JP2013131943A - Image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing device, an image processing method, and a program for executing the image processing method for performing image processing on input image data or read image data to generate output image data, thereby preventing scatter of transferred toner when printing on a medium.SOLUTION: An image processing device comprises: means for switching a condition for determining a determination region in substitution determination processing; and means for switching a density condition and a position condition for substitution target determination.

Description

  The present invention relates to an image processing apparatus, an image processing method, and a program for executing the image processing method.

  Input image (print) data or read image data sent from an input device such as a copier or printer, such as a host computer or scanner, is developed into a rasterized image, image processing is performed, and output image data is generated and output (printed) There are devices that print on media using devices and functions. Some of these have a function of correcting the generated print data in accordance with the characteristics of the output device. For example, when the output image data included in a certain area has a maximum density or a density close to it, such as a solid filled image, for example, in an electrophotographic printing apparatus, a large amount of toner is applied to the filled area. Since it adheres, it may be scattered outside the area where it should originally be placed.

  As a problem in the electrophotographic image forming process that causes such toner scattering, when fixing the toner transferred on the medium, the rapid expansion of water vapor generated when passing through the fixing device causes the pre-fixing. A phenomenon in which toner is blown off is known.

  Such a phenomenon is particularly noticeable in the case of a specific toner accumulation width with respect to the conveyance direction of the medium, and is specifically recognized for a continuous region of about 4 to 10 pixels at a resolution of 600 dpi. It is a phenomenon. If this range is exceeded, the effect of blowing off due to the expansion of water vapor is weakened, so the rate of occurrence gradually decreases. In addition, the frequency of occurrence of this phenomenon increases as the amount of applied toner increases with respect to the toner accumulation region.

  In order to prevent this, a method has been proposed in which the applied amount of toner is reduced by thinning a part of the generated output image data. According to this method, the density is reduced as compared with the case where the image is output according to the original output image data, but it is possible to suppress toner scattering due to the overload amount.

  In Patent Document 1, it is first determined whether output image data (single pixel or a plurality of pixel regions) corresponding to a window area matches a determination pattern. Next, output image data that has undergone image processing that changes in a direction to decrease the value of a pixel or pixel area at a predetermined position inside the window area that matches the determination pattern is used in a device that forms an image on a recording medium using a recording material. It presents a way to output. Further, in Patent Document 2, after performing the same determination process, output image data that has undergone image processing that changes the pixel or the pixel area in a predetermined position outside the window area that matches the determination pattern in a direction that increases the value. A method of outputting to an apparatus that forms an image on a recording medium using a recording material is presented. The purpose of this is to add the one or more pixels at an invisible level to the outside of the window area, thereby obtaining the same effect as when the pixels inside the window area are thinned out.

JP 2006-295624 A JP 2009-23283 A

  In such a process of correcting output image data, the following determination means is provided in any method of thinning out or adding pixels. That is, when extracting the image area to be corrected, it is determined whether or not the image data corresponding to the window area matches the determination pattern, and the pixel or pixel area at a predetermined position inside the window area that matches the determination pattern Are subject to correction processing.

  In the conventional technique, an image signal value is assumed such that the toner is sufficiently placed in a certain region corresponding to a state where toner scattering can occur. For example, when image data designating the maximum density is sent from the host computer to the printer, it is expected that the amount of toner loaded on the print medium will be maximized. Therefore, an image that needs to avoid toner scattering is determined by a digital signal having a maximum value (black) as a determination condition, and is basically determined in units of pixels. However, in actuality, since processing in units of pixels is heavy in terms of processing speed, in many cases, determination processing is simultaneously performed on a plurality of pixels in order to increase the speed. Even in this case, the basic idea is the determination in units of pixels, and as a result, only when all the pixels have the maximum value, they are to be replaced.

  However, since toner scattering depends on the actual amount of applied toner, it does not always occur only when the image signal has the maximum value. That is, even when all the image signals included in a certain image area are not the maximum value, and even when the image is not determined as a correction target in the related art, toner scattering may occur depending on the process conditions of the printing apparatus.

  In addition, in the case of a printing apparatus such as a printer that receives a digital input image signal from a host computer, the image data includes the same image signal uniformly in the same density region, so that the image having the same density is included. The image signal is uniform in the area. Accordingly, the correction area determination can be performed on the assumption that a uniform image signal is included in the density area where toner scattering is expected to occur. However, read image data taken from an image reading apparatus such as a copying machine generates non-uniform image signals for the same density region of the original document depending on the reading apparatus. In such an image area, if the image data of the original document has a sufficiently high density value, toner scattering may occur as a result of printing. However, since the read signal varies, all the image data in the determination area have the same density value. Not necessarily. If there is an image signal having a density that does not reach the threshold value in the determination area, the pixel or the pixel area is not regarded as a correction target range, and there is a problem that correction processing is not performed. Also, in this case, corrections may or may not be applied depending on the image data position in the window area for images that have the same density area in the original document, and the thinning or additional processing results are not uniform and correction is performed. There is a problem that the harmful effect of processing becomes conspicuous.

  FIG. 3 is an explanatory diagram of correction processing by a conventional method.

  In the conventional method, since it is basically determined whether or not it is a replacement target in units of pixels, even when the determination region is processed in units of 8 pixels in order to improve the processing speed, all 8 pixels are black pixels, and Only when all the eight pixels on the line adjacent in the downward direction are white pixels, the boundary portion is determined to be an edge (FIG. 3A). Therefore, if at least one of the eight pixels contains a white pixel, that portion is determined to be a non-edge portion (FIG. 3 (i)). Similarly, when the condition of the determination area is 3 lines or more, if all the pixels in the 3 lines are black, the area is determined to be a replacement target (FIG. (U)). If a pixel is included, the entire region is determined not to be replaced (FIG. (E)). As a result, if the image is an all black image in digital data (FIG. 3), a replacement process is executed to form a thinned image (FIG. 3). Even if the image is close to black (FIG. 3), the replacement process is not executed (FIG. 3), and toner scattering cannot be suppressed.

The concept of image formation for solving the above problems will be described with reference to FIG.
In the present invention, the average area concentration in the determination region is used as the determination condition for determining whether or not to perform the replacement process, and the edge / internal determination condition for extracting the determination area. Is determined by comparison with a threshold value (density value). In other words, even when white pixels are included in a part of the determination area, if the density is considered to be sufficient to cause toner scattering, replacement processing is executed.
Similarly, when the edge portion is extracted and the replacement process is performed, the comparison between the average area density and the threshold value is used for determining whether or not the edge portion is included.

  As a result, when it is predicted that the average area density of the image is 80% or more in terms of process conditions, toner scattering may occur unless the conventional method is 100%. The replacement process can be switched at an average area concentration of 80%. According to this, even if an image in which only one pixel out of eight pixels is a white pixel (FIG. 4A) or an image containing two white pixels out of 8 × 3 pixels (FIG. 4U), each is replaced. Processing is executed. On the other hand, if the area density is less than 80% as shown in FIG. 4 (i) or FIG. 4 (e), the replacement process is not executed.

  As a result, similar to the case of FIG. 4 (O) where the area density is 100%, the replacement process is also performed on the image of FIG. Thus, an image as shown in FIG. On the other hand, when 6 white pixels out of 24 pixels are included as shown in FIG. 4 (ke), the ratio is less than 80%, so that the replacement process is not executed and an image as shown in FIG. 4 (ko) is formed.

  According to the present invention, an image processing apparatus that performs a replacement process of image data for the purpose of adjusting a toner amount in a certain image area with a binary image as a determination target, which is input from an image input apparatus (201). In the image processing unit (205) of the image forming apparatus (202) that has received the image data, means (206) for acquiring the determination area width and height for the input image from the information storage unit (210), and the determined determination area A means (206) for determining a determination area from the width and height, a means (207) for calculating an average area density (monochrome pixel ratio) of image data included in the determination area, and the area to be replaced. Means (207) for acquiring a replacement area determination threshold value for determining whether or not it is an average area density from the information storage unit (210), and a hand for determining whether or not the area is a replacement target area (207), means (208) for acquiring from the information storage unit (210) an edge portion determination threshold value for determining whether or not the region has an edge portion, and whether or not the region has an edge inside Means (208) for acquiring an internal determination threshold for determining whether from the information storage unit (210), the edge determination threshold, the edge internal determination threshold, and the average area concentration of the determination region, respectively, With respect to the replacement area determined by the means for determining whether or not to be replaced (208) and the previous replacement area determination means (206), the replacement process determination unit (207, 208) The above-mentioned problem is solved by having a means (209) for performing replacement processing of image data.

  Further, the image processing unit (205) stores device information representing the correlation between the amount of applied toner in a predetermined area and the average area density of the image data included in the determination area, and the device Means for determining a replacement determination threshold value from the information (207) to solve the above problem.

Further, the image processing unit (205) stores device information representing the correlation between the original document density and the average area density in the determination region after the original image is read by the scanner and binarized. (210), means (208) for determining an edge determination threshold from the device information,
Means for obtaining an internal determination threshold value from the device threshold value to solve the above problem.

  Furthermore, it has means (202) for recognizing the processing mode of the image data set by the user interface (204) or the like and switching the determination area width in accordance with the processing mode, and the set processing mode is “character data”. ”Is set to a low value, and the determination area width is set wide when the set processing mode is a mode assuming“ image data ”. And the means (206).

  As a result, it is possible to realize a suppression process in which the toner scattering is sufficiently suppressed for an image region where the original image signal is not uniform, and the adverse effect due to the nonuniform image signal is not noticeable.

It is a flowchart for a problem solution. It is explanatory drawing of the software module of each apparatus. It is state explanatory drawing of the image data in a prior art. It is state explanatory drawing of the image data in this invention. It is a detailed flowchart for problem solving demonstrated in embodiment of this invention. It is a detailed flowchart for problem solving demonstrated in embodiment of this invention. It is a detailed flowchart for problem solving demonstrated in embodiment of this invention.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 2 shows a system configuration and a module configuration for carrying out the present invention.

  This configuration is an example of a copying machine provided with an image reading device or the like, but a similar embodiment is possible even in an image processing device such as a printer whose input is digital data.

  Image data generated by an image input device (201) such as a scanner is binarized and sent to an image forming device (202) such as a controller.

  The image forming apparatus includes a user interface (204) such as a panel, and functions of the image forming apparatus can be switched. The input image data sent to the image forming apparatus is treated as already binarized. The image forming apparatus includes an image processing unit (205) therein. In the image processing unit, a determination region determining unit (205) that determines a unit region for image replacement processing, a density determination unit (207) that determines whether or not to be a replacement processing target from the viewpoint of image density, A position determination unit (208) determined from a viewpoint and an execution unit (209) that actually performs a replacement process after passing through these determination processes are provided. Furthermore, an information storage unit (210) for storing information used for area determination is provided.

  The output image data subjected to the replacement process in the image forming apparatus is sent to the image printing apparatus (203) and printed on a print medium such as paper.

  Here, as a condition 1 for determining whether or not to perform the replacement process, a toner applied amount in a certain area is used as a criterion (density condition), and as a condition 2, it is determined that an image in the certain area has an edge portion. (Position condition) shall be set. These are in accordance with device conditions where toner scattering is likely to occur. Since the applied toner amount depends on the process setting of the device, the applied toner amount in a certain region and the binarized image data formed in the preceding stage have a certain correlation. That is, if the device-specific information is held, it is possible to predict the applied toner amount from the average area density of the binarized image data (black pixel occupation ratio in a certain area). In the present invention, the information storage unit (210) of the image processing apparatus holds these pieces of information.

  An embodiment of the present invention will be described in detail with reference to FIGS.

  The image input apparatus in FIG. 1 (FIG. 2201, hereinafter the same) first binarizes the image read in S101 in S102, and transfers it to the image forming apparatus (202) in S103. Thereafter, the binary image transferred in S104 in the image forming apparatus is received. In S105, it is determined whether or not the determination area is fixed. If the determination area is fixed, the fixed value is directly used as the determination area in S107. If it is variable, the determination area is selected in S106. (The variable case will be described in detail in [Other Embodiments].

  Next, in S108, the black pixels and white pixels in the determination area determined in S107 are counted, and the average area density is obtained from the monochrome ratio.

  In the replacement area determination for determining whether or not to perform the replacement process in S109, it is determined whether or not the density condition is fixed. If it is fixed, a fixed value is set as the density condition in S111. If variable, the density condition is selected in S110. Hereinafter, this process will be described in detail with reference to FIG.

  After shifting to S109, in S501, correlation information between the applied toner amount and the area density of the binarized image, which is device information, is held in the information storage unit (210) in the image processing unit (205) of the image forming apparatus (202). Judge whether to do. In the case of holding, it is determined that the density condition for determining the replacement area is variable, and the process proceeds to S502. If not, assuming that the applied toner amount is proportional to the area density, the density threshold value at which toner scattering occurs is set to the maximum value in S508. If it is variable, it is further determined in S502 whether or not the information storage unit (210) holds the density threshold value at which toner scattering occurs. If it is held, the process proceeds to S503, and if it is not held, the process proceeds to S508. If it is determined in both S501 and S502 that the information is held, the applied toner amount is calculated from the average area density in the determination region in S503. In S504, a density threshold value at which toner scattering occurs is acquired from the information storage unit (210), and the toner scattering occurrence threshold value acquired in S505 is set as the density condition of the determination region.

  In S506, the set expected toner applied amount and the toner scattering occurrence threshold value are compared. If the applied toner amount exceeds the scattering occurrence threshold value, the determination region is determined as a replacement target in S507, and if it is lower, the determination region is not determined in S509. It is determined as a replacement target, and in both cases the process proceeds to S113.

  The above processing is performed by the replacement processing density determination unit (207) of the image processing unit (205).

  When the replacement target determination 1 is completed in S112 using the results of the density determination processes S108 to S111, it is determined in S113 whether or not the determination region is a replacement target. If it is a replacement target, the process proceeds to replacement region position determination in S114. To do. In the case of non-replacement, the process proceeds to S120 without executing the replacement process.

  In step S114, it is determined whether or not the position condition is fixed when the replacement area is determined to determine whether or not to perform further replacement processing. If it is fixed, a fixed value is set as the position condition in S116. If variable, the position condition is selected in S115. Hereinafter, this process will be described in detail with reference to FIG.

  After shifting to S114, whether or not to store density difference threshold information for edge determination, which is device information, in the information storage unit (210) in the image processing unit (205) of the image forming apparatus (202) is determined in S601. to decide. If it is held, the process further proceeds to S602, where it is determined whether or not the density difference threshold information for determining the inside of the edge is also held in the information storage unit (210). If neither is held, it is assumed that the edge portion and internal density difference is proportional to the area density, and the threshold value for edge determination / internal determination is set to the maximum value in S609. If it is determined that both information is held in S601 and S602, the edge determination threshold is acquired in S603, the internal determination threshold of the edge is acquired from the information storage unit (210) in S604, and the edge determination / internal determination threshold is set in S605. .

  In S606, the average area density between adjacent lines in the determination region is calculated, the set edge determination threshold is compared with the average area density difference between adjacent lines, and an edge is determined if the density difference exceeds the edge determination threshold. In step S607, the density difference is further compared with the internal determination threshold value. If the density difference does not exceed the internal determination threshold, it is determined that the edge is inside, and it is determined in S608 that the determination area has a certain edge and internal area. If the determination condition deviates from S606 and S607, the determination area is determined to be a non-replacement target in S610, and the process proceeds to S118.

  The above processing is performed by the replacement processing position determination unit (208) of the image processing unit (205).

  After performing the above determination process, the image replacement process is executed in S119 for the determination area determined as the replacement target, and the process proceeds to S120 in the image output apparatus (203).

  Thus, the image replacement process is performed using a variable replacement target determination condition.

[Mode 2 for carrying out the invention]
Hereinafter, another embodiment for carrying out the present invention will be described with reference to the drawings.

  When an image read by the image input apparatus (201) in FIG. 1 is processed by the image forming apparatus (202), there is a function having a function of switching processing depending on what kind of image data the original document is. For example, when copying text-based text documents, the “character mode” is used to sharpen edges. When copying documents containing images such as photographic images, halftones suitable for the image are emphasized with an emphasis on density gradation. A “photo mode” using processing can be considered. Such a processing mode can be switched from a user interface (204) such as a panel of the image processing apparatus.

  According to such an image processing mode, it is possible to perform a more effective toner scattering suppression process by performing the replacement process target determination in consideration of the characteristics of the processed image.

  According to the above example, it is expected that an image area that is a replacement target of a character-based document exists in a relatively narrow unit, and an edge is clearly present in each image area. On the other hand, if the document is mainly an image image, there is a high possibility that the image area exists over a relatively wide range. If halftones are used, it may be difficult to determine the edge portion. In the present embodiment, taking these into account, processing for switching the size of the determination region according to the mode will be described with reference to FIG.

  The binary image transferred in S104 of FIG. 1 is received. In S105, it is determined whether or not the determination area is fixed. If the determination area is fixed, the fixed value is directly used as the determination area in S107. If it is variable, the determination area is selected in S106. At this time, whether it is fixed or variable is determined based on whether or not a plurality of pieces of size information of the determination area are stored in the information storage unit (210) in S701 of FIG. If a plurality is not held, a fixed value or an initial value is set as a determination size in S706. These are usually not optimal, but a general-purpose size applicable in any mode is set in advance. If it is determined in S701 that a plurality of images are held, it is determined in S702 whether or not the current processing mode is “character mode”. This obtains information from a user interface (204) connected to the image forming apparatus (202). In the character mode, if the determination area is wide, the probability of not hitting the image range increases. Therefore, a smaller determination size is selected in S703. If it is not “character mode”, it is determined in S704 whether or not it is “photo mode”. The information acquisition destination is the same. In the case of the photo mode, if the determination area is narrow, the area density becomes local and the probability of deviating from the actual density increases. Therefore, a larger determination size is selected in S703. If it is not “photo mode”, the determination size is fixed or set to an initial value in step S706 in order not to perform characteristic processing.

  Thereafter, in S707, a determination area is set according to the determination size set above, and the process proceeds to S108.

  These processes are performed by the determination area determination unit (206) in the image processing unit (205).

  At the time of the switching, it is possible to switch not only the determination area but also the density condition used by the replacement processing density determination unit (207) and the position condition used by the replacement processing position determination unit (208).

201 Image Input Device 202 Image Forming Device

Claims (4)

An image processing apparatus that performs a replacement process of image data for the purpose of adjusting a toner amount in a certain image area, and receives image data input from an image input apparatus (201). In the image processing unit (205) of the image forming apparatus (202), the means (206) for obtaining the determination area width and height for the input image from the information storage unit (210), and the determined determination area width and height Means (206) for determining the determination region, means (207) for calculating the average area density (monochrome pixel ratio) of the image data included in the determination region, and the average area concentration for which the region is to be replaced. Means (207) for acquiring a replacement area determination threshold for determining whether or not there is from the information storage unit (210), and means for determining whether or not the area is a replacement target area (207) A means (208) for acquiring an edge determination threshold value for determining whether or not the area has an edge from the information storage section (210), and whether or not the area has an edge inside Means (208) for acquiring an internal determination threshold value from the information storage unit (210), the edge determination threshold value, the edge internal determination threshold value, and the average area density of the determination region are respectively compared, and is a replacement target Replacement of the image data in the area determined as the replacement target by the replacement processing determination unit (207, 208) for the replacement area determined by the means (208) for determining whether or not and the replacement area determination means (206) in the previous period An image processing apparatus comprising: means (209) for performing processing. Means (207) for holding device information representing the correlation between the toner application amount in a fixed area and the average area density of the image data included in the determination area in the image processing unit (205); The image processing apparatus according to claim 1, further comprising means for determining a replacement determination threshold value. Means (210) for holding in the image processing unit (205) device information representing the correlation between the original document density and the average area density in the determination region after the original image is read by the scanner and binarized. The image processing according to claim 1, further comprising means for determining an edge determination threshold from the device information, and means for acquiring an internal determination threshold from the device threshold. apparatus. It has a means (202) for recognizing the processing mode of the image data set by the user interface (204) and switching the determination area width according to the processing mode, and the set processing mode is assumed to be “character data”. In the case of the selected mode, the means (206) for setting the determination area width low, and in the case where the set processing mode is assumed to be “image data”, the means (206) for setting the determination area width wide. The image processing apparatus according to claim 1, further comprising: