JP2017147592A - Image reading apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of suitably performing an inclination correction.SOLUTION: An image reading apparatus comprises: an image data acquisition part that acquires image data of an original; a first inclination detection part that detects inclination of the image data to a first direction; a first division unit number setting part that sets a division unit for dividing the image data on the basis of the detected inclination toward the first direction; and a first shift part that shifts the image data in every division unit to the first direction. The first division unit number setting part includes: a first line number calculation part that calculates the number of a pixel lines in a second direction in which the image data indicating a boundary line of the original is changed by one pixel to the first direction; a first line number setting part that, when fraction figure occurs in the number of pixel lines, sets the fractional figure of a calculation result to the division unit of the pixel line of an integer number by round-up or round-down of the fractional figure; and a first line number adjustment part that integrates the fractional figure of the pixel number of the division unit in accordance with the setting, and adjusts the pixel line number of the integer number of the division unit when an integrated value exceeds a predetermined value.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image reading apparatus, and more particularly, to inclination correction of image data of a document.

  2. Description of the Related Art In an image reading apparatus, tilt correction is conventionally performed by various methods on a document placed on a document table of an image scanner (Patent Document 1).

  For example, in Patent Document 1, a unit for shifting is obtained from the inclination of the document, and is shifted in the main scanning direction every predetermined number of lines. Then, the shift is performed in the sub-scanning direction every predetermined number of lines after the shift. A skew correction method for correcting a magnification error has been proposed.

JP 2000-188678 A

  However, when shifting in units of pixels every predetermined number of lines, there is a problem that the continuity of the image data is not maintained and the shape is distorted.

  SUMMARY An advantage of some aspects of the invention is that it provides an image reading apparatus capable of performing appropriate inclination correction.

  An image reading apparatus according to a certain aspect is detected by an image data acquisition unit that acquires image data of a document, a first tilt detection unit that detects a tilt of document image data with respect to a first direction, and a first tilt detection unit. A first division unit number setting unit for setting a division unit for dividing the image data of the document along the first direction based on the inclination, and a first for shifting the image data for each divided division unit in the first direction. And a shift unit. The first division unit number setting unit includes a first line number calculation unit that calculates the number of pixel lines arranged along a second direction in which image data indicating a document boundary line changes by one pixel in the first direction; A first line number setting unit for setting a unit of division of an integer pixel line number by rounding up or down the fraction of the calculation result of the first line number calculation unit when a fraction occurs in the number of pixel lines; A first line number adjusting unit that integrates a fraction of the number of pixel lines in the division unit according to the setting of the setting unit and adjusts the integer number of pixel lines in the division unit when the integrated value exceeds a predetermined value.

  Preferably, the line number adjustment unit resets the integrated value when an integer number of pixel lines in the division unit is adjusted.

  Preferably, after the shift in the first direction by the first shift unit, a second tilt detection unit that detects the tilt of the image data of the document with respect to a second direction different from the first direction, and a second tilt detection unit And a second division unit number setting unit for setting a division unit for dividing the image data of the original along the second direction based on the inclination detected in step B, and shifting the image data for each divided division unit in the second direction. And a second shift unit.

  Preferably, the second division unit number setting unit calculates the number of pixel lines arranged along the first direction in which the image data indicating the boundary line of the shifted document changes by one pixel in the second direction. A line number calculation unit, and a second line number setting unit configured to set a unit of division of an integer pixel line number by rounding up or down the fraction of the calculation result of the second line number calculation unit when a fraction occurs in the pixel line number The second line number adjustment is performed to integrate the fraction of the pixel line number in the division unit according to the setting of the second line number setting unit and adjust the integer pixel line number in the division unit when the integrated value exceeds a predetermined value. Part.

Preferably, the first direction is the sub-scanning direction, and the second direction is the main scanning direction.
Preferably, the image processing apparatus further includes an interpolation unit that executes a gradation interpolation process that weights and adds the gradation value of each pixel and the gradation value of a pixel adjacent to the first direction.

  Preferably, the interpolation unit adjusts the weighting value according to the distance from the reference pixel included in the division unit to the target pixel.

  Preferably, the image processing apparatus further includes an interpolation unit that executes a gradation interpolation process that adds the gradation value of each pixel and the gradation value of a pixel adjacent to the second direction by weighting.

  Preferably, the interpolation unit adjusts the weighting value according to the distance from the reference pixel included in the division unit to the target pixel.

  Preferably, a resolution conversion unit that adjusts the aspect ratio of the image data of the shifted document is further provided.

1 is a diagram schematically showing an overall configuration of an image reading apparatus 1 based on an embodiment. It is a figure which shows an example of the internal structure of the image reading part 7 based on embodiment. It is a figure which shows an example of the block configuration of the image reading apparatus 1 based on embodiment. It is a figure explaining the functional block of the control part 28 based on embodiment. It is a figure explaining the outline flow of skew correction based on an embodiment. It is a figure which detects the inclination of the image data of the document based on Embodiment. It is a figure explaining the setting of the division unit of the image data based on embodiment. It is a figure which illustrates typically the case where the image data for every division | segmentation unit based on embodiment is shifted to a subscanning direction (1st direction). It is a figure which detects the inclination of the image data of the shifted original based on embodiment. It is a flowchart which performs the skew correction process of the control part 28 based on embodiment. It is a figure explaining the subroutine processing of the setting of the number of division units based on an embodiment. It is a figure explaining the specific example of the process of the 1st line number adjustment part 40 based on embodiment. It is a figure explaining the case where the shift process based on embodiment and the conventional shift process are compared. It is a figure explaining the interpolation process in the interpolation part 54 based on embodiment. It is a figure explaining adjustment of the weighting in the interpolation part 54 based on embodiment.

  Embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

<A. Overview of overall configuration>
FIG. 1 is a diagram schematically showing an overall configuration of an image reading apparatus 1 based on the embodiment.

  The image reading apparatus 1 according to the present embodiment is a multifunction device having functions such as a copy, a scanner, a printer, and a FAX, and can transmit and receive image data to and from other communication devices via a network.

  As shown in FIG. 1, the image reading apparatus 1 includes a document image reading unit 2 provided at the top, an image forming unit 3 provided at the center, and a paper feeding unit 4 provided at the bottom. I have. An output tray 5 is provided between the document image reading unit 2 and the image forming unit 3, and output paper output by the printer function is discharged onto the output tray 5.

  The document image reading unit 2 includes an automatic document transport unit 6 and an image reading unit 7. The automatic document transport unit 6 includes a document tray 8, a transport unit 9, and a paper discharge tray 10. The document placed on the document tray 8 is transported one by one by the transport unit 9 in order from the top. The document whose image has been read by the image reading unit 7 is discharged to the discharge tray 10.

  The image reading unit 7 optically reads an image of a document and acquires image data. When reading an image of a document using the automatic document feeder 6, the image reading unit 7 operates in synchronization with the automatic document feeder 6 and reads an image when the document passes a predetermined image reading position. I do. When performing continuous automatic reading of a plurality of documents in a state where a plurality of documents are set on the document tray 8, in this embodiment, for example, after the image reading unit 7 finishes the image reading operation of one document. The automatic document feeder 6 starts conveying the next document.

  An operation panel 11 that can be operated by the user is provided on the front side of the document image reading unit 2. The operation panel 11 includes an operation unit 12 including a plurality of operation keys and a display unit 13 that displays various types of information to a user who operates the operation panel 11. The operation unit 12 receives user operations related to various settings related to jobs, job execution, and the like and inputs them to the image reading apparatus 1. The display unit 13 displays a menu to be displayed to the user, a job execution status, information on the acquired image, and the like. In addition, when the toner is consumed, the output paper is jammed, or the output paper needs to be replenished to the paper feeding cassette tray, the display unit 13 displays guidance information for prompting the user to perform various operations. .

  The paper feed unit 4 includes paper feed cassette trays 14, 15, and 16, and can store a plurality of output sheets in each paper feed cassette tray. The sheet feeding unit 4 takes out the output sheets stored in the sheet feeding cassette trays 14, 15, and 16 one by one by a transport mechanism provided inside the apparatus and supplies the output sheets to the image forming unit 3.

  The image forming unit 3 forms a toner image based on, for example, input image data, and forms the image by transferring and fixing the toner image on the output paper supplied from the paper feeding unit 4. The image forming unit 3 includes a reversing mechanism, and can perform duplex printing on output paper. The output paper on which image formation has been performed in the image forming unit 3 is discharged to the output tray 5 described above by a transport mechanism inside the apparatus. The image forming unit 3 can record an image on output paper in parallel with the image reading operation by the image reading unit 7, and can perform, for example, a scan job and a print job at the same time in the image reading apparatus 1. ing.

FIG. 2 is a diagram illustrating an example of an internal structure of the image reading unit 7 based on the embodiment.
As shown in FIG. 2, the image reading unit 7 transmits an image reading module 17 that reads an image of a document, a motor 18 that moves the image reading module 17, and a driving force of the motor 18 to the image reading module 17. And a drive transmission unit 19 such as a belt or a wire provided for this purpose. The image reading module 17 also includes a lamp 20 that illuminates the surface to be read of the document, and an image sensor 21 that receives the reflected light from the surface to be read of the document and performs photoelectric conversion to generate image data. Yes.

  The image sensor 21 in the present embodiment is a line sensor in which a plurality of light receiving elements (pixels) are arranged in one direction (X-axis direction). The image sensor 21 is configured to be movable in the sub-scanning direction (Y-axis direction) orthogonal to the main scanning direction (X-axis direction) that is the arrangement direction of the light receiving elements.

  The document image reading unit 2 can read an image of the document while automatically conveying the document set on the document tray 8 of the automatic document conveying unit 6. Further, the document image reading unit 2 scans the document placed on the document surface glass 22 of the image reading unit 7 by scanning the image reading module 17 inside the image reading unit 7, thereby obtaining an image of the document. Can be read.

  When performing image reading, the image reading module 17 is moved directly below the predetermined image reading position P1 inside the image reading unit 7 and is brought into a stationary state at that position. When the document conveyed by the automatic document conveyance unit 6 passes through the image reading position P1, the image sensor 21 mainly illuminates the reading target surface (lower surface of the document) with the lamp 20 through the reading glass 23. The original image is read for each line in the scanning direction. When the trailing edge of the document passes the image reading position P1, the reading operation is finished and image data is generated.

  When image reading is performed, the image reading module 17 scans the image reading module 17 in the Y-axis direction (sub-scanning direction) inside the image reading unit 7 while reading the surface of the document placed on the document surface glass 22 (document lower surface). The image sensor 21 reads the image of the document for each line in the main scanning direction. Then, when the reading of the entire reading target surface of the document is completed, image data is generated.

FIG. 3 is a diagram illustrating an example of a block configuration of the image reading apparatus 1 based on the embodiment.
As shown in FIG. 3, the image reading apparatus 1 includes an automatic document feeder 6, an image reading unit 7, an image forming unit 3, and an operation panel 11. The image reading apparatus 1 also includes a communication interface (I / F) unit 26 for communicating with other communication devices via a network, and a non-volatile storage unit such as a solid state drive (SSD). And a control unit 28 having a CPU and a memory.

  The storage unit 27 includes an image storage unit 29 that stores an image obtained by the scanning operation. The image reading apparatus 1 is configured such that these components can mutually input and output data via the data bus DB.

  The control unit 28 executes skew correction processing by the CPU executing a program stored in the memory.

FIG. 4 is a diagram illustrating functional blocks of the control unit 28 based on the embodiment.
Referring to FIG. 4, the control unit 28 includes a first inclination detection unit 30, a first shift unit 32, a first division unit number setting unit 34, a second inclination detection unit 42, and a second shift unit 44. A second division unit number setting unit 46, an interpolation unit 54, and a resolution conversion unit 56.

  The first inclination detection unit 30 detects an inclination angle of document image data with respect to the sub-scanning direction (first direction). An angle θ1 between a line perpendicular to the sub-scanning direction (first direction) and one side of the boundary line of the document image data is detected.

  The first division unit number setting unit 34 sets a division unit for dividing the image data of the document along the sub-scanning direction (first direction) based on the inclination angle θ1 detected by the first inclination detection unit 30. The first shift unit 32 shifts the divided image data for each division unit in the sub-scanning direction (first direction).

  The second inclination detector 42 detects the inclination of the document image data with respect to the main scanning direction (second direction). An angle θ2 between a line perpendicular to the main scanning direction (second direction) and the other side of the boundary line of the document image data is detected.

  The second division unit number setting unit 46 sets a division unit for dividing the image data of the document along the main scanning direction (second direction) based on the inclination angle θ2 detected by the second inclination detection unit 42. The second shift unit 44 shifts the divided image data for each division unit in the main scanning direction (second direction).

  The first division unit number setting unit 34 includes a first line number calculation unit 36, a first line number setting unit 38, a first line number division unit 39, and a first line number adjustment unit 40.

  The first line number calculation unit 36 calculates the number of pixel lines arranged along the second direction in which the image data indicating the boundary line of the document changes by one pixel in the sub-scanning direction (first direction).

  The first line number setting unit 38, when a fraction occurs in the number of pixel lines, rounds up or down the fraction of the calculation result of the first line number calculation unit 36 and sets it as a division unit of an integer number of pixel lines.

The first line number dividing unit 39 divides the image data according to the set division unit.
The first line number adjustment unit 40 integrates the fraction of the pixel line number of the division unit according to the division of the first line number division unit 39, and when the integrated value is equal to or greater than a predetermined value, the integer pixel line of the division unit Adjust the number.

  The second division unit number setting unit 46 includes a second line number calculation unit 48, a second line number setting unit 50, a second line number division unit 51, and a second line number adjustment unit 52.

  The second line number calculation unit 48 calculates the number of pixel lines arranged along the first direction in which the image data indicating the boundary line of the document changes by one pixel in the main scanning direction (second direction).

  The second line number setting unit 50, when a fraction occurs in the number of pixel lines, rounds up or down the fraction of the calculation result of the second line number calculation unit 48 and sets it as a division unit of an integer number of pixel lines.

The second line number dividing unit 51 divides the image data according to the set division unit.
The second line number adjusting unit 52 integrates the fractional number of pixel lines in accordance with the division of the second line number dividing unit 51, and when the integrated value is greater than or equal to a predetermined value, the integer number of pixel lines in the division unit Adjust the number.

  The interpolating unit 54 executes a gradation interpolation process in which the gradation value of each shifted pixel and the gradation value of the pixel adjacent to the first direction are weighted and added. Further, a gradation interpolation process is performed in which the gradation value of each shifted pixel and the gradation value of a pixel adjacent to the second direction are added with weighting.

The resolution conversion unit 56 adjusts the aspect ratio of the shifted document image data.
<B. Outline of deskew>
FIG. 5 is a diagram illustrating a schematic flow of skew correction based on the embodiment.

  Referring to FIG. 5, (1) image data of a document is acquired. (2) A division unit for dividing the image data by a predetermined number of pixel lines along the sub-scanning direction is set. As an example, the case where the division unit is set to the number X of pixel lines is shown. (3) Shift each division unit in the sub-scanning direction. (4) A division unit for dividing the image data shifted along the main scanning direction by a predetermined number of pixel lines is set. As an example, the case where the division unit is set to the number of pixel lines Y is shown. (5) Shift in units of division in the main scanning direction. (6) A gradation interpolation process is executed on the image data. (7) Adjust the aspect ratio for the image data.

FIG. 6 is a diagram for detecting the inclination of image data of a document based on the embodiment.
As shown in FIG. 6, the bending point of the image data of the document is detected. In this example, bending points A, B, C, and D are detected. As a result, the inflection points A → B → C → D → A of the original image data are also detected.

  Based on the detected boundary line, the inclination angle θ1 of the document image data with respect to the sub-scanning direction (first direction) of the image data is detected.

FIG. 7 is a diagram illustrating setting of the division unit of image data based on the embodiment.
As shown in FIG. 7, the boundary line of the image data is shown. Further, the number of pixel lines arranged along the second direction in which the boundary line changes by one pixel in the first direction to be shifted is shown.

  Here, the number X of pixel lines arranged along the second direction in which the boundary line changes by one pixel in the first direction is calculated based on the tilt angle θ1. The number X of pixel lines is expressed by the following equation.

1 / X = tan θ1 (Formula 1)
X = cos θ1 / sin θ1 (Formula 2)
In this example, the boundary line of the image data changes by 1 pixel in the first direction based on the inclination angle θ1 of the image data. The number X of pixel lines arranged along the second direction is rounded down to 6 The case of is shown.

Therefore, the division unit is set every 6 pixel lines.
FIG. 8 is a diagram schematically illustrating a case where image data for each division unit based on the embodiment is shifted in the sub-scanning direction (first direction).

  As shown in FIG. 8, the length of the image data when the image data for each division unit is shifted in the sub-scanning direction (first direction) is expressed as R / cos θ1.

FIG. 9 is a diagram for detecting the inclination of image data of a shifted document based on the embodiment.
As shown in FIG. 9, the bending point of the image data of the shifted document is detected. In this example, bending points E, F, G, and H are detected. As a result, the boundary line of the image data of the shifted document connecting the bending points E → F → G → H → E of the image data of the document is also detected.

  Then, an inclination angle θ2 of the image data of the document with respect to the main scanning direction (second direction) of the image data is detected based on the detected boundary line. Specifically, an angle θ2 between the line perpendicular to the main scanning direction (second direction) and the other side of the boundary line of the shifted document image data is detected.

  Here, the number Y of pixel lines arranged along the first direction in which the boundary line changes by one pixel in the second direction is calculated based on the tilt angle θ2. The pixel line number Y is expressed by the following equation.

1 / Y = tan θ2 (Equation 3)
Y = cos θ2 / sin θ2 (Formula 4)
Regarding the inclination angles θ1 and θ2, the relationship of the following equation is established.

tanθ2 = Rsinθ1 / (R / cosθ1) = cosθ1 × sinθ1 (Formula 5)
Based on the formulas (2), (4), and (5), Y = X + 1 / X (Expression 6).

  Therefore, if X is set to 6, the number of pixel lines arranged along the first direction in which the boundary line of the image data changes by one pixel in the second direction based on the inclination angle θ2 of the image data Y is rounded down to 6.

<C. Flow>
FIG. 10 is a flowchart for executing the skew correction processing of the control unit 28 based on the embodiment.

  Referring to FIG. 10, control unit 28 acquires image data (step S2). Specifically, the image data read by the image reading unit 7 is acquired.

  Next, the control unit 28 detects an inclination angle θ1 with respect to the sub-scanning direction (first direction) (step S4). As described with reference to FIG. 6, the first inclination detection unit 30 detects the bending point, and detects the inclination angle θ1 of the document image data with respect to the sub-scanning direction (first direction) based on the detected boundary line. .

  Next, the control unit 28 sets the number of division units for dividing the image data along the first direction (step S6). The first division unit number setting unit 34 sets the division unit number for dividing the image data along the first direction. Details of setting the number of division units will be described later.

  Next, the control unit 28 executes a process of shifting in the first direction (step S8). The first shift unit 32 shifts in the sub-scanning direction (first direction) for each divided unit.

  Next, the control unit 28 detects an inclination angle θ2 with respect to the main scanning direction (second direction) (step S10). As described with reference to FIG. 9, the second inclination detection unit 42 detects the bending point, and detects the inclination angle θ2 of the document image data with respect to the main scanning direction (second direction) based on the detected boundary line. .

  Next, the control unit 28 sets the number of division units for dividing the image data along the second direction (step S12). The second division unit number setting unit 46 sets the number of division units for dividing the image data along the second direction. Details of setting the number of division units will be described later.

  Next, the control unit 28 executes a process of shifting in the second direction (step S14). The second shift unit 44 shifts in the main scanning direction (second direction) for each divided unit.

  Next, the control part 28 performs an interpolation process (step S16). The interpolating unit 54 executes a gradation interpolation process in which the gradation value of each shifted pixel and the gradation value of the pixel adjacent to the first direction are weighted and added. Further, a gradation interpolation process is performed in which the gradation value of each shifted pixel and the gradation value of a pixel adjacent to the second direction are added with weighting. Details of the interpolation processing will be described later.

  Next, the control unit 28 executes resolution conversion processing (step S18). The resolution conversion unit 56 adjusts the aspect ratio of the shifted document image data.

Then, the process ends (END).
FIG. 11 is a diagram for explaining the subroutine processing for setting the number of division units based on the embodiment. This is processing in the first division unit number setting unit 34 and the second division unit number setting unit 46. As an example, the first division unit number setting unit 34 will be described.

  As shown in FIG. 11, the first division unit number setting unit 34 calculates the number of lines (step S20).

  Specifically, the first line number calculation unit 36 sets the number of pixel lines arranged along a second direction in which image data indicating a document boundary line changes by one pixel in the sub-scanning direction (first direction). Is calculated.

  Next, the first division unit number setting unit 34 sets the number of lines based on the calculation result (step S22). The first line number setting unit 38 divides the calculation result of the first line number calculation unit 36 by rounding up or down to a whole number of pixel line division units when the pixel line number has a fraction based on the calculation result Set to.

  Next, the first division unit number setting unit 34 divides the image data according to the set number of lines (step S24). The first line number dividing unit 39 divides the image data according to the set division unit.

  Next, the 1st division | segmentation unit number setting part 34 integrates a fraction (step S28). The first line number adjustment unit 40 integrates the fraction of the pixel line number in the division unit according to the division of the first line number division unit 39.

  Next, the first division unit number setting unit 34 determines whether or not the integrated fraction is greater than or equal to a predetermined value (step S30). The first line number adjustment unit 40 determines whether or not the integral of the fraction is equal to or greater than a predetermined value.

  Specifically, when the fraction is rounded down and set as a division unit of an integer number of pixel lines, the fraction is a positive decimal value. In this example, it is determined whether or not a positive decimal value is accumulated to become a predetermined value 1 or more.

  On the other hand, when the fraction is rounded up and set as a division unit of an integer number of pixel lines, the fraction is a negative decimal value. In this example, it is determined whether or not the negative decimal values are integrated and become a predetermined value −1 or less.

  In step S30, the first division unit number setting unit 34 adjusts the number of lines (step S32) when it determines that the integrated fraction is greater than or equal to a predetermined value (YES in step S30). The first line number adjustment unit 40 adjusts the number of lines set as a division unit when it is determined that the integral of the fraction is equal to or greater than a predetermined value. Specifically, when the fraction is rounded down and set as a division unit of an integer number of pixel lines, 1 is added to the number of lines.

  On the other hand, when the fraction is rounded up and set to the division unit of the integer number of pixel lines, 1 is subtracted from the number of lines.

  Then, the first division unit number setting unit 34 resets the integration, and returns to step S24. The first line number adjustment unit 40 resets the fractional integration.

  After returning to step S24, the first division unit number setting unit 34 divides by the adjusted number of lines. The first line number dividing unit 39 divides the image data according to the adjusted number of lines. The first line number adjustment unit 40 adds up the fractions again. Further, the first line number dividing unit 39 executes division with the initially set number of lines.

  On the other hand, if the first division unit number setting unit 34 determines in step S30 that the integrated fraction is less than the predetermined value (NO in step S30), it skips steps S32 and S34 and returns to step S24. The first line number dividing unit 39 executes division with the initially set number of lines.

  In addition, in the above, although the process of the 1st division | segmentation unit number setting part 34 was mainly demonstrated, it is the same also about the process of the 2nd division | segmentation unit number setting part 46. FIG.

  FIG. 12 is a diagram illustrating a specific example of the process of the first line number adjustment unit 40 based on the embodiment.

  As shown in FIG. 12A, here, a case is shown in which the pixel line number X = 10 is set as a division unit for dividing the image data by a predetermined number of pixel lines along the sub-scanning direction. . In this case, based on Formula (6), it is expressed as Y = 10.1. The fraction D = 0.1. The figure shows a case where the pixel line number Y = 10 is set as a division unit for dividing the image data shifted along the main scanning direction by rounding down the fraction D by a predetermined number of pixel lines.

  In FIG. 12B, in the process of dividing the image data by the division unit of the pixel line number Y set along the main scanning direction, the division unit of the pixel line number Y + 1 when the fraction D becomes 1 or more. The case of dividing by is shown.

  FIG. 13 is a diagram illustrating a case where the shift process based on the embodiment is compared with the conventional shift process.

13A and 13B are diagrams for explaining the conventional shift processing.
As shown in FIG. 13A, when the fraction is rounded down, the pixel line number Y is smaller than the desired value, and the number of divisions is increased.

  Therefore, when the division unit is shifted, since the number of divisions is large, distortion that tilts to the left side due to an increase in the shift amount occurs. Therefore, even when the aspect ratio is finally adjusted, image data in which distortion that tilts to the left occurs is formed.

  As shown in FIG. 13B, when the fraction is rounded up, the pixel line number Y becomes larger than a desired value, so that the number of divisions decreases.

  Therefore, when the division unit is shifted, since the number of divisions is small, distortion that tilts to the right side due to a reduction in the shift amount occurs. Therefore, even when the aspect ratio is finally adjusted, image data in which distortion tilting to the right occurs is formed.

On the other hand, FIG. 13C shows a shift process based on the embodiment.
When the fraction is integrated and the integrated value is equal to or greater than a predetermined value, the shift amount becomes an appropriate value by adjusting the number of division units, and distortion can be suppressed.

  Therefore, when the division unit is shifted, it is possible to avoid the occurrence of distortion by appropriately adjusting the number of divisions. Accordingly, tilt-corrected image data that does not cause distortion even when the aspect ratio is finally adjusted is formed.

FIG. 14 is a diagram illustrating the interpolation processing in the interpolation unit 54 based on the embodiment.
As shown in FIG. 14A, the shift is performed for each division unit.

  As shown in FIG. 14B, the continuity is interrupted by the shift for each division unit. Therefore, it becomes difficult to maintain continuous gradation.

FIG. 14C is a diagram for explaining gradation interpolation processing in the interpolation unit 54.
Specifically, the interpolation unit 54 executes a gradation interpolation process in which the gradation value of each pixel and the gradation value of the pixel adjacent to the shift direction are respectively weighted and added. Specifically, the weighting value is adjusted according to the distance from the rotation reference pixel included in the division unit to the target pixel.

  The rotation reference pixel in the division unit is the rotation reference pixel when the value by which the division unit shifts to the left increases. On the other hand, when the value by which the division unit is shifted to the right increases, the leftmost pixel included in the division unit becomes the rotation reference pixel.

FIG. 15 is a diagram illustrating adjustment of weighting in the interpolation unit 54 based on the embodiment.
As shown in FIG. 15, the weight is calculated from the distance between the center of the pixel and the center of gravity position.

The position of the center of gravity is set by the number of lines in each shift unit.
When the shift unit is 6 lines, the barycentric position of the line closer to the rotation reference pixel (right end) coincides with the center of the target pixel.

  In the case of the first line, the weight of the target pixel is 100% and the weight of the adjacent pixel is 0%. The weights of other pixels vary according to the distance from the rotation reference side.

  In the case of the second line, the weight of the target pixel is 100 × 1/6 = 16.7%, and the weight of the adjacent pixel is 100 × 5/6 = 83.3%.

  In the case of the third line, the weight of the target pixel is 100x2 / 6 = 33.3%, and the weight of the adjacent pixel is 100x4 / 6 = 66.7%.

  In the case of the fourth line, the weight of the target pixel is 100x3 / 6 = 50.0%, and the weight of the adjacent pixel is 100x3 / 6 = 50.0%.

  In the case of the fifth line, the weight of the target pixel is 100 × 4/6 = 66.7%, and the weight of the adjacent pixel is 100 × 2/6 = 33.3%.

  In the case of the sixth line, the weight of the target pixel is 100x5 / 6 = 83.3%, and the weight of the adjacent pixel is 100x1 / 6 = 16.7%.

A calculation formula for obtaining the gradation after interpolation is expressed by the following formula.
Gradation after interpolation = gradation of target pixel × weight of target pixel + gradation of adjacent pixel × weight of adjacent pixel Therefore, the weight during interpolation varies depending on the number of lines in shift units.

  It is possible to maintain continuous gradation by the gradation interpolation processing in the interpolation unit 54 and to generate image data without a sense of incongruity.

  Note that the gradation interpolation processing in the interpolation unit 54 described above is performed for each of the division unit shifted in the sub-scanning direction (first direction) and the division unit shifted in the main scanning direction (second direction). It may be executed, or only one of them may be executed.

  As mentioned above, although embodiment based on this invention was described, embodiment disclosed this time is an illustration and restrictive at no points. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Image reader, 3 Image formation part, 4 Paper feed part, 5 Output tray, 6 Automatic document conveyance part, 8 Document tray, 9 Conveyance unit, 10 Paper discharge tray, 11 Operation panel, 12 Operation part, 13 Display part, 14, 15, 16 Paper feed cassette tray, 17 Image reading module, 18 Motor, 19 Drive transmission unit, 20 Lamp, 21 Image sensor, 22 Original glass, 23 Glass, 27 Storage unit, 28 Control unit, 29 Image storage , 30 first inclination detection unit, 32 first shift unit, 34 first division unit number setting unit, 36 first line number calculation unit, 38 first line number setting unit, 39 first line number division unit, 40 1 line number adjustment unit, 42 second inclination detection unit, 44 second shift unit, 46 second division unit number setting unit, 48 second line number calculation unit, 50 second line number setting unit 51 second line number of divided portions, 52 second line number adjustment unit, 54 interpolation unit 56 resolution conversion unit.

Claims (10)

An image data acquisition unit for acquiring image data of a document;
A first inclination detector for detecting an inclination of the image data of the document with respect to a first direction;
A first division unit number setting unit for setting a division unit for dividing the image data of the document along a first direction based on the inclination detected by the first inclination detection unit;
A first shift unit that shifts the divided image data for each division unit in a first direction;
The first division unit number setting unit includes:
A first line number calculation unit that calculates the number of pixel lines arranged along a second direction in which image data indicating a boundary line of the document changes by one pixel in the first direction;
A first line number setting unit configured to round up or down the fraction of the calculation result of the first line number calculation unit and set it as a division unit of an integer pixel line number when a fraction occurs in the pixel line number;
The first line number for adjusting the integer pixel line number for the division unit when the fractional value of the pixel line number for the division unit is integrated according to the setting of the first line number setting unit and the integrated value exceeds a predetermined value. An image reading apparatus including an adjustment unit.   The image reading apparatus according to claim 1, wherein the line number adjusting unit resets the integrated value when an integer number of pixel lines in the division unit is adjusted. A second inclination detection unit that detects an inclination of image data of the document with respect to a second direction different from the first direction after the first shift unit shifts in the first direction;
A second division unit number setting unit for setting a division unit for dividing the image data of the document along a second direction based on the inclination detected by the second inclination detection unit;
The image reading apparatus according to claim 1, further comprising: a second shift unit that shifts the divided image data for each division unit in the second direction. The second division unit number setting unit includes:
A second line number calculation unit for calculating the number of pixel lines arranged along a first direction in which image data indicating a boundary line of the shifted document changes by one pixel in the second direction;
A second line number setting unit configured to round up or down the fraction of the calculation result of the second line number calculation unit and set it as a division unit of an integer pixel line number when a fraction occurs in the pixel line number;
A second line number for adjusting the integer pixel line number for the division unit when the fractional value of the pixel line number for the division unit is integrated according to the setting of the second line number setting unit and the integrated value exceeds a predetermined value. The image reading apparatus according to claim 3, further comprising an adjustment unit.   The image reading apparatus according to claim 4, wherein the first direction is a sub-scanning direction and the second direction is a main scanning direction.   The image reading apparatus according to claim 1, further comprising: an interpolation unit that executes a gradation interpolation process that weights and adds the gradation value of each pixel and the gradation value of a pixel adjacent to the first direction.   The image reading apparatus according to claim 6, wherein the interpolation unit adjusts a weighting value in accordance with a distance from a reference pixel included in a division unit to a target pixel.   The image reading apparatus according to claim 3, further comprising: an interpolation unit that executes a gradation interpolation process that weights and adds the gradation value of each pixel and the gradation value of a pixel adjacent to the second direction.   The image reading apparatus according to claim 8, wherein the interpolation unit adjusts a weighting value according to a distance from a reference pixel included in a division unit to a target pixel.   The image reading apparatus according to claim 1, further comprising a resolution conversion unit that adjusts an aspect ratio of the shifted image data of the document.

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