JP5901560B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus.

  For example, in an image reading apparatus having an automatic document feeder, if dust adheres to contact glass or the like, the light to be incident on the document is blocked by the dust, so that the document image output from the image reading apparatus is not related to the document. Black streaks and other streaks occur.

  In a certain image processing apparatus, the pixel value in the black stripe is interpolated with the values of the peripheral pixels of such a black stripe to remove the black stripe in the image (see, for example, Patent Documents 1 and 2).

JP 2007-142671 A JP 2011-023920 A

  When the black streak is removed by interpolation as described above, as the black streak becomes wider, there is a higher possibility that the image quality of the portion where the black streak has deteriorated. For example, when the original image is a repetitive image such as a halftone dot, if the width of the black stripe becomes wide, the regularity of the halftone dot is lost at the location where the black stripe is present, so the black stripe is removed. The image quality will be low and will be noticeable.

  Therefore, it is preferable not to perform the interpolation process for black stripe removal except at the black stripe portion. However, in the above-described image processing apparatus, once black streaks are detected, interpolation processing is continuously performed at the same location where black streaks are detected. Even if the position of the line moves or becomes thicker, interpolation processing is continuously performed on the same part, interpolation processing is performed on parts other than black streaks, and interpolation processing is performed on black streak parts. There is a possibility that image quality will be degraded.

  The present invention has been made in view of the above problems, and an object of the present invention is to obtain an image processing apparatus that reduces image quality degradation caused by streak removal.

An image processing apparatus according to the present invention detects a streak extending in a sub-scanning direction in a document image and specifies a streak range in the main scanning direction of the streak, and removes the streak in the document image. A correction processing unit that corrects a pixel value in the streak range along the sub-scanning direction, and enlargement, reduction, and movement of the streak based on the value of the pixel in the streak range and the value of the pixel around the streak range When detecting at least one of the above, a streak range variation detection for changing the streak range in which the pixel value is corrected by the correction processing unit according to at least one of expansion, reduction, and movement of the detected streak A part. Further, the streak range variation detection unit is a value at which a pixel value of a number of pixels equal to or larger than a predetermined threshold continuous in the sub-scanning direction at a pixel position adjacent to one end of the streak range is determined as the streak. In some cases, the streak range is enlarged, and the pixel values of a number of pixels equal to or larger than a predetermined threshold that are continuous along the sub-scanning direction at the pixel position at one end of the streak range are not the values determined as the streak The streak range is reduced, or the streak range variation detection unit performs sub-scanning at all pixel positions in the peripheral range in a peripheral range from a certain pixel position to one end of the streak range in the main scanning direction. When the pixel values of a number of pixels that are equal to or greater than a predetermined threshold continuous along the direction are values determined as the streaks, the streak range is expanded so as to include the entire peripheral range. That.

  According to the present invention, it is possible to obtain an image processing apparatus that reduces the deterioration in image quality caused by streak removal.

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 the streak detection by the streak detection unit 31 in FIG. FIG. 4 is a flowchart for explaining the operation of the streak range variation detector 33 in FIG. 2 (1/2). FIG. 5 is a flowchart for explaining the operation of the streak range variation detector 33 in FIG. 2 (2/2). FIG. 6 is a diagram illustrating an example of streak movement in the main scanning direction. FIG. 7 is a diagram illustrating an example of a streak range to be corrected when the streak moves as illustrated in FIG. 6. FIG. 8 is a diagram illustrating an example of the streak range to be corrected when the streak range upper limit width is set to be larger than the width of the streak range specified by the streak detection unit 31.

  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.

  As shown in FIG. 2, the image data of the original image obtained by the image reading unit 21 is supplied to the line correction unit 22.

  The streak correction unit 22 includes a streak detection unit 31, a correction processing unit 32, a streak range variation detection unit 33, and a storage unit 34. The streak correction 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 streak detection unit 31 detects a streak extending in the sub-scanning direction in the document image and specifies a streak range in the main scanning direction of the streak.

  FIG. 3 is a diagram for explaining the streak detection by the streak detection unit 31 in FIG.

  For example, the streak detection unit 31 specifies a range in which the pixel value is equal to or less than a predetermined threshold among a plurality of predetermined lines L1 to LN in the document image, and is common to the lines L1 to LN among the ranges. The part is detected as a streak range.

  In addition, the streak detection unit 31 generates streak range data that designates a streak range in the main scanning direction for each detected one or more streaks. For example, the stripe range data has a pixel position PS at the start position of the stripe range in the main scanning direction and a width W of the stripe range.

  The correction processing unit 32 corrects the pixel values in the streak range along the sub-scanning direction in order to remove the streaks in the document image. For example, the correction processing unit 32 changes the pixel value in the stripe range to the pixel value obtained by interpolation based on the pixel values around the stripe range.

  The correction processing unit 32 sequentially selects one line of the document image as a target line, and corrects the pixel value in one or a plurality of line ranges specified by the line range data in the target line.

  The streak range variation detection unit 33 enlarges or reduces the detected streak when detecting at least one of the enlargement, reduction, and movement of the streak based on the values of the pixels in the streak range and the pixels around the streak range. In accordance with at least one of the movement, the stripe range in which the pixel value is corrected by the correction processing unit 32 (that is, the above-described stripe range data) is changed.

  In this embodiment, the streak range variation detection unit 33 detects the streak range pixel values of pixels equal to or larger than a predetermined threshold (for example, 4) continuous along the sub-scanning direction at the pixel position adjacent to one end of the streak range. When the value is determined to be a value, the streak range is expanded, and the pixel values of a number of pixels equal to or larger than a predetermined threshold continuous in the sub-scanning direction at the pixel position at one end of the streak range are determined to be streak If not, reduce the stripe range.

  The “value determined as a streak” is a color value of a streak detected by the streak detection unit 31. Hereinafter, the color of “value determined to be a streak” is referred to as a streak color. For example, the streak detection unit 31 identifies a range in which the pixel value is equal to or less than a predetermined threshold among a plurality of predetermined lines L1 to LN in the document image, and is common to those lines L1 to LN in the range. When a portion is detected as a streak range, the “value determined to be a streak” is a value equal to or less than the predetermined threshold.

  In this embodiment, the streak range variation detection unit 33 sets a streak range upper limit width corresponding to the width W of the streak range specified by the streak detection unit 31, and the pixel position adjacent to one end of the streak range. In the case where the pixel values of the number of pixels equal to or larger than the above-mentioned threshold value continuous along the sub-scanning direction are values determined as streaks, when the width of the expanded streak range does not exceed the streak range upper limit width, When the streak range is expanded and the width of the expanded streak range exceeds the streak range upper limit width, the streak range is not expanded.

  Further, in this embodiment, the streak range variation detection unit 33 is arranged along the sub-scanning direction at all pixel positions in the peripheral range from a certain pixel position in the main scanning direction to one end of the streak range. When the pixel values of the number of pixels equal to or larger than the above-described threshold value are values determined to be streaks, the streak range is expanded so as to include all the peripheral ranges.

  For example, one end of the current streak range is the pixel position X6, and in the peripheral range from the pixel position X7 to the pixel position X8, at the pixel position X7, streak-colored pixels continue in the sub-scanning direction for a predetermined threshold number or more. When the streak color pixels continue in the sub-scanning direction at the pixel position X8 for a predetermined threshold number or more, the streak range is expanded to the pixel position X8.

  In this case, at the pixel position X7, streak pixels continue in the sub-scanning direction for the predetermined threshold number or more, but at pixel position X8, the streak-colored pixels exceed the predetermined threshold number in the sub-scanning direction. If not continuous, the streak range is expanded to the pixel position X7.

  Further, in this case, streak pixels are continuous in the sub-scanning direction at the pixel position X8 by a predetermined threshold value or more. However, at pixel position X7, the streak-colored pixels have a predetermined threshold value in the sub-scanning direction. If the number is not continuous, the streak area is not expanded.

  The storage unit 34 is a storage device such as a memory that holds the above-described stripe range data. The streak detector 31 writes streak range data specifying one or a plurality of streak ranges in the storage unit 34. The correction processing unit 32 reads the line range data stored in the storage unit 34 for each line, specifies the line range, and performs the above-described correction process on the line range. The streak range variation detection unit 33 reads out the streak range data stored in the storage unit 34, identifies the current streak range, and performs at least the expansion, reduction, and movement of the streak with respect to the current streak range. Detect one.

  The streak detection unit 31 detects streaks in the first page of the document image, and the correction processing unit 32 performs correction processing on the second page and subsequent document images and the streak range variation detection unit 33 monitors the streak range. Alternatively, the streak detection unit 31 may detect a streak in a predetermined portion of the original image of the first page, and the correction processing by the correction processing unit 32 and the streak range may be performed on the original image after the predetermined portion. You may make it monitor the stripe range by the fluctuation | variation detection part 33. FIG.

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

  4 and 5 are flowcharts for explaining the operation of the streak range variation detector 33 in FIG.

  FIG. 6 is a diagram illustrating an example of streak movement in the main scanning direction. Note that hatched pixels in the figure are streak-colored pixels, and whitened pixels are pixels that are not streaked. In the example illustrated in FIG. 6, the line is from the pixel position X1 to the pixel position X6 in the main scanning direction up to the line Y6, but the line is from the pixel position X5 to the pixel position between the line Y7 and the line Y14. It has moved to the range up to X10.

  When dust or the like adheres to the contact glass 1b and a streak occurs in the original image, the streak detection unit 31 detects the streak, and the pixel value within the streak range is corrected by the correction processing unit 32.

  When the correction processing by the correction processing unit 32 is started, the streak range variation detection unit 33 first acquires streak range data from the storage unit 34 (step S1), and one or a plurality of streak ranges (that is, streak ranges). The initial value of the start position and width is specified, and the following processing is performed for each stripe range (that is, each stripe).

  The streak range variation detection unit 33 specifies a streak expansion range from each end of the streak range in the target line, with the line for which the correction processing has been started as the target line (step S2).

  The “streaked range” is a range of pixels having a streak color continuously from the end of the streak range. For example, when the streak range is from pixel position X1 to pixel position X6, the pixels at pixel position X7 and pixel position X8 in a certain line have a streak color, and the pixel at pixel position X9 does not have a streak color In this case, the “line expansion range” of this line is from the pixel position X7 to the pixel position X8.

  The streak range variation detection unit 33 increases the value of the enlargement counter data corresponding to each pixel position in the streak enlargement range by 1 (step S3). When there is no enlarged counter data corresponding to the pixel position, the enlarged counter data is generated and the value is set to 1. Further, the streak range variation detection unit 33 resets the value of the enlargement counter data corresponding to each pixel position outside the streak enlargement range to zero (step S4).

  If there is no streak enlargement range, the streak range variation detection unit 33 resets the values of the enlargement counter data corresponding to all pixel positions to zero.

  Further, the streak range variation detection unit 33 specifies a streak reduction range from each end of the streak range in the target line (step S5).

  The “streaks reduction range” is a range of pixels that do not have a streak color continuously from the end of the streak range to the inside. For example, when the streak range is from the pixel position X1 to the pixel position X6, when the pixels at the pixel position X1 and the pixel position X2 in a certain line do not have a streak color, and the pixel at the pixel position X3 has a streak color, The “line reduction range” of this line is from the pixel position X1 to the pixel position X2.

  The streak range variation detection unit 33 increases the value of the reduction counter data corresponding to each pixel position in the streak reduction range by 1 (step S6). When there is no reduction counter data corresponding to the pixel position, the reduction counter data is generated and the value is set to 1. Further, the streak range variation detection unit 33 resets the value of the reduction counter data corresponding to each pixel position outside the streak reduction range to zero (step S7).

  Then, the streak range variation detection unit 33 determines whether there is a pixel position where the value of the reduction counter data is equal to or greater than a predetermined threshold (for example, 4) (step S8).

  When there is a pixel position where the value of the reduction counter data is equal to or greater than the predetermined threshold, the streak range variation detection unit 33 reduces the streak range so as to exclude the pixel position from the current streak range (step S9). At this time, the streak range variation detection unit 33 changes the width W of the streak range data stored in the storage unit 34, or the width W and the start position PS.

  When there is no pixel position where the value of the reduction counter data is equal to or greater than the predetermined threshold, the process of step S9 is not performed.

  Next, the streak range variation detection unit 33 determines whether there is a pixel position where the value of the enlarged counter data is equal to or greater than the above-described threshold (for example, 4) (step S10).

  When there is a pixel position where the value of the enlarged counter data is equal to or greater than the threshold, the streak range variation detection unit 33 determines whether the pixel position is within the streak range upper limit width (step S11).

  For example, when the width of the streak range specified by the streak detection unit 31 is 6 (6 pixels), the streak range upper limit width is set to 7, and the current pixel position X1 to the pixel position X6, If the pixel position where the value of the enlargement counter data is equal to or greater than the threshold is X7, it is within the range of the stripe range upper limit width, and if it is X8, it is outside the range of the stripe range upper limit width.

  For example, when the width of the streak range specified by the streak detection unit 31 is 6 (6 pixels), the streak range upper limit width is set to 7, and the current pixel position X2 to the pixel position X6 If the pixel position where the value of the enlarged counter data is equal to or larger than the threshold is X7 or X8, the pixel range is within the range of the stripe range upper limit width, and if it is X9, it is outside the range of the line range upper limit width.

  When the pixel position where the value of the enlarged counter data is equal to or greater than the threshold value is within the range of the streak range upper limit width, the streak range variation detection unit 33 sets the streak range so as to add the pixel position to the current streak range. Enlarge (step S12). At this time, the streak range variation detection unit 33 changes the width W of the streak range data stored in the storage unit 34, or the width W and the start position PS.

  On the other hand, when there is no pixel position where the value of the enlargement counter data is equal to or greater than the above threshold, the streak range is not enlarged. Further, when the pixel position where the value of the enlargement counter data is equal to or greater than the threshold value is outside the range of the streak range upper limit, the streak range is not enlarged for the pixel position.

  Then, the streak range variation detection unit 33 determines whether or not there is a next line (step S13). If there is a next line, the line is set as a target line (step S14), and the processing after step S2 is performed. If there is no next line, this process is terminated.

  Here, a specific example will be described.

  Specific Example 1

  FIG. 7 is a diagram illustrating an example of a streak range to be corrected when the streak moves as illustrated in FIG. 6. In the case shown in FIG. 7, the threshold value is set to 4. The numerical value in the hatched pixel indicates the value of the above-described enlarged counter data, and the numerical value in the whitened pixel indicates the value of the above-described reduced counter data.

  In the example shown in FIG. 7, the streak range is expanded and reduced at the lines Y11, Y13, Y16, and Y18. As a result, the streak range gradually increases from the range of X1 to X6 to the range of X5 to X10. Has moved.

  Specific Example 2

  FIG. 8 is a diagram illustrating an example of the streak range to be corrected when the streak range upper limit width is set to be larger than the width of the streak range specified by the streak detection unit 31. In the case illustrated in FIG. 8, the above-described threshold value is set to 4, and the above-described stripe range upper limit width is set to 7 (that is, the initial value of the width of the stripe range + 1).

  The streak shown in FIG. 8 is substantially the same as the streak shown in FIG. 6, but the pixel at the pixel position X2 on the line Y8 does not have a streak color, and the pixel at the pixel position X1 on the line Y9 has a streak color. doing.

  In this example, since the value of the expansion counter data at the pixel position X7 is 4 in the line Y10, the pixel position X7 is included in the streak range, and the streak range is expanded. As a result, the width of the stripe range becomes 7.

  Thereafter, the pixel position X1 is included in the stripe range to be corrected up to the line Y13. On the other hand, in the line Y12, the value of the expansion counter data at the pixel position X8 is 4, but at this time, if the pixel position X8 is included in the streak range, the width of the streak range exceeds the upper limit width of the streak range. The pixel position X8 is not included in the stripe range.

  Since the pixel positions X1 and X2 are excluded from the streak range in the line Y13, the pixel position X8 is included in the streak range at this time. That is, in the line Y13, both the reduction and enlargement of the streak range are performed.

  As described above, according to the above-described embodiment, the streak detection unit 31 detects a streak extending in the sub-scanning direction in the document image, specifies a streak range in the main scanning direction, and the correction processing unit 32 In order to remove streaks in the original image, the pixel values in the streaks are corrected along the sub-scanning direction. Then, the streak range variation detection unit 33 enlarges the detected streak when it detects at least one of streak expansion, reduction, and movement based on the values of the pixels in the streak range and the pixels around the streak range. The streak range in which the pixel value is corrected by the correction processing unit 32 is changed according to at least one of reduction, reduction, and movement.

  As a result, for example, even if dust on the contact glass 1b moves or deforms to change the width or position of the streak, the streak range for correcting the pixel value is changed following the change. The resulting degradation in image quality is reduced.

  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.

  The present invention can be applied to, for example, an image forming apparatus such as a scanner machine, a facsimile machine, a copier, or a multifunction machine having an image reading function.

1b Contact glass 21 Image reading unit 31 Line detection unit 32 Correction processing unit 33 Line range variation detection unit

Claims (4)

A streak detection unit for detecting streaks extending in the sub-scanning direction in the document image and identifying a streak range in the main scanning direction of the streaks;
A correction processing unit that corrects pixel values in the streak range along the sub-scanning direction in order to remove the streaks in the document image;
When at least one of enlargement, reduction, and movement of the streak is detected based on the values of the pixels within the streak range and the pixels around the streak range, the detected enlargement, reduction, and movement of the streak In accordance with at least one, a streak range variation detection unit that changes the streak range in which a pixel value is corrected by the correction processing unit;
Equipped with a,
The streak range variation detection unit is configured such that, at a pixel position adjacent to one end of the streak range, pixel values of a number of pixels equal to or greater than a predetermined threshold value continuous along the sub-scanning direction are values determined as the streak. , When the streak range is enlarged, and the pixel values of a number of pixels equal to or larger than a predetermined threshold continuous along the sub-scanning direction at the pixel position at one end of the streak range are not determined as the streak, Reducing the stripe range,
An image processing apparatus. The streak range variation detection unit sets a streak range upper limit width corresponding to the width of the streak range specified by the streak detection unit, and follows the sub-scanning direction at a pixel position adjacent to one end of the streak range. When the pixel value of a number of pixels equal to or larger than a predetermined threshold is a value determined as the streak, the streak range is enlarged when the streak range after enlargement does not exceed the width of the upper limit width of the streak range. and, when the width of the streak range after enlargement exceeds the streak range upper limit width, the image processing apparatus according to claim 1, characterized in that it does not expand the streak range. A streak detection unit for detecting streaks extending in the sub-scanning direction in the document image and identifying a streak range in the main scanning direction of the streaks;
A correction processing unit that corrects pixel values in the streak range along the sub-scanning direction in order to remove the streaks in the document image;
When at least one of enlargement, reduction, and movement of the streak is detected based on the values of the pixels within the streak range and the pixels around the streak range, the detected enlargement, reduction, and movement of the streak In accordance with at least one, a streak range variation detection unit that changes the streak range in which a pixel value is corrected by the correction processing unit;
With
The streak range variation detector is a number greater than or equal to a predetermined threshold value that is continuous along the sub-scanning direction at all pixel positions in the peripheral range in a peripheral range from a certain pixel position in the main scanning direction to one end of the streak range. pixel value of the pixel is, the streak and if it is determined values, images processor you characterized by enlarging said stripe range to include all the peripheral range. A contact glass; an automatic document feeder that passes a document so as to pass over the contact glass; and an image reading unit that reads an image of the document that passes over the contact glass;
The streak detection unit detects a streak extending in the sub-scanning direction in the document image by using the image read by the image reading unit as the document image, and specifies a streak range in the main scanning direction of the streak;
The image processing apparatus according to any one of claims 1 to 3, characterized in.

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