JP5968263B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus.

  When an image processing apparatus such as a scanner scans an image, if a document on the platen glass is placed in a tilted state or a document skew occurs during document feeding by an automatic document feeder (ADF), The read original image is tilted.

  In a first apparatus, the leading end of a document to be transported is detected by two sensors, and used for transporting from the detection of the leading end by one sensor to the detection of the leading end by the other sensor. The number of steps of the stepping motor is measured, and the inclination of the document is detected based on the number of steps (see, for example, Patent Document 1).

  In another second apparatus, the average value of the peripheral pixel values in the range of 5 × 5 pixels is calculated as reference data for each pixel in the entire width in the main scanning direction in the reading data of the backing portion of the document, and the main data is calculated. For each pixel position in the scanning direction, the reference data and the image data are compared to detect the edges of the four sides of the document, and tilt correction is performed based on the edge information (see, for example, Patent Document 2).

JP-A-5-176133 JP 2005-273033 A

  However, since it is necessary to install a sensor in the first device, the cost of the device increases. Further, in the second apparatus, it is necessary to provide a line memory that holds a pixel value (for example, an 8-bit value indicating gradation) for each pixel of the full width in the main scanning direction, which increases the cost of the apparatus.

  Further, when obtaining the average value of the pixel values in the peripheral area of 5 × 5 pixels, it is necessary to further provide line memories for two lines before and after the line to which the pixel of interest belongs, which further increases the cost of the apparatus.

  SUMMARY An advantage of some aspects of the invention is that it provides an image processing apparatus that detects the inclination of an original image at low cost.

The image processing apparatus according to the present invention includes a plurality of divided blocks obtained by dividing one or a plurality of lines obtained in the main scanning direction by reading a background portion located on the rear side of the document as viewed from the optical system when the document image is read. Based on pixel values of a plurality of pixels, a reference data generation unit that generates a plurality of reference values corresponding to each of the plurality of divided blocks as reference data, and a line along the sub-scanning direction are selected and selected An edge in the sub-scanning direction of the document image is detected based on the read pixel value for a plurality of predetermined pixel positions in the main scanning direction in the line and the reference value corresponding to the divided block to which the pixel position belongs. A document image edge detection unit configured to detect the document image based on edges in the sub-scanning direction of the document image detected for the predetermined plurality of pixel positions. Comprising an image attribute specifying unit for detecting gas, and a streak region specifying unit for specifying a streak area in the main scanning direction. The document image edge detection unit, for each of a plurality of predetermined lines in the sub-scanning direction, the read pixel value of each pixel position in the main scanning direction in the line and the reference corresponding to the divided block to which the pixel position belongs. An edge in the main scanning direction of the document image is detected based on the value, and the image attribute specifying unit is configured to detect an edge in the sub scanning direction of the document image or an edge in the sub scanning direction of the document image and the document. The inclination of the original image is detected based on the edge of the image in the main scanning direction. Further, the document image edge detection unit, outside the streak area, based on the read pixel value of each pixel position in the line and the reference value corresponding to the divided block to which the pixel position belongs, The main scanning direction of the original image is detected based on the read pixel value at each pixel position in the line and the read pixel value at the adjacent pixel position in the line in the stripe area. Detect edge in direction.

  According to the present invention, an image processing apparatus that detects the inclination of a document image can be obtained at low cost.

FIG. 1 is a side view showing an internal configuration of an image processing apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image processing apparatus according to the embodiment of the present invention. FIG. 3 is a diagram for explaining detection of divided blocks and leading edge and trailing edge of a document image in the embodiment of the present invention. FIG. 4 is a diagram for explaining detection of the left end edge and the right end edge of the document image in the embodiment of the present invention. FIG. 5 is a diagram illustrating an example of a streak area. FIG. 6 is a flowchart for explaining the operation of the image processing apparatus according to the embodiment of the present invention.

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

  FIG. 1 is a side view showing an internal configuration of an image processing apparatus according to an embodiment of the present invention. The image processing apparatus shown in FIG. 1 is an apparatus such as a scanner, a copier, a facsimile machine, or a multifunction machine.

  The image processing apparatus shown in FIG. 1 includes contact glasses 1 a and 1 b, carriages 2 and 3, an imaging lens 4, an image sensor 5, a white reference patch 6, and a document cover 7.

  The contact glass 1 a is installed on the upper surface of the image processing apparatus main body, and is used to place an original when reading an image without using an automatic document feeder (ADF) of the original cover 7.

  Further, the contact glass 1b is installed on the upper surface of the image processing apparatus main body, and when the image is read while the document is automatically conveyed by the ADF of the document cover 7, the document passes therethrough.

  The ADF described above passes the document so as to pass over the contact glass 1b, and the image reading unit 21 reads the image of the document passing over the contact glass 1b.

  In the image reading unit 21, the carriage 2 is installed so as to be movable in the sub-scanning direction by a drive source (not shown). The carriage 2 has a light source 11 and a mirror 12. The light source 11 is arranged along the main scanning direction, and emits light with, for example, a plurality of light emitting diodes arranged. The light emitted from the light source 11 is reflected by an original placed on the contact glass 1a, an original passing through the contact glass 1b, or the like according to the position of the carriage 2. The mirror 12 reflects reflected light from a document or the like. When the image of a document is read using the ADF of the document cover 7, the carriage 2 is fixedly disposed below the contact glass 1b.

  The carriage 3 is installed so as to be movable in the sub-scanning direction together with the carriage 2 by a drive source (not shown). The carriage 3 has mirrors 13 and 14. The mirrors 13 and 14 reflect the light from the mirror 12 of the carriage 2 and emit it along the sub-scanning direction.

  The imaging lens 4 focuses the light from the mirror 14 on the image sensor 5. The image sensor 5 is a one-dimensional image sensor having light receiving elements with a predetermined number of pixels arranged in the main scanning direction, and outputs an electrical signal corresponding to the amount of light received for the pixels with the number of pixels for each line. For example, a CCD (Charge Coupled Device) is used as the image sensor 5.

  The white reference patch 6 is a plate-like member that is disposed on the top surface inside the apparatus and is used to acquire white reference data.

  The document cover 7 is a member that can be brought into surface contact with the contact glass 1a and is rotatably mounted. The document cover 7 closely contacts the document with the contact glass 1a, and ambient light is incident on the inside of the apparatus from the contact glass 1 at the time of image reading. To prevent. Further, the document cover 7 has an ADF, and the documents placed on the document tray 7a are conveyed one by one by the conveyance roller 7b and passed over the contact glass 1b.

  FIG. 2 is a block diagram showing an electrical configuration of the image processing apparatus according to the embodiment of the present invention. FIG. 3 is a diagram for explaining detection of divided blocks and leading edge and trailing edge of a document image in the embodiment of the present invention. FIG. 4 is a diagram for explaining detection of the left end edge and the right end edge of the document image in the embodiment of the present invention. FIG. 5 is a diagram illustrating an example of a streak area.

  As shown in FIG. 2, image data of a read image including a document image obtained by the image reading unit 21 is supplied to the image processing unit 22.

  The image processing unit 22 includes a reference data generation unit 31, a streak area specifying unit 32, a document image edge detecting unit 33, an image attribute specifying unit 34, and a document image processing unit 35. The image processing unit 22 may be realized as hardware such as an ASIC (Application Specific Integrated Circuit) or may be realized as software by executing a program on a computer.

  The reference data generation unit 31 applies each of the plurality of divided blocks based on the pixel values of the plurality of pixels in the plurality of divided blocks obtained by dividing one or more lines obtained by reading the background part in the main scanning direction. A plurality of corresponding reference values are generated as reference data and stored in a memory (not shown). For example, as shown in FIG. 3, when 16 divided blocks having Lref line widths in the sub-scanning direction are set, 16 reference values are held in the memory.

  The background portion is a portion located on the rear side of the original when viewed from the optical system (contact glass 1a, 1b, etc. in FIG. 1) when reading the original image, and the original cover 7 presses the original on the contact glass 1a against the contact glass 1a. And a document transport guide, a document transport roller, and the like above the contact glass 1b.

  The above-mentioned reference value is the mode value of the pixel values in the divided block corresponding to the reference value when the divided block is one line, and corresponds to the reference value when the divided block is a plurality of lines. Alternatively, the average value of the mode values of the pixel values in each line in the divided block may be set. By doing so, the above-mentioned reference value can be obtained without requiring a lot of line memory. For example, the reference data generation unit 31 generates a histogram of pixel values (density values) and specifies the mode value from the histogram.

  In addition, when the divided block has one line, the above-described reference value is an average value of pixel values in the divided block corresponding to the reference value. When the divided block has a plurality of lines, the reference value corresponds to the reference value. You may make it be the average value about the average value of the pixel value in each line in a division block. By doing so, the above-mentioned reference value can be obtained without requiring a lot of line memory.

  In this way, since one reference value is determined for one divided block having a long width in the main scanning direction, variations in reading luminance in the main scanning direction due to characteristics of the light source 11, the image sensor 5, and the like. The influence is suppressed and the influence of noise is also suppressed.

  The streak area specifying unit 32 detects streaks extending in the sub-scanning direction in the read image due to dust attached to the contact glass 1b, and specifies streak areas in the main scanning direction of the streaks.

  The document image edge detection unit 33 selects lines along the sub-scanning direction, and reads pixel values (pixel values obtained by the image reading unit 21) for a plurality of predetermined pixel positions in the selected line. Based on the reference value corresponding to the divided block to which the pixel position belongs, the edge in the sub-scanning direction of the document image is detected.

  In this embodiment, the document image edge detection unit 33 for each of a plurality of predetermined lines in the sub-scanning direction, the reference pixel value corresponding to the read pixel value of each pixel position in the line and the divided block to which the pixel position belongs. Based on the value, an edge in the main scanning direction of the document image is detected.

  In this embodiment, the document image edge detection unit 33 detects the leading edge and trailing edge of the document image in the sub-scanning direction, and detects the left edge and right edge of the document image in the main scanning direction.

  For example, as shown in FIG. 3, for each of predetermined pixel positions P1 to P4, leading edge positions (that is, lines where leading edges exist) LS1 to LS4 and trailing edge positions LE1 to LE4 in the sub-scanning direction are detected. The

  For example, as shown in FIG. 4, for each of the predetermined lines L1 to L4, left end edge positions (that is, pixel positions where the left end edges exist) PL1 to PL4 and right end edge positions PR1 to PR4 in the main scanning direction are detected. Is done.

  Specifically, when the color of the background portion is white, the document image edge detection unit 33 determines that the value obtained by subtracting the read pixel value from the reference value corresponding to the divided block for the selected line is a predetermined threshold value. In the case of the first line as described above, it is determined that there is a leading edge in the sub-scanning direction of the document image at the target pixel position of the selected line.

  In addition, when the color of the background part is a color other than white, the document image edge detection unit 33 subtracts the read pixel value from the reference value corresponding to the divided block at the target pixel position in the selected line. If the absolute value of the value obtained in this way is the first line that is equal to or greater than a predetermined threshold value, it is determined that the leading edge in the sub-scanning direction of the document image exists at the target pixel position of the selected line.

  Further, when the background part color is white, the document image edge detection unit 33 obtains a value obtained by subtracting the read pixel value from the reference value corresponding to the divided block after the leading edge is detected. If it is the last line that is equal to or greater than a predetermined threshold, it is determined that there is a trailing edge in the sub-scanning direction of the document image at the target pixel position of the selected line.

  In addition, when the color of the background part is a color other than white, the document image edge detection unit 33 subtracts the read pixel value from the reference value corresponding to the divided block at the target pixel position in the selected line. If the absolute value of the values obtained in this way is the last line that has changed below a predetermined threshold value, it is determined that there is a trailing edge in the sub-scanning direction of the document image at the target pixel position of the selected line.

  More specifically, when the color of the background portion is white, the document image edge detection unit 33 obtains the target pixel position in the line by subtracting the read pixel value from the reference value corresponding to the divided block. When the value is the first pixel position whose value is equal to or greater than a predetermined threshold, it is determined that the left edge of the original image in the main scanning direction is present at the target pixel position of the line.

  In addition, when the color of the background part is a color other than white, the document image edge detection unit 33 sets the value of the target pixel position in the line to a value obtained by subtracting the read pixel value from the reference value corresponding to the divided block. If it is the first pixel position whose absolute value is equal to or greater than a predetermined threshold, it is determined that the left edge in the main scanning direction of the document image is present at the target pixel position of the line.

  More specifically, when the color of the background portion is white, the document image edge detection unit 33 obtains the target pixel position in the line by subtracting the read pixel value from the reference value corresponding to the divided block. When the value is the last pixel position whose value is equal to or greater than a predetermined threshold value, it is determined that the right edge in the main scanning direction of the document image exists at the target pixel position of the line.

  In addition, when the color of the background part is a color other than white, the document image edge detection unit 33 sets the value of the target pixel position in the line to a value obtained by subtracting the read pixel value from the reference value corresponding to the divided block. When the absolute value is the last pixel position that has changed below a predetermined threshold, it is determined that the right edge in the main scanning direction of the document image exists at the target pixel position of the line.

  Further, as described above, the document image edge detection unit 33 outside the streak area, based on the read pixel value of each pixel position in the line and the reference value corresponding to the divided block to which the pixel position belongs, as described above. The edge in the main scanning direction of the original image is detected based on the read pixel value of each pixel position in the line and the read pixel value of the adjacent pixel position of the pixel position in the line area. Is detected.

  As for the left edge, in the streak area, the left edge in the main scanning direction of the document image is determined based on the read pixel value at each pixel position in the line and the read pixel value at the pixel position adjacent to the left side of the pixel position. Detect edges. Specifically, when the value obtained by subtracting the read pixel value of the pixel position adjacent to the left side of the pixel position from the read pixel value of the target pixel position in the line is equal to or greater than a predetermined threshold value, It is determined that there is a left edge in the main scanning direction of the document image.

  The right edge in the main scanning direction of the document image in the streak area is based on the read pixel value at each pixel position in the line and the read pixel value at the pixel position adjacent to the right side of the pixel position. Detect edges. Specifically, when the value obtained by subtracting the read pixel value of the pixel position adjacent to the right side of the pixel position from the read pixel value of the target pixel position in the line is equal to or greater than a predetermined threshold value, the target pixel position It is determined that the right edge of the document image in the main scanning direction exists.

  For example, in the example shown in FIG. 5, for the lines L1 and L2, the right end edge and the left end edge are detected in the streak area, and for the lines L3 and L4, the right end edge and the left end edge are detected outside the streak area. The

  The streak area specifying unit 32 generates mask data for switching edge detection in the streak area as described above. The mask data is 1-bit data per pixel corresponding to the entire width, and is data indicating whether the line area is inside or outside the line area. The document image edge detection unit 33 refers to the mask data to determine whether or not the target pixel position is within the streak area.

  The streak area specifying unit 32 generates mask data so that pixels satisfying one condition selected from the following four conditions are within the streak area, and other pixels are out of the streak area.

  Condition # 1: Pixels arranged in the sub-scanning direction within the range of lines used for reference data generation with respect to the target pixel position in the main scanning direction (the pixel position where it should be specified whether or not it is within the streak area) Among them, at least one of the R value, G value, and B value of the read pixel value (RGB value) of at least one pixel is equal to or less than a predetermined threshold value.

  Condition # 2: At the target pixel position in the main scanning direction, the read pixel value (RGB value) of at least one pixel among the pixels arranged along the sub-scanning direction within the range of the line used for generating the reference data ) All of R value, G value and B value are below a predetermined threshold.

  Condition # 3: R value of read pixel values (RGB values) of all pixels arranged along the sub-scanning direction within the range of lines used for generating reference data for the target pixel position in the main scanning direction, G At least one of the value and the B value is less than or equal to a predetermined threshold value.

  Condition # 4: R value of read pixel values (RGB values) of all the pixels arranged along the sub-scanning direction within the range of lines used for generating reference data for the target pixel position in the main scanning direction, G All of the values and B values are below a predetermined threshold.

  Returning to FIG. 2, the image attribute specifying unit 34 detects the inclination of the document image based on the edges in the sub-scanning direction of the document image detected for the predetermined plurality of pixel positions in the main scanning direction.

  Further, the image attribute specifying unit 34 may detect the inclination of the document image based on the edge of the document image in the sub-scanning direction and the edge of the document image in the main scanning direction.

  In this embodiment, the image attribute specifying unit 34 specifies the position of the document image based on the leading edge and the trailing edge of the document image in the sub-scanning direction and the left edge and right edge of the document image in the main scanning direction. .

  The manuscript image processing unit 35 rotates the manuscript image so that the manuscript image stands upright according to the detected inclination angle, and the manuscript image has, for example, a predetermined reading size according to the position of the manuscript image. The document image is moved so as to be positioned at the center in the image.

  Next, the operation of the image processing apparatus will be described. FIG. 6 is a flowchart for explaining the operation of the image processing apparatus according to the embodiment of the present invention.

  The image processing unit 22 acquires the read pixel value of each line line by line from the top of the image read by the image reading unit 21.

  First, the reference data generation unit 31 generates reference data as described above (step S1).

  Thereafter, the document image edge detection unit 32 sequentially selects a target line along the sub-scanning direction in the read image, and at the predetermined pixel positions P1 to P4 in the target line, the leading edge or the rear edge in the sub-scanning direction. Whether or not the end edge exists is determined as described above (step S2).

  Further, when the target line is the predetermined lines L1 to L4, the document image edge detection unit 32 determines whether or not the left end edge and the right end edge in the main scanning direction exist in the target line as described above. (Step S3).

  When the leading edge, the trailing edge, the left edge, and the right edge are detected by the document image edge detection unit 32, the image attribute specifying unit 34 determines the position, size, and inclination angle of the document image in the read image. Identification is made based on the positions of the leading edge, the trailing edge, the left edge, and the right edge (step S4).

  The document image processing unit 35 determines whether or not editing (rotation, movement, etc.) of the document image is necessary based on the position, size, and tilt angle of the document image in the read image (step S5). If it is determined that editing is necessary, the necessary editing is performed on the document image (step S6).

  As described above, according to the above embodiment, the reference data generation unit 31 includes a plurality of pixels in a plurality of divided blocks obtained by dividing one or a plurality of lines obtained by reading a background part in the main scanning direction. Based on the pixel value, a plurality of reference values corresponding to each of the plurality of divided blocks are generated as reference data, and the document image edge detection unit 33 selects a line along the sub-scanning direction, and the selected line An edge in the sub-scanning direction of the document image is detected based on a read pixel value for a plurality of predetermined pixel positions in the image and a reference value corresponding to the divided block to which the pixel position belongs. Then, the image attribute specifying unit 34 detects the inclination of the document image based on the edge in the sub-scanning direction of the document image detected for a plurality of predetermined pixel positions.

  This eliminates the need to store pixel values for the entire width in the line memory as reference data, thereby reducing the cost of the apparatus.

  The above-described embodiments are preferred examples of the present invention, but the present invention is not limited to these, and various modifications and changes can be made without departing from the scope of the present invention. is there.

  For example, in the above embodiment, when only the inclination of the document image needs to be detected, the edge of the document image in the sub-scanning direction may be detected and the edge of the document image in the main scanning direction may not be detected.

  The present invention can be applied to, for example, a scanner, a copier, and a multifunction machine.

31 Reference data generation unit 32 Line area specifying unit 33 Document image edge detecting unit 34 Image attribute specifying unit 35 Document image processing unit

Claims (4)

Based on pixel values of a plurality of pixels in a plurality of divided blocks obtained by dividing one or a plurality of lines in the main scanning direction obtained by reading a background portion located on the rear side of the document as viewed from the optical system when reading a document image. A reference data generation unit that generates a plurality of reference values corresponding to each of the plurality of divided blocks as reference data;
A line is selected along the sub-scanning direction, and the read pixel value for a plurality of predetermined pixel positions in the main scanning direction in the selected line and the reference value corresponding to the divided block to which the pixel position belongs are selected. A document image edge detection unit for detecting an edge of the document image in the sub-scanning direction,
An image attribute specifying unit that detects an inclination of the document image based on edges in the sub-scanning direction of the document image detected for the predetermined plurality of pixel positions;
A streak area specifying unit for specifying a streak area in the main scanning direction;
Equipped with a,
The document image edge detection unit, for each of a plurality of predetermined lines in the sub-scanning direction, the read pixel value of each pixel position in the main scanning direction in the line and the reference corresponding to the divided block to which the pixel position belongs. And an edge in the main scanning direction of the document image based on the value,
The image attribute specifying unit detects an inclination of the document image based on an edge of the document image in a sub-scanning direction, or an edge of the document image in a sub-scanning direction and an edge of the document image in a main scanning direction;
The document image edge detection unit, outside the streak area, based on the read pixel value of each pixel position in the line and the reference value corresponding to the divided block to which the pixel position belongs, An edge in the scanning direction is detected, and in the stripe area, the original image in the main scanning direction of the document image is detected based on the read pixel value of each pixel position in the line and the read pixel value of the adjacent pixel position of the pixel position. Detecting edges,
An image processing apparatus. A document image processing unit;
The document image edge detection unit detects a leading edge and a trailing edge in a sub-scanning direction of the document image, and detects a left edge and a right edge in a main scanning direction of the document image;
The image attribute specifying unit specifies the position of the document image based on a leading edge and a trailing edge in a sub-scanning direction of the document image and a left edge and a right edge in a main scanning direction of the document image;
The document image processing unit rotates the document image according to the detected inclination angle and moves the document image according to the position of the document image;
The image processing apparatus according to claim 1 . The reference value is a mode value of pixel values in the divided block corresponding to the reference value when the divided block is one line, and corresponds to the reference value when the divided block is a plurality of lines. average value is the fact the image processing apparatus according to claim 1 Symbol mounting characterized for most frequent value of the pixel values in each line of the divided block to be. The reference value is an average value of pixel values in the divided block corresponding to the reference value when the divided block is one line, and corresponds to the reference value when the divided block is a plurality of lines. average value is the fact the image processing apparatus according to claim 1 Symbol mounting characterized for the average value of pixel values in each line of the divided blocks.

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