JP2017073750A - Image processing apparatus, image inspection apparatus, image processing method, and image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately determine gradation characteristics of an apparatus based upon an output result even when printed matter which is output principally includes line drawings.SOLUTION: An image processing method comprises: acquiring, as an analysis unit, an image within a predetermined range of a master image; calculating a contiguity value by counting the number of pixels which adjoin a pixel determined to be colored and are determined to be plain; acquiring, as analysis units, an image within a predetermined range of an analysis unit having a continuity value calculated and an image within a predetermined range of a positioned read image; generating a density value as information associated with a density of an analysis unit based upon pixel values of pixels included in the analysis unit; acquiring pairs of contiguity values and density values respectively for a plurality of images within the predetermined range included in the master image; and estimating variation in gradation characteristics based upon pairs of contiguity values and density values using information showing correlation between both.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an image processing device, an image inspection device, an image processing method, and an image processing program.

  Conventionally, a method of determining a change with time in gradation characteristics of an apparatus by evaluating print quality has been used (see, for example, Patent Document 1). In the technique disclosed in Patent Document 1, the reflection intensity of each pixel in the printed image is classified into three or more gradation levels, and the print quality is evaluated based on the histogram of the number of pixels for each reflection density. Yes.

  In the technique disclosed in Patent Document 1, light is irradiated to a printed object having a predetermined pattern configured by arranging a plurality of patches that are halftone images, and based on the received light intensity of the reflected light. Processing is in progress. Such a configuration is premised on that the patch formed by the halftone image has a wider range than the exposure spot of the light beam and obtains the grayscale of the halftone image.

  Accordingly, when the image forming apparatus is normally operated, when the image drawn on the printed matter to be output is mainly a line drawing with a narrow print range such as a figure or a character drawn by a line, In many cases, the exposure spot exceeds the printing range of the halftone image. As a result, the reflected light intensity in the printing range cannot be acquired appropriately, and the grayscale of the halftone image cannot be acquired. As a result, the gradation characteristics of the apparatus cannot be accurately determined.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately estimate the gradation characteristics of an apparatus based on an output result even when a printed matter to be output is mainly a line drawing.

  In order to solve the above-described problem, according to one embodiment of the present invention, image processing for determining a state of an image forming apparatus that performs image formation output based on a read image obtained by reading an image formed and output on a recording medium. An information acquisition unit that acquires the read image and a confirmation image corresponding to the read image; and an image in a predetermined range in the confirmation image is acquired as an analysis unit, and the pixels included in the analysis unit Of these, an adjacent value calculation unit that counts the number of pixels that are adjacent to pixels that are determined to be colored and that is determined to be plain and calculates an adjacent value that is a value according to the number of plain pixels that are adjacent to the colored pixels And an image of a predetermined range in the read image aligned with the image of the predetermined range of the analysis unit for which the adjacent value is calculated as an analysis unit, and based on the pixel value of the pixel included in the analysis unit A density value calculation unit that generates a density value that is information about density in an analysis unit, and an analysis value acquisition that acquires a set of adjacent values and density values for each of the plurality of images in the predetermined range included in the confirmation image And a change in tone characteristics according to a result of halftone dot analysis for a predetermined image including an image whose halftone tone can be analyzed, and a change in the density value in the set of the adjacent value and the density value described above And a state change estimator for estimating a change in gradation characteristics based on the set of the adjacent value and the density value based on the information indicating the correlation with.

  According to the present invention, even when the printed matter to be output is mainly a line drawing, the gradation characteristics of the apparatus can be accurately estimated based on the output result.

1 is a diagram illustrating a configuration of an image forming system including an inspection apparatus according to an embodiment of the present invention. It is a block diagram which shows the hardware constitutions of the test | inspection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the function structure of DFE which concerns on embodiment of this invention, an engine controller, a print engine, and an inspection apparatus. It is a figure which shows the aspect of the comparison test | inspection which concerns on embodiment of this invention. 1 is a diagram illustrating a configuration of a print engine according to an embodiment of the present invention. It is a block diagram which shows the function structure of the master image process part which concerns on embodiment of this invention. It is a figure which shows the function structure of the test | inspection control part which concerns on embodiment of this invention. It is a flowchart which shows the test | inspection operation | movement which concerns on embodiment of this invention. It is a block diagram which shows the function structure of the gradation characteristic determination part which concerns on embodiment of this invention. It is a figure which shows the aspect of the adjacent rate calculation process which concerns on embodiment of this invention. It is a figure which shows the aspect of the adjacent rate calculation process which concerns on embodiment of this invention. It is a figure which shows the aspect of the adjacent rate calculation process which concerns on embodiment of this invention. It is a flowchart which shows the calculation operation | movement of the pseudo gradation parameter which concerns on embodiment of this invention. It is a figure which shows the time-dependent change aspect of a halftone dot gradation value and a pseudo | simulation gradation value. It is a figure which shows the time-dependent change aspect of a halftone dot gradation value and a pseudo | simulation gradation value. It is a figure which shows the correlation of a halftone dot value and a pseudo tone value.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, an image inspection system including an inspection apparatus that inspects an output result by comparing a read image obtained by reading an output result by image formation output with a master image will be described as an example. In such a system, even when the output image is mainly a line drawing, it is a feature according to the present embodiment that the time-dependent change in the gradation characteristics of the apparatus is estimated based on the result of the print output. FIG. 1 is a diagram illustrating an overall configuration of an image forming system according to the present embodiment.

  As shown in FIG. 1, the image forming system according to the present embodiment includes a DFE (Digital Front End) 1, an engine controller 2, a print engine 3, an inspection device 4, and an interface terminal 5. The DFE 1 is an image processing apparatus that generates image data to be printed based on a received print job, that is, bitmap data that is an output target image, and outputs the generated bitmap data to the engine controller 2.

  The engine controller 2 controls the print engine 3 based on the bitmap data received from the DFE 1 to execute image formation output. Further, the engine controller 2 uses the bitmap data received from the DFE 1 as information serving as a basis of an inspection image to be referred to when the inspection device 4 inspects the result of image formation output by the print engine 3. Send to.

  The print engine 3 is an image forming apparatus that executes image formation output on a sheet as a recording medium based on bitmap data in accordance with control of the engine controller 2. As the recording medium, in addition to the above-described paper, a sheet-like material such as a film or plastic can be used as long as it is an object for image formation output.

  The inspection device 4 generates a master image based on the bitmap data input from the engine controller 2. The inspection device 4 is an image inspection device that inspects an output result by comparing a read image generated by reading a sheet output from the print engine 3 with a reading device with the generated master image.

  When the inspection device 4 determines that the output result is defective, the inspection device 4 notifies the engine controller 2 of information indicating the page determined as defective. Thereby, reprint control of the defective page is executed by the engine controller 2.

  In addition, the inspection apparatus 4 according to the present embodiment has a function of determining gradation characteristics of an image formed on the recording medium by the print engine 3 by analyzing the read image. In such a gradation characteristic determination function, the function corresponding to the case where the image output by the print engine 3 is mainly a line drawing with a narrow print range such as a figure or a character drawn by a line is implemented in this embodiment. It is one of the gist which concerns on a form.

  The interface terminal 5 is an information processing terminal for displaying a GUI (Graphical User Interface) for confirming a defect determination result by the inspection apparatus 4 and a GUI for setting parameters in the inspection, and is a PC (Personal Computer). This is realized by a general information processing terminal such as.

  Here, hardware constituting the DFE 1, the engine controller 2, the print engine 3, the inspection apparatus 4, and the interface terminal 5 according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating a hardware configuration of the inspection apparatus 4 according to the present embodiment. In FIG. 2, the hardware configuration of the inspection apparatus 4 is shown, but the same applies to other apparatuses.

  As shown in FIG. 2, the inspection apparatus 4 according to the present embodiment has the same configuration as an information processing apparatus such as a general PC (Personal Computer) or a server. That is, the inspection apparatus 4 according to the present embodiment includes a CPU (Central Processing Unit) 10, a RAM (Random Access Memory) 20, a ROM (Read Only Memory) 30, an HDD (Hard Disk Drive) 40, and an I / F 50. Connected through. Further, an LCD (Liquid Crystal Display) 60, an operation unit 70, and a dedicated device 80 are connected to the I / F 50.

  The CPU 10 is a calculation means and controls the operation of the entire inspection apparatus 4. The RAM 20 is a volatile storage medium capable of reading and writing information at high speed, and is used as a work area when the CPU 10 processes information. The ROM 30 is a read-only nonvolatile storage medium and stores a program such as firmware. The HDD 40 is a non-volatile storage medium that can read and write information, and stores an OS (Operating System), various control programs, application programs, and the like.

  The I / F 50 connects and controls the bus 90 and various hardware and networks. The LCD 60 is a visual user interface for the user to check the state of the inspection apparatus 4. The operation unit 70 is a user interface such as a keyboard and a mouse for the user to input information to the inspection apparatus 4.

  The dedicated device 80 is hardware for realizing a dedicated function in the engine controller 2, the print engine 3, and the inspection apparatus 4. In the case of the print engine 3, a transport mechanism that transports a sheet that is an image formation output target, A plotter device that executes image formation output on a paper surface. Further, the engine controller 2 and the inspection device 4 are dedicated arithmetic devices for performing image processing at high speed. Such an arithmetic unit is configured as an ASIC (Application Specific Integrated Circuit), for example. A reading device that reads an image output on a paper surface is also realized by the dedicated device 80.

  In such a hardware configuration, the software control unit is configured by the CPU 10 performing calculations in accordance with a program stored in the ROM 30 or a program read to the RAM 20 from a recording medium such as the HDD 40 or an optical disk (not shown). The A functional block that realizes the functions of the DFE 1, the engine controller 2, the print engine 3, the inspection apparatus 4, and the interface terminal 5 according to the present embodiment is configured by a combination of the software control unit configured as described above and hardware. Is done.

  FIG. 3 is a block diagram illustrating functional configurations of the DFE 1, the engine controller 2, the print engine 3, and the inspection device 4 according to the present embodiment. In FIG. 3, data transmission / reception is indicated by a solid line, and the flow of paper is indicated by a broken line. As illustrated in FIG. 3, the DFE 1 according to the present embodiment includes a job information processing unit 101 and a RIP processing unit 102. The engine controller 2 includes a data acquisition unit 201, an engine control unit 202, and a bitmap transmission unit 203. The print engine 3 includes a print processing unit 301. The inspection device 4 includes a reading device 400, a read image acquisition unit 401, a master image processing unit 402, an inspection control unit 403, and a comparative inspection unit 404.

  The job information processing unit 101 executes image formation output based on a print job input from outside the DFE 1 via a network or a print job generated based on image data stored in the DFE 1 by an operator's operation. Control. When executing the image formation output, the job information processing unit 101 causes the RIP processing unit 102 to generate bitmap data based on the image data included in the print job.

  The RIP processing unit 102 generates bitmap data for the print engine 3 to execute image formation output based on the image data included in the print job, under the control of the job information processing unit 101. Bitmap data is information of each pixel constituting an image to be imaged and output.

  The print engine 3 according to the present embodiment executes image formation output based on binary images of CMYK (Cyan, Magenta, Yellow, blackK). On the other hand, generally, image data included in a print job is a multi-valued image in which one pixel is expressed by multi-gradation such as 256 gradations. Therefore, the RIP processing unit 102 converts the image data included in the print job from a multi-valued image to a small-valued image, generates CMYK binary data for each color, and transmits it to the engine controller 2.

  The data acquisition unit 201 acquires bitmap data input from the DFE 1 and operates the engine control unit 202 and the bitmap transmission unit 203, respectively. The engine control unit 202 causes the print engine 3 to execute image formation output based on the bitmap data transferred from the data acquisition unit 201. The bitmap transmission unit 203 transmits the bitmap data acquired by the data acquisition unit 201 to the inspection apparatus 4 for generating a master image.

  The print processing unit 301 is an image forming unit that acquires bitmap data input from the engine controller 2, executes image formation output on printing paper, and outputs printed paper. The print processing unit 301 according to the present embodiment is realized by a general electrophotographic image forming mechanism, but other image forming mechanisms such as an ink jet method can also be used.

  The reading device 400 is an image reading unit that reads an image formed on a sheet of printing paper output by printing performed by the print processing unit 301 and outputs a read image. The reading device 400 is, for example, a line scanner installed in a conveyance path inside the inspection device 4 for printing paper output by the print processing unit 301. The scanning device 400 scans the paper surface of the printing paper to be conveyed on the paper surface. Read the formed image.

  The read image generated by the reading device 400 is an inspection target by the inspection device 4. Since the read image is an image generated by reading the paper surface of the paper output by the image forming output, the read image is an image indicating the output result. The read image acquisition unit 401 acquires information of a read image generated by reading the paper surface of the printing paper by the reading device 400. The information of the read image acquired by the read image acquisition unit 401 is input to the comparison inspection unit 404 for comparison inspection. Note that the input of the read image to the comparison inspection unit 404 is executed under the control of the inspection control unit 403. At that time, the inspection control unit 403 obtains the read image and inputs it to the comparison inspection unit 404.

  The master image processing unit 402 acquires the bitmap data input from the engine controller 2 as described above, and generates a master image that is an inspection image for comparison with the inspection target image. That is, the master image processing unit 402 functions as an inspection image generation unit that generates a master image, which is a confirmation image for performing inspection of a read image, based on an output target image. The master image generation processing by the master image processing unit 402 will be described in detail later.

  The inspection control unit 403 is a control unit that controls the operation of the entire inspection apparatus 4, and each component included in the inspection apparatus 4 operates according to the control of the inspection control unit 403. The comparison inspection unit 404 compares the read image input from the read image acquisition unit 401 with the master image generated by the master image processing unit 402, and determines whether or not the intended image formation output is being executed. . The comparison inspection unit 404 is configured by the ASIC described above in order to quickly process a huge amount of calculation. In the present embodiment, the inspection control unit 403 functions as an image inspection unit by controlling the comparative inspection unit 404 and also functions as an inspection result acquisition unit that acquires an inspection result by the comparative inspection unit 404.

  In the comparison inspection unit 404, as described above, the 200 dpi read image and the master image expressed in 8 bits for each RGB color are compared for each corresponding pixel, and the difference value between the 8 bit pixel values for each RGB color described above for each pixel. Is calculated. Based on the magnitude relationship between the difference value thus calculated and the threshold value, the inspection control unit 403 determines the presence or absence of a defect in the read image. That is, the inspection control unit 403 functions as an image inspection unit by controlling each unit included in the inspection apparatus 4.

  When comparing the read image and the master image, the comparison inspection unit 404 superimposes the master image divided for each predetermined range on the read image corresponding to the divided range, as shown in FIG. The pixel value of the pixel, that is, the density difference is calculated. Such processing is realized by the inspection control unit 403 acquiring images in the overlapping range from the master image and the read image and inputting them to the comparison inspection unit 404.

  Further, the inspection control unit 403 shifts the position where the divided range is superimposed on the read image vertically, that is, while shifting the range of the image acquired from the read image vertically and horizontally, the total difference value calculated is calculated. The smallest position is determined as an accurate overlay position, and the difference value of each pixel calculated at that time is adopted as a comparison result. Therefore, the comparison inspection unit 404 can output the vertical and horizontal deviation amounts when determined as the alignment position together with the difference value of each pixel.

  As shown in FIG. 4, each square divided into a grid is a predetermined range in which the difference values of the pixels described above are summed. In addition, the size of each division range illustrated in FIG. 4 is determined based on a range in which the comparison / inspection unit 404 configured by the ASIC can compare pixel values at a time as described above, for example.

  By such processing, the difference value is calculated after the read image and the master image are aligned. By comparing the difference value calculated in this way with a predetermined threshold value, a defect in the image is determined. Further, for example, even if there is a difference in scale between the entire read image and the entire master image, the influence of the scale is reduced by dividing and positioning for each range as shown in FIG. Is possible.

  Further, in each of the divided ranges as shown in FIG. 4, it is predicted that the amount of positional deviation between adjacent ranges is relatively close. Therefore, when performing the comparison inspection for each divided range, the calculation is performed while shifting the image in the vertical and horizontal directions by performing the above-described calculation while shifting the image in the vertical and horizontal directions with the positional deviation amount determined by the comparative inspection of the adjacent region as the center. Even if the number of times of performing is reduced, there is a high possibility that the calculation based on the accurate overlay position is executed, and the calculation amount as a whole can be reduced.

  Further, as described above, the inspection control unit 403 according to the present embodiment determines the gradation characteristics of the print engine 3 by analyzing the read image. This function will be described in detail later.

  Next, the mechanical configuration of the print engine 3 and the inspection apparatus 4 and the paper conveyance path will be described with reference to FIG. As shown in FIG. 5, the print processing unit 301 included in the print engine 3 according to the present embodiment includes the photosensitive drums 12 </ b> Y, 12 </ b> M, 12 </ b> C, and 12 </ b> K (hereinafter referred to as “photosensitive drums”) along the conveyance belt 11 that is an endless moving unit. In general, the photosensitive drum 12 is arranged in a row, and is called a so-called tandem type. That is, along the conveyance belt 11 that is an intermediate transfer belt on which an intermediate transfer image to be transferred to a sheet (an example of a recording medium) fed from the sheet feed tray 13 is formed, Photosensitive drums 12Y, 12M, 12C, and 12K are arranged in order from the upstream side.

  Each color image developed with toner on the surface of the photosensitive drum 12 for each color is superimposed on the conveyor belt 11 and transferred to form a full color image. The full-color image formed on the transport belt 11 in this way has a sheet surface of the paper transported on the path by the function of the transfer roller 14 at a position closest to the paper transport path indicated by a broken line in the drawing. Transcribed above.

  The paper on which the image is formed on the paper surface is further conveyed, the image is fixed by the fixing roller 15, and then conveyed to the inspection device 4. In the case of double-sided printing, the sheet on which an image is formed and fixed on one side is conveyed to the reversing path 16 and is reversed and conveyed to the transfer position of the transfer roller 14 again.

  The reading device 400 is configured by an information processing device inside the inspection device 4 by reading each surface of the paper conveyed from the print processing unit 301 in the paper conveyance path inside the inspection device 4 and generating a read image. The image is output to the read image acquisition unit 401. Further, the paper whose surface is read by the reading device 400 is further conveyed through the inside of the inspection device 4 and discharged to the paper discharge tray 410. 5 shows an example in which the reading device 400 is provided only on one side of the paper in the paper transport path in the inspection device 4, but in order to enable inspection of both sides of the paper, The reading device 400 may be arranged on each of both sides.

  Next, a functional configuration of the master image processing unit 402 according to the present embodiment will be described. FIG. 6 is a block diagram illustrating an internal configuration of the master image processing unit 402. As illustrated in FIG. 6, the master image processing unit 402 includes a small-value / multi-value conversion processing unit 421, a resolution conversion processing unit 422, a color conversion processing unit 423, and an image output processing unit 424. Note that the master image processing unit 402 according to the present embodiment is realized by operating the dedicated device 80 described in FIG. 2, that is, hardware configured as an ASIC, according to software control.

  The low-value / multi-value conversion processing unit 421 generates a multi-value image by performing low-value / multi-value conversion processing on a binary image expressed in colored / colorless. The bitmap data according to the present embodiment is information to be input to the print engine 3, and the print engine executes image formation output based on CMYK (Cyan, Magenta, Yellow, blackK) color binary images. On the other hand, the read image, which is the image to be inspected, is a multi-valued image of RGB (Red, Green, Blue), which is the basic three primary colors, and is a multi-valued image. The image is converted into a multi-valued image. As the multivalued image, for example, an image expressed by 8 bits for each of CMYK can be used.

  The small value / multivalue conversion processing unit 421 performs an 8-bit extension process and a smoothing process as the small value / multivalue conversion process. The 8-bit extension process is a process of converting 0/1 data, which is 1 bit, into 8 bits, converting “0” to “0” and converting “1” to “255”. The smoothing process is a process of smoothing an image by applying a smoothing filter to 8-bit data.

  In this embodiment, the print engine 3 executes image formation output based on CMYK binary images, and the master image processing unit 402 includes a low-value multi-value conversion processing unit 421. Is an example. That is, when the print engine 3 executes image formation output based on a multi-value image, the low-value multi-value conversion processing unit 421 can be omitted.

  In addition, the print engine 3 may have a function of performing image formation output based on a low-value image such as 2 bits instead of 1 bit. In this case, it can be dealt with by changing the function of the 8-bit extension processing. That is, in the case of 2 bits, the gradation value is four values of 0, 1, 2, and 3. Therefore, in the case of 8-bit expansion, “0” is converted to “0”, “1” is converted to “85”, “2” is converted to “170”, and “3” is converted to “255”.

  The resolution conversion processing unit 422 performs resolution conversion so that the resolution of the multi-value image generated by the small-value multi-value conversion processing unit 421 matches the resolution of the read image that is the image to be inspected. In the present embodiment, since the reading device 400 generates a 200 dpi read image, the resolution conversion processing unit 422 converts the resolution of the multi-valued image generated by the small-value multi-value conversion processing unit 421 to 200 dpi. In addition, the resolution conversion processing unit 422 according to the present embodiment determines the size of the image after resolution conversion based on a predetermined magnification in consideration of the shrinkage of the paper output by the print processing unit 301 during resolution conversion. adjust.

  The color conversion processing unit 423 acquires an image whose resolution has been converted by the resolution conversion processing unit 422, and performs gradation conversion and color expression format conversion. The tone conversion processing is color tone conversion processing for matching the color tone of the master image with the color tone of the image formed on the paper surface by the print processing unit 301 and the color tone of the image read and generated by the reading device 400. .

  Such processing includes, for example, an image including color patches of various gradation colors formed on the paper surface by the print processing unit 301, and the gradation value of each color patch in the read image generated by reading the paper. This is performed using a gradation conversion table in which the gradation values in the original image for forming each color patch are associated with each other. That is, the color conversion processing unit 423 converts the gradation value of each color of the image output from the resolution conversion processing unit 422 based on such a gradation conversion table.

  The color representation format conversion process is a process for converting an image in the CMYK format into an image in the RGB format. As described above, since the read image according to this embodiment is an RGB format image, the color conversion processing unit 423 converts the CMYK format image that has been subjected to the gradation conversion processing into an RGB format. This color representation format conversion process is executed in the same manner as the above-described gradation conversion process, except that it is executed using a calculation formula for calculating the values of each color in the RGB format based on the values of each color in the CMYK format. , Based on a conversion table in which CMYK format values and RGB format values are associated with each other.

  Note that the above-described gradation conversion and color expression format conversion are performed by using a conversion table in which CMYK format values and RGB format values are associated with each other and considering the above-described gradation conversion. It is also possible to execute them simultaneously. Such processing can reduce the processing load.

  Through the processing up to the color conversion processing unit 423, a 200 dpi multi-value image expressed by RGB each color 8 bits (24 bits in total) is generated for each pixel. The image generated in this way is used as a master image.

  The image output processing unit 424 outputs the master image generated by the processing up to the color conversion processing unit 423. As a result, the inspection control unit 403 acquires a master image from the master image processing unit 402.

  Next, a functional configuration of the inspection control unit 403 according to the present embodiment will be described. FIG. 7 is a block diagram illustrating a functional configuration of the inspection control unit 403 according to the present embodiment. FIG. 8 is a flowchart showing an image inspection operation for one page by the inspection control unit 403 according to the present embodiment. As shown in FIG. 7, the inspection control unit 403 according to the present embodiment includes an information input unit 431, a difference image acquisition unit 432, a defect determination unit 433, a controller communication unit 434, and a gradation characteristic determination unit 500.

  In the inspection control unit 403 according to the present embodiment, as illustrated in FIG. 8, first, the information input unit 431 acquires a master image from the master image processing unit 402 (S801), and acquires a read image from the read image acquisition unit 401. Obtain (S802). Since the process of S801 and the process of S802 are not restricted in context, they may be executed in the reverse order or may be executed in parallel.

  As described with reference to FIG. 4, the information input unit 431 that has acquired the master image and the read image extracts a predetermined range of images from the master image and the read image and inputs the images to the comparison inspection unit 404, thereby comparing the inspection unit. In step S <b> 803, the image is subjected to a comparison inspection 404.

  By the processing of S803, a difference image indicating a difference value between each pixel constituting the read image and each pixel constituting the master image is generated, and the difference image acquisition unit 432 acquires the generated difference image. Defect determination is performed by the defect determination unit 433 based on the difference image acquired by the difference image acquisition unit 432 (S804).

  In S804. The defect determination unit 433 determines whether each page includes a defect by comparing the value of each pixel constituting the difference image with a preset threshold value. In addition, by performing a labeling process or the like of the pixel determined as a defect, information indicating a defect determination result is generated by specifying a defect position, specifying a defect type, or the like.

  In addition, the gradation characteristic determination unit 500 acquires the read image and the master image from the information input unit 431, and performs gradation characteristic determination (S805). The gradation characteristic determination process in S805 will be described in detail later. Note that the processes of S803 and S804 and the process of S805 may be executed in the reverse order or may be executed in parallel. When the defect determination process and the gradation characteristic determination process are completed, the controller communication unit 434 executes engine control such as a reprint request or a gradation characteristic change with time based on the defect determination result and the gradation characteristic determination result ( S806). By such processing, the image inspection operation according to the present embodiment is completed.

  Next, the gradation characteristic determination operation in S805 will be described. FIG. 9 is a block diagram illustrating a detailed functional configuration of the gradation characteristic determination unit 500 according to the present embodiment. A program for configuring functional blocks as shown in FIG. 9 is used as an image processing program for determining the apparatus state according to the present embodiment.

  A read image and a master image are input from the information input unit 431 to the gradation characteristic determination unit 500. The input read image and master image are input to the halftone gradation calculation unit 501 and the information acquisition unit 502, respectively.

  A halftone gradation calculator 501 calculates a halftone gradation. The halftone gradation is a gradation value corresponding to the halftone dot ratio. Accordingly, the halftone gradation calculation unit 501 analyzes the master image to be analyzed to obtain the halftone dot ratio for each position in the image, and analyzes the read image to analyze the master image for each position in the image. Find the key value. Then, the halftone dot gradation is obtained by associating the halftone dot ratio obtained from the master image with the gradation value obtained from the corresponding position in the read image.

  The information acquisition unit 502 performs control for calculating a pseudo gradation value as characteristic processing according to the present embodiment. The pseudo gradation value is a value that represents a halftone dot rate based on the number of white pixels adjacent to a colored pixel. Therefore, the information acquisition unit 502 extracts an image of a predetermined range from the input master image, inputs the image as an analysis unit image to the adjacent value calculation unit 504, and extracts the range aligned with the image from the read image. To the density value calculation unit 503. The analysis unit image according to the present embodiment is, for example, an image of 8 pixels in the vertical and horizontal directions and a total of 64 pixels.

  The density value calculation unit 503 calculates the gradation value by summing up the pixel values of each pixel constituting the input read image. The gradation value is a value related to the density of the input read image, and a luminance value, a brightness value, or the like can be used.

  The adjacent value calculation unit 504 is one of modules that perform characteristic processing according to the present embodiment. The adjacent value calculation unit 504 obtains, as an adjacent rate, the ratio of the number of pixels that are solid pixels that do not carry color and are adjacent to colored pixels in the input master image to the number of colored pixels. .

  The analysis value acquisition unit 505 acquires the calculation results from the density value calculation unit 503 and the adjacent value calculation unit 504, respectively, and manages a set of the adjacent rate and the gradation value as one set of parameters. This set of parameters is used as an analysis value. The meaning of this parameter is one of the features according to this embodiment. The meaning of this parameter will be described below.

  10 to 12 are diagrams for explaining the significance of the adjacent rate according to the present embodiment, and are diagrams illustrating examples of images in a predetermined range input from the information acquisition unit 502 to the adjacent value calculation unit 504. . In FIG. 10 to FIG. 12, the shaded area is a colored pixel. The main purpose of this embodiment is to determine the gradation characteristics of the print engine 3 by calculating halftone gradation.

  A method for determining the halftone gradation is generally a method for determining the density of an image reading result on the assumption that the image is formed with a uniform dot ratio. In this case, it is necessary to print out and read a patch having a uniform halftone dot ratio over a certain area. Therefore, it is difficult to determine the gradation characteristics of a line drawing-based image such as a figure or a character drawn by a line.

  On the other hand, the tone characteristics of the halftone dot are greatly affected at the boundary between the plain pixel and the colored pixel. Therefore, the gradation value corresponding to the adjacency rate is analyzed using the ratio of the number of images located at the boundary between the plain pixels and the colored pixels and the number of color pixels in the predetermined range image as the parameter “adjacency rate”. Thus, it is one of the gist according to the present embodiment to determine the pseudo gradation characteristics.

  FIG. 10 is a diagram illustrating an example when three colored pixels are included in an 8 × 8 range. In this case, the number of adjacent pixels adjacent to the colored pixel is 12 pixels as shown by being surrounded by a broken line in the drawing. Therefore, the adjacency rate described above is 12/3 = 4, which is “4”.

  FIG. 11 is a diagram illustrating an example in which 6 × 6 colored pixels are included in an 8 × 8 range. In this case, as shown by being surrounded by a broken line in the figure, the number of adjacent pixels adjacent to the colored pixel is 14 pixels. Therefore, the above-described adjacency ratio is 14 / 6≈2.33, which is “2.33”.

  FIG. 12 is a diagram illustrating an example in which 9 × 9 colored pixels are included in an 8 × 8 range. In this case, the number of adjacent pixels adjacent to the colored pixel is 16 pixels as shown by being surrounded by a broken line in the drawing. Therefore, the above-described adjacency ratio is 16 / 9≈1.78, which is “1.78”. As described above, the “adjacent rate” according to the present embodiment is a value corresponding to the number of white pixels adjacent to the colored pixel among the pixels included in the analysis unit image. This value is used as a value corresponding to the halftone dot ratio in the pseudo gradation value.

  The information acquisition unit 502 selects the entire range of the master image as the analysis unit image, and repeatedly executes the calculation of the set of parameters described above. As a result, a plurality of parameters having the same “adjacent rate” may be calculated, but the gradation values associated with the same “adjacent rate” are not necessarily the same.

  Therefore, the analysis value acquisition unit 505 inputs the gradation value included in the parameter having the same “adjacent rate” to the average processing unit 506 and calculates the average value. As a result, a parameter in which each gradation value is associated with a plurality of “adjacent ratios” is generated. The parameters generated in this way are input to the page unit management unit 507.

  The page unit management unit 507 inputs a page unit parameter generated based on the analysis image to the correlation analysis unit 508. The correlation analysis unit 508 compares the tone value for each halftone dot rate calculated by the halftone tone calculation unit 501 with the pseudo tone value for each page, and analyzes the correlation between them. The correlation between the halftone gradation and the pseudo gradation thus analyzed is input to the state change estimation unit 509 and held by the state change estimation unit 509.

  That is, in the gradation characteristic determination unit 500 according to the present embodiment, the halftone gradation calculation unit 501 calculates the gradation value according to the halftone ratio based on the analysis image, and the above-described pseudo-level. A key value parameter is generated. Based on the information thus calculated, the correlation between the halftone dot value change with time and the pseudo tone value change with time is calculated.

  The above-described analysis image is an image that can analyze at least halftone gradation, and is therefore an image including patches in a predetermined range or more formed at the same halftone ratio. The above-described correlation can be calculated by analyzing halftone dots and pseudo gradations for such an analysis image.

  In the normal operation after the correlation is analyzed as described above, the page unit management unit 507 inputs a page unit parameter to the state change estimation unit 509. The state change estimation unit 509 estimates the tone characteristics of the print engine 3 based on the above-described correlation information based on the page-wise pseudo tone value parameter input from the page unit management unit 507, and results thereof. Is output.

  Next, the operation of the gradation characteristic determination unit 500 according to the present embodiment will be described with reference to the flowchart of FIG. As shown in FIG. 13, first, the information acquisition unit 502 sets an 8 × 8 frame to be analyzed for the input master image (S1301). Information on the master image within the set frame is input to the adjacent value calculation unit 504 as an analysis unit image.

  The adjacent value calculation unit 504 refers to one pixel constituting the input analysis unit image as a target pixel (S1302), and determines whether the pixel is a white pixel (S1303). The master image according to the present embodiment is an image of 256 gradations having values of RGB colors “0” to “255”. In S1303, the adjacent value calculation unit 504 determines whether or not the pixel is a white pixel based on the gradation values of each RGB color.

  In the determination in S1303, for example, it may be determined whether or not all the RGB are “255” and are pixels that are completely white, or the range that is determined to be white may have a certain range. good. In order to give a certain range to the range determined to be white, for example, a threshold is set for all RGB values, and if all the RGB gradation values exceed the threshold, it is determined to be a white pixel.

  As a result of the determination in S1303, when it is determined that the target pixel is a white pixel (S1303 / YES), the adjacent value calculation unit 504 next refers to the eight pixels in the vertical and horizontal directions adjacent to the target pixel, and there is a colored pixel. It is determined whether or not to perform (S1304). When determining a colored pixel, if it is not a white pixel, it may be determined as a colored pixel, or may be determined as a colored pixel if it has a certain density.

  As a result of the determination in S1304, if the adjacent pixel is colored (S1304 / YES), the adjacent value calculation unit 504 determines that the selected pixel is the pixel to be analyzed described in FIGS. The value of the number a of pixels adjacent to the colored pixel is incremented and counted (S1305). On the other hand, if the adjacent pixel is not colored (S1304 / NO), the adjacent value calculation unit 504 proceeds directly to the next process.

  On the other hand, if it is determined in S1303 that the pixel is not a white pixel, the adjacent value calculation unit 504 increments the value of the number of colored pixels b (S1306). The adjacent value calculation unit 504 repeatedly executes the processing from S1302 to S1306 until the selected analysis unit image is completed (S1307 / NO). When the processing is completed for the selected analysis unit image, the value of a / b is calculated (S1308). This value is the adjacency ratio and is used as a parameter of the above-described pseudo gradation value. In other words, the value calculated in S1308 is the ratio of the number of white pixels adjacent to the colored pixel to the colored pixel, and is used as the adjacent value.

  Upon completion of the calculation for one analysis unit image, the information acquisition unit 502 inputs a read image at a position aligned with the currently selected analysis unit image to the density value calculation unit 503. Accordingly, the density value calculation unit 503 calculates a total gradation value obtained by summing the gradation values of the pixels included in the input read image (S1309). A set of the adjacent rate and the total gradation value generated in this way is used as the parameter described above.

  The information acquisition unit 502 repeats the process for the entire range of the input master image for one page until the process from S1301 ends (S1310 / NO). Then, when the processing is completed for the master image for one page (S1310 / YES), the processing is terminated.

  FIG. 14 shows a plot of the parameter value calculated by such an operation with the adjacency rate on the horizontal axis and the pseudo gradation value on the vertical axis, and the halftone scale calculated by the halftone gradation calculation unit 501. It is a figure which compares with the plot which took the halftone dot rate on the horizontal axis, and made the gradation value the vertical axis | shaft about a tone. As shown in FIG. 14, as the number of print outputs by the print engine 3 increases to 1, 100, and 1000, both the gradation value of the halftone gradation and the pseudo gradation value decrease. In FIG. 14, the plot on one sheet is shown by small dots on 100 sheets and 1000 sheets.

  As shown in FIG. 15, the correlation analysis unit 508 calculates pseudo tone value change values ΔYa1, ΔYa2,... According to the number of printed output sheets to obtain an average value ΔYa. Also, change values ΔYb1, ΔYb2,... Of halftone values are calculated to obtain an average value ΔYb. Then, correlation analysis section 508 obtains a set of a plurality of ΔYa and ΔYb according to the number of print outputs, with ΔYa and ΔYb obtained for the change amount of the same print output number as one set.

  When the set of ΔYa and ΔYb thus obtained is plotted in a space with ΔYa and ΔYb on the vertical axis and ΔYb on the horizontal axis, respectively, a graph as shown in FIG. 16 is obtained. By obtaining an approximate expression for such a plot, it is possible to estimate a change in ΔYb corresponding to a change in ΔYa. That is, the correlation analysis unit 508 obtains an approximate expression for obtaining a change in ΔYb with respect to a change in ΔYa as correlation information. The approximate expression obtained in this way is held by the state change estimation unit 509.

  Thereafter, the gradation characteristic determination unit 500 generates a pseudo gradation parameter for each page by the operation described with reference to FIG. The pseudo gradation parameter generated in such a manner is input to the state change estimation unit 509 as ΔYa described above. The state change estimation unit 509 estimates the change in the gradation characteristics of the print engine 3 by obtaining ΔYb based on the input ΔYa based on the approximate expression of the plot as shown in FIG.

  As described above, the inspection apparatus 4 according to the present embodiment has a function of obtaining a gradation value according to the “adjacency ratio” determined according to the number of white pixels adjacent to the colored pixels in the master image. Have. The change in the gradation value according to the adjacency ratio has a strong correlation with the change in the gradation value of the halftone dot in the change in the gradation characteristics accompanying the change with time of the apparatus. Therefore, by grasping such a correlation, it is possible to determine the tone characteristics of the print engine 3 based on the change in tone value according to the adjacency ratio.

  Then, when obtaining the gradation value of the halftone dot gradation, it is necessary to read a patch formed with the same halftone dot ratio over a predetermined area. If so, there is no such restriction, and it can be obtained from an image mainly composed of line drawings. Therefore, by using the method according to the present embodiment, it is possible to obtain the gradation characteristics of the print engine 3 even from an image mainly composed of line drawings.

  In the above embodiment, the case where the value obtained by dividing the number of white pixels adjacent to a colored pixel by the number of colored pixels is used as an example of the horizontal axis value for the pseudo gradation shown in FIG. However, this is only an example, and the meaning of the value on the horizontal axis is that when it is difficult to obtain the halftone dot ratio because there is no image area of a predetermined size or more formed with the same halftone dot ratio. It is a value used instead of the point rate.

  In the present embodiment, the number of white pixels adjacent to the colored pixel is mainly used in the present embodiment based on the fact that the change in the gradation characteristics at the same halftone dot ratio is most affected by the density of the white pixel adjacent to the colored pixel. Used. Therefore, the final value of the horizontal axis is not limited to the value obtained by dividing the number of white pixels adjacent to the colored pixel by the number of colored pixels, but may be any value as long as it is a value according to the number of white pixels adjacent to the colored pixel. This aspect is also applicable.

  However, the total value of the gradation values of the pixels included in the analysis unit image increases as the number of colored pixels in the original image increases. Therefore, even when a value corresponding to the horizontal axis in FIG. 14 is obtained in a manner different from the above-described manner, it is possible to perform a suitable analysis by considering the number of colored pixels.

  In the above-described embodiment, a case where the gradation characteristic determination unit 500 is provided in the inspection apparatus 4 that determines whether the image is formed as intended by comparing the read image with the master image. Described as an example. This is an efficient configuration in that the master image and the read image are used as described above, but is not essential, and an image processing device having the function of the gradation characteristic determination unit 500 is provided separately from the inspection device 4. May be. Even in this case, the same function as described above can be realized by inputting the master image and the read image.

  Further, in the above embodiment, the density value calculation unit has been described as an example in which the pseudo gradation value is calculated by adding all the gradation values of the pixels included in the analysis unit image. However, this is only an example, and other modes may be used as long as a value related to the density of the read image in the region aligned with the analysis unit image can be obtained.

1 DFE
2 Engine Controller 3 Print Engine 4 Inspection Device 5 Interface Terminal 10 CPU
20 RAM
30 ROM
40 HDD
50 I / F
60 LCD
70 Operation Unit 80 Dedicated Device 90 Bus 11 Conveyor Belt 12, 12Y, 12M, 12C, 12K Photosensitive Drum 13 Paper Tray 14 Transfer Roller 15 Fixing Roller 16 Reverse Path 101 Job Information Processing Unit 102 RIP Processing Unit 201 Data Acquisition Unit 202 Engine control unit 203 Bitmap transmission unit 301 Print processing unit 400 Reading device 401 Read image acquisition unit 402 Master image processing unit 403 Inspection control unit 404 Comparison inspection unit 410 Paper discharge tray 421 Low-value multi-value conversion processing unit 422 Resolution conversion processing unit 423 Color conversion processing unit 424 Image output processing unit 431 Information input unit 432 Difference image acquisition unit 433 Defect determination unit 434 Controller communication unit 500 Gradation characteristic determination unit 501 Halftone gradation calculation unit 502 Information acquisition unit 503 Density value calculation unit 504 Adjacent value calculation Output unit 505 Analysis value acquisition unit 506 Average processing unit 507 Page unit management unit 508 Correlation analysis unit 509 State change estimation unit

Japanese Patent Laid-Open No. 3-44542

Claims (9)

An image processing apparatus that determines a state of an image forming apparatus that executes image forming output based on a read image obtained by reading an image formed and output on a recording medium,
An information acquisition unit for acquiring the read image and a confirmation image corresponding to the read image;
An image of a predetermined range in the confirmation image is acquired as an analysis unit, and among the pixels included in the analysis unit, the number of pixels that are adjacent to the pixel determined to be colored and determined to be plain is counted. An adjacent value calculation unit that calculates an adjacent value that is a value according to the number of plain pixels adjacent to the colored pixel;
An image of a predetermined range in a read image that is aligned with an image of a predetermined range of the analysis unit in which the adjacent value is calculated is acquired as an analysis unit, and the analysis unit based on a pixel value of a pixel included in the analysis unit A density value calculation unit that generates a density value that is information about the density;
An analysis value acquisition unit that acquires a set of the adjacent value and the density value for each of the plurality of images in the predetermined range included in the confirmation image;
Correlation between a change in gradation characteristics according to a result of halftone dot analysis of a predetermined image including an image that can analyze halftone gradation and a change in the density value in the above-described set of adjacent value and density value An image processing apparatus, comprising: a state change estimation unit that estimates a change in gradation characteristics based on the set of adjacent values and density values based on information indicating a relationship.   The adjacent value calculation unit is based on the count value of the number of pixels adjacent to the pixel determined to be colored and determined to be plain and the count value of the number of colored pixels included in the analysis unit. The image processing apparatus according to claim 1, wherein an adjacent value is calculated.   The adjacent value calculating unit divides the count value of the number of pixels adjacent to the pixel determined to be colored and determined to be plain by the count value of the number of colored pixels included in the analysis unit. The image processing apparatus according to claim 2, wherein an adjacent value is calculated.   The image processing apparatus according to claim 1, wherein the density value calculation unit obtains the density value by summing pixel values of pixels included in the analysis unit. A correlation analysis unit that generates information indicating the correlation;
The correlation analysis unit
As a change in gradation characteristics based on the result of halftone dot analysis for a predetermined image including an image that can be analyzed for halftone gradation, the amount of change in the gradation value according to the halftone dot ratio is obtained for a plurality of halftone dot ratios. An average value is obtained according to a change with time of the image forming apparatus,
As the change of the density value in the set of the adjacent value and the density value described above, a value obtained by averaging the change amount of the density value according to the adjacent value with respect to a plurality of adjacent values is obtained according to the change with time of the image forming apparatus. Acquired,
5. The image processing apparatus according to claim 1, wherein information indicating a correlation between changes with time is generated.   The information indicating the correlation includes the change in the gradation characteristics according to the analysis result of the halftone gradation of the predetermined image including the image capable of analyzing the halftone gradation, and the above-described set of the adjacent value and the density value. The image processing apparatus according to claim 1, wherein the image processing apparatus is an approximate expression of a correlation with the change in the density value.   Comparison of the inspection of the read image obtained by reading the image formed and output on the paper with the confirmation image generated based on the image used in the image forming apparatus at the time of image formation output of the image corresponding to the read image An image inspection apparatus comprising: the image processing apparatus according to any one of claims 1 to 6. An image processing method for determining a state of an image forming apparatus that executes image formation output based on a read image obtained by reading an image formed and output on a recording medium,
Obtaining the read image and a confirmation image corresponding to the read image;
An image of a predetermined range in the confirmation image is acquired as an analysis unit, and among the pixels included in the analysis unit, the number of pixels that are adjacent to the pixel determined to be colored and determined to be plain is counted. Calculate an adjacent value that is a value according to the number of plain pixels adjacent to the colored pixel,
An image of a predetermined range in a read image that is aligned with an image of a predetermined range of the analysis unit in which the adjacent value is calculated is acquired as an analysis unit, and the analysis unit based on a pixel value of a pixel included in the analysis unit Generate density values that are information about density,
For each of the plurality of images in the predetermined range included in the confirmation image, a set of the adjacent value and the density value is acquired,
Correlation between a change in gradation characteristics according to a result of halftone dot analysis of a predetermined image including an image that can analyze halftone gradation and a change in the density value in the above-described set of adjacent value and density value An image processing method characterized by estimating a change in gradation characteristics based on a set of adjacent values and density values based on information indicating a relationship. An image processing program for determining a state of an image forming apparatus that executes image forming output based on a read image obtained by reading an image formed and output on a recording medium,
Obtaining the read image and a confirmation image corresponding to the read image;
An image of a predetermined range in the confirmation image is acquired as an analysis unit, and among the pixels included in the analysis unit, the number of pixels that are adjacent to the pixel determined to be colored and determined to be plain is counted. Calculating an adjacent value that is a value according to the number of plain pixels adjacent to the colored pixel;
An image of a predetermined range in a read image that is aligned with an image of a predetermined range of the analysis unit in which the adjacent value is calculated is acquired as an analysis unit, and the analysis unit based on a pixel value of a pixel included in the analysis unit Generating a density value that is information about the density;
Obtaining a set of adjacent values and density values for each of the plurality of images in the predetermined range included in the confirmation image;
Correlation between a change in gradation characteristics according to a result of halftone dot analysis of a predetermined image including an image that can analyze halftone gradation and a change in the density value in the above-described set of adjacent value and density value An image processing program that causes an information processing apparatus to execute a step of estimating a change in gradation characteristics based on a set of adjacent values and density values based on information indicating a relationship.