JP5332912B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus and an image forming apparatus.

  2. Description of the Related Art Conventionally, in an image reading apparatus that reads a document by relatively moving the document and the light receiving element array in the sub-scanning direction, ground color detection is performed when the width of the section where the document exists in the read line reaches a set width. It is known to reduce the influence of document skew in ground color detection by starting (see, for example, Patent Document 1).

JP-A-8-79521

However, according to the conventional image reading apparatus, even if the width of the section where the document exists in the read line reaches the set width, there is an area outside the document in the line. May be detected as the background color.
The present invention has been completed based on the above circumstances, and an object of the present invention is to provide an image reading apparatus and an image forming apparatus that can accurately detect a ground color even when a document is inclined.

According to a first aspect of the present invention, there is provided an image reading apparatus based on a reading unit that reads an original to generate image data, an inclination detecting unit that detects an inclination of the original, and an inclination detected by the inclination detecting unit. Inclination correction means for correcting the inclination of the image represented by the image data; ground color detection means for detecting the background color of the document on the image whose inclination is corrected by the inclination correction means; and the ground color detection means. And a ground color correction unit that corrects a ground color of at least one of the image before tilt correction and the image after tilt correction based on the ground color detected in step (b).
Since the area outside the document is reduced on the image whose inclination is corrected, it is possible to reduce erroneous detection of the color of the area outside the document as the ground color.
Therefore, according to the present invention, it is possible to accurately detect the ground color even when the document is inclined.

A second invention is the image reading apparatus according to the first invention, wherein the ground color detecting means detects the ground color of the document on a predetermined line of the image whose inclination is corrected by the inclination correcting means. To do.
According to the present invention, since the ground color is detected on a predetermined line, the ground color can be detected with a smaller processing amount than in the case where the ground color is detected from the entire image.

A third invention is the image reading apparatus according to the second invention, wherein the predetermined line is near the tip of the image.
Since there is little possibility that an image drawn on the document exists near the leading edge of the image, the ground color can be detected with higher accuracy by detecting the ground color on the line near the leading edge.

A fourth invention is the image reading apparatus of the second or third invention, wherein the predetermined line is a plurality of lines.
If the background color of the document is detected based on a plurality of lines, the background color can be detected with higher accuracy.

A fifth invention is the image reading apparatus according to any one of the second to fourth inventions, wherein the ground color detecting means detects the brightest color among the colors on the line as a ground color.
An original read by an image reading apparatus is often the lightest background color, such as a document original having a white background (light color) and black characters (dark color). For this reason, if the brightest color is detected as the ground color, the ground color can be detected with high probability.

A sixth invention is the image reading apparatus according to any one of the first to fifth inventions, comprising setting means for setting an inclination correction mode for correcting the inclination of the image, wherein the inclination correction mode is set. If so, the ground color of the image after the inclination correction is corrected.
When the tilt correction mode is set, there is a high possibility that the user wants to correct the tilt of the image regardless of whether or not the ground color is corrected. Can reduce the burden of feeling. Further, since the ground color of the image after tilt correction is corrected, an image subjected to tilt correction and ground color correction can be obtained.

A seventh invention is the image reading apparatus according to any one of the first to sixth inventions, wherein the ground color correcting means has at least the same color as the ground color detected by the ground color detecting means in the image. Convert to another color.
For example, if you scan a manuscript with black characters printed on a gray background, such as a newspaper, the character may appear difficult to read on the image due to the small contrast between the characters and the background color. is there. In such a case, for example, by correcting the gray (ground color) to white (other colors) in the image, it is possible to make the characters easier to read.

An eighth invention is an image forming apparatus, and forms an image on a recording medium based on the image reading apparatus according to any one of the first to seventh inventions and image data generated by the image reading apparatus. Image forming means.
According to the present invention, the ground color can be accurately detected even when the document is inclined.

  According to the present invention, it is possible to accurately detect the ground color even when the document is inclined.

1 is a schematic diagram of an image reading apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram showing an electrical configuration of the image reading apparatus. A graph for explaining ground color correction. The schematic diagram which looked at the image reading apparatus from the upper part. The schematic diagram of the image which image data represents. 10 is a flowchart of processing for reading a document. The schematic diagram for demonstrating the correction | amendment of the inclination of image data.

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS.
(1) Configuration of Image Reading Device FIG. 1 is a schematic diagram of an image scanner 1 (an example of an image reading device). The image scanner 1 is configured as a so-called flat bed (FB) type scanner device, and includes an apparatus main body 3 having a platen glass 13 on which an original is placed, and an FB cover provided above the apparatus main body 3 so as to be openable and closable. 5.

  The apparatus body 3 includes a platen glass 13 that constitutes a first reading surface 11 and a second reading surface 12, a housing 20 that supports the platen glass 13, and a document placed on the first reading surface 11. , A white reference plate 19 having a predetermined reflectance, a reading device 21, an FB motor 23 that moves the reading device 21, and a belt mechanism 25.

  The surface of the platen glass 13 is divided into a first reading surface 11 and a second reading surface 12 by a positioning member 17 that is detachably attached to the housing 20. The first reading surface 11 is an area for a user to read a document placed on the surface, and is covered with the FB cover 5 with the FB cover 5 closed. The second reading surface 12 is an area for reading a document P conveyed by an ADF 40 (Auto Document Feeder) provided on the FB cover 5.

  A reading device 21 (an example of a reading unit) is accommodated on the back surface of the platen glass 13 so as to be movable in a sub-scanning direction (D direction in the drawing) parallel to the platen surface of the platen glass 13. The reading device 21 is fixed to a belt 25b wound around a pair of rollers 25a provided in the belt mechanism unit 25, and moves in the sub-scanning direction together with the belt 25b that is rotated by the power generated by the FB motor 23.

  The white reference plate 19 is disposed between the positioning member 17 and the platen glass 13 in a posture extending in the main scanning direction perpendicular to the paper surface. The white reference plate 19 is a white member having a high reflectance, and is used to generate white level data for light amount adjustment and shading correction of the light source 22 (see FIG. 2).

  When reading the document P conveyed on the second reading surface 12 by the operation of the ADF 40 provided on the FB cover 5, the reading device 21 is moved below the second reading surface 12 and stopped. Further, when reading a document on the first reading surface 11, the reading device 21 is conveyed in the sub-scanning direction on the back side of the first reading surface 11 by operations of the FB motor 23 and the belt mechanism unit 25.

  The FB cover 5 includes the ADF 40 as described above, and conveys the original P placed on the paper feed tray 41 onto the second reading surface 12 as described below, and the second reading surface 12. The original P read by the reading device 21 is discharged onto a paper discharge tray 42.

  The ADF 40 includes paper feed rollers 44 and 45 at the start point of the transport path, and the document placed on the paper feed tray 41 is transported downstream of the transport path by the paper feed rollers 44 and 45. The original P conveyed by the paper feed rollers 44 and 45 is further conveyed downstream of the conveyance path by the conveyance rollers 47 and 48.

  An upper plate 49 that opposes the second reading surface 12 is provided downstream of the conveying rollers 47 and 48 in the conveying path with a predetermined gap from the second reading surface 12. The document P conveyed by the conveyance rollers 47 and 48 passes between the upper plate 49 and the second reading surface 12, and is further moved by a pair of conveyance rollers 51 and 52 provided further downstream in the conveyance path. Then, the paper is discharged onto a paper discharge tray 42 by a pair of paper discharge rollers 51 and 52.

(2) Electrical Configuration of Image Scanner FIG. 2 is a block diagram showing the electrical configuration of the image scanner 1. The image scanner 1 includes an ASIC 100, a CPU 101, a ROM 102, a RAM 103, an EEPROM 104, an FB motor 23, an FB motor driving circuit 105, an ADF motor 110, an ADF motor driving circuit 106, a reading device 21, a current control circuit 121, and an A / D conversion circuit 123. The operation unit 130 is provided.

  As shown in the figure, an FB motor drive circuit 105, an ADF motor drive circuit 106, a current control circuit 121, an A / D conversion circuit 123, an operation unit 130, and the like are connected to the ASIC 100 (an example of an inclination correction unit and a ground color correction unit). Has been. The ASIC 100 controls these under the control of the CPU 101 and performs shading correction, gamma correction, inclination correction, ground color correction, color space conversion, and other various image processing on the pixel values output from the A / D conversion circuit 123. And image data having three pixel values of RGB for each pixel is generated.

  The reading device 21 includes a line sensor 26 in which a plurality of light receiving elements are arranged in a row in the main scanning direction, and a plurality of LEDs that emit red (R) light in a row in the extending direction of the line sensor 26. A light source 22R, a light source 22G in which a plurality of LEDs emitting green (G) light are arranged in a row, and a light source 22B in which a plurality of LEDs emitting blue (B) light are arranged in a row. The light source 22 is provided. Each of the light sources 22R, 22G, and 22B is lit with brightness according to the magnitude of the current supplied from the current control circuit 121 (also referred to as the light intensity of the light source 22 or the light emission amount of the light source 22). The reading device 21 receives the reflected light reflected by the original irradiated with the light from the light source 22 by the line sensor 26 and outputs a voltage corresponding to the electric charge accumulated in each light receiving element of the line sensor 26.

  A light source 22 is connected to the current control circuit 121. The current control circuit 121 supplies current to the light source 22 based on the PWM signal output from the ASIC 100.

The A / D conversion circuit 123 is a circuit that adjusts the gain of the voltage output from the reading device 21 and converts the amplified voltage into a digital output value (pixel value).
The operation unit 130 (setting unit) is provided in front of the apparatus main body 3 and includes various operation switches. By operating the operation unit 130, the user can set an inclination correction mode for correcting the inclination of the image, instruct reading, and the like.

  A CPU 101 (an example of an inclination detection unit and a background color detection unit) controls each unit of the image scanner 1 by executing a program stored in the ROM 102.

  The RAM 103 is used as a main storage device for the CPU 101 to execute various processes. The RAM 103 is an image processing buffer that temporarily stores the image data output from the A / D conversion circuit 123, a tilt-corrected buffer that temporarily stores the image data after tilt correction, and the generated image. It is also used as an image storage buffer for saving and other various buffers. These buffers are configured as ring buffers.

(3) Outline of ground color correction For example, in the case of a manuscript in which characters are formed in black on a gray ground color, the character may be difficult to read depending on the person because of the small contrast between gray and black. is there. In such a case, if the ground color gray is converted to white (brighter color), the difference in brightness between the ground color and the character becomes clearer, and the character becomes easier to read.

  Therefore, in this embodiment, the lightest color (gray in the above example) in the image represented by the image data generated by reading the document is assumed to be the ground color of the document, and the ground color on the image is converted to a lighter color. Perform background color correction.

In order to facilitate understanding, in the present embodiment, a monochrome image having one pixel value for each pixel will be described as an example. Note that the monochrome image may be an image in which three pixel values of RGB are equal to each other.
In this embodiment, the pixel value is expressed by 8 bits (0 to 255), the pixel value of a pixel representing white is represented by 255, and the pixel value of a pixel representing black is represented by 0. It is assumed that the color whose pixel value is closer to 255 is brighter.

  FIG. 3 is a graph for explaining ground color correction. In FIG. 3, a solid line 61 indicates the relationship between the pixel value before ground color correction and the pixel value after ground color correction. A broken line 62 is a comparative example, and shows a case where the ground color correction is not performed. When the ground color correction is not performed, the pixel value does not change.

Formula 1 shown below shows a ground color correction formula according to this embodiment.
f (x) = (255 / ground color value) × x Equation 1
The ground color value is a pixel value of the ground color. According to Equation 1, when the pixel value x before correction is a ground color value, the pixel value f (x) after correction is 255 as shown in Equation 2 below.
f (x) = (255 / ground color value) × ground color value = 255 Formula 2
Thus, according to Equation 1, the color of the pixel representing the ground color is converted to white (255).

  In the present embodiment, not only the ground color is corrected, but the colors other than the ground color are also corrected by Equation 1, so that the ground color is converted into another color at the same ratio as the corrected ratio. That is, in the present embodiment, colors other than the ground color are also corrected according to the ground color correction. However, when the character is black as in the above-described example, the pixel value is 0 (zero) or almost 0, and therefore the pixel value hardly changes even if correction is performed.

(4) Document Reading Process FIG. 4 is a schematic view of the image scanner 1 as viewed from above, and shows a state in which the document W is placed inclined with respect to the main scanning direction.
FIG. 5 is a schematic diagram illustrating an image 64 represented by image data stored in the image processing buffer by reading the document illustrated in FIG. 4. In this embodiment, it is assumed that the buffer capacity of the image processing buffer is 16 lines. When reading an original, the image scanner 1 reads a rectangular reading target area including the original. In this case, when the document is not tilted, the area to be read does not include the area outside the document, only the document is read, and the image represented by the image data does not include the area outside the document. On the other hand, when the document is placed at an angle, the area outside the document is included in the read target area, and an area 65 (representing the back surface of the FB cover 5 is displayed on the image 64 as shown in FIG. Area outside the document). Since the back surface of the FB cover 5 is generally white, the color of the outside area 65 is white. Note that, in the rectangular area including the document read by the image scanner 1, the short side and the long side of the rectangle are parallel to the main scanning direction or the sub-scanning direction, respectively.

In FIG. 5, a plurality of broken lines 66 each indicate one line. In the present embodiment, a line refers to a pixel row arranged in a direction corresponding to the main scanning direction. Note that a line can also be referred to as a pixel row that the reading device 21 reads and outputs a document for one line. Note that pixel rows arranged in a direction corresponding to the sub-scanning direction may be referred to as a line.
Assuming that the background color (largest pixel value) of the document is detected on any line 66 of the image 64, the document outside area 65 is placed on any line 66 when the document is placed at an angle. Therefore, white (the color of the back surface of the FB cover 5) is detected as the ground color.
Therefore, in the present embodiment, the ground color is corrected after correcting the inclination of the image 64.

FIG. 6 is a flowchart of processing for reading a document. When the user wants to correct the inclination of the document, he / she operates the operation unit 130 to set the inclination correction mode, and when it is not necessary to correct the inclination, the user instructs reading of the original without setting the inclination correction mode. This process is started when the user instructs reading of the document.
In the following description, reading a document placed on the first reading surface 11 of the platen glass 13 is referred to as “FB scan”, and reading a document conveyed by the ADF 40 is referred to as “ADF scan”. Here, an FB scan will be described as an example.

In S101, the CPU 101 determines whether or not the tilt correction mode is set. If it is set, the process proceeds to S102, and if it is not set, the process proceeds to S110.
In S <b> 102, the CPU 101 reads the document line by line from the leading edge of the document by the reading device 21. When the reading device 21 reads a document for a predetermined number of lines (for example, eight lines), it transfers the read image data to the image processing buffer.

In step S103, the CPU 101 detects the leading edge of the document based on the image data stored in the image processing buffer.
FIG. 5 described above shows an image obtained by reading a document placed away from the side of the frame (rectangular frame for document positioning constituted by the casing 20 and the positioning member 17, see FIG. 4). When the document is placed apart from the side of the frame, the pixel values for one line are all 255 or close to the value until the line sensor 26 reaches the leading edge of the document. Then, when the line sensor 26 reaches the leading edge of the document, a shadow generated on the edge of the document is read, so that some pixel values become smaller than a threshold value (for example, 128). The CPU 101 determines that a line that first includes a pixel value smaller than the threshold is a line representing the leading edge of the document. Thereby, the leading edge of the document is detected. The method for detecting the leading edge of the document is not limited to this, and any method can be used as long as the leading edge of the document can be detected.
If the leading edge of the document can be detected, the CPU 101 proceeds to S104. If not detected, the CPU 101 returns to S102 and repeats the process until it can be detected.

In S104, the CPU 101 detects the document inclination angle θ based on the image data stored in the image processing buffer.
Specifically, for example, the CPU 101 applies a differential filter to the image 64 stored in the image processing buffer, and generates a differential image representing an edge on the image 64 (a boundary between pixels having a large pixel value difference). The differential image is substantially the same as the image shown in FIG.

  The sides of the document appear as straight edges on the differential image. If the document is placed at an angle, this edge is also inclined. First, the CPU 101 detects a linear edge. If a straight edge is detected, the CPU 101 determines whether or not the length of the edge matches the width of the document in order to determine whether or not the edge represents the side of the document. Judging. If the length of the straight edge matches the width of the document, the CPU 101 determines that the side of the document is an edge, and obtains the inclination angle θ of the straight edge. As a result, the inclination angle θ of the document is detected.

In this embodiment, the capacity of the image processing buffer is set to 16 lines. However, if the capacity of the image processing buffer is small, the sides of the original do not fit in the image 64, which makes it difficult to detect the tilt angle θ. Therefore, it is desirable that the capacity of the image processing buffer has a certain margin so that at least one side of the tilted original can be accommodated in the image 64.
Further, the method for detecting the edge representing the side of the document is not limited to this, and for example, a straight edge closest to each side of the frame may be used as an edge representing the side of the document.

  If the CPU 101 has detected the document inclination angle θ, the CPU 101 proceeds to S105. When the inclination angle θ of the original cannot be detected (when an edge having a length that matches the width of the original cannot be detected), the CPU 101 reads image data for the next eight lines by the reading device 21. The process waits until it is stored in the processing buffer, and after the image data for the next eight lines is stored in the image processing buffer, the process of S104 is repeated.

In S105, the ASIC 100 corrects the inclination of the image 64 based on the inclination angle θ.
FIG. 7 is a schematic diagram for explaining the inclination correction of the image 64. Various methods have been proposed as a method for correcting the inclination of the image. Here, an example is described in which the inclination is corrected by rotating each pixel by the inclination angle θ around the pixel P representing the leading edge of the document. Explained. Note that the method of correcting the tilt can be selected as appropriate, and other methods may be used.

  The CPU 101 first detects an edge representing each side of the document on the image 64, thereby specifying the document region 67 on the image 64. Next, the CPU 101 calculates the coordinates after rotation for each pixel on the specified document area 67, and sets the pixel value of the pixel to the calculated coordinates to generate an image with corrected inclination. The CPU 101 stores the tilt-corrected image 70 in the tilt-corrected buffer. In the image 70, the area other than the document area 67 is an area for which the pixel value has not yet been determined.

  In step S <b> 106, the CPU 101 detects the background color of the document on the image 70 stored in the post-tilt correction buffer (excluding areas where pixel values are not determined). Since the image outside area 65 is not included in the image 70 stored in the post-tilt correction buffer, when the background color of the document is detected on the image 70, the white color of the outside area 65 is detected as the background color. You can avoid it.

  However, the original may have ruled lines and bands extending in the entire main scanning direction. If a background color is detected on a line representing such a ruled line or band, the background color is erroneously detected. Will end up. Incidentally, in general, ruled lines, bands, and the like are often formed at a certain distance from the leading edge of the document to the inside of the document. For this reason, if the ground color is detected on the line near the leading edge of the document, it is possible to reduce the possibility that the ground color is erroneously detected due to ruled lines or bands. Therefore, the CPU 101 detects the background color of the document on a line near the leading edge of the document.

In the image 70 shown in FIG. 7, a broken line 68 indicates a tip line. The line in the vicinity of the front end of the document may be the front end line 68 itself, or a line that is generally unlikely to form a ruled line or a band, such as a line next to the front end line 68 or the next line. If so, it may be a line other than the tip line 68.
Further, the number of lines for detecting the ground color is not limited to one, but may be a plurality of lines such as two to three. When the ground color of the document is detected from a plurality of lines, the largest pixel value on the plurality of lines may be detected as the ground color.

  When detecting the ground color, the largest pixel value may be the ground color, or the average value of the upper predetermined number of pixel values may be the ground color. When the average value of the upper predetermined number of pixel values is set as the ground color, the pixel value is affected by some external factor, such as when electrical noise affects the voltage output from the reading device 21. The ground color can be detected more stably.

  In S107, the ASIC 100 corrects the pixel value of each pixel (excluding pixels for which the pixel value is not determined) included in the image 70 stored in the post-tilt correction buffer based on Equation 1, and after the ground color correction Transfer the image data to the image storage buffer.

  In S108, the ASIC 100 waits until the image data for the next eight lines is read by the reading device 21 and stored in the image processing buffer. When the image data for the next eight lines is stored in the image processing buffer, Similar to S105 and S107, tilt correction and ground color correction are performed. Since the inclination angle and the ground color have already been detected in S104 and S106, the inclination angle and the ground color are not detected.

In step S109, the CPU 101 determines whether the reading of the document has been completed. When the reading of the original is completed, the shadows generated at the edges of the original are not read, so that the pixel values for one line are all 255 (or the vicinity thereof). For this reason, if there is a line in which the pixel values for one line are all 255 in the image data stored in the image processing buffer, the CPU 101 ends the process on the assumption that the reading of the document has ended. Note that the method for determining the end of reading of the document is not limited to this, and any method can be used as long as the end of reading of the document can be detected.
If the reading of the document is not completed, the CPU 101 returns to S108 and repeats the process until the reading of the document is completed.

  In S110, the CPU 101 causes the reading device 21 to read the document. Since the tilt correction is not performed in S110, the read image includes an area outside the document. In S110, ground color correction is not performed.

  Although the FB scan has been described here, the same applies to the ADF scan.

(5) Effects of the Embodiment According to the image scanner 1 according to the first embodiment of the present invention described above, the ground color is corrected after the inclination is corrected. Since the document outside area 65 is not present on the image whose inclination is corrected, it is possible to reduce erroneous detection of the color of the document outside area 65 as a ground color. Therefore, the image scanner 1 can accurately detect the ground color even when the document is inclined.
When correcting the inclination of the image, for example, it may be possible to leave an area outside the document in a frame shape around the image. In such a case, an area outside the document remains in the image after the inclination correction, but since at least the area outside the document is reduced, it is possible to reduce erroneous detection of the background color of the document.

Further, according to the image scanner 1, since the ground color of the document is detected on a predetermined line of the image 70 whose inclination is corrected, the ground color is detected with a smaller processing amount than when the ground color is detected from the entire image. it can.
In the above embodiment, the line is a line extending in a direction corresponding to the main scanning direction. In image processing, processing is generally performed in units of lines extending in the direction corresponding to the main scanning direction. Therefore, if the ground color is detected on the line extending in the direction corresponding to the main scanning direction, the ground is detected on the inclined line. The ground color can be detected by a simple process compared to the case of detecting the color.

  Furthermore, according to the image scanner 1, the ground color is detected on a line near the leading edge of the image. Since there is little possibility that an image drawn on the document exists near the leading edge of the image, the ground color can be detected with higher accuracy by detecting the ground color on the line near the leading edge.

  Furthermore, according to the image scanner 1, the ground color can be detected more stably by detecting the ground color on a plurality of lines.

  Furthermore, according to the image scanner 1, the brightest color among the colors on the line is detected as the ground color. An original read by an image reading apparatus is often the lightest background color, such as a document original having a white background (light color) and black characters (dark color). For this reason, if the brightest color is detected as the ground color, the ground color can be detected with high probability.

  Further, according to the image scanner 1, when the inclination correction mode is set, the inclination is corrected regardless of whether or not the ground color is corrected. When the tilt correction mode is set, there is a high possibility that the user wants to correct the tilt of the image regardless of whether or not the ground color is corrected. It is possible to reduce the burden of feeling that it is done. Further, since the ground color of the image after tilt correction is corrected, an image subjected to tilt correction and ground color correction can be obtained.

  Further, according to the image scanner 1, the same color as the ground color detected in the image is converted into another color. For example, if you scan a manuscript with black characters printed on a gray background, such as a newspaper, the character may appear difficult to read on the image due to the small contrast between the characters and the background color. is there. In such a case, for example, by correcting the gray (ground color) to white (other colors) in the image, it is possible to make the characters easier to read.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

(1) In the above embodiment, it is determined whether or not the “tilt correction mode” is set in S101 of FIG. 6, but the “ground color correction mode” is selectable, and the “ground color correction mode” is selected. It may be determined whether or not is set. In this case, both the tilt correction and the ground color correction are performed when the “ground color correction mode” is set, and the tilt correction and the ground color correction are performed when the “ground color correction mode” is not set. There will be no.

(2) In the above embodiment, the case where it is determined that the “tilt correction mode” is not set has been described as an example in which neither the tilt correction nor the ground color correction is performed, but the “tilt correction mode” is not set. In this case, the ground color correction may be performed without performing the inclination correction. In this case, instead of correcting the ground color of the image 70 stored in the buffer after tilt correction, the ground color of the image 64 (image before tilt correction) stored in the image processing buffer is corrected. Become.

  Further, both “tilt correction mode” and “ground color correction mode” may be selectable. In this case, when the “tilt correction mode” is not set and the “ground color correction mode” is set, the ground color correction is performed without performing the tilt correction.

In the ground color correction in this case, the slope may be corrected only for detecting the ground color, or the ground color may be detected on an image that has not been tilt-corrected.
When correcting the inclination only to detect the background color, it is only necessary to detect the background color, so there is no need to correct the inclination of the entire image.For example, the background color is corrected by correcting the inclination only at the leading edge of the document. You may make it detect.
When a ground color is detected on an image that has not been tilt-corrected, since the tilt correction is not performed, the processing time is shortened, but the accuracy of the ground color correction is reduced.

(3) In the above embodiment, the case where the ground color is converted to white has been described as an example. However, the conversion destination color is not limited to white, and can be selected as appropriate.

(4) In the above embodiment, the case where a color other than the ground color is corrected has been described as an example. However, only the ground color may be corrected. For example, the detected ground color or a color slightly darker than that with a margin may be used as a reference value, and only a color brighter than the reference value (a pixel having a large pixel value) may be corrected by Equation 1. Thereby, for example, only the background color of characters can be converted from gray to white without changing the color.

(5) In the above-described embodiment, an example has been described in which the CPU performs tilt detection and ground color detection, and the ASIC performs tilt correction and ground color correction. Whether it is performed by the CPU can be appropriately selected. For example, all of these processes may be performed by the ASIC or all by the CPU.

(6) Although the image scanner has been described as an example of the image reading apparatus in the above embodiment, a so-called composite having a scanner function (an example of an image reading apparatus), a printer function (an example of an image forming unit), a copy function, a facsimile function, and the like. The present invention may be applied to a machine (an example of an image forming apparatus).

1. Image scanner (image reading device)
21: Reading device (reading means)
100... ASIC (tilt correction means, ground color correction means)
101... CPU (tilt detection means, ground color detection means)
130 ... operation unit (setting means)

Claims (7)

Reading means for reading a document and generating image data;
An inclination detecting means for detecting an inclination of the original;
Setting means for setting an inclination correction mode for correcting the inclination of the image;
When the tilt correction mode is set, the tilt of the image represented by the image data is corrected based on the tilt detected by the tilt detection unit, and when the tilt correction mode is not set, Inclination correcting means for correcting the inclination of the image represented by the image data based on the inclination detected by the inclination detecting means in order to detect the ground color of the image ;
Ground color detection means for detecting the ground color of the document on the image whose inclination is corrected by the inclination correction means;
When the tilt correction mode is set, the ground color of the image after tilt correction is corrected based on the ground color detected by the ground color detection means, and when the tilt correction mode is not set, Ground color correction means for correcting the ground color of the image before inclination correction based on the ground color detected by the ground color detection means;
An image reading apparatus comprising: The image reading apparatus according to claim 1,
The ground color detection unit is an image reading apparatus that detects a ground color of the document on a predetermined line of the image whose tilt is corrected by the tilt correction unit. The image reading apparatus according to claim 2,
The image reading apparatus, wherein the predetermined line is in the vicinity of the leading edge of the image. The image reading apparatus according to claim 2 or 3, wherein
The image reading apparatus, wherein the predetermined line is a plurality of lines. An image reading apparatus according to any one of claims 2 to 4,
The ground color detection means is an image reading device that detects the brightest color among the colors on the line as a ground color. An image reading apparatus according to any one of claims 1 to 5,
The ground color correction unit converts the same color as the ground color detected by the ground color detection unit in the image into another color. An image reading apparatus according to any one of claims 1 to 6,
Image forming means for forming an image on a recording medium based on image data generated by the image reading device;
An image forming apparatus comprising:

Images