JP5307661B2 - Color misregistration determination apparatus, color misregistration correction apparatus, and image reading apparatus - Google Patents

Description

  The present invention relates to a color misregistration determination apparatus, a color misregistration correction apparatus, and an image reading apparatus that determine a color misregistration area that occurs when a read target such as a document (sheet) is read in color.

  2. Description of the Related Art Conventionally, in an image reading apparatus such as a scanner, for example, light is applied to a document in the order of red (R), green (G), and blue (B), and an image is read line by line based on the reflected light. An image sensor is used. In such a conventional image reading apparatus, the RGB reading positions are different.

  For this reason, when a document including a monochrome area is read in color, so-called color misregistration that may be read in a color different from the color existing in the document may occur in a portion where the color of the document has changed.

  Therefore, in order to correct such color misregistration, for example, a color misregistration pattern generated in a black and white edge portion that changes from white to black or from black to white is stored in advance, and the read pattern is compared with the color misregistration pattern. However, a color misregistration correction method is known in which a color misregistration region in which both patterns match is corrected to white or black (see, for example, Patent Document 1).

  However, in the color misregistration correction method disclosed in Patent Document 1, a wide variety of color misregistration patterns are predicted and stored in advance, for example, when the color misregistration area sandwiched between white and black is relatively large. There was a problem that it had to be placed, lacked flexibility, and was not practical.

  For example, with the conventional color misregistration correction method, it is difficult to correct color misregistration in the following cases for a document including an area in which white and black are alternately replaced every other pixel as shown in FIG. There's a problem. In the following example, when the white portion is read, the maximum luminance value (255) is returned regardless of the color, and when the black portion is read, the minimum value (0) is returned regardless of the color. As shown in FIG. 11, for example, when reading is performed by a one-line sensor so that one pixel is formed in each of white and black regions, the output A “(R, G, B) = (255, 255, 255), (0, 0, 0), (255, 255, 255), (0, 0, 0), (255, 255, 255) ".

  When the original is read in this manner, if the original can be read ideally when the reading position is shifted forward by a distance corresponding to one-third pixel, the output B “(R, G, B) = (255, 255, 255), (85, 85, 85), (170, 170, 170), (85, 85, 85), (170, 170, 170) It is output as an intermediate color according to the ratio of white and black.

  However, in the one-line sensor, the output C “(R, G, B) = (255, 255, 255), (255, 0, 0), (0, 255, 255), (255, 0, 0), (0, 255, 255) ". If such a color misregistration is to be processed by a conventional color misregistration correction method, an image that should originally be output as a color is erroneously detected, and as a result, it may be erroneously corrected. .

  In the above-described example, the case where the color is applied over four pixels has been described. However, the area where the color is applied continues as long as the part where the white area and the black area are replaced at a fine interval continues. become. For example, in the case where a portion illustrated as an actual document in FIG. 11 continues, if the reading position is shifted by a distance of one third pixel as described above, the following pattern continues. It will be.

  For example, (R, G, B) = (255, 255, 255), (255, 0, 0), (0, 255, 255), (255, 0, 0), (0, 255, 255), (255, 0, 0), (0, 255, 255), (255, 0, 0), (0, 255, 255), and the patterns (255, 0, 0), (0, 255, 255) Will continue forever.

  If a pattern that covers all the patterns is prepared so that all such pattern areas can be detected, the area to be determined becomes substantially large, so the processing becomes enormous and the practicality is impaired.

  Note that the above-described problem does not occur only in the image reading apparatus, and may occur in a processing apparatus having an image reading function, for example.

JP 04-280575 A

  SUMMARY OF THE INVENTION In view of the circumstances described above, an object of the present invention is to provide a color misregistration determination apparatus, a color misregistration correction apparatus, and an image reading apparatus that can flexibly cope with various color misregistration patterns and are practical. .

  In order to achieve the above object, a color misregistration determination apparatus according to the present invention generates pixel classification data by classifying image data obtained by reading a read target including a monochrome area in color for each color pixel and monochrome pixel. Based on a pixel classification unit and a color shift determination reference pattern including a first pattern continuous from the monochrome pixel to the color pixel, a color shift area including a color pixel area continuous to the monochrome pixel is included in the image data. Color misregistration determining means for determining whether or not the image is detected.

  In order to achieve the above object, a color misregistration correction apparatus according to the present invention generates pixel classification data by classifying image data obtained by reading a read target including a monochrome area in color for each color pixel and monochrome pixel. Based on a pixel classification unit and a color shift determination reference pattern including a first pattern continuous from the monochrome pixel to the color pixel, a color shift area including a color pixel area continuous to the monochrome pixel is included in the image data. A color misregistration determining unit that determines whether or not the color misregistration is performed; and a color misregistration correction unit that corrects the color misregistration region by predetermined image processing.

  In order to achieve the above object, an image reading apparatus of the present invention includes an image reading unit that reads a sheet to be read including a monochrome area in color, and image data obtained by the image reading unit for each color pixel and monochrome pixel. And a pixel classification means for generating pixel classification data by classifying the image data, and a color continuous to the monochrome pixel in the image data based on a color shift determination reference pattern including a first pattern continuous from the monochrome pixel to the color pixel. A color misregistration determination unit that determines whether or not a color misregistration region including a pixel region is included, and a color misregistration correction unit that corrects the color misregistration region by predetermined image processing. .

  The present invention predicts various color misregistration patterns and can flexibly cope with various color misregistration patterns without storing them in advance as a comparison pattern. There is an effect that it can be performed.

FIG. 2 is a schematic cross-sectional view of the image reading apparatus according to the first embodiment. FIG. 3 is a control block diagram of the image reading apparatus according to the first embodiment. FIG. 3 is a control block diagram illustrating an image processing unit of the image reading apparatus according to the first embodiment. Schematic which shows color misregistration determination reference data. Schematic which shows the example of an image to determine. FIG. 3 is a flowchart illustrating an image processing procedure of the image reading apparatus according to the first embodiment. FIG. 9 is a flowchart illustrating an image processing procedure of the image reading apparatus according to the second embodiment. Schematic which shows the relationship between the reading position and the light quantity in the resolution of an image reading apparatus. FIG. 10 is a flowchart illustrating an image processing procedure of the image reading apparatus according to the fifth embodiment. FIG. 10 is a schematic diagram illustrating color misregistration determination reference data according to a sixth embodiment.

  Hereinafter, the present invention will be described in detail based on embodiments.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of an image reading apparatus according to Embodiment 1 of the present invention. FIG. 2 is a control block diagram of the image reading apparatus according to the first embodiment of the present invention.

  As shown in FIG. 1, in the image reading apparatus 100 of the present embodiment, a paper feed tray 2 on which documents (sheets) are stacked is supported to be openable and closable with respect to the apparatus main body 1A via a hinge portion 2a. That is, the sheet feed tray 2 covers the document sheet feed port 13 in the closed state (broken line in FIG. 1), and the document is stacked on the stacking surface 2b in the opened state (solid line in FIG. 1).

  A plurality of documents stacked on the sheet feed tray 2 are separated and fed one by one from the lowermost document to the conveyance path by the feed roller 4 and the separation pad 5. The document fed to the conveyance path is conveyed downstream by the conveyance roller pair 6. Further, the original is scanned on the front and back surfaces by the image reading units (image reading means) 8 and 9, and is then discharged out of the apparatus by the conveying roller pair 7.

  The image reading apparatus 100 having such a configuration is connected to an information processing apparatus such as a computer, and the reading operation is controlled by an operation from the information processing apparatus. The image reading apparatus 100 and the information processing apparatus can be connected by, for example, a USB cable, a SCSI cable, a LAN cable, or wirelessly.

  Further, in the information processing apparatus to which the image reading apparatus of the present embodiment is connected, the software (control program) that can control the image reading apparatus 100 is executed, whereby the image reading apparatus 100 can be controlled. Become.

  In practice, the user can set the image reading conditions such as the resolution, the number of colors, the number of gradations, the reading surface, and the reading area from the control screen of the image reading apparatus 100 displayed by executing the software. It can be set. That is, the image reading apparatus 100 is configured to perform a reading operation according to setting conditions specified by the user.

  Further, the image reading apparatus 100 transmits image data read by the image reading units 8 and 9. For example, as shown in FIG. 2, in the image reading apparatus according to the present embodiment, the control unit 102 including the CPU controls the image data read by the image reading units 8 and 9 to be transmitted to the outside by the communication unit 101. It has become.

  Here, although not shown, the image reading units 8 and 9 are composed of a light irradiating unit composed of an LED or the like that irradiates a conveyed document with light of a plurality of colors, and a light receiving unit that receives reflected light from the document. In this embodiment, the image reading units 8 and 9 irradiate R (red), G (green), and B (blue) light as a plurality of colors of light that irradiate the document, and reflect reflected light from the document. It was supposed to be read in one line. In addition, the timing which irradiates light by such a light irradiation part is controlled by the control part 102. FIG.

  Further, as shown in FIG. 1, when the control unit 102 receives a document reading command from an information processing apparatus such as a PC, the feed roller 4 and the separation pad 5 feed the documents on the sheet feeding tray 2 one by one. To feed separately. Subsequently, the document is conveyed toward the image reading units 8 and 9 by the conveyance roller pair 6. Although not shown, a registration sensor for detecting the arrival and passage of the document is provided between the conveying roller pair 6 and the image reading units 8 and 9. When the control unit detects the arrival of the document by the registration sensor, the control unit controls the image reading units 8 and 9 to start reading from the image reading start position P set before the image reading units 8 and 9. .

  Specifically, when the original reaches the image reading start position P, R (red) light is turned on from the light irradiation unit, and the light reflected by the light receiving unit reads one line. Subsequently, G (green) light is turned on by the light irradiation unit and one line is read by the light receiving unit, and further, B (blue) light is turned on by the light irradiation unit and one line is read by the light receiving unit. Then, the image data for one line of each RGB is transferred to the image processing unit 103 (see FIG. 2). During this time, the conveying roller pair 6 and 7 are always rotated to convey the document. As described above, the image reading apparatus 100 repeatedly performs the above-described operation, thereby reading a document in color and outputting image data.

  Here, the image processing unit 103 in the image reading apparatus 100 of the present embodiment will be described in detail with reference to FIGS. 3 and 4. FIG. 3 is a control block diagram illustrating the image processing unit of the image reading apparatus according to the first embodiment of the present invention. FIG. 4 is a schematic diagram showing color misregistration determination reference data.

  As shown in FIG. 3, the image processing unit 103 determines whether or not color misregistration has occurred and details the image data (RGB data) received from the image reading units 8 and 9. A function is provided for performing correction processing on the misaligned portion. Specifically, the image processing unit 103 includes a color misregistration determination unit (color misregistration determination unit) 110 and a color misregistration correction unit (color misregistration correction unit) 120 that performs a predetermined correction process for color misregistration.

  The color misregistration determination unit 110 includes a pixel classification unit (pixel classification unit) 111 that classifies image data for each color pixel and monochrome pixel to generate pixel classification data. The pixel classification unit 111 has a function of classifying what color the pixel data of the input image belongs to. In this embodiment, for example, the color belonging to five colors of white, red, blue, green, and black is classified. Here, the pixel classification of the image data is, for example, based on the saturation, as shown in the following equation, the maximum RGB value [Max (R, G, B)] and the minimum value [Min (R, G, B). B)].

  Saturation = (Max (R, G, B) −Min (R, G, B)) / Max (R, G, B)

  Based on the above formula, a pixel having low saturation and having a high brightness [Max (R, G, B)] is set to white, and a pixel having a low brightness is set to black. A pixel with high saturation is red when the R value is the largest among the RGB values, green when the G value is the largest, and blue when the B value is the largest. Of the five colors, white and black are monochrome pixels, and the other red, blue, and green are color pixels.

  In addition, the color misregistration determination unit 110 includes a pattern storage unit 112 that stores a color misregistration determination reference pattern that serves as a determination reference in color misregistration determination. As the color misregistration determination reference pattern, for example, in the present embodiment, a first pattern in which monochrome pixels continue to color pixels, a second pattern in which color pixels continue in the first pattern, and a third pattern in which color pixels continue into monochrome pixels Pattern is included. Examples of the first pattern of the color misregistration determination reference pattern include combinations such as white to red and black to blue as shown in FIG. Examples of the second pattern include combinations of red to blue and blue to red. Examples of the third pattern include combinations of blue to white, red to black, and the like. Of course, the present invention is not limited to these patterns.

  Such a color misregistration determination unit 110 has a function of determining color misregistration based on a color misregistration determination reference pattern stored in the pattern storage unit 112. For example, in this embodiment, the color misregistration determining unit 110 compares the pixel classification data generated by the pixel classifying unit 111 with a color misregistration determination reference pattern, and first, color pixels that are continuous with monochrome pixels in the image data. It is determined whether or not a color misregistration area consisting of the above area (area corresponding to the first pattern) is included. That is, if a pattern in which color pixels are continuous with monochrome pixels exists in the pixel classification data, the color pixel region is a color shift region. Here, since it is possible to determine the combination of two pixels, the color misregistration pattern can be flexibly changed as the color misregistration determination reference pattern. Moreover, since such a reference pattern is based on a combination of two pixels, it is advantageous for speeding up the determination process.

  Further, the color misregistration determination unit 110 determines a color area formed by combining such different colors as a color misregistration area for a pattern in which a plurality of different color pixels are continuous.

  Here, with regard to the color misregistration determination based on the first pattern and the second pattern described above, for example, when a plurality of color pixels of the same color are consecutive, such a color region is often not a color misregistration region. It may be excluded from the target of the shift determination, or may be set in advance so as not to perform the color shift correction of the color area after once determined as the color shift area. Also, the green pixel may be excluded from the color misregistration target pixels and determined as a color pixel.

  Further, the color misregistration determination unit 110 determines whether or not the pixel classification data includes a monochrome pixel region (region corresponding to the third pattern) that continues from the color pixel. Here, when the region corresponding to the third pattern is included in the pixel classification data, the color misregistration determination unit 110 determines the first end of the color misregistration region whose one end is determined by the monochrome pixel of the first pattern. The determination is based on the presence or absence of two patterns of monochrome pixels.

  Thus, for example, the color misregistration determination unit 110 determines one end of the color misregistration area from the monochrome pixel in the pixel classification data, and if different color pixels are continuous from the monochrome pixel, the color misregistration area is determined as a continuous color misregistration area. In these determinations, the other end of the color misregistration region is determined based on monochrome pixels that are continuous with the color pixels. For this reason, it is possible to flexibly determine not only a color misregistration region composed of various combinations but also a relatively large color misregistration region. Since it is not necessary to predict color misalignment determination reference data for all patterns by predicting a wide variety of combination patterns, it is possible to reduce the load of the determination process and to increase the speed of the determination process.

  In the present embodiment, the determination result determined as the color misregistration region by the color misregistration determination unit 110 described above is stored in the color misregistration result storage unit 130 provided in the image processing unit 103. The color misregistration result storage unit 130 may be provided outside the image processing unit 103. Further, the color misregistration correction unit 120 is connected to the color misregistration result storage unit 103. That is, the color misregistration area stored in the color misregistration result storage unit 130 is corrected by the color misregistration correction unit 120 by predetermined image processing.

  The color misregistration correction unit 120 has a function of performing at least one image processing of graying correction, saturation correction, and brightness correction according to a combination pattern of monochrome pixels and color pixels. For example, in this embodiment, when the color misregistration determination unit 110 designates a color misregistration area, gray processing is performed on each pixel in the color misregistration area.

  Further, the color misregistration correction unit 120 may apply, for example, an average value of RGB values ((R + G + B) / 3) to the pixel to be corrected, or brightness (0.3 × R + 0. 59 × G + 0.11 × B) may be obtained and applied. In addition, since the processing for obtaining the average value as described above and the processing for obtaining the luminance with a small number in the calculation formula are often heavy, the lighting order of the image reading units (actually LEDs and the like) 8 and 9 is 2 The second value may be doubled, then the sum of RGB values may be taken and divided by 4. In this embodiment, since the light irradiation part is lit in the order of red, green and blue, (R + G × 2 + B) / 4 may be used instead of the average value. At the edge from white to black or from black to white, the second reading result is more likely to be closer to the average value than the first and third reading results, and divided by 4 rather than dividing by 3 The process becomes lighter and the time required for correction can be reduced.

  Hereinafter, a specific example of the processing procedure of the image processing unit 103 including the color misregistration determination unit 110 and the color misregistration correction unit 120 described above will be described in detail with reference to FIGS. 5 and 6. FIG. 5 is a schematic diagram illustrating an example of an image to be determined. FIG. 6 is a flowchart showing an image processing procedure of the image reading apparatus according to the first embodiment of the present invention.

  The image example shown in FIG. 5 is a one-line image arranged in the sub-scanning direction. Specifically, the image 201 is one line of the document to be read illustrated in the sub-scanning direction. An image 202 is a result of reading the image 201 by the image reading unit 8. An image 203 illustrates a portion where correction processing has been performed on the image 202. Note that the portion where correction processing has been performed is gray, but this is assumed to be either white or black depending on the actual reading position. The image 204 is an example of an image to be output.

  Here, the procedure from color reading of the above-described image of FIG. 5 to image processing for color misregistration determination and color misregistration correction will be described below. Here, in the coordinates (x, y) of the image input from the image reading unit 8, it is assumed that the x value is the coordinate in the main scanning direction and the y value is the coordinate in the sub scanning direction.

  First, when an image is input from the image reading unit 8 (step S101), the first pixel (x, y) is set as y = 0 to be a target pixel (step S102). It should be noted that the coordinates of the line to be corrected are entered in the x value. It is determined whether the pixel (x, y) that is the target pixel is a monochrome pixel (step S103). If the pixel (x, y) is not a monochrome pixel in step S103, a search is made as to whether there is a pixel (x, y + 1) (step S104). If there is a pixel (x, y + 1) in step S104, the next pixel (x, y + 1) is set as the target pixel (step S105), and the process is performed again after step S102. If it is determined in step S104 that there is no pixel (x, y + 1), the process ends (step S199).

  If it is determined in step S103 that the pixel (x, y) is a monochrome pixel, the y value is stored in the color misregistration result storage unit 130 (step S106). Next, it is determined whether or not there is a pixel (x, y + 1) (step S107). If there is no pixel (x, y + 1) in step S107, the process is terminated (step S199).

  If there is a pixel (x, y + 1) in step S107, the color misregistration determination unit determines whether the same combination as the combination of the pixel (x, y) and the pixel (x, y + 1) is in the color misregistration determination reference data. Determination is made (step S108). If the combination of the pixel (x, y) and the pixel (x, y + 1) is not included in the color misregistration determination reference data in step S108, the flow returns to step S104.

In step S108, if the color misregistration determination reference data is found, it is checked whether the pixel (x, y + 1) is a monochrome pixel (step S109).
If the pixel (x, y + 1) is determined to be a monochrome pixel, the color shift is performed with respect to the pixels between the pixels (x, y + 1) determined to be a monochrome pixel from the value stored in step S106. Correction processing is performed by the correction unit (step S110), and the process returns to the flow of step S104. If the pixel (x, y + 1) is not a monochrome pixel, the process proceeds to the next pixel (step S111), and the processing from step S107 is repeated. The above processing is performed for each line in the sub-scanning direction, and color misregistration of the entire image is detected.

  Hereinafter, an example in which the processing procedure of the image processing unit described above is applied to the image of FIG. 5 will be described. Specifically, when image data is input in step S101, it is read as a pixel of interest from pixel A in step S102. The image A here is black, that is, a monochrome pixel. Therefore, it is determined as a monochrome pixel in step S103, and pixel A is stored in step S106.

  Subsequently, the next pixel after the pixel A is searched in step S107. Here, after pixel A is pixel B, which is blue. That is, in step S108, the combination of the pixel A and the pixel B, that is, the combination of (black + blue) is compared with the color misregistration determination reference data. Based on FIG. 4, the combination of (black + blue) is included in the color misregistration determination reference data. In addition, since blue is a color pixel, it is considered to be changed to the target pixel B in step S109.

  Next, in step S108, the next combination, that is, the combination of pixel B and pixel C (blue + white) is searched. This (blue + white) combination is also included in the color misregistration determination reference data. However, white is a monochrome pixel in step S109. For this reason, in step S110, the pixel B (blue) continuous from the pixel A (black) becomes the color shift region.

  If the above procedure is repeated, it can be seen that the pixels B, F, and G are determined as color misregistration regions in the image in FIG. The remaining pixels D, I, J, and L are determined not to be color misregistration regions. Here, the monochrome pixel H (white) is followed by the color pixels I (red) and J (red) in the same color system. In the present embodiment, such an area in which the color pixels of the same color system continue. Is determined as a color area. Further, although the color pixel L (green) is continuous with the monochrome pixel K (white), this region is also set to be determined as a color region. This is because the combination of these colors does not cause a color shift. These pixels B, F, and G are each subjected to gray correction as shown in FIG.

  As described above, in the image reading apparatus 100 according to the present embodiment, based on the color misregistration determination reference pattern including the first pattern continuous from the monochrome pixel to the color pixel, the color pixel continuous to the monochrome pixel in the image data. Since the color misregistration area composed of the areas is determined, it is possible to flexibly cope with a wide variety of color misregistration patterns and to perform practical color misregistration determination.

  That is, the image reading apparatus 100 according to the present embodiment does not need to predict various color misregistration patterns and store them in advance as comparison patterns as in the prior art. Therefore, according to the image reading apparatus 100 of the present embodiment, for example, even when the color misregistration area to be determined is large, it is possible to cope flexibly without increasing the color misregistration determination reference pattern. Practical.

(Embodiment 2)
FIG. 7 is a flowchart showing an image processing procedure of the image reading apparatus according to the second embodiment of the present invention. FIG. 8 is a schematic diagram showing the relationship between the reading position and the light amount at the resolution of the image reading apparatus.

  The image reading apparatus of this embodiment is the same as that of Embodiment 1 described above except that the color misregistration area is determined based on the relationship between the level of resolution and the saturation of image data.

  Specifically, in the case of high resolution and low saturation, or in the case of low resolution and high saturation, even if a plurality of same color system pixels are connected to a monochrome pixel, these same color systems The pixel area is processed as a color shift area.

  Specifically, the processing when detecting the color misregistration area will be described with reference to FIG. First, as in FIG. 6, after an image is input from the image reading apparatus 101, the resolution of the image is examined and stored (FIG. 6: step S106). Thereafter, as shown in FIG. 7, when it is determined in step S109 that the pixel (x, y + 1) is not a monochrome pixel, whether or not the pixel is a color shift is determined based on the resolution level and the saturation of the image data. Check (step S201).

  In this case, with respect to the color misregistration determination reference data, an intermediate color pattern (combination pattern with a monochrome pixel) classified by the threshold value of brightness and saturation is considered in consideration of the relationship between the level of resolution and the brightness and saturation of the image data. , Combination patterns between colors, etc.). Examples of the intermediate color include yellow, light blue, light green, or reddish purple, brown, dark blue, deep green, or blue-violet.

  In step S201, for example, when the resolution is high, it is checked whether the saturation of the pixel (x, y + 1) is equal to or less than a predetermined threshold corresponding to the resolution. On the other hand, when the resolution is low, it is checked whether the saturation of the pixel (x, y + 1) is equal to or higher than a predetermined threshold value. When the condition is satisfied, the process of step S112 in FIG. 6 is performed. If the condition is not satisfied, the process of step S104 in FIG. 6 is performed. The threshold value can be set as appropriate in consideration of the relationship between the resolution level and the saturation.

  Here, FIG. 7 shows the relationship between the reading position and the amount of light applied to the reading position. It is assumed that all irradiated light is reflected in the white area and all irradiated light is absorbed in the black area. It can be seen that the reading positions of R, G and B are almost different at low resolution. Conversely, when the resolution is high, there are many portions where the reading positions of R, G, and B overlap. For this reason, when the resolution is low, a difference is easily generated between the R value and the B value in the color misregistration pixel. Conversely, in the case of the high resolution, the difference between the R, G, and B values in the color misregistration pixel tends to be small. is there.

  For this reason, it is possible to easily detect the color misregistration area by considering the saturation as described above in the determination processing for the color misalignment at the high resolution and the determination processing for the color misregistration at the low resolution. it can. In particular, when a plurality of color pixels of the same color system are connected to a monochrome pixel, it is possible to determine with high accuracy whether the color pixel is the color misregistration region.

(Embodiment 3)
The image reading apparatus according to the present embodiment is the same as that of the first or second embodiment described above except that the determination of the monochrome pixel can be satisfactorily performed based on the brightness of the image data.

  Hereinafter, description will be made with reference to FIG. 4 of the first embodiment and FIGS. 7 and 8 of the second embodiment. First, after an image is input from the image reading apparatus 101, the brightness of the pixels of the entire image is examined, and a histogram (statistical table or the like) is created based on the brightness and the number of pixels. Then, a value having the largest number of pixels when the lightness is equal to or higher than a predetermined threshold (white lightness) and a value having the largest number of pixels when the lightness is equal to or lower than the predetermined threshold (black lightness) are stored. Here, in obtaining the whiteness and the blackness, an intermediate value (for example, 128) can be set as a threshold value.

  When it is determined in step S109 that the pixel (x, y + 1) is not a monochrome pixel, it is checked in step S201 whether the pixel is a color shift pixel based on whiteness and blackness. For example, when the whiteness is high and the blackness is low, it is checked whether the saturation of the pixel (x, y + 1) is equal to or higher than a predetermined threshold corresponding to the whiteness and blackness. When the whiteness is low and the blackness is low, it is checked whether the brightness of the pixel (x, y + 1) is equal to or less than a threshold corresponding to the whiteness.

  Further, when the black brightness is high, it is checked whether the saturation of the pixel (x, y + 1) is equal to or less than a threshold value corresponding to the white brightness and the black brightness. If the above condition is satisfied, the process of step S112 is performed. Conversely, if the above condition is not satisfied, the process of step S104 is performed.

  Here, in the tendency of color misregistration, when the brightness of white is w and the brightness of black is b (w> b), for example, the monochrome pixel portions are (w, w, w), (w, w, w). ), (B, b, b), assuming that the image is shifted forward by a distance of one third pixel, (w, w, w), (w, w, b), (b, b, b).

  At this time, the brightness of the middle pixel, which is a colored pixel, is x, and the saturation is (w−b) / w. That is, it can be seen that the larger b is, the smaller the saturation is, and the smaller w is, the smaller the brightness is. Therefore, by controlling the processing as described above, it is possible to correctly detect a color misregistration region even if a relatively thin black character document or the document itself is gray.

(Embodiment 4)
This embodiment is the same as Embodiments 1 to 3 described above except that color misregistration correction is performed according to the background of the document.

  Specifically, when detecting the color misregistration area, the following process is added to the processes of the first to third embodiments. First, after an image is input from the image reading apparatus, a histogram of the RGB values and the corresponding number of pixels in the pixels of the entire input image is created, and the RGB value having the largest number of pixels is used as the background color. Here, if the background color is white, the color misregistration area is detected as before.

  On the other hand, if the background is colored, when it is determined whether the pixel is a monochrome pixel in step S103 or step S109 in FIG. 6, it is also determined whether the color is the background.

  For example, when the color of the background is yellow and it is desired to detect a color misregistration pixel that occurs at the edge of the black area, instead of determining whether it is a monochrome pixel, it is determined whether the background color is yellow or black. . Therefore, when it is determined in step S104 of FIG. 6 that the pixel is yellow or black, the process of step S107 is performed. If not, the process of step S105 is performed.

  Similarly, in step S111 of FIG. 6, the process of step S113 is performed when it is determined that the pixel is yellow or black, and conversely, the process of step S105 is performed otherwise. By switching the processing in this way, it is possible to detect color misregistration pixels that are difficult to determine due to the background.

  In the present embodiment, the background of the document is detected from the image. However, other means may be used as a method for detecting the background of the document. A dedicated sensor may be used, or input from the outside may be performed when reading a document.

(Embodiment 5)
FIG. 9 is a flowchart showing an image processing procedure of the image reading apparatus according to the fifth embodiment of the present invention.

  This embodiment is the same as Embodiments 1 to 4 described above except that the color misregistration area is determined when the number of color pixels continuous to monochrome pixels is a predetermined number or more.

  Specifically, when detecting the color misregistration region, the process of FIG. 9 is added to the processes of the first to fourth embodiments described above. From step S106 in FIG. 6, first, the monochrome pixel that is the starting point is determined, the counter is initialized when the coordinates are stored (step S301), and the process of step S107 in FIG. 6 is performed.

  Next, in step S109 in FIG. 6, it is determined whether the next pixel is a monochrome pixel. If the next pixel is not a monochrome pixel, it is checked whether the counter is larger than a predetermined value (step S311). When the threshold value is equal to or greater than the predetermined threshold, since the combinations that sufficiently cause the color shift are continuous, the pixels from the starting pixel (color pixel continuous to the monochrome pixel) to the target pixel are determined as the color shift pixels (step S312).

  Subsequently, the target pixel is set as a starting pixel (step S313). Then, the counter is initialized (step S314), and the process returns to step S113. If the counter is less than the threshold, the counter is incremented by one and the process returns to step S113. By doing so, it is possible to reduce the amount of buffer stored for performing the color misregistration correction process.

(Embodiment 6)
FIG. 10 is a schematic diagram showing color misregistration determination reference data according to Embodiment 6 of the present invention.

  This embodiment is the same as Embodiments 1 to 6 described above except that the color misregistration determination is performed in consideration of a combination pattern having a high probability of color misregistration and a low combination pattern.

  Specifically, as shown in FIG. 10, among the combination patterns shown in FIG. 5 of the first embodiment described above, there are a combination having a high probability of color shift and a combination having a low probability of color shift. In this embodiment, (red, blue), (blue, red) is a combination with a low probability of color misregistration, other (white, red), (red, black), (black, blue), (blue, White) is a combination with a high probability of color misregistration.

  First, when detecting a color misregistration area, the presence / absence of the same combination pattern as a combination having a low probability of color misregistration is stored. When the correction process is performed on the color misregistration area, the area determined as the color misregistration area only by a combination having a high probability of being the color misregistration area is (R + 2 × G + B) / 4 with respect to R, G, and B. Perform graying process to assign a value.

  Conversely, when it is determined that the color misregistration region is a combination using a low probability of being a color misregistration region, the R value is (R × 2 + G + B) / 4, the G value is (R + G × 2 + B) / 4, and the B value is A reduction process for substituting (R + G + B × 2) / 4 is performed. Actually, in the latter process, the saturation does not become zero, so that a little color remains. By performing this process, it is possible to reduce image deterioration due to the graying process when an area that should originally be a color is erroneously detected as a color shift area.

  Hereinafter, a case where the above-described processing is applied to the image 201 in FIG. 6 of the first embodiment described above will be described. First, since the combinations used for the pixels A, B, and C are all combinations having a high probability of being color misregistration regions, graying processing is performed. Since the combination of R and G is (red, blue) and the probability of the color misregistration region is low for the pixels E, F, G, and H, reduction processing is performed.

  Further, it is divided whether the combination is a thin line area such as (red, blue) and (blue, red) shown in FIG. 10, and when the color misregistration area is detected, it is a color misregistration area using the combination that is the thin line area. Is stored.

  At this time, when it is determined that the region is a color misregistration region using a combination that is a thin line region, brightness correction processing is performed by adding a value obtained by multiplying each RGB value by 3/4. When it is determined that the region is a color misregistration region without using a combination that is a thin line region, graying processing is performed.

  By performing such processing, it is possible to emphasize the blurred pixels E, F, G, and H in the correction processing in the first embodiment, and it is possible to make the black thin line clear.

(Other embodiments)
As mentioned above, although this invention was demonstrated based on Embodiment 1-6, this invention is not limited to Embodiment 1-6 mentioned above. For example, in the above-described first embodiment and the like, “white, red, green, blue, black” has been described as an example for explanation. However, the present invention is of course not limited to this, and various combinations are defined with more detailed definitions. It may be determined, or conversely, “monochrome, color” may be determined. Further, as an exceptional measure, green or the like that is unlikely to cause color misregistration may be excluded from the determination target and processed.

  In the first embodiment and the like described above, the color combination pattern is described as a combination of two pixels continuous in the sub-scanning direction. However, the present invention is of course not limited to this, and for example, 3 continuous in the sub-scanning direction. Two or more combinations may be used.

  Furthermore, in the first embodiment and the like described above, the color misregistration determination is performed by comparing the color misregistration determination reference pattern with the image data. However, the present invention is of course not limited to this. The determination may be made based on the result of arithmetic processing with image data, or may be determined by other processing. In any case, color misregistration (false color) may be determined based on a color misregistration determination reference pattern including a first pattern continuous from monochrome pixels to color pixels.

  Further, in the above-described first embodiment and the like, the case where the image processing function is provided in the image reading apparatus has been described. However, the present invention is of course not limited thereto, and for example, output after output from a communication unit or the like. The destination may perform the process. For example, the image reading apparatus may be connected to a personal computer, and the image may be directly transferred from the image reading unit, and correction processing may be performed by the personal computer.

  In the above-described first embodiment and the like, an image reading apparatus (sheet-through scanner) that reads a document has been described as an example. The present invention can be widely applied to a check scanner such as a check, a copying machine having an image reading function, a multifunction machine, and the like. Note that the present invention is not limited to the image reading apparatus as in the first embodiment described above, and is widely applied to, for example, a color misregistration determination apparatus and a color misregistration correction apparatus.

DESCRIPTION OF SYMBOLS 100 Image reading apparatus 101 Paper feed roller 102 1st roller pair 103 2nd roller pair 104 Separation pad 105 Image reading means (1st reading part)
106 Image reading means (second reading unit)
107 Document table 108 Registration sensor

Claims (15)

Pixel classification means for generating pixel classification data by classifying image data obtained by reading a read target including a monochrome area in color for each color pixel and monochrome pixel;
Whether or not the image data includes a color shift area including a color pixel area continuous with the monochrome pixel based on a color shift determination reference pattern including a first pattern continuous from the monochrome pixel to the color pixel. A color misregistration determination apparatus comprising: a color misregistration determination means for determining. The color misregistration determination reference pattern includes a second pattern in which a plurality of color pixels are continuous,
The color misregistration determination unit is configured to determine whether or not a color misregistration area including an area including the plurality of color pixels is included based on the color misregistration determination reference pattern. The color misregistration determination apparatus according to 1.   The color misregistration determining apparatus according to claim 2, wherein the color misregistration determining unit determines the color misregistration region when the number of continuous color pixels as the second pattern is a predetermined number or more. The color misregistration determination reference pattern includes a third pattern continuous from color pixels to monochrome pixels,
The color misregistration determining means determines the other end of the color misregistration area, one end of which is determined by the monochrome pixel of the first pattern, by the monochrome pixel of the third pattern. The color misregistration determination device according to item.   The color misregistration determination apparatus according to claim 1, wherein the color misregistration determination unit performs color misregistration determination based on a resolution level of the image data.   The color misregistration determination apparatus according to claim 1, wherein the color misregistration determination unit performs determination of the monochrome pixel based on brightness of the image data. Pixel classification means for generating pixel classification data by classifying image data obtained by reading a read target including a monochrome area in color for each color pixel and monochrome pixel;
Whether or not the image data includes a color shift area composed of areas of color pixels continuous to the monochrome pixel, based on a color shift determination reference pattern including a first pattern continuous from the monochrome pixel to the color pixel. Color misregistration determining means for determining
A color misregistration correction apparatus comprising: color misregistration correction means for correcting the color misregistration area by predetermined image processing.   The color misregistration correction apparatus according to claim 7, wherein the color misregistration correction unit performs color misregistration correction according to a background of the read target. Image reading means for reading in color a sheet to be read including a monochrome area;
Pixel classification means for classifying image data obtained by the image reading means for each color pixel and monochrome pixel to generate pixel classification data;
Whether or not the image data includes a color shift area composed of areas of color pixels continuous to the monochrome pixel, based on a color shift determination reference pattern including a first pattern continuous from the monochrome pixel to the color pixel. Color misregistration determining means for determining
An image reading apparatus comprising: a color misregistration correction unit that corrects the color misregistration area by predetermined image processing.   The image reading apparatus according to claim 9, wherein the image reading unit irradiates the sheet with light of a plurality of colors and reads the reflected light with a one-line sensor.   The image reading apparatus according to claim 9, wherein the pixel classification data includes pattern information including a plurality of pixels arranged in a sub-scanning direction of the image reading unit.   The color misregistration correction unit switches at least one of the image processing of graying correction, saturation correction, and brightness correction according to a combination pattern of the monochrome pixel and the color pixel included in the first pattern. The image reading apparatus according to claim 9, wherein the image reading apparatus is performed.   13. The image reading apparatus according to claim 12, wherein the color misregistration correction unit performs the graying correction on a color misregistration region based on a predetermined pattern having a high color misregistration occurrence probability among the predetermined combination patterns.   The image reading apparatus according to claim 12 or 13, wherein the color misregistration correction unit performs the saturation correction on a color misregistration region based on a predetermined pattern having a low color misregistration occurrence probability among the predetermined combination patterns. .   The image reading apparatus according to claim 12, wherein the color misregistration correction unit performs the brightness correction on a color misregistration area that is a thin line area.

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