JP2021180397A - Image processing apparatus, control program, and control method - Google Patents

Abstract

To provide an image processing apparatus that can eliminate density unevenness without blurring an image.SOLUTION: An image forming apparatus includes a CPU. The CPU detects, of a plurality of pixels constituting a read image read by an image reading unit, a pixel group including a predetermined number or more of pixels having characteristics related to each other, determines whether a pixel value of the pixels constituting the pixel group is included in a density unevenness range that is a range to the extent that the range can be referred to as density unevenness, when determining that the pixel value of the pixels constituting the pixel group is included in the density unevenness range, corrects the pixel value of the pixels constituting the pixel group to a predetermined pixel value, and when not determining that the pixel value of the pixels constituting the pixel group is included in the density unevenness range, does not correct the pixel value of the pixels constituting the pixel group.SELECTED DRAWING: Figure 8

Description

The present invention relates to an image processing device, a control program and a control method, and relates to an image processing device, a control program and a control method for removing density unevenness of a scanned image based on an image of a document.

An example of an image processing apparatus of the background technique is disclosed in Patent Document 1. In the image processing apparatus of this background technique, mirror data obtained by using a certain image and an inverted image obtained by inverting the image symmetrically is generated, and the mirror data shows a plurality of intensities corresponding to a plurality of spatial frequencies. It is converted into a spectrum, low-frequency components showing density unevenness are extracted from the spectrum, and the extracted low-frequency components are subtracted from the original image to remove density unevenness composed of low-frequency components from the original image. NS.

Japanese Unexamined Patent Publication No. 2013-0083163

However, in the image processing device of the background technology, components other than density unevenness contained in the low frequency component, for example, frequency components of elements having a long period such as a border of a chart with a wide interval may be lost. .. In such a case, there is a problem that the corrected image from which the density unevenness is removed becomes a blurred image.

Therefore, a main object of the present invention is to provide a novel image processing device, control program and control method.

Another object of the present invention is to provide an image processing device, a control program, and a control method capable of removing density unevenness without blurring an image.

The first invention is an image processing apparatus, which includes an image reading unit, a pixel group detecting means, a determining means, and a correction means. The image reading unit reads the image of the original. The pixel group detecting means detects a pixel group composed of a predetermined number or more of pixels having characteristics related to each other among a plurality of pixels constituting the scanned image read by the image reading unit. The determination means determines whether or not the pixel values of the pixels constituting the pixel group are included in a predetermined range. When it is determined that the pixel values of the pixels constituting the pixel group are included in a predetermined range, the correction means corrects the pixel values of the pixels constituting the pixel group to a predetermined pixel value to form the pixel group. When it is not determined that the pixel value of the pixel to be included is included in the predetermined range, the pixel value of the pixel constituting the pixel group is not corrected.

The second invention is an image processing apparatus subordinate to the first invention, and the correction means corrects the pixel values of the pixels constituting the pixel group so as to be substantially uniform.

A third invention is an image processing apparatus dependent on the first or second invention, further comprising a closed area extraction means for extracting a closed area occupying a predetermined area from a scanned image, and the pixel group detecting means is a pixel group detecting means. A pixel group composed of pixels included in the closed region extracted by the closed region extraction means is detected.

The fourth invention is an image processing apparatus dependent on the first or second invention, and is detected by a pixel value detecting means and a pixel value detecting means for detecting the pixel values of a plurality of pixels constituting the scanned image. Further, a classification means for classifying each pixel into one of a plurality of classes according to the pixel value of each pixel, and a most frequent class detecting means for detecting the most frequent class including the most pixels among the plurality of classes. The pixel group detecting means detects a pixel group composed of pixels included in one or more classes including at least the most frequent class.

A fifth aspect of the present invention is an image processing apparatus subordinate to any one of the first to fourth inventions, wherein a halftone dot area detecting means for detecting a halftone dot area from a scanned image and a halftone dot area detecting means are used for a net. When a point region is detected, a smoothing processing means for smoothing the halftone dot region of the scanned image is further provided, and the pixel group detecting means is smoothing in which the halftone dot region is smoothed by the smoothing processing means. A pixel group is detected from the scanned image after the conversion process.

The sixth invention is an image processing apparatus dependent on any one of the first to fifth inventions, and the determination means is that the pixel value of each pixel constituting the pixel group corresponds to the fading color. The correction means determines whether or not it is included in the range, and when the pixel value of each pixel constituting the pixel group is included in the specific range, the pixel value of the pixel constituting the pixel group is set to a pixel value other than the fading color. Correct to the pixel value corresponding to the color.

According to a seventh aspect of the present invention, a processor of an image processing apparatus including an image reading unit for reading an image of a document has a predetermined number or more of a plurality of pixels constituting the scanned image read by the image reading unit, which have characteristics related to each other. A step of detecting a pixel group composed of the pixels of the above, a step of determining whether or not the pixel value of the pixel constituting the pixel group is included in a predetermined range, and a predetermined pixel value of the pixel constituting the pixel group. When it is determined that the pixel value is included in the range of, the pixel value of the pixel constituting the pixel group is corrected to a predetermined pixel value, and it is not determined that the pixel value of the pixel constituting the pixel group is included in the predetermined range. In this case, it is a control program that executes a step of not correcting the pixel values of the pixels constituting the pixel group.

The eighth invention is a control method of an image processing apparatus including an image reading unit for reading an image of a document, and has features related to each other among a plurality of pixels constituting the scanned image read by the image reading unit. A detection step for detecting a pixel group composed of a predetermined number of pixels or more, a determination step for determining whether or not the pixel values of the pixels constituting the pixel group are included in a predetermined range, and a pixel constituting the pixel group. When it is determined that the pixel value of is included in a predetermined range, the pixel value of the pixel constituting the pixel group is corrected to a predetermined pixel value, and the pixel value of the pixel constituting the pixel group is within the predetermined range. This is a control method including a correction step that does not correct the pixel values of the pixels constituting the pixel group when it is not determined to be included.

According to the present invention, uneven density can be removed without blurring the image.

The above-mentioned object, other object, feature and advantage of the present invention will be further clarified from the detailed description of the following examples with reference to the drawings.

FIG. 1 is an illustrated diagram showing a schematic configuration when the image forming apparatus according to the first embodiment of the present invention is viewed from the front. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus shown in FIG. FIG. 3 is an illustrated diagram showing an example of a scanned image. FIG. 4 is an illustrated diagram showing an example of a case where a closed region is detected from a scanned image. FIG. 5 is an illustrated diagram showing an example of a corrected image obtained by correcting the scanned image of FIG. FIG. 6 is an illustrated diagram showing an example of a method of detecting a pixel group to be corrected from a class corresponding to a pixel value. FIG. 7 is a diagram showing an example of the memory map of the RAM shown in FIG. FIG. 8 is a flow chart showing an example of the CPU correction process shown in FIG. FIG. 9 is a diagram showing an example of a RAM memory map in the second embodiment. FIG. 10 is a flow chart showing an example of the correction process in the second embodiment. FIG. 11 is a flow chart showing an example of the correction process in the third embodiment.

[First Example]
With reference to FIG. 1, the image processing apparatus according to the first embodiment of the present invention is an image forming apparatus 10 having an image reading function (scanner function). In this embodiment, the image forming apparatus 10 is a multifunction device (MFP: Multifunction Peripheral) having a copying function, a printer function, a scanner function, a facsimile function, and the like. It should be noted in advance that the present invention is not limited to the multifunction device and can be applied to any image processing device having a scanner function.

First, the basic configuration of the image forming apparatus 10 will be schematically described. As shown in FIG. 1, the image forming apparatus 10 includes an apparatus main body 12 and an image reading apparatus 14 arranged above the apparatus main body 12.

The image reading device 14 includes a document mounting table 16 made of a transparent material such as platen glass. A document holding cover 18 can be opened and closed above the document mounting table 16 via a hinge or the like. The document holding cover 18 is provided with an automatic document feeder (ADF: Auto Document Feeder) 24 that automatically feeds the documents placed on the document placing tray 20 one by one to the image reading position 22. Be done.

Further, the image reading device 14 has a built-in image reading unit 26 including a light source, a plurality of mirrors, an imaging lens, a line sensor, and the like. The image reading unit 26 exposes the surface of the document with a light source, and guides the reflected light reflected from the surface of the document to the imaging lens by a plurality of mirrors. Then, the reflected light is imaged on the light receiving element of the line sensor by the imaging lens. The line sensor detects the luminance and chromaticity of the reflected light imaged on the light receiving element, and generates an image signal (read image data) based on the image on the surface of the document. As the line sensor, a CCD (Charge Coupled Device), a CIS (Contact Image Sensor), or the like is used.

The scanning unit including the light source and the plurality of mirrors is fixedly positioned below the image reading position 22 when reading the document fed by the ADF 24, and the document placed on the document mounting table 16 is placed. When reading, the image is moved in the sub-scanning direction (the left-right direction when the image forming apparatus 10 is viewed from the front).

The apparatus main body 12 has a built-in control unit 28 including a CPU 80 and a memory (RAM 84 and a storage unit 86) described later (see FIG. 2). The control unit 28 transmits a control signal to each part of the image forming apparatus 10 in response to an input operation (user operation) to the image forming apparatus 10, and causes the image forming apparatus 10 to perform various operations. The control unit 28 is also a control device for the image reading device 14 in order to control the entire image forming device 10.

Further, the image forming unit 30 and the like are built in the apparatus main body 12. The image forming unit 30 includes an exposure unit 32, a developer 34, a photoconductor drum 36, a cleaner unit 38, a charger 40, an intermediate transfer belt unit 42, a transfer roller 44, a fixing unit 46, and the like, and is conveyed from a paper feed tray 48. An image is formed on the paper to be formed by an electrophotographic method, and the image-formed paper is ejected to the paper ejection tray 50. As the printed image data for forming an image on the paper, the scanned image data read by the image reading unit 26, the image data transmitted from an external computer, or the like is used.

The image data handled by the image forming apparatus 10 corresponds to four color images of black (K), cyan (C), magenta (M), and yellow (Y). Therefore, each of the developer 34, the photoconductor drum 36, the cleaner unit 38, and the charger 40 is provided so as to form four types of latent images corresponding to each color, whereby four image stations are provided. It is composed.

In such an apparatus main body 12, a first paper transport path L1 for feeding the paper from the paper feed tray 48 to the paper discharge tray 50 via the resist roller 68, the transfer roller 44, and the fixing unit 46 is formed. NS. Further, when double-sided printing is performed on paper, the paper after single-sided printing is completed and has passed through the fixing unit 46 is returned to the first paper transport path L1 on the upstream side of the transfer roller 44 in the paper transport direction. The second paper transport path L2 is formed. A plurality of transport rollers 66 for transporting paper in the paper transport direction are appropriately provided in the first paper transport path L1 and the second paper transport path L2.

When performing single-sided printing (image formation) in the apparatus main body 12, the paper is guided from the paper feed tray 48 to the first paper transport path L1 one by one, and is resisted by a transport roller provided in the first paper transport path L1. It is conveyed to the roller 68. Then, the resist roller 68 conveys the paper to the transfer roller 44 (transfer nip portion) at the timing when the tip of the paper and the tip of the image information on the intermediate transfer belt 54 match, and the toner image is transferred onto the paper. .. After that, by passing through the fixing unit 46 (fixing nip portion), the unfixed toner on the paper is melted and fixed by heat, and the paper is discharged onto the paper ejection tray 50.

On the other hand, when double-sided printing is performed, when the rear end of the paper that has passed through the fixing unit 46 after single-sided printing reaches the transport roller 66 near the paper output tray 50 (most downstream side), this transport roller is reached. By rotating the 66 in the reverse direction, the paper runs in the reverse direction and is guided to the second paper transport path L2. The paper guided to the second paper transport path L2 is conveyed by the transport roller 66 through the second paper transport path L2, and is guided to the first paper transport path L1 on the upstream side of the resist roller 68 in the paper transport direction. At this point, the front and back sides of the paper are reversed, and then the paper passes through the transfer roller 44 and the fixing unit 46 to print on the back side of the paper.

FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus 10 shown in FIG. With reference to FIG. 2, the image forming apparatus 10 includes a CPU 80. The CPU 80 is connected to the RAM 84, the storage unit 86, the communication circuit 88, the input control circuit 90, the display control circuit 92, the image reading unit 26, and the image forming unit 30 via the bus 82. Further, an input device 94 is connected to the input control circuit 90, and a display 96 is connected to the display control circuit 92.

The CPU 80 controls the overall control of the image forming apparatus 10. The RAM 84 is the main storage device of the image forming apparatus 10, and is used as a work area and a buffer area of the CPU 80. The storage unit 86 is an auxiliary storage device of the image forming apparatus 10, and stores various programs for controlling the operation of the image forming apparatus 10, and image data transmitted from an external computer via a communication circuit 88. Or the scanned image data read by the image reading unit 26. However, as the storage unit 86, another non-volatile memory such as an HDD, SSD, flash memory, or EEPROM is used.

The communication circuit 88 is a communication circuit for connecting to a network such as a LAN and the Internet, and communicates with an external computer by using a protocol such as TCP / IP according to an instruction from the CPU 80.

The input device 94 is provided at an appropriate position such as the front side of the document mounting table 16, and includes, for example, a touch panel. The touch panel is a general-purpose touch panel, and any method such as a capacitance method, an electromagnetic induction method, a resistance film method, and an infrared method can be used. Further, the touch panel may be provided on the display surface of the display 96, or may be provided separately from the display 96. However, a touch display in which the touch panel is integrally formed with the display 96 may be provided. When a touch panel is provided, software keys such as various buttons and icons are displayed on the display 96. Further, the input device 94 may include a hardware operation button or an operation key (hardware key).

The software key is, for example, a key or an icon reproduced by software on the display surface of the display 96. On the other hand, a hardware key is a key or a push button provided as a physical device.

The display 96 is provided on the front side of the document mounting table 16. As the display 96, for example, an LCD or an EL (Electro-Luminescence) display can be used.

The input control circuit 90 outputs an operation signal or operation data corresponding to an input operation to the input device 94 to the CPU 80. When the input device 94 is a touch panel, the input control circuit 90 applies a voltage or the like required for the touch panel, detects a touch operation (touch input) within the effective touch range of the touch panel, and detects the touch operation (touch input). The touch coordinate data indicating the position of the touch input is output to the CPU 80. Further, when the input device 94 is a hardware key, the input control circuit 90 outputs an operation signal or operation data corresponding to the operation of the hardware key to the CPU 80.

The display control circuit 92 includes a GPU, a VRAM, and the like, and under the instruction of the CPU 80, the GPU displays display image data for displaying various screens on the display 96 using the image generation data stored in the RAM 84. It is generated in VRAM, and the generated display image data is output to the display 96.

The electrical configuration of the image forming apparatus 10 shown in FIG. 2 is merely an example, and is not limited to this.

The image forming apparatus 10 of this embodiment has a function (density unevenness correction function) for removing density unevenness (shading unevenness) of an image such as a scanned image. For example, density unevenness may occur in the image of the original due to aging or physical influence (for example, rubbing). In this case, the density unevenness that occurs in the image of the original document also causes the density unevenness in the scanned image read by the image reading unit 26. The density unevenness correction function is a function of identifying a region where density unevenness occurs in a scanned image when the scanned image has density unevenness and correcting the region to an image having no density unevenness.

Hereinafter, the density unevenness correction function (density unevenness correction processing) of the image forming apparatus 10 of this embodiment will be described with reference to FIGS. 3 to 6. First, when the image forming apparatus 10 receives a predetermined operation (scanning start operation) for executing the scanning (scanning) of the original while the original is placed on the document placing table 16, the image reading apparatus 14 receives the reading operation. In, the image of the document placed on the document placing table 16 is read, and the data of the scanned image (scanned image data) corresponding to the image of the document is generated.

FIG. 3 is an example of a scanned image. Usually, the scanned image contains at least one image element (a plurality of types of elements such as characters, figures, lines, and photographs). In the example shown in FIG. 3, the scanned image includes three figures 110, 120, 130 as image elements. Further, in the example shown in FIG. 3, in the scanned image, the regions other than the figures 110, 120, and 130 are regions in which no image element exists, that is, a so-called background region.

However, the respective colors (colors) of the figures 110, 120, and 130 are at least different colors from the base area, and are different colors from each other. For example, the first figure 110 is red or substantially red (similar color of red), the second figure 120 is green or substantially green (similar color of green), and the third figure 130 is blue or omitted. It is blue (similar color of blue). Further, in the example shown in FIG. 3, the base area is not colored. Therefore, the color of the background region is the background color (ground color) of the original.

However, in the example shown in FIG. 3, each of the figures 110, 120, and 130 includes a dark-colored portion and a light-colored (pale) portion. That is, in the figures 110, 120, and 130, density unevenness occurs.

When the image forming apparatus 10 accepts the scanning start operation and the scanned image corresponding to the image of the original is generated, among the plurality of pixels constituting the scanned image, there are a predetermined number or more of pixels having characteristics related to each other. In this case, a pixel group including a plurality of pixels having characteristics related to each other (composed of a plurality of pixels having characteristics related to each other) is detected.

Having characteristics related to each other means that the positions of the pixels are related to each other, such as being included in the same closed region, and that the colors of the pixels are related to each other, such as being the same color system (similar colors). Means. The predetermined number is the number of pixels that occupy a predetermined ratio (3 to 5%: 150,000 to 250,000 pixels or more in the case of an image of 5 million pixels) among a plurality of pixels constituting the scanned image. be. If the number of pixels having characteristics related to each other is less than a predetermined number, the pixel group is not detected.

First, a case where a pixel group is detected based on a closed region will be described. For example, pixels included in the same closed region including a predetermined number or more of pixels belong to the same pixel group. That is, when there is a closed region containing a predetermined number or more of pixels, there is a pixel group composed of the pixels included in the closed region. On the other hand, when the number of pixels included in the closed region is less than a predetermined number, the pixel group is not detected. Since the number of pixels included in the closed region is proportional to the area of the closed region, when the closed region occupies a predetermined area, a pixel group composed of the pixels included in the closed region is detected. When the closed area is equal to or smaller than a predetermined area, the pixel group composed of the pixels included in the closed area is not detected.

For example, in the case of the scanned image shown in FIG. 3, as shown in FIGS. 3 and 4, the edges of the figures 110, 120, and 130 are detected, and the area surrounded by the edges is detected as a closed area and closed. A pixel group composed of pixels included in the area is detected.

The method for detecting an edge from an image is not limited to a specific method such as a Sobel filter, a Laplacian filter, and a Canny filter for the entire image, and existing techniques can be used.

In the example shown in FIG. 3, the boundary between the first figure 110 and the base area is detected as the first edge 110a, and the boundary between the second figure 120 and the base area is detected as the second edge 120a. The boundary between the figure 130 of 3 and the background region is detected as the third edge 130a.

When an edge is detected from the scanned image, a closed region is detected by raster scanning. Specifically, first, the region excluding the region surrounded by the edges is recognized as one closed region, starting from the end portion (for example, the upper left) of the scanned image. For example, an area surrounded by edges is filled with a specific color, and an area filled with the same color is recognized as one closed area.

After that, further raster scanning is performed to detect pixels not included in the recognized closed area (pixels not painted with a specific color), that is, pixels included in the unrecognized area.

First, when raster scanning is performed with the upper left of the scanned image as the starting point, the pixels on the upper left of the scanned image are detected as pixels included in the unrecognized region. When a pixel included in the unrecognized area is detected, the area excluding the area surrounded by the edge is recognized as one closed area with the pixel as the starting point. In this embodiment, a portion other than the first region A, the second region B, and the third region C, that is, the base region is recognized as one closed region.

Next, the pixel inside the first edge 110a is detected as a pixel included in the unrecognized region. When a pixel included in the unrecognized area is detected, the area excluding the area surrounded by the edge is recognized as one closed area with the pixel as the starting point. That is, the region inside the first edge 110a is recognized as one closed region. By repeating the above processing, the region inside the second edge 120a and the region inside the third edge 130a are detected as closed regions, respectively.

As described above, when the detected closed region does not include a predetermined number or more of pixels, the closed region is not subject to the density unevenness correction processing and is excluded from the density unevenness correction processing. NS.

Therefore, as shown in FIG. 4, the first region A (inside the edge 110a) surrounded by the edge 110a corresponding to the boundary between the first figure 110 and the background region, the second figure 120, and the background region The second region B (inside the edge 120a) surrounded by the edge 120a corresponding to the boundary of the third figure 130 and the third region B (inside the edge 130a) surrounded by the edge 130a corresponding to the boundary between the third figure 130 and the base region. 3 regions C are detected. Further, a portion other than the first region A, the second region B, and the third region C, that is, the base region is detected as the fourth region D.

When the raster scan is completed, that is, when all the closed areas are detected, the pixel group is detected according to the detected closed areas. In this embodiment, the first pixel group composed of the pixels included in the first region A, the second pixel group composed of the pixels included in the second region B, and the pixels included in the third region C are used. A third pixel group composed of the third pixel group and a fourth pixel group composed of the pixels included in the fourth region D are detected.

When a pixel group is detected from the scanned image, it is determined for each detected pixel group whether or not it corresponds to the pixel group to be corrected that satisfies a predetermined determination condition. Specifically, it is determined whether or not the pixel value of each pixel (all pixels) constituting the pixel group is included in a predetermined range (density unevenness range). However, the pixel value is a value representing the color of the pixel. The density unevenness range is a range of colors (pixel values) that can be called density unevenness. When the pixel value of each pixel constituting the pixel group is included in the density unevenness range, the pixel group is treated (detected) as the pixel group to be corrected. On the other hand, when the pixel value of each pixel constituting the pixel group is not included in the density unevenness range, the pixel group is treated as a pixel group to be uncorrected.

For example, in the case of an RGB color system, the pixel value includes three color components of R (red), G (green), and B (blue), and includes a value (color value) for each color component. Each of the three color values is represented by 8 bits (0 to 255). For example, red is represented by R = 255, G = 0, B = 0, green is represented by R = 0, G = 255, B = 0, and blue is represented by R = 0, G = 0, B = 255. Be expressed. Further, black is represented by R = 0, G = 0, B = 0, and white is represented by R = 255, G = 255, B = 255.

Then, it is determined whether or not the difference between the maximum value (max) and the minimum value (min) of the color values of each color component (R, G, B) of each pixel constituting the pixel group is included in the density unevenness range. Will be done. For example, it is determined whether each of Rmax-Rmin, Gmax-Gmin, and Bmax-Bmin is within a range that can be called density unevenness (for example, within 30 in the case of 8 bits).

Here, it is determined whether or not all the color values are included in the density unevenness range. For example, when the R (red) color value and the G (green) color value are included in the density unevenness range, but the B (blue) color value is not included in the density unevenness range. Is treated as a pixel group to be uncorrected.

In addition, when the pixel value of each pixel constituting the pixel group is included in the density unevenness range, the color of each pixel is a similar color, for example, the pixels constituting the pixel group have the same color and the density is slightly different. If it is a category. Therefore, if the color of each pixel constituting the pixel group is different, it is not included in the density unevenness range. Further, even if the color tone of each pixel constituting the pixel group is the same, if the difference in density is too large (when it deviates from the category of similar colors), it is not included in the density unevenness range.

In this embodiment, the pixel value of each pixel included in the first pixel group (first region A), the pixel value of each pixel included in the second pixel group (second region B), and the fourth pixel group. It is determined that the pixel value of each pixel included in (4th region D) is included in the density unevenness range. Therefore, the first pixel group, the second pixel group, and the fourth pixel group are treated as the pixel group to be corrected.

On the other hand, it is determined that the pixel value of each pixel included in the third pixel group (third region C) is not included in the density unevenness range. That is, the third pixel group is treated as a pixel group to be uncorrected. This is because the third figure 130 has a similar color (blue or substantially blue), but the difference in density between the dark-colored portion and the light-colored portion is too large.

Then, when the pixel group to be corrected is detected, the pixel value of each pixel constituting the pixel group to be corrected is corrected to a uniform or substantially uniform pixel value (correction value) for each pixel group. However, a uniform or substantially uniform pixel value is a pixel value corresponding to the same color (same color), and the same color means each other even if they are not completely the same color. It means that they are the same to the extent that it is difficult to distinguish the colors of. On the other hand, the pixel values of the pixels constituting the non-correction target pixel group are not corrected.

Further, the correction value may be a value corresponding to the maximum value of the pixel value of each pixel constituting the pixel group, or a value corresponding to the minimum value of the pixel value of each pixel constituting the pixel group. It may be a value corresponding to the average value of the pixel values of each pixel constituting a pixel group.

In this embodiment, each pixel constituting the first pixel group, each pixel constituting the second pixel group, and each pixel constituting the fourth pixel group are corrected to the correction value for each pixel group. NS. Therefore, as shown in FIG. 5, each of the first figure 110 corresponding to the first pixel group, the second figure 120 corresponding to the second pixel group, and the background region corresponding to the fourth pixel group. The colors are corrected to be uniform (same color). That is, in the first figure 110, the second figure 120, and the base area, the tint and the color density are the same, and the density unevenness is removed.

On the other hand, since the pixel value of each pixel constituting the third pixel group is not corrected, the third figure 130 corresponding to the third pixel group has the same tint and color as the scanned image (original image) before correction. It is the density of.

Even if the pixel value of each pixel constituting a certain pixel group is included in the density unevenness range, the difference between the maximum value and the minimum value of the pixel value of each pixel constituting the pixel group is the density unevenness. When it is included in a range smaller than the range (correction determination range: for example, within 3 to 5 in the case of 8 bits), it may be treated as a non-correction target pixel group. This is because when the difference between the pixel values is small, the density unevenness is small, and if the density unevenness is such that it cannot be recognized by the human eye, it is not necessary to correct it.

Although the case where the pixel group is detected by detecting the closed region has been described above, the present invention is not limited to this. As described above, a pixel group may be detected based on the color relationship of each pixel. Hereinafter, a case where a pixel group is detected based on the color relationship of each pixel constituting the scanned image will be described.

When the pixel group is detected based on the color relationship of each pixel, first, the pixel value of each pixel constituting the scanned image is detected. Next, a plurality of classes are set according to the pixel value, and each pixel is classified into one of the plurality of classes according to the pixel value. When each pixel constituting the scanned image is classified into classes, the most frequent class including the most pixels among the plurality of classes is detected. Then, a pixel group composed of pixels included in one or more classes including at least the mode class (a predetermined range including the mode class) is detected. In the case of the RGB color system, the three color values of R, G, and B are classified into classes, and a predetermined range including the most frequent class and the most frequent class is set for each of the three color values. Then, in all the color values, a pixel group composed of pixels included in a predetermined range including the mode is detected.

FIG. 6 is a graph (histogram) showing a case where each pixel constituting a certain scanned image is classified according to a pixel value (color value) for a certain color value. The vertical axis of FIG. 6 shows the number (frequency) of pixels included in each class, and the horizontal axis of FIG. 6 shows the class according to the pixel value. In the example shown in FIG. 6, the color value is represented by 8 bits (0 to 255), and 10 pixel values are included in one class starting from the pixel value 0 (minimum value) (the width of the class is It is divided into 26 stages so that the pixel value is 10). For example, the pixel values 0 to 9 are in the class of "0", and the pixel values 10 to 19 are in the class of "10". However, the class of "250" includes six pixel values of pixel values 250 to 255. Then, each of the pixels constituting the scanned image is classified into each class according to the pixel value.

In the example shown in FIG. 6, the number of pixels included in the "210" class is the largest among the classes. That is, the class of "210" is the mode. Therefore, a pixel group composed of pixels included in one or more classes including at least the mode of "210" is detected. For example, a pixel group composed of pixels included only in the "210" class may be detected, or "210" and a class adjacent thereto (in this embodiment, the "200" class or "220"). A pixel group composed of pixels included in a plurality of classes such as class) may be detected.

However, since the graph shown in FIG. 6 only shows the color values of one color, when there are multiple color values, all the color values are within a predetermined range including the most frequent class. A pixel group composed of the included pixels is detected.

The example shown in FIG. 6 is an example, and the pixel value 255 (maximum value) may be used as a starting point. Further, the width of the class is not limited to 10 pixel values, and the width of the class can be arbitrarily set in the range of 1 to 30 pixel values.

Then, the data (corrected image data) of the image (corrected image) subjected to the density unevenness correction processing as described above can be used as print image data for forming an image on paper, or can be used by the image forming apparatus 10. It is stored in a memory (storage unit 86) or transmitted to an external computer via a communication circuit 88.

The above-mentioned operation of the image forming apparatus 10 is realized by the CPU 80 executing a control program stored in the RAM 84. The specific processing will be described later using a flow chart.

FIG. 7 is a diagram showing an example of the memory map 300 of the RAM 84 shown in FIG. The RAM 84 includes a program storage area 302 and a data storage area 304, and the control program of the image forming apparatus 10 is stored in the program storage area 302. However, since the image forming apparatus 10 includes the image reading apparatus 14, this control program includes the control program of the image reading apparatus 14.

As shown in FIG. 7, the control program stored in the program storage area 302 includes a display program 302a, an operation detection program 302b, an image reading program 302c, a pixel group detection program 302d, a determination program 302e, a pixel value correction program 302f, and the like. include.

The display program 302a is a program for generating display image data corresponding to various screens to be displayed on the display 96 using image generation data including polygon data and texture data, and outputting the display image data to the display 96.

The operation detection program 302b is a program for detecting an input operation to the input device 94. For example, the operation detection program 302b is a program for acquiring the touch coordinate data output from the input control circuit 90 when the touch panel is operated and detecting that the software key displayed on the display 96 is operated. Is. Further, the operation detection program 302b is a program for acquiring the operation data output from the input control circuit 90 when the hardware key is operated and detecting that the hardware key is operated.

The image scanning program 302c is a program for scanning (scanning) an image of a document and outputting an image signal (scanned image data 304c) corresponding to the scanned image.

The pixel group detection program 302d is a program for detecting a pixel group having features related to each other and including a predetermined number or more of pixels among a plurality of pixels constituting the scanned image. The pixel group detection program 302d includes a closed area detection program for detecting the same closed area including a predetermined number or more of pixels, and a pixel group composed of pixels included in the closed area detected according to the closed area detection program. It is also a program for detection. Further, the pixel group detection program 302d has a plurality of pixels according to the pixel value detection program for detecting the pixel value of each pixel constituting the scanned image and the pixel value of each pixel detected according to the pixel value detection program. Includes a classification program for classifying into one of the classes and a most frequent class detection program for detecting the most frequent class containing the most pixels among multiple classes, and was detected according to the most frequent class detection program. It is also a program for detecting a pixel group composed of pixels included in one or more classes including the most frequent class.

The determination program 302e is a program for determining whether or not the pixel values of each pixel (all pixels) constituting the pixel group are included in the density unevenness range. That is, the determination program 302e is for determining whether the pixel group detected according to the pixel group detection program 302d is a pixel group to be corrected whose pixel value of each pixel constituting the pixel group is included in the density unevenness range. It's also a program.

When the pixel value correction program 302f determines that the pixel value of each pixel constituting the pixel group is included in the density unevenness range according to the determination program 302e, the pixel value correction program 302f determines the pixel value of each pixel constituting the pixel group to be predetermined. This is a program for correcting to the correction value.

Although not shown, the program storage area 302 also stores other programs for realizing the functions included in the image forming apparatus 10, such as a communication program and an image forming program.

Further, the image generation data 304a, the operation data 304b, the read image data 304c, the pixel group data 304d, the determination condition data 304e, and the corrected image data 304f are stored in the data storage area 304.

The image generation data 304a is image data including polygon data, texture data, and the like for generating display image data for various screens displayed on the display 96. Further, the image generation data 304a also includes image data of a software key and the like. The operation data 304b is touch coordinate data and / or operation data detected according to the operation detection program 302b.

The scanned image data 304c is the data of the scanned image output according to the scanning program 302c. Further, the scanned image data 304c includes information about the pixel value of each pixel constituting the scanned image.

The pixel group data 304d is data of a pixel group detected according to the pixel group detection program 302d, and includes data for each pixel group when a plurality of pixel groups exist. Further, the pixel group data 304d includes information about the pixel value of each pixel constituting the pixel group.

The determination condition data 304e is data of the determination condition for determining whether or not the pixel group detected according to the pixel group detection program 302d is the pixel group to be corrected. As described above, in the present embodiment, it is determined whether or not the pixel value of each pixel constituting the pixel group is included in the density unevenness range. Therefore, the determination condition data 304e is data for defining the density unevenness range. Is.

The corrected image data 304f is data of an image (corrected image) obtained by subjecting the scanned image to density unevenness correction processing. That is, the corrected image data 304f is the data of the corrected image after the pixel value of each pixel constituting the pixel group to be corrected is corrected to a predetermined correction value based on the scanned image.

Although not shown, the data storage area 304 stores other data such as image generation data necessary for executing the control program, and other flags necessary for executing the control program. Or something.

FIG. 8 is a flow chart showing an example of the density unevenness correction process of the CPU 80 shown in FIG. As shown in FIG. 8, when the CPU 80 starts the density unevenness correction process, the image of the original is read in step S1 and a scanned image is generated, and in step S3, whether or not there is a pixel group (pixel group is detected). Or) Judge whether or not. Here, it is determined whether or not there are a predetermined number or more of pixels having characteristics related to each other among the plurality of pixels constituting the scanned image.

If it is "NO" in step S3, that is, if it is determined that there is no pixel group, the density unevenness correction process is terminated. On the other hand, if "YES" in step S3, that is, if it is determined that there is a pixel group, it is determined in step S5 whether or not there is a pixel group to be corrected. Here, it is determined whether or not the pixel group detected in step S3 satisfies a predetermined determination condition, that is, whether or not the pixel value of each pixel constituting the pixel group is included in the density unevenness range.

If it is "NO" in step S5, that is, if it is determined that there is no pixel group to be corrected, the density unevenness correction process is terminated. On the other hand, if "YES" in step S5, that is, if it is determined that there is a pixel group to be corrected, the pixel value of each pixel constituting the pixel group to be corrected is set to a predetermined correction value in step S7. Correct and end the density unevenness correction process.

According to this first embodiment, among a plurality of pixels constituting the scanned image, a pixel group composed of a predetermined number or more of pixels having characteristics related to each other is detected, and the pixels of each pixel constituting the pixel group are detected. When the value is included in the density unevenness range, the pixel value of each pixel constituting the pixel group is corrected to a uniform or substantially uniform correction value, so that the density unevenness can be removed without blurring the image. Can be done.

Further, in the first embodiment, the pixel group may be detected based on the closed region. That is, a pixel group may be detected based on the relationship between the positions of the pixels. In this case, uneven density of image elements such as figures included in the scanned image can be appropriately removed.

Further, according to the first embodiment, the pixel group may be detected based on the color relationship of each pixel regardless of the position of each pixel constituting the scanned image. Specifically, each pixel constituting the scanned image is classified according to the pixel value, and a pixel group composed of pixels included in at least one or more classes including the mode is detected. In this case, it is possible to appropriately remove the density unevenness of the background region of the scanned image or a plurality of image elements of similar colors.

[Second Example]
The image forming apparatus 10 of the second embodiment is the same as that of the first embodiment except that when the scanned image contains a halftone dot region, the halftone dot region is smoothed and then the density unevenness correction processing is performed. Therefore, the contents different from those of the first embodiment will be described, and duplicated explanations will be omitted.

In the second embodiment, when the scanned image is generated, the region separation process is performed before the density unevenness correction process is executed. The area separation process is a process of separating each pixel of image data into areas such as a halftone dot area, a character area, a photographic area, a background area, and an indefinite area. In this embodiment, it is sufficient that at least the halftone dot region can be separated from the scanned image. A specific example of the region separation process is described in Japanese Patent Application Laid-Open No. 2004-272557 by the present applicant, so please refer to it.

When the halftone dot region is separated from the scanned image, that is, when the halftone dot region is included in the scanned image, a smoothing process for smoothing the halftone dot region is executed. For the smoothing process, smoothing with a spatial filter or the like is used. When the smoothing process is executed, a pixel group is detected from the scanned image (processed image) after the smoothing process. Since the processing after the detection of the pixel group is the same as that of the first embodiment, detailed description thereof will be omitted.

FIG. 9 is a diagram showing an example of the memory map 300 of the RAM 84 in the second embodiment. As shown in FIG. 9, and in the second embodiment, the control program includes at least the area separation program 302 g for executing the area separation process for separating the halftone dot area from the scanned image and the halftone dot area smoothing. A smoothing processing program 302h for executing the smoothing processing to be performed is included. Further, in the second embodiment, the halftone dot area data 304g, which is the data of the halftone dot area, is stored in the data storage area 304. The halftone dot area data 304g is image data corresponding to the halftone dot area.

Hereinafter, the density unevenness correction processing in the second embodiment will be described with reference to the flow chart. However, the same reference numerals are given to the same processing as the density unevenness correction processing described in the first embodiment, and the duplicated contents are described. , The explanation will be omitted or briefly explained.

FIG. 10 is a flow chart showing an example of the density unevenness correction process of the second embodiment. As shown in FIG. 10, when the CPU 80 starts the density unevenness correction process, the scanned image is generated in step S1 and the area separation process is executed in step S31. Subsequently, in step S33, it is determined whether or not there is a halftone dot region. Here, it is determined whether or not the halftone dot region is separated from the scanned image.

If it is "NO" in step S33, that is, if it is determined that there is no halftone dot area, the process proceeds to step S3. On the other hand, if "YES" in step S33, that is, if it is determined that there is a halftone dot region, in step S35, a smoothing process for smoothing the halftone dot region is executed, and the process proceeds to step S3.

Since the contents of the processes after step S3 are the same as those in the first embodiment, the description thereof will be omitted.

According to the second embodiment, when the halftone dot region is included in the scanned image, the halftone dot region is smoothed and then the density unevenness correction processing is performed. Therefore, the image includes the halftone dot region. However, uneven density can be appropriately removed.

[Third Example]
When the pixel values of the pixels constituting the pixel group are included in a specific range corresponding to the fading color, the image forming apparatus 10 of the third embodiment sets the pixel values of the pixels constituting the pixel group to the fading color. Since it is the same as the first embodiment except that the correction value is corrected to correspond to a specific color other than the above, the contents different from those of the first embodiment will be described, and the duplicated description will be omitted.

In the third embodiment, when the pixel group to be corrected is detected, it is determined whether or not the pixel value of each pixel constituting the pixel group to be corrected is included in a specific range corresponding to the fading color. That is, it is determined whether or not the pixel group to be corrected is a pixel group corresponding to the fading color. The fading color means a yellowish color due to sunburn, deterioration over time, or the like. Being included in the specific range corresponding to the fading color means that the color value of R (red) is within the range of 240 ≦ 255, the color value of G (green) is within the range of 245 ≦ 255, and B ( It means that the color value of blue) is within the range of 150 ≦ 200.

Further, the fact that the pixel value of each pixel of the pixel group to be corrected is included in a specific range may mean that the pixel values of all the pixels constituting the pixel group to be corrected are included in the above range. The average value of the pixel values of each pixel constituting the target pixel group may be included in the above range.

When the pixel value of each pixel constituting the pixel group to be corrected is included in a specific range corresponding to the fading color, the pixel value of the pixel constituting the pixel group becomes a specific color other than the fading color. It is corrected to the corresponding value (specific value). Specifically, it is corrected to a value corresponding to white (R = 255, G = 255, B = 255).

When the pixel value of each pixel constituting the pixel group to be corrected is not included in the specific range, the same processing as in the first embodiment is executed.

In the third embodiment, the control program includes a fading determination program for determining whether or not the pixel value of each pixel constituting the pixel group to be corrected is included in a specific range corresponding to the fading color. .. Further, in the third embodiment, the pixel value correction program 302f configures the pixel group when the pixel value of each pixel constituting the pixel group to be corrected is included in a specific range corresponding to the fading color. It is also a program for correcting the pixel value of a pixel to be corrected to a correction value corresponding to a specific color.

Hereinafter, the density unevenness correction processing in the third embodiment will be described with reference to the flow chart. However, the same reference numerals are given to the same processing as the density unevenness correction processing described in the first embodiment, and the duplicated contents are described. , The explanation will be omitted or briefly explained.

FIG. 11 is a flow chart showing an example of the density unevenness correction process of the third embodiment. As shown in FIG. 11, if “YES” in step S5, that is, if it is determined that the pixel group to be corrected is detected, it is determined in step S51 whether or not there is a pixel group corresponding to the brown color. do. Here, it is determined whether or not the pixel value of each pixel constituting the pixel group to be corrected is included in a specific range.

If it is "NO" in step S51, that is, if it is determined that there is no pixel group corresponding to the brown color, the process proceeds to step S57 described later. On the other hand, if "YES" in step S51, that is, when it is determined that there is a pixel group corresponding to the brown color, the pixel values of the pixels constituting the pixel group corresponding to the brown color are specified in step S53. After correcting to a specific value corresponding to the color, in step S55, it is determined whether or not there is another pixel group, that is, a pixel group other than the pixel group corresponding to the brown color. If it is "NO" in step S55, that is, if it is determined that there is no other pixel group, the density unevenness correction process is terminated. On the other hand, if "YES" in step S55, that is, if it is determined that there is another pixel group, the pixel value of each pixel constituting the other pixel group is set to a uniform or substantially uniform correction value in step S57. (Same process as in step S9), and the density unevenness correction process is completed.

According to the third embodiment, when the pixel value of the pixel constituting the pixel group is included in a specific range corresponding to the fading color, the pixel value of the pixel constituting the pixel group is specified other than the fading color. Since the correction value is adjusted to correspond to the color of the above, it is possible to appropriately correct the change in the image of the original due to the fading and eliminate the uneven density.

The embodiment shown in the third embodiment can be adopted in combination with the second embodiment.

Further, the specific configuration and the like given in the above-described embodiment are examples, and can be appropriately changed according to the actual product. Further, the order in which each step of the flow chart shown in the above-described embodiment is processed can be appropriately changed as long as the same result can be obtained.

10 ... Image forming device 14 ... Image reading device 26 ... Image reading unit 80 ... CPU
84 ... RAM

Claims (8)

Image reader that reads the image of the original,
A pixel group detecting means for detecting a pixel group composed of a predetermined number or more of pixels having characteristics related to each other among a plurality of pixels constituting the scanned image read by the image reading unit.
A determination means for determining whether or not the pixel values of the pixels constituting the pixel group are included in the predetermined range, and a case where it is determined that the pixel values of the pixels constituting the pixel group are included in the predetermined range. In addition, the pixel value of the pixel constituting the pixel group is corrected to a predetermined pixel value, and the pixel group is configured when it is not determined that the pixel value of the pixel constituting the pixel group is included in the predetermined range. An image processing device including a correction means that does not correct the pixel value of the pixel to be used. The image processing apparatus according to claim 1, wherein the correction means corrects the pixel values of the pixels constituting the pixel group so as to be substantially uniform. Further provided with a closed area extraction means for extracting a closed area occupying a predetermined area from the scanned image.
The image processing apparatus according to claim 1 or 2, wherein the pixel group detecting means detects a pixel group composed of pixels included in the closed region extracted by the closed region extracting means. A pixel value detecting means for detecting the pixel values of a plurality of pixels constituting the scanned image,
A classification means for classifying each pixel into one of a plurality of classes according to the pixel value of each pixel detected by the pixel value detecting means, and a mode class including the most pixels among the plurality of classes. Further equipped with the mode detection means to detect
The image processing apparatus according to claim 1 or 2, wherein the pixel group detecting means detects a pixel group composed of pixels included in at least one or more classes including the mode. When the halftone dot region is detected by the halftone dot region detecting means for detecting the halftone dot region from the scanned image and the halftone dot region detecting means, smoothing is performed to smooth the halftone dot region of the scanned image. With more processing means,
The pixel group detecting means according to any one of claims 1 to 4, wherein the pixel group detecting means detects the pixel group from the read image after the smoothing processing in which the halftone dot region is smoothed by the smoothing processing means. Image processing equipment. The determination means determines whether or not the pixel value of each pixel constituting the pixel group is included in a specific range corresponding to the fading color.
When the pixel value of each pixel constituting the pixel group is included in the specific range, the correction means sets the pixel value of the pixel constituting the pixel group to a pixel value corresponding to a color other than the fading color. The image processing apparatus according to any one of claims 1 to 5, which is corrected to. For the processor of an image processing device equipped with an image reader that reads the image of the original,
A step of detecting a pixel group composed of a predetermined number or more of pixels having characteristics related to each other among a plurality of pixels constituting the scanned image read by the image reading unit.
A step of determining whether or not the pixel values of the pixels constituting the pixel group are included in a predetermined range, and
When it is determined that the pixel values of the pixels constituting the pixel group are included in the predetermined range, the pixel values of the pixels constituting the pixel group are corrected to the predetermined pixel values to form the pixel group. A control program for executing a step of not correcting the pixel values of the pixels constituting the pixel group when it is not determined that the pixel values of the pixels are included in the predetermined range. It is a control method of an image processing device provided with an image reader for reading an image of a document.
A detection step for detecting a pixel group composed of a predetermined number or more of pixels having characteristics related to each other among a plurality of pixels constituting the scanned image read by the image reading unit.
A determination step for determining whether or not the pixel values of the pixels constituting the pixel group are included in a predetermined range, and
When it is determined that the pixel values of the pixels constituting the pixel group are included in the predetermined range, the pixel values of the pixels constituting the pixel group are corrected to the predetermined pixel values to form the pixel group. A control method including a correction step that does not correct the pixel values of the pixels constituting the pixel group when it is not determined that the pixel values of the pixels are included in the predetermined range.

Images