in the reduced image, detects a connected pixel group that continuously extends along the vertical direction, The detected position information of the connected pixel group is stored in a memory or the like. Thereafter, the ruled line specifying unit 23 specifies the position of the ruled line in the vertical direction corresponding to the connected pixel group in the original image from the detected position of the connected pixel group. In the example shown in FIG. 3, two ruled lines in the vertical direction in the original image are specified.

  (C) Detection of dashed ruled lines

  FIG. 4 is a diagram for explaining the detection of broken ruled lines in the original image in the image processing apparatus shown in FIG.

  By the above-described processing, not only a solid ruled line but also a broken ruled line is detected. For example, as shown in FIG. 4, a dashed ruled line whose line segment is one pixel with a density of 100% and whose line segment interval is one pixel appears as a connected pixel group with a density of 50% in a reduced image with a reduction ratio of 50%. .

  Therefore, the connected pixel group detection unit 22 detects the connected pixel group in the reduced image, and the ruled line specifying unit 23 determines the position of the ruled line corresponding to the connected pixel group in the original image from the detected position of the connected pixel group. By specifying, the broken line ruled line is specified without being distinguished from the solid line ruled line.

  (D) Detection of table area

  Then, the table area specifying unit 24 (a) based on the end points of the horizontal ruled line and the vertical ruled line specified by the ruled line specifying unit 23, one or a plurality of continuous rectangles constituted by these ruled lines (B) specifying a circumscribed rectangle for the specified one or a plurality of continuous rectangles, and (c) at least one of a horizontal ruled line and a vertical ruled line existing in the circumscribed rectangle is a predetermined value ( For example, 3) it is determined whether or not there exists, and (d) when at least one of a horizontal ruled line and a vertical ruled line existing in the circumscribed rectangle is greater than or equal to a predetermined value, the circumscribed rectangle is displayed in the table area. As specified. The predetermined value may be set by the user.

  As a result, even when a broken line is used for a part of the table in the original image, the table area is accurately detected.

  FIG. 5 is a diagram showing an example of a table area specified by the table area specifying unit 24 in the image processing apparatus shown in FIG. For example, as shown in FIG. 5, ruled lines (two horizontal solid ruled lines and two horizontal dashed ruled lines, and two vertical solid ruled lines and one vertical dashed ruled line) are detected. In this case, six rectangles are specified, and a circumscribed rectangle by the six rectangles is specified. Then, the number of vertical ruled lines in the circumscribed rectangle is specified as 3, and the number of horizontal ruled lines in the circumscribed rectangle is specified as 4. For example, when the predetermined value is 3, the circumscribed rectangle (that is, the four sides of the circumscribed rectangle and the inner area of the four sides) is specified as the table region.

  As described above, according to the above embodiment, the reduction processing unit 21 sets one of the horizontal direction and the vertical direction as the reduction direction, and does not reduce along the direction perpendicular to the reduction direction. The original image is reduced at a predetermined reduction rate along the reduction direction to generate a reduced image. The connected pixel group detection unit 22 detects a connected pixel group that continuously extends in the reduction direction in the reduced image, and the ruled line specifying unit 23 detects the connected pixel group detected in the reduced image based on the reduction rate. The position of the ruled line in the original image is specified from the position. Then, the table area specifying unit 24 specifies (a) one or a plurality of continuous rectangles configured by the ruled lines specified by the ruled line specifying unit 23, and (b) about the specified one or a plurality of continuous rectangles. Specify the circumscribed rectangle, (c) determine whether at least one of the horizontal ruled lines and the vertical ruled lines existing in the circumscribed rectangle is greater than or equal to a predetermined value, and (d) exist in the circumscribed rectangle When at least one of a horizontal ruled line and a vertical ruled line exists at a predetermined value or more, the circumscribed rectangle is specified as a table area.

  As a result, the density of the connected pixel group in the reduced image becomes sufficiently high, and objects other than the ruled line are less likely to be erroneously detected as ruled lines, so that the ruled lines in the original image are accurately detected. As a result, the surface area in the original image is accurately detected.

  Various changes and modifications to the above-described embodiment will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. That is, such changes and modifications are intended to be included within the scope of the claims.

  For example, in the above embodiment, the reduction processing unit 21 sets the horizontal direction as the reduction direction, reduces the original image at a predetermined reduction rate along the reduction direction, generates a horizontal reduced image, and changes the vertical direction to the vertical direction. In the reduction direction, the original image is reduced at a predetermined reduction rate along the reduction direction to generate a vertical reduction image, and the connected pixel group detection unit 22 continuously extends in the horizontal direction in the horizontal reduction image. A horizontal connection pixel group is detected, a vertical connection pixel group continuously extending in the vertical direction in the vertically reduced image is detected, and the ruled line specifying unit 23 determines the horizontal ruled line in the original image from the position of the horizontal connection pixel group. The position is specified, the position of the vertical ruled line in the original image is specified from the position of the vertically connected pixel group, and the position of the table in the original image is determined based on the position of the specified horizontal ruled line and the specified vertical ruled line. I will identify It may be. In that case, for example, the intersection of the horizontal ruled line and the vertical ruled line is specified, the cell in the table set is specified based on the position of the intersection, and the position of the entire table set is specified.

  Further, in the above embodiment, the processing time can be shortened by configuring the reduction processing unit 21 with dedicated hardware.

  The present invention can be applied to an image forming apparatus such as a copying machine or a multifunction machine.

21 Reduction processing unit 22 Connected pixel group detection unit 23 Ruled line specifying unit 24 Table area specifying unit

Claims (5)

One of the horizontal direction and the vertical direction is set as a reduction direction, and the original image is reduced at a predetermined reduction rate along the reduction direction without reduction along the direction perpendicular to the reduction direction. A reduction processing unit for generating an image;
In the reduced image, a connected pixel group detection unit that detects a connected pixel group extending continuously along the reduction direction;
A ruled line specifying unit that specifies the position of the ruled line in the original image from the position of the connected pixel group detected in the reduced image based on the reduction ratio;
(A) specifying one or a plurality of continuous rectangles configured by the ruled lines specified by the ruled line specifying unit; (b) specifying a circumscribed rectangle for the specified one or a plurality of continuous rectangles; ) It is determined whether or not at least one of a horizontal ruled line and a vertical ruled line existing in the circumscribed rectangle is greater than a predetermined value, and (d) a horizontal ruled line and a vertical direction existing in the circumscribed rectangle A table area specifying unit that specifies the circumscribed rectangle as a table area when at least one of the ruled lines is greater than or equal to a predetermined value;
An image processing apparatus comprising:   The table area specifying unit determines whether the ruled line is a broken line ruled line or a solid line ruled line for each of a horizontal ruled line and a vertical ruled line existing in the circumscribed rectangle. When at least one of the arrangement of the solid line ruled line and the arrangement of the broken line ruled line satisfies a specific condition, even if at least one of the horizontal ruled line and the vertical ruled line existing in the circumscribed rectangle exists more than a predetermined value, The image processing apparatus according to claim 1, wherein the circumscribed rectangle is not specified as a table region.   The reduction processing unit converts a plurality of pixels in the original image into one pixel in the reduced image, and calculates an average value of pixel values of the plurality of pixels in the original image as one pixel in the reduced image. The image processing apparatus according to claim 1, wherein the pixel value is a pixel value.   The image processing apparatus according to claim 1, wherein the reduction ratio is set corresponding to an interval between line segments in a broken line of a broken line to be detected in the original image. The reduction processing unit sets a horizontal direction as the reduction direction, generates a horizontal reduced image by reducing the original image at a predetermined reduction rate along the reduction direction, sets a vertical direction as the reduction direction, and reduces the reduction direction. A vertical reduced image is generated by reducing the original image at a predetermined reduction ratio along
The connected pixel group detection unit detects a horizontally connected pixel group that continuously extends along the reduction direction in the horizontal reduced image, and a vertical connection that continuously extends along the reduction direction in the vertical reduced image. Detect pixel group,
The ruled line specifying unit specifies a position of a horizontal ruled line in the original image from the position of the horizontal connected pixel group, and specifies a position of a vertical ruled line in the original image from the position of the vertical connected pixel group. Specifying the position of the table in the original image based on the position of the horizontal ruled line and the position of the specified vertical ruled line;
The image processing apparatus according to claim 1.

Images