JP4140519B2 - Image processing apparatus, program, and recording medium - Google Patents

Description

  The present invention relates to a technique for detecting an inclination of an image showing a document and correcting the inclination.

  Image data obtained when the document is read by an image scanner or image data received by a facsimile machine is analyzed, character recognition processing is performed on the area where characters in the image are written, and the document is read as an image A technique for extracting sentences from a document is known. In this technique, the fact that the read image has no inclination, that is, no skew, is a precondition for accurately extracting the original text. If the read image has skew, the skew is corrected. There is a need. Conventionally, as a technique for correcting the skew, for example, techniques described in Patent Documents 1 to 4 are known.

  The document tilt correction apparatus described in Patent Document 1 first rotates a binary image by sequentially changing the angle, and creates a rectangle that circumscribes the rotated image. Next, the document tilt correction apparatus sets an angle at which the rectangular area is minimum as an image skew angle, and corrects the image tilt based on the skew angle.

  The image processing apparatus described in Patent Document 2 first sets a rectangular area while examining the connectivity of pixels representing an image, and assumes a range where the rectangular area exists in the image, and within this range, a rectangular area is set. The coordinate values of the end points of the area are projected in a predetermined direction, and a projection histogram is obtained. Next, the image processing apparatus detects an angle at which the histogram of the projection is maximized as a skew angle.

  Patent Document 3 describes a technique for detecting a skew angle using Hough transform. The data processing apparatus described in Patent Document 3 first performs a filtering process on an input image and generates a binary image by performing a binarization process on an image in which the density difference is emphasized by this process. . Next, this data processing device performs a Hough transform on each pixel of the generated binary image, creates a histogram on the Hough space, and extracts coordinates whose frequency is equal to or higher than a predetermined threshold in the Hough space. . The data processing apparatus groups the extracted coordinates, then extracts representative point coordinates for each group, and estimates the tilt angle of the image from the extracted coordinates. Further, in Patent Document 3, after extracting coordinates having a frequency equal to or higher than a predetermined threshold in the Hough space, a histogram is created by adding the number of extracted coordinates for each angle, and the angle at which the frequency is maximum is obtained. A technique for estimating the tilt angle of an image is also described.

Patent Document 4 describes a technique for detecting a skew angle using Hough transform, as in Patent Document 3. The image processing apparatus described in Patent Document 4 first performs a binarization process on an input image to generate a binary image, performs a Hough transform on each pixel of the generated binary image, Create a histogram on the Hough space. Next, this image processing apparatus performs a predetermined calculation process on the frequency in the Hough space, and then accumulates the frequency of the calculation process for each angle to create a histogram, so that the frequency becomes maximum. Let the angle be the tilt angle of the image.
JP-A-2-170280 JP-A-6-203202 JP 11-328408 A JP 2002-84420 A

  According to the techniques described in Patent Documents 1 to 4, it is possible to correct the skew of an image indicating a document. However, the techniques described in Patent Documents 1 to 4 have the following problems.

  In the technique described in Patent Document 1, it is necessary to sequentially rotate the binary image at different angles when obtaining the inclination. The process of rotating the image has a problem that it takes a long processing time because a pixel to be a black pixel by rotation must be obtained for each pixel. In the technique described in Patent Document 1, a rectangle circumscribing the rotated image is created, and an angle at which the area of the rectangle is minimized is set as an image skew angle. For example, as illustrated in FIG. 22, when a part of the image is a protruding image, even if the image is rotated, the area of the circumscribed rectangle is hardly changed, so that the skew angle cannot be accurately detected. There is.

  The technique described in Patent Document 2 projects a coordinate value of an end point of a rectangular area in a predetermined direction, obtains a histogram of projection, and detects a skew angle from this histogram. When the row position is shifted between columns, there is a problem that the skew angle cannot be detected accurately. Further, since the technique described in Patent Document 2 is basically a technique for a character area, there is a problem that a skew angle cannot be accurately detected when there are few characters included in an image. .

  In the technique described in Patent Document 3, when a binarization process is performed, if a photographic image or an image indicated by a halftone dot is included in the document, the photographic image or the halftone dot is included in the image. In other words, a binary image in which black pixels are present is generated, or a binary image in which each halftone dot is a black pixel is generated. When the Hough transform is performed on such a binary image, there are problems that the processing time increases and the skew angle is detected erroneously.

  The technique described in Patent Document 4 performs Hough transform and histogram processing on the entire input image. For this reason, as illustrated in FIG. 23, when a document has a multi-column set and lines are evenly shifted between the stages, the direction in which the shift occurs is erroneously detected as a skew angle. There's a problem.

  The present invention has been made in view of such problems, and even when a document indicated by an input image includes elements other than characters and is divided into a large number of regions by columns or the like, An object of the present invention is to provide a technique capable of detecting and correcting a skew angle.

In order to solve the above-described problems, the present invention includes a storage unit that stores image data, a binarization unit that binarizes image data stored in the storage unit, and generates binary image data. An area dividing unit that divides an image indicated by the binary image data generated by the binarizing unit into a plurality of areas and generates divided binary image data indicating the divided image, and the divided binary image data Hough transform for generating histogram data representing the frequency of coordinates on polar coordinates obtained by Hough transform for each divided image area, and polar coordinates for each histogram data generated by the Hough transform means The frequency calculation means for generating projection histogram data representing the frequency density at each angle above, and the projection histogram data generated by the frequency calculation means are added together to obtain a total histogram Stored in the storage means, an overall frequency detecting means for generating Ram data, an overall angle detecting means for detecting an inclination angle of the image indicated by the image data based on the overall histogram data generated by the overall frequency calculating means, and There is provided an image processing apparatus having image rotation means for rotating an image indicated by image data in accordance with an inclination angle obtained by the overall angle detection means.
According to another aspect of the present invention, there is provided a computer including a storage unit that stores image data, a binarization unit that binarizes image data stored in the storage unit, and generates binary image data, and the binarization. An area dividing unit that divides an image indicated by the binary image data generated by the unit into a plurality of areas and generates divided binary image data indicating the divided image, and a Hough transform on the divided binary image data. Histogram data representing the frequency of polar coordinates obtained by the Hough transform is generated for each divided image area, and for each histogram data generated by the Hough transform means each polar coordinate A frequency calculation means for generating projection histogram data representing the frequency density in the angle, and the projection histogram data generated by the frequency calculation means are added to obtain an overall histogram. Stored in the storage means, an overall frequency calculating means for generating data, an overall angle detecting means for detecting an inclination angle of the image indicated by the image data based on the overall histogram data generated by the overall frequency calculating means, and There are provided a program for causing an image indicated by image data to function as an image rotating unit that rotates an image according to an inclination angle obtained by the overall angle detecting unit, and a computer-readable recording medium on which the program is recorded.
According to this image processing apparatus, program, and recording medium, the image represented by the image data is divided into a plurality of regions, and Hough transform is performed for each divided region to generate histogram data. From the generated histogram data Projection histogram data representing the frequency density at each angle on the polar coordinates is generated. When the projection histogram data is generated, the generated projection histogram data is added to generate whole histogram data. When the whole histogram data is generated, an angle at which the frequency is maximum is obtained in the whole histogram data, and this angle is set as the skew angle of the image represented by the image data.

Further, the present invention provides storage means for storing image data, binarization means for binarizing image data stored in the storage means, and generating binary image data, and generation by the binarization means. The divided binary image data is divided into a plurality of regions, divided into a plurality of regions, region dividing means for generating divided binary image data indicating the divided images, and divided binary image data for each of the divided binary image data. An area angle detecting means for obtaining an angle of the image to be represented, an overall angle detecting means for obtaining an inclination angle of the entire image from the angles obtained by the area angle detecting means for each divided binary image data, and stored in the storage means An image processing apparatus having image rotation means for rotating an image indicated by existing image data according to an inclination angle obtained by the overall angle detection means.
According to another aspect of the present invention, there is provided a computer including a storage unit that stores image data, a binarization unit that binarizes image data stored in the storage unit, and generates binary image data, and the binarization. A region dividing unit that divides an image represented by the binary image data generated by the unit into a plurality of regions and generates divided binary image data indicating the divided image; and a divided binary for each of the divided binary image data. An area angle detection means for obtaining an angle of an image represented by the image data, an overall angle detection means for obtaining an inclination angle of the entire image from the angles obtained by the area angle detection means for each divided binary image data, and the storage means A program for causing the image indicated by the stored image data to function as an image rotation means for rotating the image according to the inclination angle obtained by the overall angle detection means, and a computer storing the program. Yuta provide readable recording medium.
According to the image processing device, the program, and the recording medium, the image represented by the image data is divided into a plurality of regions, and Hough transform is performed for each divided region to generate histogram data. From the generated histogram data Projection histogram data representing the frequency density at each angle on the polar coordinates is generated. When the projection histogram data is generated, an angle at which the frequency is maximum is obtained for each projection histogram data, and the skew angle of the image represented by the image data is obtained using the obtained angle.

  According to the present invention, it is possible to detect and correct an image skew angle even when a document indicated by an input image includes elements other than characters and is divided into a large number of regions by columns or the like.

  Embodiments of the present invention will be described below with reference to the drawings.

[1. First Embodiment]
<Configuration>
FIG. 1 is a block diagram illustrating the configuration of an image processing apparatus according to an embodiment of the present invention. As shown in FIG. 1, each unit of the image processing apparatus is connected to a bus 9, and data is exchanged between the units via this bus 9.

  The arithmetic control unit 3 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory) storing a control program for controlling each part of the image processing apparatus ( (All are not shown). When power is supplied from a power supply (not shown), the CPU reads and executes a control program from the ROM, and controls each unit of the image processing apparatus using the RAM as a work area.

  The image input unit 1 includes, for example, an image scanner, and a document placed on the platen of the image scanner under the control of the arithmetic control unit 3 is R (Red), G (Green), and B (Blue). ) For each color component. When the document is read, the image input unit 1 generates data representing the read document, and image data (hereinafter referred to as RGB image data) in which each pixel is represented by a plurality of bits in each pixel.

  The data storage unit 2 includes, for example, a hard disk device that permanently stores data. Under the control of the arithmetic control unit 3, the RGB image data generated by the image input unit 1, the tone correction unit 4, The image data subjected to image processing in the skew correction unit 5 and the color signal conversion unit 6 is stored.

  The gradation correction unit 4 corrects the gradation of the RGB image data generated by the image input unit 1. The gradation correction unit 4 is suitable for performing various image processing on the gradation of the image indicated by the RGB image data stored in the data storage unit 2 in consideration of the device characteristics of the image scanner included in the image input unit 1. Correct the tone.

  The skew correction unit 5 corrects the skew of the image indicated by the RGB image data. The skew correction unit 5 performs a process of correcting the skew on the RGB image data supplied from the data storage unit 2 via the bus 9, and generates image data with the skew corrected. Details of the skew correction unit 5 will be described later.

  The image display unit 7 includes, for example, a display device such as a CRT (Cathode Ray Tube) display device or a liquid crystal display device, and is controlled according to image data stored in the data storage unit 2 under the control of the arithmetic control unit 3. The document indicated by the image data is displayed.

  The color signal converter 6 generates image data used when printing on paper. Specifically, the color image indicated by the RGB image data is converted into color components of Y (Yellow), M (Magenta), C (Cyan), and K (Black / Black), which are basic colors of ink in color printing. The image data is converted into image data (hereinafter referred to as YMCK image data).

  The image output unit 8 has a printing mechanism for printing characters and images on printing paper, and the YMCK image data indicates according to the YMCK image data generated by the color signal conversion unit 6 under the control of the arithmetic control unit 3. Print the image on paper.

<Configuration of Skew Correction Unit 5>
Next, the configuration of the skew correction unit 5 will be described with reference to FIG. As shown in FIG. 2, the skew correction unit 5 includes a binarization unit 100, a contour extraction unit 101, a skew angle detection unit 102, and an image rotation unit 103, and the binarization unit 100. The image rotation unit 103 receives the RGB image data stored in the data storage unit 2.

The binarization unit 100 binarizes pixels in which the shading is represented by a plurality of bits in RGB image data. As illustrated in FIG. 3, the binarization unit 100 and the floating binarization are performed. A part 301, an expansion part 302, and a contraction part 303 are provided.
The color component selection unit 300 extracts G component (Green component) data having the highest contribution to the information of the image from the input RGB image data. The color component selection unit 300 outputs the extracted image data to the floating binarization unit 301 as G image data.

  The floating binarization unit 301 performs floating binarization processing of the target pixel, that is, dynamic threshold binarization processing, using pixels around the target pixel. The floating binarization unit 301 performs dynamic binarization processing of the target pixel using pixels around the target pixel, as described in, for example, Japanese Patent Application Laid-Open No. 2002-84420 related to the applicant of the present application, The value of a pixel belonging to a dark area in the G image data, that is, the value of a pixel indicating a character, a line, a picture or a photograph is “1”, and the value of a pixel corresponding to the background such as a character, a line, a picture or a photograph is “ Binary image data set to “0” is generated, and the generated binary image data is output to the expansion unit 302 (hereinafter, a pixel having a pixel value “0” is a LOW pixel, and a pixel value is “1”). The pixel is referred to as a HIGH pixel.)

The expansion unit 302 sequentially operates pixels of the image indicated by the binary image data output from the floating binarization unit 301, and performs expansion processing on the HIGH pixels. As shown in FIG. 4, when the pixel of interest is “X” and the pixels near its periphery 8 are “A” to “H”, the expansion unit 302 is configured to display the pixel of interest “X” and the pixels near the periphery 8. Among them, if there is at least one HIGH pixel, the target pixel “X” is set as a HIGH pixel, and if the target pixel “X” and all the pixels in the vicinity of the surrounding 8 are LOW pixels, the target pixel is set as a LOW pixel. The binary image data generated by the expansion unit 302 is output to the contraction unit 303. The dilation processing is not limited to the mode in which the dilation processing is performed by paying attention to the pixel of interest and the pixels in the vicinity of the surrounding 8; for example, a 5 × 5 pixel area centered on the pixel of interest, or Of course, the expansion process may be performed focusing on a larger area.
As described above, the expansion unit 302 performs the HIGH pixel expansion process on the binary image data, so that the pixels included in the image and the pixels in the halftone area are changed to 2 in the floating binarization unit 301. Even if a LOW pixel is partially formed by the value conversion processing, a pixel that has become a LOW pixel can be a HIGH pixel, and the entire photograph or halftone dot region can be continued with the HIGH pixel.

The contraction unit 303 sequentially operates the pixels of the image indicated by the binary image data output from the expansion unit 302, and performs contraction processing on the HIGH pixels. As shown in FIG. 4, when the pixel of interest is “X” and the pixels near its periphery 8 are “A” to “H”, the expansion unit 302 is configured to display the pixel of interest “X” and the pixels near the periphery 8. Among these, if there is at least one LOW pixel, the target pixel “X” is set as the LOW pixel, and if all the pixels in the vicinity of the target pixel “X” and the surrounding 8 are HIGH pixels, the target pixel is set as the HIGH pixel. The binary image data generated by the contraction unit 303 is output to the contour extraction unit 101 shown in FIG. The contraction process is not limited to the aspect in which the contraction process is performed by focusing on the pixel of interest and the pixels in the vicinity of the surrounding 8; for example, a 5 × 5 pixel region centered on the pixel of interest, or Of course, the contraction process may be performed focusing on a larger area.
As described above, the contraction unit 303 performs the HIGH pixel contraction process on the binary image data, so that the expansion process can separate a photograph or halftone dot region that has been connected (coupled) with another region. it can.

Next, returning to FIG. 2, the contour extraction unit 101 will be described. The contour extraction unit 101 extracts a contour of a region composed of HIGH pixels from the binary image data output from the contraction unit 303 of the binarization unit 100. As illustrated in FIG. 4, when the target pixel is “X” and the pixels in the vicinity of the surrounding 8 are “A” to “H”, the contour extraction unit 101 determines that the target pixel “X” is a LOW pixel. It is determined that the pixel of interest is not a pixel indicating the outline of a region composed of HIGH pixels. In addition, the contour extraction unit 101 indicates the contour of a region formed by HIGH pixels even when the pixel of interest “X” is a HIGH pixel and all the pixels in the vicinity of the surrounding 8 are HIGH pixels. Judge that it is not a pixel. On the other hand, when the pixel of interest “X” is a HIGH pixel and any of the pixels in the vicinity of the surrounding 8 is a LOW pixel, the contour extraction unit 101 is a pixel indicating the contour of an area composed of HIGH pixels. Judge that there is.
The contour extraction unit 101 extracts pixels indicating the contour of the region composed of HIGH pixels in the image by this process, and generates contour binary image data indicating the contour of the region composed of HIGH pixels. For example, when binary image data indicating an image as illustrated in FIG. 5 is input, contour binary image data indicating an image illustrated in FIG. 6 is generated. The contour extraction unit 101 outputs the generated contour binary image data to the skew angle detection unit 102.

  The skew angle detection unit 102 obtains the skew angle of the image indicated by the contour binary image data from the input contour binary image data. As shown in FIG. 7, the skew angle detection unit 102 includes an area dividing unit 200, a Hough transform unit 201, a Hough space data storage unit 202, a Hough space data calculation projection unit 203, and a calculation projection data storage unit 204. And the whole data calculation unit 205 and the angle detection unit 206, and the binary contour image data input to the skew angle detection unit 102 is supplied to the region division unit 200 and the Hough space data calculation unit 203. The

  The region dividing unit 200 divides the image indicated by the contour binary image data output from the contour extracting unit 101 into a plurality of regions. For example, as shown in FIG. 8, the area dividing unit 200 recognizes an object in an image, that is, a paragraph, a figure, and a photograph. Divide the image. The area dividing unit 200 generates divided image data indicating the divided image for each divided image, and outputs the generated divided image data to the Hough transform unit 201.

The Hough conversion unit 201 performs a Hough conversion process on the divided image data output from the region dividing unit 200. Here, the Hough conversion process will be described first. When the position of a pixel is represented by an x coordinate and ay coordinate, if the straight line distance from the origin to the pixel is ρ, and the angle between the straight line from the origin to the pixel and the x axis is θ, the coordinate on the xy coordinate All straight lines passing through the pixel located at (x, y) can be expressed by the following formula (1).
ρ = x cos θ + ysin θ (0 ≦ θ <π) (1)

  Then, as shown in FIG. 9, for the pixel located at the position of the coordinates (x, y), θ in Expression (1) is sequentially changed from 0 to π, and ρ obtained corresponding to the change in θ is changed. When plotted on the ρ-θ coordinates as shown in FIG. 10, all straight lines passing through a certain pixel can be expressed as curves on the ρ-θ coordinates (on the polar coordinates). This curve is called a Hough curve, and the process for obtaining a Hough curve is called a Hough transform.

  Next, the flow of processing performed by the Hough transform unit 201 will be described with reference to FIG. When the divided image data is input, the Hough transform unit 201 generates a two-dimensional array table composed of θ and ρ in the Hough space data storage unit 202 as shown in FIG. First, the Hough transform unit 201 assigns “0” to all the array elements of the array table, and initializes the array table (step S101).

  Next, the Hough conversion unit 201 determines whether there is a HIGH pixel that has not been subjected to the Hough conversion process in the supplied divided image data (step S102). When the Hough conversion unit 201 determines that there is no HIGH pixel that has not been subjected to the Hough conversion process (step S102; NO), the Hough conversion process for the input divided image data is terminated. If the Hough transforming unit 201 determines that there is a HIGH pixel that has not been subjected to the Hough transform process (step S102; YES), the HIGH pixel that has not been subjected to the Hough transform process is extracted from the divided image data, and the extracted HIGH pixel Is substituted for the variable x, and the y coordinate of the HIGH pixel is substituted for the variable y (step S103).

  Next, the Hough transform unit 201 assigns 0 (rad) to the variable θ as an initial value in order to perform the calculation of Expression (1) while sequentially changing the angle θ (step S104). Next, the Hough transform unit 201 determines whether the value of θ is θ ≧ π (step S105). When determining that the value of θ is θ ≧ π, the Hough conversion unit 201 ends the Hough conversion process for the extracted HIGH pixel, and returns to Step S102. If the Hough transforming unit 201 determines in step S105 that the value of θ is θ <π, it uses the variable x, the variable y, and the variable θ to perform the calculation of the right side of the equation (1), and the calculation result is represented as a variable. Substitute for ρ. Since the value of ρ usually has a value less than the decimal point, the value less than the decimal point is rounded down, rounded up, rounded off, etc., and converted into an integer.

  When performing the calculation of the right side of Expression (1), the Hough transform unit 201 adds “1” to the numerical value stored in the array element specified by the variable ρ and the variable θ (step S107). Specifically, for example, assume that ρ is calculated to be a when θ is A3 for a pixel located at the coordinates (x, y). In this case, as shown in FIG. 12, in the array table, the numerical value stored in the array element corresponding to θ = A3 and ρ = a is increased by 1, and the frequency is set to “1”.

  Next, in order to perform the Hough transform by sequentially changing the angle θ, the Hough transform unit 201 adds a predetermined value step_a to the value of the variable θ, and substitutes the value obtained as a result of the addition into the variable θ (Step). S108). This value is determined by the resolution of the skew angle to be obtained. When the skew angle is to be obtained in units of 1 degree, step_a = π / 180 (rad).

  When the process of step S108 ends, the Hough conversion unit 201 returns to step S105, and repeats the process from step S105 to step S108. The Hough transforming unit 201 performs the processing from Step S105 to Step S105 until θ becomes θ ≧ π. When the Hough transforming process for one HIGH pixel is completed, the process returns to Step S102, and the Hough transform is performed on all HIGH pixels. Until the processing is performed, the processing from step S102 to step S108 is repeated.

  Through the processing described above, the array table generated in the Hough space data storage unit 202 stores data indicating the frequency of coordinates specified by the angle θ and the distance ρ, as illustrated in FIG. The Hough transform unit 201 performs this process for each input divided image data, and generates an array table for each divided image data. Since the data stored in the array table can represent the frequency distribution of each coordinate on the ρ-θ coordinate as illustrated in FIG. 13, hereinafter, the data stored in the array table is referred to as histogram data. Called.

  Next, the Hough space data calculation projection unit 203 will be described. The Hough space data calculation projection unit 203 reads the histogram data stored in the Hough space data storage unit 202 for each divided image area, and obtains a frequency density for each angle θ using a predetermined calculation formula. is there.

  The flow of processing performed by the Hough space data calculation unit 203 is shown in FIG. As shown in FIG. 15, the Hough space data calculation unit 203 generates a projection data table that stores the frequency density for each angle θ in the calculation projection data storage unit 204. First, the Hough space data calculation unit 203 assigns “0” to all array elements of the projection data table to initialize the projection data table (step S201).

Next, the Hough space data calculation unit 203 obtains the width and height of the image indicated by the input contour binary image data, substitutes a value indicating the width of the contour binary image data for the variable width, and sets the contour to the variable high. A value indicating the height of the binary image data is substituted. Thereafter, the Hough space data calculation unit 203 performs the calculation of the following equation (2) (step S202).
max_d = sqrt (width ² + high ² ) (2)

Here, sqrt represents a square root. max_d indicates the length of the diagonal line of the image indicated by the contour binary image, the maximum value of the distance ρ determined by the Hough transform is ≦ max_d, and the minimum value of the distance ρ determined by the Hough transform is ≧ −max_d Become.
Next, the Hough space data computing unit 203 initializes the variable θ by substituting “0” into the variable θ in order to obtain the frequency density for each angle θ (step S203). Next, the Hough space data calculation unit 203 determines whether the value of θ is θ ≧ π (step S204). When the Hough space data calculation unit 203 determines that the value of θ is θ ≧ π, the process is terminated. When determining that the value of θ is θ <π, the Hough space data calculation unit 203 substitutes “−max_d” for the variable ρ and “0” for the variable w.

  Next, the Hough space data calculation unit 203 compares the value of the variable ρ with the value indicated by the variable max_d (step S206). When the Hough space data calculation unit 203 determines that the variable ρ ≦ max_d is satisfied (step S206; NO), the array element specified by the variable θ and the variable ρ in the array table stored in the Hough space data storage unit 202 Is read, and the read frequency is assigned to the variable v. Next, the Hough space data calculation unit 203 performs a predetermined calculation f () on the value substituted with the variable v, and adds the calculation result to the variable w (step S208). The calculation performed in step S208 may be any calculation as long as the frequency density can be calculated for each angle θ. Here, the predetermined calculation f () includes, for example, f (v) = v * v. Next, the Hough space data calculation unit 203 adds “1” to the value of the variable ρ, and the process returns to step S206.

  On the other hand, when the Hough space data calculation unit 203 determines in step S206 that the variable ρ> max_d is satisfied (step S206; YES), the calculation of the frequency density at the angle specified by the variable θ ends, and the variable w Is stored in the array element of the projection data table specified by the variable θ (step S210). Next, the Hough space data calculation unit 203 adds the predetermined value step_a to the value of the variable θ in order to perform the processing from step S204 to step S210 by sequentially changing the angle θ, and uses the value obtained as a result of the addition. Substitute into the variable θ (step S211). When the process of step S211 is completed, the Hough space data calculation unit 203 returns to step S204 and performs the processes of step S204 to step S211 until θ is θ ≧ π.

  With this process, the projection data table generated in the calculation projection data storage unit 204 stores data indicating the frequency density for each angle θ. The calculation projection data storage unit 204 performs this process for each arrangement table stored in the Hough space data storage unit 202, and generates a projection data table for each arrangement table. Since the data stored in the projection data table can represent a histogram representing the relationship between the angle θ and the frequency density as illustrated in FIG. 16, hereinafter, the data stored in the projection data table is stored in the projection data table. The data is referred to as projection histogram data.

  Next, the overall data calculation unit 205 will be described. The entire data calculation unit 205 generates projection histogram data of the entire image from the projection histogram data for each region stored in the calculation projection data storage unit 204. The overall data calculation unit 205 sequentially reads the projection histogram data stored in the calculation projection data storage unit 204, extracts data indicating frequency density from each projection histogram data for each angle θ, and extracts the extracted data. to add. The overall data calculation unit 205 supplies data obtained as a result of the addition to the angle detection unit 206 as projection histogram data of the entire image (hereinafter referred to as overall histogram data).

  The angle detection unit 206 detects the skew angle of the image from the whole histogram data supplied from the whole data calculation unit 205. The angle detection unit 206 obtains the angle θ at which the density is maximum from the supplied whole histogram data, and uses the obtained angle θ as the skew angle of the whole image. The angle detection unit 206 outputs skew angle data indicating the obtained angle θ to the image rotation unit 103.

  Next, returning to FIG. 2, the image rotation unit 103 will be described. The image rotation unit 103 rotates the image indicated by the input RGB image data using a known method such as Affine conversion, and corrects the skew. The image rotation unit 103 rotates the image indicated by the RGB image data using the skew angle data output from the skew angle detection unit 102, and image data indicating the rotated image (hereinafter referred to as skew correction RGB image data). Is generated. The generated RGB image data after skew correction is stored in the data storage unit 2 under the control of the arithmetic control unit 3.

<Operation of First Embodiment>
Next, an operation when the image processing apparatus performs the skew correction process will be described with reference to FIG.
When the user of the image processing apparatus places a document on the image scanner included in the image input unit 1 and then operates a key (not shown) to instruct to read the document, the arithmetic control is performed. The image input unit 1 is controlled by the unit 3, and the placed document is read for each RGB color component. When the reading of the document is completed, the arithmetic control unit 3 stores the RGB image data indicating the read document generated by the image input unit 1 in the data storage unit 2 (step S301).

  The arithmetic control unit 3 stores the RGB image data in the data storage unit 2, and then supplies the RGB image data to the gradation correction unit 4. When the RGB image data is supplied, the gradation correction unit 4 performs gradation correction processing on the supplied RGB image data to correct the gradation of the RGB image data. When the gradation correction of the RGB image data is completed in the gradation correction unit 4, the gradation-corrected RGB image data is stored in the data storage unit 2 under the control of the arithmetic control unit 3 (step S302). Thereafter, the arithmetic control unit 3 supplies the RGB image data subjected to the gradation correction processing to the skew correction unit 5 (step S303). When the RGB image data is supplied to the skew correction unit 5, the supplied RGB image data is supplied to the binarization unit 100 and the image rotation unit 103.

  The data supplied to the binarization unit 100 is first input to the color component selection unit 300. The color component selection unit 300 extracts G component data from the input data, and outputs the extracted image data as G image data. The output G image data is input to the floating binarization unit 301. In the floating binarization unit 301, a process is performed in which pixels belonging to the dark area are HIGH pixels and pixels belonging to the light area are LOW pixels, and binary image data is generated. The binary image data is input to the expansion unit 302, and a HIGH pixel expansion process is performed. The data subjected to the expansion process in the expansion unit 302 is input to the contraction unit 303, and the HIGH pixel contraction process is performed.

  The binary image data that has undergone the contraction process is input to the contour extraction unit 101. In the contour extraction unit 101, pixels indicating the contour of a region composed of HIGH pixels are extracted from the input binary image data, and contour binary image data composed of the extracted pixels is generated. The The contour binary image data is output from the contour extracting unit 101 and input to the region dividing unit 200 of the skew angle detecting unit 102.

  The area dividing unit 200 to which the contour binary image data is input recognizes characters, figures, and photographs in the image, and divides the image into areas that include characters, areas that include figures, and areas that include photographs. Divided image data indicating the divided image is generated for each divided image and output to the Hough transform unit 201. When the divided image data is input to the Hough transform unit 201, the Hough transform unit 201 performs a Hough transform process on the input divided image data, and writes the result of the Hough transform in the Hough space data storage unit 202. Thereby, histogram data for each divided image area is generated in the Hough space data storage unit 202.

When the Hough transform processing is completed in the Hough transform unit 201, the Hough space data calculation projection unit 203 reads out the histogram data stored in the Hough space data storage unit 202 for each divided image area, and the frequency is dense for each angle θ. The degree is obtained and projection histogram data is generated.
When the Hough space data calculation projection unit 203 finishes generating the projection histogram data,
The overall data calculation unit 205 reads the projection histogram data stored in the calculation projection data storage unit 204, adds the read histograms, and generates projection histogram data of the entire image. When the generation of the whole histogram data is completed, the whole data calculation unit 205 supplies the whole histogram data to the angle detection unit 206.

When the whole histogram data is supplied, the angle detection unit 206 obtains the angle θ at which the density is maximum from the supplied whole histogram data, and the skew angle data indicating the obtained angle θ is obtained as the image rotation unit. To 103.
When the skew angle data is input to the image rotation unit 103, the angle data output from the angle detection unit 206 is the image indicated by the RGB image data supplied from the data storage unit 2 under the control of the calculation control unit 3. The angle is rotated by the angle indicated by the angle data in the opposite direction. When image rotation ends, the image rotation unit 103 generates skew-corrected RGB image data indicating the image after rotation. When the image rotation unit 103 finishes generating the skew-corrected RGB image data, the arithmetic control unit 3 stores the skew-corrected RGB image data in the data storage unit 2 (step S304).

As described above, the present embodiment divides an image into a plurality of regions such as a character region, a photo region, and a graphic region, and is suitable for detecting a skew angle for each divided image region. To extract. Then, the extracted pixels are used to perform Hough transform for each divided image region, and the skew angle of the entire image is obtained from the result of Hough transform for each image region.
In this way, the Hough transform is not performed on the entire image, but the Hough transform is performed for each image region, and the image skew angle is obtained based on the result of the Hough transform of each image region. As illustrated, the skew of the image can be corrected without erroneously detecting the skew angle even in the case of a document arranged in columns.

[2. Second Embodiment]
Next, a second embodiment of the present invention will be described. In addition, since the structure of 2nd Embodiment of this invention is substantially the same as 1st Embodiment, the same code | symbol is attached | subjected about the same part as 1st Embodiment, and the description is abbreviate | omitted.

As shown in FIG. 18, the second embodiment of the present invention is different from the first embodiment in the configuration of the skew angle detection unit 102.
When the divided image data is sequentially input from the region dividing unit 200, the Hough transform unit 201 according to the second embodiment generates an identification number for identifying the divided image data for each divided image data. When generating the arrangement table, the Hough conversion unit 201 generates the arrangement table in the Hough space data storage unit 202 in association with the generated identification number.

  The Hough space data calculation unit 203 according to the second embodiment reads the identification number associated with the array table when reading the histogram data stored in the array table of the Hough space data storage unit 202. Further, when generating the projection data table, the Hough space data calculation unit 203 generates a projection data table in the calculation projection data storage unit 204 in association with the read identification number.

  The region attribute determining unit 207 determines the attribute of the image indicated by the divided image data sequentially input from the region dividing unit 200. The area attribute determination unit 207 determines whether the image indicated by the divided image data represents a character, a photograph, a line drawing, or a pattern, and generates attribute data indicating the determined attribute for each divided image data. When the divided image data is sequentially input from the region dividing unit 200, the region attribute determining unit 207 generates an identification number for identifying the divided image data for each divided image data. When the region attribute determination unit 207 generates the attribute data and the identification number, the region attribute determination unit 207 stores the generated attribute data in association with the identification number in the calculation projection data storage unit 204.

  The overall data calculation unit 205 generates projection histogram data of the entire image from the projection histogram data stored in the calculation projection data storage unit 204. The overall data calculation unit 205 sequentially reads the projection histogram data stored in the calculation projection data storage unit 204, extracts data indicating frequency density from each projection histogram data for each angle θ, and extracts the extracted data. to add. When reading the projection histogram data, the overall data calculation unit 205 reads the identification number associated with the projection histogram data. When reading the identification number, the overall data calculation unit 205 reads the attribute data stored in association with the same identification number as this identification number. The overall data calculation unit 205 extracts data indicating the frequency density from each projection histogram data for each angle θ, and when adding the extracted data, the attribute indicated by the read attribute data is, for example, a photograph or a picture Is added, the read projection histogram data is not added, and if a character or line drawing is shown, the read projection histogram data is added. When the addition of the projection histogram data is completed, the entire data calculation unit 205 supplies the entire histogram data obtained as a result of the addition to the angle detection unit 206. If the attribute indicated by the read attribute data indicates, for example, a photograph or a picture, the overall data calculation unit 205 adds projection histogram data with a low weight (low addition rate), for example. Also good.

  As described above, according to the present embodiment, it is easy to discriminate the inclination by excluding a photo or a picture area where it is difficult to discriminate the inclination or by reducing the contribution rate to the angle calculation of the picture or the picture area. Since skew angles are detected using text and line drawings, it is possible to detect more accurate skew angles and correct skew more accurately than when skew angles are detected including photographs and pictures. Can do.

[3. Third Embodiment]
Next, a third embodiment of the present invention will be described. In addition, since the structure of 3rd Embodiment of this invention is substantially the same as 1st Embodiment, the same code | symbol is attached | subjected about the part same as 1st Embodiment, and the description is abbreviate | omitted.

  As shown in FIG. 19, in the third embodiment of the present invention, the skew angle detection unit 102 replaces the entire data calculation unit 205 and the angle detection unit 206 with an area angle detection unit 208, an area angle storage unit 209, and The difference from the first embodiment is that an overall angle detector 210 is provided.

  The area angle detection unit 208 detects an inclination angle for each area from the projection histogram data for each divided area stored in the calculation projection data storage unit 204. The area angle detection unit 208 sequentially reads the projection histogram data for each divided area, obtains the angle θ at which the density is the maximum among the read histogram data, and the image area obtained by dividing the obtained angle θ. The skew angle. When the area angle detection unit 208 obtains the skew angle, the area angle storage unit 209 stores the skew angle data indicating the obtained skew angle for each divided image area.

  The overall angle detection unit 210 calculates the skew angle of the entire image. The overall angle detection unit 210 reads the skew angle data for each image area stored in the area angle storage unit 209. The overall angle detection unit 210 obtains the frequency of the skew angle indicated by the skew angle data using the read skew angle data, sets the skew angle having the highest frequency as the skew angle of the entire image, and indicates the skew angle indicating the skew angle. Output data.

  According to the present embodiment, a skew angle is obtained for each image region, and a skew angle having a high frequency is set as the skew angle of the entire image. For this reason, even if there are areas where it is difficult to obtain an accurate skew angle such as a photograph or figure in the image, the angles calculated from those areas do not concentrate on a certain angle, and as a result, The skew angle calculated from the region is excluded, and a more accurate skew angle can be detected.

[4. Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In addition, since 4th Embodiment of this invention is as substantially the same as 3rd Embodiment of this invention, about the part which has the same structure, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 20, the fourth embodiment of the present invention is different from the third embodiment in the configuration of the skew angle detection unit 102.

  When the divided image data is sequentially input from the area dividing unit 200, the Hough transform unit 201 according to the fourth embodiment generates an identification number for identifying the divided image data for each divided image data. When generating the arrangement table, the Hough conversion unit 201 generates the arrangement table in the Hough space data storage unit 202 in association with the generated identification number.

  The Hough space data calculation unit 203 according to the fourth embodiment reads the identification number associated with the sequence table when reading the histogram data stored in the sequence table of the Hough space data storage unit 202. When generating the projection data table, the Hough space data calculation unit 203 generates a projection data table in the calculation projection data storage unit 204 in association with the read identification number.

  The area angle detection unit 208 detects an inclination angle for each area from the projection histogram data for each divided area stored in the calculation projection data storage unit 204. The area angle detection unit 208 sequentially reads out the projection histogram data stored in the projection data table for each divided area, and obtains an angle θ at which the degree of congestion is maximum among the read histogram data. Let the angle θ be the skew angle of the divided image area. Further, the area angle detection unit 208 reads the identification number associated with the projection data table when reading the projection histogram data. When the area angle detection unit 208 obtains the skew angle, the area angle storage unit 209 stores the skew angle data indicating the obtained skew angle in association with the read identification number.

  The area attribute determination unit 207 determines the attribute of the image indicated by the divided image data that is sequentially input from the area dividing unit 200. The area attribute determination unit 207 determines whether the image indicated by the divided image data represents a character, a photograph, a line drawing, or a pattern, and generates attribute data indicating the determined attribute for each divided image data. When the divided image data is sequentially input from the region dividing unit 200, the region attribute determining unit 207 generates an identification number for identifying the divided image data for each divided image data. When generating the attribute data and the identification number, the region attribute determination unit 207 stores the generated attribute data in the region angle storage unit 209 in association with the identification number.

The overall angle detection unit 210 generates overall skew angle data indicating the inclination angle of the entire image from the skew angle data for each region stored in the region angle storage unit 209.
The overall angle detection unit 210 sequentially reads the skew angle data stored in the region angle storage unit 209. Further, when reading the skew angle data, the overall angle detection unit 210 reads an identification number associated with the skew angle data. When the total angle detection unit 210 calculates the average value of the angles indicated by the read skew angle data, if the attribute indicated by the read attribute data indicates, for example, a photograph or a picture, the read skew angle data is displayed. When a character or a line drawing is shown instead of calculating the average value, the read skew angle data is used for calculating the average value. When the calculation of the average value of the skew angle is completed, the overall angle detection unit 210 supplies the overall skew angle data indicating the obtained average value of the skew angle to the angle detection unit 206. When the overall angle detection unit 210 obtains the average value of the angles indicated by the read skew angle data, if the attribute indicated by the read attribute data indicates, for example, a photograph or a picture, for example, a low weight is used. The skew angle data read at (low contribution rate) may be used for calculating the average value.

  According to the present embodiment, by using a character or a line drawing that makes it easy to determine the inclination by excluding an area of a photograph or a picture that is difficult to determine the inclination, or by reducing the contribution rate to the angle calculation of the picture or the picture area. Since the skew angle is detected, a more accurate skew angle can be detected, and the skew can be corrected more accurately than when the skew angle is detected including a photograph or a picture.

[5. Modified example]
Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be implemented in various other forms. For example, the present invention may be implemented by modifying the above-described embodiment as follows.

In the embodiment described above, the area dividing unit 200 performs area division on the contour binary image data. However, the area dividing unit 200 may perform area division on the RGB image data instead of the contour binary image data. Good. Since RGB image data has information related to gradation, it is possible to perform region division more accurately than in the case of dividing a binary image into regions.
In the above-described embodiment, the area dividing unit 200 divides an image for each attribute such as a character area, a photo area, and a graphic area. Instead, for example, as shown in FIG. 21, it may be divided into a plurality of rectangular regions of N rows × M columns (N and M are integers).

  In the embodiment described above, the image input unit 1 reads the document for each of the RGB color components, but the document may be read as a monochrome binary image.

In the above-described embodiment, the image processing apparatus reads a document placed on the image scanner of the image input unit 1, generates image data, and corrects an image skew indicated by the generated image data. The image processing apparatus is not limited to this mode.
For example, the image processing apparatus may include communication means, receive RGB image data transmitted from a computer apparatus, and perform skew correction on the received RGB image data. Also, skew correction may be performed on image data transmitted via a telephone line as in a facsimile machine.

In the above-described embodiment, the processing performed by the skew correction unit 5 may be realized by software.
Further, for example, the processing described in the first embodiment and the processing described in the third embodiment are performed, the reliability of the skew angle obtained by each processing method is obtained, and the higher reliability is obtained. The skew angle may be the skew angle of the entire image.
As a method of obtaining the reliability, when the histogram data of the entire image is generated by adding the projection histogram data and the skew angle of the entire image is obtained from the generated overall histogram data, the maximum density of the entire histogram data is determined. The ratio between the value and the average value of the density is obtained, and the obtained value is set as the reliability of the skew angle. In addition, when the skew angle is obtained for each divided area and the skew angle of the entire image is obtained from the obtained angle for each area, the frequency of the obtained skew angle is obtained, and the obtained frequency and the number of divided image areas are obtained. The ratio is defined as the reliability. For example, when an image is divided into 10 areas, there are 5 areas where the skew angle is 1 degree, 3 areas where the skew angle is 2 degrees, and 2 areas where the skew angle is 3 degrees. The skew angle of the entire image is 1 degree, and the reliability of the skew angle is 5/10 = 0.5.
Then, for each reliability, it is determined whether or not the reliability is larger than a predetermined value determined for each processing method, and one of the reliability is smaller than the predetermined value, and the other reliability is When it is larger than the predetermined value, the skew angle obtained by the method in which the reliability higher than the predetermined value is calculated may be used as the skew angle of the entire image.
In any method, when the reliability is smaller or larger than a predetermined value, the skew angle obtained by any one of the methods specified in advance may be used as the skew angle of the entire image.

In the above-described embodiment, the attribute of the image is obtained for each divided image area. However, the weighting factor of the image may be obtained, and the skew angle may be obtained in consideration of the weighting factor. Specifically, for example, a weighting factor is obtained for each region according to the number of HIGH pixels in the divided region. The weighting factor may be determined according to the attribute data. For example, when the divided area indicates a character area, the weighting factor is set to high, and when the photographed area is displayed, the weighting factor is set to be high. The value may be low.
For example, if the number of regions = N, the angle calculated from each region = αi, and the weighting coefficient calculated from each region = Wi, the weighted average angle considering the weight is (Σ (αi × Wi)) / (ΣWi). Thus, according to the aspect of obtaining the skew angle in consideration of the weighting factor, the weight of the data relating to the photographic area is reduced, so that even if the input image is an image including the photographic area, the skew angle of the image is more accurately determined. Can be sought.
The weighting factor may be obtained by detecting an object in the image indicated by the RGB image data, dividing the image, and obtaining the weighting factor based on the divided image. As for the attribute of the divided image, the object in the image indicated by the RGB image data may be detected to divide the image, and the attribute data may be obtained based on the divided image.

  In the embodiment described above, the object is detected from the contour binary image data. However, the object may be detected from the RGB image data, and the contour binary image data may be divided based on the result.

1 is a block diagram illustrating a configuration of an image processing apparatus according to an embodiment of the present invention. It is a block diagram which illustrates the composition of skew correction part 5 concerning the embodiment. It is a block diagram which illustrates the composition of binarization part 100 concerning the embodiment. It is a figure for demonstrating each process performed by the expansion part 302 and the contraction part 303. FIG. It is a figure for demonstrating the process performed in the outline extraction part. It is a figure for demonstrating the process performed in the outline extraction part. 3 is a block diagram illustrating a configuration of a skew angle detection unit 102. FIG. It is a figure for demonstrating the area division which the area division part 200 performs. It is a figure for demonstrating a Hough conversion process. It is a figure for demonstrating a Hough conversion process. 4 is a flowchart illustrating the flow of processing performed by a Hough conversion unit 201. It is a figure which illustrates the arrangement | sequence table which the Hough space data storage part 202 memorize | stores. It is a figure which illustrates the histogram showing distribution of the frequency of each coordinate on (rho) -theta coordinate. It is a flowchart which illustrates the flow of the process which the Hough space data calculation projection part 203 performs. It is a figure which illustrates the format of a projection data table. It is a figure which illustrates the histogram showing the relationship between angle (theta) and the density w. It is a flowchart which illustrates the flow of the process which the arithmetic control part 3 performs. It is a block diagram which illustrates the composition of skew angle detection part 102 concerning a 2nd embodiment. It is a block diagram which illustrates the composition of skew angle detection part 102 concerning a 3rd embodiment. It is a block diagram which illustrates the composition of skew angle detection part 102 concerning a 4th embodiment. It is a figure for demonstrating the modification of this invention. It is a figure for demonstrating the problem of a prior art. It is a figure for demonstrating the problem of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image input part, 2 ... Data storage part, 3 ... Calculation control part, 4 ... Gradation correction part, 5 ... Skew correction part, 6 ... Color signal conversion part, 7 ... Image display unit, 8 ... Image output unit, 9 ... Bus, 100 ... Binarization unit, 101 ... Contour extraction unit, 102 ... Skew angle detection unit, 103 ..Image rotating unit, 200... Region dividing unit, 201... Hough transform unit, 202... Hough space data storage unit, 203. Storage unit 205... Overall data calculation unit 206... Angle detection unit 207... Area attribute determination unit 208... Region angle detection unit 209. -Whole angle detection unit, 300 ... color component selection unit, 301 ... floating binarization unit, 302 ... Zhang section, 303 ... constriction.

Claims (17)

Storage means for storing image data;
Binarization means for binarizing the image data stored in the storage means to generate binary image data;
Area dividing means for dividing the image indicated by the binary image data generated by the binarizing means into a plurality of areas, and generating divided binary image data indicating the divided images;
A Hough transform unit that performs Hough transform on the divided binary image data, and generates histogram data representing the frequency of coordinates on polar coordinates obtained by the Hough transform for each divided image region;
For each histogram data generated by the Hough transform means, a frequency calculation means for generating projection histogram data representing the frequency density at each angle on polar coordinates;
Adding the projection histogram data generated by the frequency calculation means to generate overall histogram data; and
An overall angle detection means for detecting an inclination angle of the image indicated by the image data based on the overall histogram data generated by the overall frequency calculation means;
An image processing apparatus comprising: an image rotation unit configured to rotate an image indicated by the image data stored in the storage unit according to an inclination angle obtained by the overall angle detection unit. The region dividing unit detects an object in the image represented by the binary image data, divides the image for each detected object, and generates divided binary image data;
Attribute data generating means for generating attribute data indicating an object in the image indicated by the divided binary image data;
The image processing apparatus according to claim 1, wherein the overall frequency calculation unit adds the projection histogram data according to attribute data corresponding to the projection histogram data. The region dividing unit detects an object in the image represented by the image data, and divides the image represented by the binary image data based on the detected object to generate divided binary image data,
Attribute data generation means for generating attribute data indicating an object in the image represented by the divided binary image data;
The image processing apparatus according to claim 1, wherein the overall frequency calculation unit adds the projection histogram data according to attribute data corresponding to the projection histogram data. Storage means for storing image data;
Area dividing means for dividing the image indicated by the image data stored in the storage means into a plurality of areas, and generating divided image data indicating the divided images;
Binarization means for binarizing the divided image data generated by the area dividing means to generate divided binary image data;
A Hough transform unit that performs Hough transform on the divided binary image data, and generates histogram data representing the frequency of coordinates on polar coordinates obtained by the Hough transform for each divided image region;
For each histogram data generated by the Hough transform means, a frequency calculation means for generating projection histogram data representing the frequency density at each angle on polar coordinates;
Adding the projection histogram data generated by the frequency calculation means to generate overall histogram data; and
An overall angle detection means for detecting an inclination angle of an image represented by image data based on the overall histogram data generated by the overall frequency calculation means;
An image processing apparatus comprising: an image rotation unit configured to rotate an image indicated by the image data stored in the storage unit according to an inclination angle obtained by the overall angle detection unit. The area dividing unit detects an object in the image indicated by the image data, and generates divided image data by dividing the image represented by the image data for each detected object,
Attribute data generating means for generating attribute data indicating an object in the image indicated by the divided image data;
The image processing apparatus according to claim 4, wherein the overall frequency calculating unit adds the projection histogram data according to attribute data corresponding to the projection histogram data. Attribute data generation means for generating attribute data indicating an object in the image represented by the divided binary image data;
The image processing apparatus according to claim 4, wherein the overall frequency calculating unit adds the projection histogram data according to attribute data corresponding to the projection histogram data. Weight coefficient generation means for generating a weight coefficient of an image indicated by the divided image data;
The image processing apparatus according to claim 4, wherein the overall frequency calculation unit adds the projection histogram data according to a weighting factor corresponding to the projection histogram data. Weight coefficient generation means for generating a weight coefficient of an image indicated by the divided binary image data;
The image processing apparatus according to claim 1, wherein the overall frequency calculation unit adds the projection histogram data in accordance with a weighting factor corresponding to the projection histogram data. Storage means for storing image data;
Binarization means for binarizing the image data stored in the storage means to generate binary image data;
Area dividing means for dividing the image represented by the binary image data generated by the binarizing means into a plurality of areas and generating divided binary image data indicating the divided images;
A Hough transform unit that performs Hough transform on the divided binary image data, and generates histogram data representing the frequency of coordinates on polar coordinates obtained by the Hough transform for each divided image region;
For each histogram data generated by the Hough transform means, a frequency calculation means for generating projection histogram data representing the frequency density at each angle on polar coordinates;
Adding the projection histogram data generated by the frequency calculation means to generate overall histogram data; and
First global angle detection means for obtaining an angle at which the frequency is maximum in the overall histogram data generated by the overall frequency calculation means;
First reliability calculation means for determining the reliability of the angle determined by the first overall angle detection means;
Area angle detection means for obtaining the angle at which the frequency is maximum in the projection histogram data generated by the frequency calculation means for each projection histogram data;
Of the angles obtained by the region angle detection means, second overall angle detection means for obtaining the most frequent angle;
Second reliability calculation means for determining the reliability of the angle determined by the second overall angle detection means;
An overall angle determination means for obtaining an inclination angle of the entire image based on the reliability obtained by the first reliability calculation means and the reliability obtained by the second reliability calculation means;
An image processing apparatus comprising: an image rotation unit that rotates an image indicated by image data stored in the storage unit according to an inclination angle obtained by the overall angle determination unit. Storage means for storing image data;
Area dividing means for dividing the image represented by the image data stored in the storage means into a plurality of areas and generating divided image data indicating the divided images;
Binarization means for binarizing the divided image data generated by the area dividing means to generate divided binary image data;
A Hough transform unit that performs Hough transform on the divided binary image data, and generates histogram data representing the frequency of coordinates on polar coordinates obtained by the Hough transform for each divided image region;
For each histogram data generated by the Hough transform means, a frequency calculation means for generating projection histogram data representing the frequency density at each angle on polar coordinates;
Adding the projection histogram data generated by the frequency calculation means to generate overall histogram data; and
First global angle detection means for obtaining an angle at which the frequency is maximum in the overall histogram data generated by the overall frequency calculation means;
First reliability calculation means for determining the reliability of the angle determined by the first overall angle detection means;
Area angle detection means for obtaining the angle at which the frequency is maximum in the projection histogram data generated by the frequency calculation means for each projection histogram data;
Of the angles obtained by the region angle detection means, second overall angle detection means for obtaining the most frequent angle;
Second reliability calculation means for determining the reliability of the angle determined by the second overall angle detection means;
An overall angle determining means for obtaining an inclination angle of the entire image based on the reliability obtained by the first reliability calculating means and the reliability obtained by the second reliability calculating means;
An image processing apparatus comprising: an image rotation unit that rotates an image indicated by image data stored in the storage unit according to an inclination angle obtained by the overall angle determination unit. The second overall angle detecting means, the most frequent place of the high angle image processing apparatus according to claim 9 or claim 10, wherein the determination of the average angle of angles is the region angle detecting means obtained . The overall angle determination means compares the reliability obtained by the first reliability calculation means with the reliability obtained by the second reliability calculation means,
When the reliability obtained by the first reliability calculation means is higher than the reliability obtained by the second reliability calculation means, the angle obtained by the first overall angle detection means is set as the angle of the entire image, and When the reliability obtained by the second reliability calculation means is higher than the reliability obtained by the first reliability calculation means, the angle obtained by the second overall angle detection means is set as the inclination angle of the entire image. The image processing apparatus according to claim 9 or 10 , wherein: When the reliability obtained by the first reliability calculation means is equal to or greater than a predetermined threshold, the overall angle determination means sets the angle obtained by the first overall angle detection means as the inclination angle of the entire image, The angle obtained by the second overall angle detection means is set as the inclination angle of the whole image when the reliability obtained by the first reliability calculation means is less than a predetermined threshold value. The image processing apparatus according to claim 9 or 10 . When the reliability determined by the second reliability calculation means is equal to or greater than a predetermined threshold, the overall angle determination means sets the angle determined by the second global angle detection means as the inclination angle of the entire image, The angle obtained by the first overall angle detection means is used as the inclination angle of the whole image when the reliability obtained by the second reliability calculation means is less than a predetermined threshold value. The image processing apparatus according to claim 9 or 10 . Computer
Storage means for storing image data;
Binarization means for binarizing the image data stored in the storage means to generate binary image data;
Area dividing means for dividing the image indicated by the binary image data generated by the binarizing means into a plurality of areas, and generating divided binary image data indicating the divided images;
A Hough transform unit that performs Hough transform on the divided binary image data, and generates histogram data representing the frequency of coordinates on polar coordinates obtained by the Hough transform for each divided image region;
For each histogram data generated by the Hough transform means, a frequency calculation means for generating projection histogram data representing the frequency density at each angle on polar coordinates;
Adding the projection histogram data generated by the frequency calculation means to generate overall histogram data; and
An overall angle detection means for detecting an inclination angle of the image indicated by the image data based on the overall histogram data generated by the overall frequency calculation means;
A program for causing an image indicated by image data stored in the storage means to function as an image rotating means for rotating the image according to the inclination angle obtained by the overall angle detecting means. Computer
Storage means for storing image data;
Area dividing means for dividing the image indicated by the image data stored in the storage means into a plurality of areas, and generating divided image data indicating the divided images;
Binarization means for binarizing the divided image data generated by the area dividing means to generate divided binary image data;
A Hough transform unit that performs Hough transform on the divided binary image data, and generates histogram data representing the frequency of coordinates on polar coordinates obtained by the Hough transform for each divided image region;
For each histogram data generated by the Hough transform means, a frequency calculation means for generating projection histogram data representing the frequency density at each angle on polar coordinates;
Adding the projection histogram data generated by the frequency calculation means to generate overall histogram data; and
An overall angle detection means for detecting an inclination angle of an image represented by image data based on the overall histogram data generated by the overall frequency calculation means;
A program for causing an image indicated by image data stored in the storage means to function as an image rotating means for rotating the image according to the inclination angle obtained by the overall angle detecting means. The computer-readable recording medium which recorded the program of Claim 15 or Claim 16 .

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