JP2018180054A - Image forming apparatus, control method of image forming apparatus, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce time required for processing of determining the maximum value of the amount of applied toner in an image while keeping precision.SOLUTION: An image formation device for controlling temperature of a fixation unit on the basis of the amount of applied color material of an object in a page image, comprises: color line detection means for detecting, from among a plurality of lines constituting the page image, color lines for which one or plural colors are used; continuous color line detection means for detecting, from the detected color lines, continuous color lines which appear continuously in a longitudinal direction; maximum-applied-amount per line derivation means for counting an applied amount per unit area for each of the detected continuous color lines and deriving the maximum applied amount per line constituting the page image; and maximum-applied-amount per page image derivation means for, on the basis of the maximum applied amount per line, deriving the maximum applied amount per page image.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a temperature control technique when fixing toner on a recording medium by heat.

  Patent Document 1 discloses a technique for controlling the temperature of the fixing unit based on the provisional value of the amount of applied toner when the calculation of the maximum value of the amount of applied toner within the image is not completed within a predetermined time.

JP, 2015-206984, A

  In Patent Document 1, the amount of applied toner per unit area is calculated in the entire area of the image, and the maximum value is obtained from the calculated amount of applied toner, which requires a large amount of time for processing. Therefore, in view of the above problems, the present invention has an object of shortening the processing time for obtaining the maximum value of the amount of applied toner in an image while maintaining accuracy.

  The present invention is an image forming apparatus that controls the temperature of a fixing unit based on the amount of color material applied to an object in a page image, and one or more colors are selected from a plurality of lines forming the page image. Color line detecting means for detecting a color line to be used, continuous color line detecting means for detecting a continuous color line appearing continuously in the vertical direction out of the detected color lines, and each of the detected continuous color lines The page image based on the maximum bearing amount deriving means per line for counting the bearing amount per unit area and deriving the maximum bearing amount per line making up the page image, and the maximum bearing amount per line derived. According to another aspect of the present invention, there is provided an image forming apparatus comprising: a maximum loading amount deriving unit per page image for deriving a maximum loading amount per portion.

  According to the present invention, it is possible to shorten the processing time for obtaining the maximum value of the amount of applied toner in the image while maintaining the accuracy.

Schematic configuration of image forming apparatus Hardware configuration of image forming apparatus Relationship between the amount of applied toner and the fixing temperature Flow chart of image processing in the first embodiment Flowchart of Color Line Detection Process in Embodiment 1 Flow chart of continuous color line detection processing in the first embodiment Application Example of Example 1 Flowchart of Maximum Load Amount Detection Processing Per Line in Embodiment 1 Flowchart of Maximum Load Amount Detection Process Per Page Image in Embodiment 1 Flowchart of maximum loading amount derivation process in the second embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Example 1
<Schematic Configuration of Image Forming Apparatus>
FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus in the present embodiment. As illustrated, the image forming apparatus 1 includes an image reading unit 101, an image processing unit 102, a storage unit 103, a CPU 104, and an image output unit 105. The image forming apparatus 1 is connected to a server that manages image data, a personal computer (hereinafter referred to as a PC) that instructs execution of printing, and the like via a network or the like, and can mutually transmit and receive data.

  The image reading unit 101 reads an original, acquires image data, and outputs the acquired image data to the image processing unit 102.

  The image processing unit 102 converts print data including image data input from an external apparatus connected to the image forming apparatus 1 or the image reading unit 101 into intermediate data, and converts the converted intermediate data into the storage unit 103. Store. Further, the image processing unit 102 generates bitmapped image data based on the intermediate data, and stores the generated bitmapped image data in the storage unit 103. At this time, the image processing unit 102 performs color conversion processing, density correction processing, and pseudo halftone processing. Details of these processes will be described later.

  The storage unit 103 includes a ROM, a RAM, a hard disk (hereinafter referred to as HD) and the like. The ROM stores various control programs and image processing programs that the CPU 104 executes. The RAM is used as a work area in which the CPU 104 temporarily stores data and various information. The processing in the present embodiment described below is executed by the program stored in the ROM being expanded and executed in the RAM. The image data of each page is stored in the RAM or HD, and the stored image data is used to execute sorting processing in which the image data of a plurality of pages are arranged in output order. The image data after the sorting process is continuously stored in the RAM or the HD, and the printing process such as printing of a plurality of copies is executed based on the stored image data. In this example, a 32-bit CPU is used as the CPU 104.

  The image output unit 105 forms an image on a recording medium such as a recording sheet using a color material based on the image data received from the image processing unit 102.

<Hardware Configuration of Image Forming Apparatus>
The hardware configuration of the image forming apparatus in the present embodiment will be described below. FIG. 2 is a cross-sectional view showing a hardware configuration of the image forming apparatus 1 in the present embodiment.

  In the image reading unit 101, an original 204 to be read is placed between the pressure plate 202 and the original table 203. The original 204 is illuminated by the light emitted from the lamp 205, and this light is reflected by the original 204. Reflected light from the document 204 is guided by the mirror 206 and the mirror 207, and an image is formed on the three-line sensor 210 by the lens 208. The lens 208 is provided with an infrared cut filter 231. Due to the driving force transmitted from the motor (not shown), the mirror unit including the lamp 205 and the mirror 206 moves at a velocity V, and the mirror unit including the mirror 207 moves at a velocity V / 2 along the direction of the arrow. That is, these mirror units move along a direction (sub-scanning direction) perpendicular to the scanning direction (main scanning direction) of the 3-line sensor 210, and scan the entire surface of the document 204.

  The 3-line sensor 210 is composed of 3-line CCDs 210-1, 210-2, and 210-3. The 3-line sensor 210 color-separates input light, reads each color component of R (red), G (green), and B (blue), and sends a signal of the color component to the image processing unit 102. In this example, the CCDs constituting the 3-line sensor 210 have light receiving elements for 5000 pixels each, and the lateral direction (297 mm) of the A3-sized document which is the maximum size of the document that can be placed on the document table 203 ) Can be read at a resolution of 600 dpi.

  The image processing unit 102 electrically processes signals input from the 3-line sensor 210 to generate image data of C (cyan), M (magenta), Y (yellow), and K (black) colors. Here, the C (cyan) image data is image data in which each pixel has a cyan pixel value. Similarly, M (magenta) image data is image data in which each pixel has a magenta pixel value, and Y (yellow) image data is image data in which each pixel has a yellow pixel value, and K (black) The image data of) is image data in which each pixel has a black pixel value. The image processing unit 102 outputs the generated CMYK image data to the image output unit 105. The image data output at this time is the CMYK image data subjected to pseudo halftone processing such as dither processing.

  In the image output unit 105, each of the CMYK image data sent from the image processing unit 102 is sent to the laser driver 212. The laser driver 212 modulates and drives the semiconductor laser element 213 in accordance with the input image data. The laser beam output from the semiconductor laser element 213 scans the photosensitive drum 217 via the polygon mirror 214, the fθ lens 215, and the mirror 216 to form an electrostatic latent image on the photosensitive drum 217.

  The developing device unit includes a magenta developing device 219, a cyan developing device 220, a yellow developing device 221, and a black developing device 222. These four developing devices are in contact with the photosensitive drum 217 in order. A toner image is formed by developing the electrostatic latent image formed on the photosensitive drum 217 with the toner of the corresponding color. The recording paper supplied from the recording paper cassette 225 is wound around the transfer drum 223, and the toner image formed on the photosensitive drum 217 is transferred onto the wound recording paper.

  The recording sheet on which the four color (CMYK) toner images are sequentially transferred in this manner is sent to the fixing unit 226. When the recording sheet passes through the fixing unit 226, the toner image transferred to the recording sheet is fixed, and the recording sheet on which the toner image is fixed is discharged out of the image forming apparatus 1. Inside the fixing unit 226, pressure and heat are applied to the recording sheet to fix a four-color (CMYK) toner image on the recording sheet. If the amount of heat at the time of transfer is insufficient with respect to the applied amount, fixing failure may occur and a normal image may not be obtained. In order to prevent such a fixing failure, a temperature sensor (not shown) is attached to the fixing unit 226, and the CPU 104 adjusts the temperature of the fixing unit 226, and the temperature becomes a temperature sufficient for toner fixing. If it does, control is performed to perform the fixing operation. The control by the CPU 104 is executed based on the temperature of the fixing unit 226 acquired by the temperature sensor and the maximum value of the toner mounting amount in the page image derived by the maximum mounting amount deriving process (hereinafter, the maximum mounting amount). Ru. The details of the maximum loading amount deriving process will be described later.

<Relationship between the amount of applied toner and the temperature of the fixing unit>
The relationship between the amount of applied toner (hereinafter also simply referred to as the amount applied) and the temperature of the fixing unit 226 will be described below. The applied amount (unit:%) means the amount of toner per unit area on the image. In this example, the maximum value of the application amount of each color of CMYK is set to 100%. Since each color has gradation, the applied amount of each color takes any one value in the range of 0 or more and 100 or less. For example, the applied amount is 200% in an image in which two different colors with an applied amount of 100% overlap each other.

  In full-color printing, high-quality color printing is performed by expressing arbitrary colors within the reproducible color range of these toners using four color (CMYK) toners. If the quantity is secured, high quality printing can be guaranteed. Therefore, the maximum value of the application amount in the image of each page in full color printing is 240%. On the other hand, in single-color printing, only one toner is used as represented by monochrome printing, the maximum value of the application amount is 100%, which is the maximum value of the application amount of one color.

  Thus, the maximum value of the loading amount differs depending on the printed matter. If the temperature of the fixing unit 226 is always controlled to a temperature that enables fixing at 240%, which is the expected maximum value of the applied amount in full color printing, the above-mentioned fixing failure does not occur. . However, always setting the temperature of the fixing unit 226 at such a high temperature can obtain a normal image in monochrome printing or full-color printing when printing an image with a small amount of text-based coverage, etc. It will be excessive temperature and waste power. However, when the temperature necessary for toner fixing can not be secured, the toner is not fixed and a normal image can not be obtained. Therefore, it is important to control the temperature so as to suppress the power consumption while securing the temperature necessary for toner fixing.

  FIG. 3 is a graph showing the relationship between the applied amount in the image forming apparatus 1 and the temperature (fixed temperature) of the fixing unit 226 required for toner fixing. The horizontal axis indicates the amount of application, and the vertical axis indicates the fixing temperature. As shown, when the loading amount is 200%, the fixing temperature is T1, and when the loading amounts are 150%, 100% and 50%, the fixing temperatures are T2, T3 and T4, respectively.

  If the temperature of the fixing unit 226 has risen to such a temperature that the object whose appearance amount appears in the image becomes maximum in the image can not be fixed. Further, in order to fix an image of a continuous page reliably, the fixing unit 226 is always controlled to be equal to or higher than a predetermined minimum temperature. The reasons for defining the minimum temperature are as follows. For example, after fixing the first page having the maximum loading amount of 50%, the case of fixing the second page having the maximum loading amount of 200% will be described as an example. In this case, the temperature of the fixing unit 226 is increased between the fixing of the first page and the fixing of the second page, but since the interval between pages when fixing the continuous pages is constant, the fixing unit The temperature of 226 must be spiked. Therefore, it is necessary to define in advance a minimum temperature at which the temperature of the fixing unit 226 can be raised to the fixing temperature corresponding to the maximum value of the assumed loading amount.

<About image processing>
Hereinafter, image processing in the present embodiment will be described. The image processing in this embodiment includes processing of generating a page image (data) to be finally output to the image output unit 105, and deriving the maximum application amount in the page image in order to obtain the fixing temperature of the page image. And processing.

  Hereinafter, this image processing will be described with reference to FIG. The following processing starts at timing when printing processing based on image data input from an external apparatus connected to the image forming apparatus 1 or the image reading unit 101 is instructed, and the image processing unit 102 or It is executed by the CPU 104.

In step S401, the image processing unit 102 performs color conversion processing to convert RGB image data in which each pixel has an RGB pixel value into CMYK image data in which each pixel has a CMYK pixel value. Although this color conversion process may be performed using any method, in this example, the color conversion process is performed using a known method using a three-dimensional lookup table. The image data subjected to the color conversion process in step S401 is , And CMYK are data representing toner amounts of each color, and the pixel values of CMYK in each pixel are each expressed by 8 bits (takes any value of 0 to 255). In the three-dimensional lookup table used in step S401, the sum of the pixel values of CMYK at each pixel of the image data after the color conversion process in step S401 is a predetermined threshold (240%, which is the expected maximum value of the coverage amount) It is pre-defined not to exceed

  This will be specifically described. That the pixel value of each color of CMYK is 0 for any one pixel means that the pixel is a white pixel for which toner is not used. On the other hand, that the pixel value of each of the colors of CMYK for one arbitrary pixel means that the density of the pixel is high. For example, if the pixel value of C is 255, it means that the density of C is maximum (the amount of coverage 100%). As described above, the pixel value of CNYK in the pixel can take any value from 0 to 255, but as long as the above-described three-dimensional lookup table is used, the sum of the pixel values of CMYK is 1020 (= 255 × 4, corresponding to the amount of loading 400%) never. By using a predefined three-dimensional look-up table, for example, if the maximum value of the application amount assumed for full-color printing is 240%, the sum of the CMYK pixel values is adjusted not to exceed 612. There is. The three-dimensional lookup table is stored in the storage unit 103, and is loaded as needed during color conversion processing.

  In step S402, the image processing unit 102 executes density correction processing on the CMYK image data derived in the color conversion processing of step S401. As a method of density correction processing, any method such as a method of using a density correction table in which an input density level and an output density level are associated with each color of CMYK, a method of obtaining by calculation using a predetermined function, etc. You may adopt the method of In this example, a method using a density correction table is employed, and the density correction table used in this step is stored in the storage unit 103, and is loaded when necessary in density correction processing.

  In step S403, the image processing unit 102 performs pseudo halftone processing on the CMYK image data after density conversion derived in the density conversion process of step S402. Usually, the laser driver 212 can often output only low gradations such as 2, 4 and 16 gradations. Therefore, in order to enable stable halftone expression even with a small number of gradations, in this step, pseudo halftone processing such as error diffusion processing or dither processing using a threshold value matrix is performed. In this example, dither processing using a threshold value matrix is adopted as the pseudo halftone processing, and the threshold value matrix is stored in the storage unit 103, and is loaded when necessary in the pseudo halftone processing. . At the stage where pseudo halftoning is performed, gradation expression is performed using a certain area or more. For example, if the number of gradations per pixel is 4, the pixel value of each pixel is from 0 to 3 Rounded to the value of. Therefore, the amount of data per pixel is 2 bits, and the amount of data of image data is suppressed to a very small size compared to the past. Hereinafter, the description will be continued assuming that the amount of data per pixel after this step is 2 bits. The data after the processing of this step can be stored in the memory in a state where data for four pixels are packed per byte. At the end of this step, page image data to be output to the image output unit 105 is completed.

  In step S <b> 404, the CPU 104 executes a process for deriving a maximum coverage of the page image data derived in the pseudo-intermediate process of step S <b> 403. As described above, since the amount of heat necessary for fixing varies depending on the maximum amount of application, the maximum amount of application in the (page) image to be processed is derived in this step. Then, temperature control of the fixing unit 226 is executed based on the maximum bearing amount derived in this step.

  Whether or not the object is a target for which the amount of application is to be obtained when the maximum amount of application is derived in step 404 is determined by the size of the object. Specifically, a detection minimum size is defined to determine whether the object is an object for which the amount of application is to be obtained. Here, the detection minimum size is a size that allows toner fixing at the minimum temperature regardless of how large the mounting amount is for an object of a smaller size. In this embodiment, the minimum detection size is set to a rectangular size of M pixels (horizontal direction) × N pixels (vertical direction).

  The maximum applied amount deriving process in step 404 includes a color line detecting process, a continuous color line detecting process, a maximum applied amount detecting process per line, and a maximum applied amount detecting process per page image. These processes are executed based on each of the CMYK images derived in step S403 and stored in the storage unit 103. Hereinafter, these processes will be described in detail.

<About color line detection processing>
The color line detection process in the present embodiment determines how many colors out of CMYK are used in each area obtained by dividing the line for each of a plurality of lines constituting an image, and a number of colors exceeding a predetermined threshold is used. It is a process to flag the line in which the area exists. The threshold value of the number of colors used here is determined in advance according to the minimum temperature of the fixing unit 226. If the minimum temperature is equal to the fixing temperature (see FIG. 3, for example, T4) corresponding to the applied amount in the range of 0% or more and less than 100%, the temperature of the fixing unit 226 is increased to T3 if there is only one color in the line. A need may arise. Therefore, in this case, the color number threshold is set to zero. Alternatively, if the minimum temperature is equal to the fixing temperature (e.g., T2) corresponding to the applied amount in the range of 100% or more and less than 200%, the temperature of the fixing unit 226 needs to be raised from the minimum if there is only one color in the line. Absent. Therefore, in this case, the color number threshold is set to 1. The color line detection process will be described below with reference to FIG.

  In step S501, 0 is set as an initial flag value for all the lines constituting each image of CMYK. Next, the process proceeds to step S502. This flag takes one of values 0 and 1, where 0 is an area of a predetermined size with a number of colors that can potentially require heat treatment to raise the temperature of the fuser unit 226 from the lowest temperature. , Which means not included in the line. On the other hand, 1 means that such a region is included in the line. Therefore, the flag of all lines in the image being 0 means that the fixing unit 226 can be fixed at the minimum temperature without the need to raise the temperature of the fixing unit 226. The flag value is updated if it is found that the line contains a region of a predetermined size with a number of colors that may require heat treatment to raise the temperature of the fuser unit 226 in a subsequent process. It becomes one.

  In step S502, the top line (top line) of the image is set as a line of interest. Next, the process proceeds to step S503.

  In step S503, a search window of a predetermined size is set at the beginning of the line of interest. Then, it progresses to step S504. In this example, the size of the search window is 16 pixels (horizontal direction) × 1 pixel (vertical direction). The reason for making such a size is as follows. That is, as a result of the above-described pseudo-halftone processing (step S403), each pixel is represented by 2 bits, the data size of 16 consecutive pixels is 32 bits, and when the CPU 104 is a 32 bit CPU, In order to

  In step S504, it is determined whether the number of colors exceeding a predetermined threshold value exists in a predetermined divided area. Specifically, in each of the CMYK images, it is determined whether the pixel value of the pixel in the set search window is 0 or not. For example, in the image of C, when all pixel values of pixels in the set search window are 0, it is determined that C does not exist in a predetermined area, while at least one of the pixel values is not 0, It is determined that C is present in the region. Then, based on such determination results for each of the CMYK images, it is determined whether or not a number of colors exceeding a predetermined threshold exists in the predetermined area. As described above, the threshold value of the number of colors used in this step is determined in advance according to the minimum temperature of the fixing unit 226.

  If YES in step S504, the flag value of the target line is updated to 1 in step S505. By this processing, the processing for this attention line ends, and then, the process proceeds to step S508. As mentioned above, a flag value of 1 means that the line contains a region of a predetermined size with a number of colors that can potentially require heat treatment to raise the temperature of the fuser unit 226 from the lowest temperature. Do.

  In the case of NO in step S504, it is determined in step S506 whether or not the area in which the search window has been set in the line of interest is the back end of the line of interest. If the determination result is true, the process proceeds to step S508, while if the determination result is false, the process proceeds to step S507.

  In the case of NO at step S506, at step S507, a search window is set to the next area in the line of interest. As described above, in this example, since the search window of 16 × 1 size is used, the search window is set in the region shifted to the right by 16 pixels. Thereafter, the process of steps S504 to S506 is repeatedly performed for each divided area with respect to each area in the line of interest. Assuming that the number of pixels in the horizontal direction of the image is W, processing is performed W / 16 times at most per line.

  Following step S505, or if YES in step S506, it is determined in step S508 whether the target line is the final line. If the determination result is true, the color line detection process is ended, while if the determination result is false, the process proceeds to step S509.

  In step S509, the next line is set as the target line, and then the process returns to step S503. The above is the contents of the color line detection process in the present embodiment.

<Continuous color line detection processing>
In the continuous color line detection process in the present embodiment, color lines which continuously appear for a predetermined number of lines or more are detected from color lines (lines having a flag value of 1) detected by the color line detection process described above. It is a process. As described above, in the present embodiment, since the minimum detection size is M × N, it is not necessary to detect a color line which is not continuous in the vertical direction by N or more. Therefore, in the continuous color line detection process, the flag value of color lines not continuous in the vertical direction by N or more is set to 0. The lines for which the flag value has become 0 in the continuous color line detection process are regarded as lines that do not require heating of the fixing unit, and the amount of loading using the search window in the subsequent processing described below (maximum loading amount detection processing per line) It can be excluded from the subject of counting process). The continuous color line detection process will be described below with reference to FIG.

  In step S601, the run of the flag value 1 that appears first from the top of the row of flag values derived in the color line detection process is set as the run of interest. Next, the process proceeds to step S602.

  In step S602, the length of the run of interest is counted, and the run length of the run of interest is acquired. Next, the process proceeds to step S603.

  In step S603, it is determined whether the run length acquired in step S602 is N or more, which is the vertical length of the minimum size to be detected, and if the determination result is false, the flag value included in the run is updated and 0 (Step S604), and the process proceeds to step S605. On the other hand, if the determination result in step S603 is true, the process proceeds to step S605 without updating the flag value.

  In step S605, it is determined whether the run of interest is the last run (whether 1 is present in the subsequent flag value). If the determination result is true, the continuous color line detection process is ended, whereas if the determination result is false, the process proceeds to step S606.

  In step S606, the run of the flag value 1 appearing next is set as the run of interest. Next, the process returns to step S602. The above is the contents of the continuous color line detection process in this embodiment.

<On application example of color line detection processing and continuous color line detection processing>
FIG. 7 shows how flag values are generated by the color line detection process described above and how the flag values generated by the continuous color line detection process described above are updated. In this example, the size of a rectangle of 5 (horizontal direction) × 4 (vertical direction) is assumed to be the detection minimum size. The objects having a size equal to or larger than the detection minimum size in the figure are an object 702 and an object 703. The size of the object 701 is 4 × 3, which is smaller than the minimum detection size. Similarly, the size of each of the characters (A to E) is smaller than the minimum detection size.

  Reference numeral 704 indicates the result of the color line detection process. In the color line detection process, 0 is given to a line in which nothing is drawn, and 1 is given to a line to be drawn in some way. As described above, in the present example, as a result of the color line detection process, a flag of 1 is set for the 23 lines of the 32 lines excluding the line where nothing is drawn.

  Reference numeral 705 indicates the result of the continuous color line detection process. By the continuous color line detection process, the flag value of the color line not continuous with the vertical size (4 in this example) of the detection minimum size is updated. In the case of this example, the flag value for 11 lines out of the 23 lines to which 1 is given in the color line detection process is changed from 1 to 0. As a result, 12 lines are finally given 1's. As described above, while leaving the flag value 1 in the line for drawing the object 702 and the object 703 having the detection minimum size or more, the flag value for the line for drawing the object (object 701 and the like) smaller than the detection minimum size may be set to 0. is made of. In the subsequent processing, the processing is executed only for the line having a flag value of 1 (details will be described later), so in the example shown in FIG. 7, it is sufficient to process only the area of 12/32 of the entire image. It will be.

<About the maximum loading amount detection process per line>
The maximum loading amount detection processing per line in the present embodiment is processing for obtaining the maximum loading amount in each line. More specifically, the sum of the applied amounts of pixels included in the range of the predetermined size in each line is repeatedly determined (repeated calculation), and the largest of the determined sums is determined. This process takes the longest time among the four processes included in the maximum load amount deriving process. However, in the present process, the above-described repetitive operation is not executed for the line with the flag value of 0. Therefore, the time required for the present process can be reduced by increasing the number of lines with the flag value of 0 in the process up to this point. As a result, the overall time for image processing can be shortened. Hereinafter, the maximum applied amount detection processing per line will be described with reference to FIG.

  In step S801, the top line of the image is set as a line of interest. Next, the process proceeds to step S802.

  In step S802, the maximum loading amount per line of interest is set to zero. Next, the process proceeds to step S803.

  In step S803, it is determined whether the flag value of the line of interest is one. If the determination result is true, the process proceeds to step S804, while if the determination result is false, the process proceeds to step S812.

  If YES in step S803, in step S804, a search window of a predetermined size is set at the beginning of the target line. This step is executed for each image of CMYK, and the size of the search window set in this step is M × 1 size, the size in the lateral direction being equal to the lateral size of the detection minimum size. Next, the process proceeds to step S805.

  In step S805, the sum of the pixel values of the pixels included in the search window is calculated in each of the CMYK images, and the sum of the calculated sums of each of the CMYK images is calculated. The sum of the sums for each of the CMYK images derived in this step is referred to as the CMYK search window coverage amount. Here, as an example, a case where one pixel is expressed by 2 bits and each pixel takes any value of 0 to 3 will be examined. In this case, since the sum of the pixel values of the pixels included in the search window per color is at most 3 × M (corresponding to the applied amount 100%), the maximum value of the applied amount within the CMYK search window is theoretically It is 12 × M.

  In step S806, it is determined whether the amount of application of the CMYK search window derived in step S805 is equal to or greater than an estimated maximum amount of application (hereinafter, assumed maximum amount of application). Here, the assumed maximum loading amount means the loading amount that needs to be fixed at the highest possible temperature of the fixing unit. If the determination result in this step is true, the process proceeds to step S 807, while if the determination result is false, the process proceeds to step S 808.

  A case where it is determined in step S806 that the loading amount in the CMYK search window is equal to or larger than the estimated maximum loading amount (YES in step S806) will be described. In this case, it is no longer necessary to find on the line of interest the amount of application within the CMYK search window that is equal to or greater than the amount of application within the CMYK search window derived in the most recent step S805. Therefore, in step S 807, the maximum loading amount per line of the target line is set to the assumed maximum loading amount, and the processing for the target line is ended. Next, the process proceeds to step S812.

  A case where it is determined in step S806 that the loading amount in the CMYK search window is not equal to or larger than the estimated maximum loading amount (NO in step S806) will be described. In this case, in step S808, it is determined whether or not the applied amount in the CMYK search window derived in the latest step S805 is larger than the maximum applied amount per line. If the determination result is true, the process proceeds to step S809, whereas if the determination result is false, the process proceeds to step S810.

  In step S809, the maximum loading amount per line is updated to the value of the loading amount within the CMYK window derived in the latest step S805. Next, the process proceeds to step S810.

  In step S810, it is determined whether the search window is set at the rear end of the target line. If the determination result is true, the process proceeds to step S812, while if the result of the determination is false, the process proceeds to step S811.

  In step S811, the search window is shifted by one pixel in the target line and set. After step S811, the process returns to step S805. For example, when the number of pixels indicating the horizontal width of the image to be processed is W, this step is executed at most W-M + 1 times.

  If NO in step S803, YES in step S810, or following step S807, it is determined in step S812 whether the target line is the final line. If the determination result is true, the processing for detecting the maximum amount of applied toner per line is ended, while if the determination result is false, the process proceeds to step S813.

  In step S813, the next line is set as the target line. Next, the process returns to step S802.

  As described above, the maximum applied amount per line is derived for all the lines constituting the image. The above is the contents of the processing for detecting the maximum amount of load per line in the present embodiment.

<About a specific example of the maximum loading amount detection process per line>
Reference numeral 706 in FIG. 7 denotes the result of the maximum adhesion amount detection processing per line (FIG. 8) executed based on the flag generated in the color line detection processing and updated in the continuous color line detection processing. . As described above, since the loading amount is counted only for the line where the flag value is 1 (YES in step S803 → step S805), the maximum loading amount per line for the line where the flag value is 0 is It will be 0. On the other hand, the maximum loading amount per line for a line with a flag value of 1 is larger than 0. FIG. 7 shows the case where only one color is used, and the maximum value of the maximum amount of application per line is 100%. On the other hand, in the case of using four colors (C, M, Y, K), the maximum application amount per line is derived by the sum of four colors, and the maximum value thereof is 240%.

  Thus, as a result of the processing for detecting the maximum loading amount per line, a row of maximum loading amounts for each line is generated. If the maximum applied amount detection processing per line is executed without generating a row of update flag values as indicated by reference numeral 705, it is necessary to execute the applied amount count processing for more color lines as indicated by reference numeral 707. And it takes a lot of processing time. In the present embodiment, the speed-up of the image processing is realized by performing control not to execute the loading amount count using the search window for the line in which the flag value is 0.

<About maximum loading amount detection processing per page image>
The maximum loading amount detection process per page image in the present embodiment is processing for detecting the maximum loading amount in a page image. More specifically, the average applied amount of a plurality of continuous color lines is calculated based on the maximum applied amount of each line derived by the maximum applied amount detection processing per line, and the largest applied amount among the calculated average applied amounts is determined. , It is processing to obtain as the maximum loading amount per page image. Hereinafter, the maximum loading amount detection process per page image will be described with reference to FIG.

  In step S901, 0 is set as an initial value of the maximum loading amount per page image. Next, the process proceeds to step S902.

  In step S902, a search window of a predetermined size is set at the head of the column of the maximum applied amount per line (symbol 706 in FIG. 7) derived by the maximum applied amount detection processing per line. The search window set in this step has a 1 × N size whose vertical size is equal to the vertical size of the detected minimum size. Next, the process proceeds to step S903.

  In step S903, the average value of the maximum loading amount per line in the search window is calculated. Next, the process proceeds to step S904.

  In step S904, it is determined whether the average value calculated in step S903 is equal to or larger than the estimated maximum loading amount. If the determination result of this step is true, the process proceeds to step S905, while if the determination result is false, the process proceeds to step S906.

  A case where it is determined in step S904 that the average value of the maximum loading amounts per line in the window is equal to or larger than the estimated maximum loading amount (YES in step S904) will be described. In this case, it is no longer necessary to find in the page image the applied amount that is equal to or greater than the average value calculated in the most recent step S903. Therefore, in step S905, the maximum loading amount per page image is updated to the value of the assumed maximum loading amount, and the maximum loading amount detection processing per page image is ended.

  The case where it is determined in step S904 that the average value of the maximum loading amounts per line in the search window is not equal to or larger than the estimated maximum loading amount (NO in step S904) will be described. In this case, in step S906, it is determined whether the average value calculated in the most recent step S903 is larger than the maximum loading amount per page image. If the determination result is true, the process proceeds to step S 907, while if the determination result is false, the process proceeds to step S 908.

  In step S 907, the maximum loading amount per page image is updated to be the average value calculated in the most recent step S 903. Next, the process proceeds to step S908.

  In step S 908, it is determined whether the maximum loading amount per line corresponding to the final line exists in the search window. If the determination result is true, the processing for detecting the maximum applied amount per page image is ended, while if the determination result is false, the process proceeds to step S909.

  In step S909, the search window is shifted downward by one pixel and set. Next, the process returns to step S903.

  The above is the contents of the processing for detecting the maximum loading amount per page image in the present embodiment. The maximum loading amount per page image derived in this processing is a final product of the maximum loading amount deriving processing in step S404, and the temperature of the fixing unit 226 is controlled based on this value. The image data derived in the pseudo intermediate processing (step S403) is sent to the laser driver 212, and the fixing amount per page image derived in this step is notified to the fixing unit 226. As a result, in the image output unit 105, the fixing unit 226 is controlled so that the temperature thereof becomes the fixing temperature corresponding to the maximum applied amount per page image, and the toner fixing at the fixing temperature is executed.

  As described above, in the present embodiment, only for the lines for which the flag value is 1 in the color line detection process and the continuous color line detection process, the application amount using the search window in the maximum application amount detection process per line The count is executed (YES in step S803 → step S805). Note that even if color line detection processing and continuous color line detection processing are not performed, flag value 1 is set for all lines, and maximum applied amount detection processing per line and maximum applied amount detection processing per page image are executed. If so, it is possible to determine the maximum loading amount necessary for temperature control. However, in this case, repeated loading amount count processing using the search window in the maximum loading amount detection processing per line is performed for all lines constituting an image, which requires a large processing time. In this embodiment, the color line detection process and the continuous color line detection process are executed, and for the line for which the flag value is 0, the target of the repeat process of the coating amount count using such a search window By excluding from the above, the time required for image processing is shortened.

<On a Modification of Embodiment 1>
In the above-described embodiment, the process is performed on all the lines, but in consideration of the trade-off relationship between the detection accuracy and the processing speed, a certain number (the length in the vertical direction of the minimum detection size Speeding up may be achieved by thinning out the processing of the lines (numbers smaller than the number of pixels shown). Similarly, in the maximum applied amount detection process per line, the applied amount count process is executed for all pixels by shifting the search window horizontally by one pixel, but this process also includes a plurality of searched windows. It may be set every few pixels, and may be performed every several pixels.

Further, in the above-described embodiment, the minimum detection size is defined as a size that allows toner fixing at the minimum temperature regardless of how large the mounting amount is for an object of a smaller size. However, the minimum detection size is not necessarily equal to the size at which the temperature increase of the fixing unit is required. For example, although a size having a data amount of 2 ⁿ bits such as the above-mentioned 32 bits can be considered as a size desirable for high-speed processing, such a size does not necessarily coincide with the size that requires a temperature rise. A size smaller than the size required for temperature rise and suitable for high speed processing may be used as the minimum detection size.

  Further, in the above-described embodiment, a flag is used to indicate whether there is an area in which the number of colors exceeding the threshold is used. However, instead of such a flag, the coordinates where the color was first found in the line may be used. Specifically, when an area where the number of colors exceeding the threshold is used in the color line detection process is found, the position of the search window used at this time is used. That is, by setting the start position of the processing in the maximum applied amount detection processing per line as the position of the search window, it is possible to omit the processing from the head of the line to that position. In the color line detection process, when the area where the number of colors exceeding the threshold is not found in the line, the flag value in the above embodiment is 0 by outputting the position of the end of the line. As in the case, it may be controlled not to execute the subsequent processing on the line. In the continuous color line detection process at this time, instead of counting the length (run length) of the continuous flag value 1, it is counted how long the line for which the color line detection process is completed continues in the middle of the line. Become. This is because, in the present modification, as a result of the color line detection process being executed to the end without ending in the middle of the line, no area in which the number of colors exceeding the threshold is used is found in the line. This is because, in the example, the flag value of the line is the same as being 0.

Example 2
In the first embodiment, the four processes included in the maximum applied amount deriving process (step S404 in FIG. 4) for an image are sequentially performed. That is, first, the color line detection process is executed, the continuous color line detection process is executed after the color line detection process, the maximum application amount detection process per line is executed after the continuous color line detection process, and finally the page image The maximum loading amount is executed.

  However, when the four processes are sequentially executed as described above, it is necessary to keep all the image data in the storage unit 103. Therefore, it is impossible to send the area of the image, for which processing has been completed, to the image output unit 105 in advance to free the use area of the storage unit 103. Further, in the first embodiment, it is necessary to count the applied amount using the search window in the processing for detecting the maximum applied amount per line, which takes a particularly long time, for all lines having a flag value of 1. Therefore, in the present embodiment, in view of these problems, four processes included in the maximum placement amount deriving process are executed in parallel (specifically, for each line constituting an image).

  In the following, the contents different from the first embodiment will be mainly described, and the description of the same contents as the first embodiment, such as the configuration of the image forming apparatus, will be omitted.

<About the maximum loading amount derivation process>
Hereinafter, the maximum loading amount deriving process in the present embodiment will be described with reference to FIG. The following processing is executed by the CPU 104.

  In step S1001, the top line of the image is set as a line of interest. Next, the process proceeds to step S1002.

  In step S1002, 0 is set as an initial value of the maximum loading amount per page image. Next, the process proceeds to step S1003.

  In step S1003, the flag value of the line of interest is derived by performing the same processing as that of the first embodiment (specifically, steps S503 to S507 of FIG. 5) on the line of interest. Next, the process proceeds to step S1004.

  In step S1004, it is determined whether the flag value of the line of interest is one. If the determination result is true, the process proceeds to step S1005, while if the determination result is false, the process proceeds to step S1006.

  First, the case where it is determined in step S1004 that the flag value of the attention line is 1 (YES in step S1004) will be described. In this case, in step S1005, the run length of the flag value 1 is counted up. Next, the process proceeds to step S1007.

  In step S1007, it is determined whether the run length of the flag value 1 is greater than or equal to the vertical length N of the minimum detection size. If the determination result is true, the process proceeds to step S1008, while if the determination result is false, the process proceeds to step S1010.

  In step S1008, the processing for detecting the maximum applied amount per line for the line of interest is executed. More specifically, the same processing as in the first embodiment (specifically, steps S804 to S811 in FIG. 8) is performed on the line of interest to obtain the maximum amount of application per line for the line of interest. Next, the process proceeds to step S1009.

  In step S1009, the maximum loading amount per page image is updated based on the maximum loading amount per line obtained in the latest step S1008. In more detail, as in the first embodiment (steps S904 to S907 in FIG. 9), the maximum per line corresponding to each of flag values 1 included in N 1 runs including flag value 1 of the target line Calculate the average value of the loading amount. Then, when the calculated average value satisfies the predetermined condition, the maximum loading amount per page image is updated. Next, the process proceeds to step S1011.

  Next, the case where it is determined in step S1004 that the flag value of the attention line is not 1 (NO in step S1004) will be described. In this case, in step S1006, the count value of the run length of the flag value 1 is reset to 0. Next, the process proceeds to step S1010.

  In step S1010, it is determined whether the line of interest is the final line. If the determination result is true, the maximum toner adhesion amount derivation process is ended, while if the determination result is false, the process proceeds to step S1011.

  In step S1011, the next line is set as a line of interest, and then the process returns to step S1003.

  Although not shown in FIG. 10, in step S1009, when the maximum loading amount per page image becomes equal to or larger than the estimated maximum loading amount, it is not necessary to continue the processing at this time. Therefore, in this case, as in the first embodiment (in the case of YES in step S904 in FIG. 9), it is possible to end the maximum applied toner amount derivation process. The above is the contents of the maximum loading amount derivation process in the present embodiment.

  According to this embodiment, since it is not necessary to keep all the image data held in the storage unit 103, it is also possible to send the area of the image for which processing has been completed to the image output unit 105 in advance to free the use area of the storage unit 103. It will be possible. In addition, processing can be skipped for the subsequent lines when the maximum loading amount per page exceeds the expected maximum loading amount, so the maximum loading amount detection processing per line is not performed for all lines having a flag value of 1. There are times when it is good. Therefore, there is a possibility that the time required for the image processing can be shorter than that of the first embodiment.

[Other embodiments]
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. Can also be realized. It can also be implemented by a circuit (eg, an ASIC) that implements one or more functions.

Claims (15)

An image forming apparatus that controls the temperature of a fixing unit based on the amount of applied color material of an object in a page image.
Color line detection means for detecting a color line in which one or more colors are used among a plurality of lines constituting the page image;
Continuous color line detection means for detecting continuous color lines appearing continuously in the vertical direction out of the detected color lines;
A maximum applied amount per line deriving unit which counts the applied amount per unit area in each of the detected continuous color lines and derives the maximum applied amount per line constituting the page image;
An image forming apparatus comprising: a maximum loading amount per page image for deriving the maximum loading amount per page image based on the derived maximum loading amount per line;   2. The image forming apparatus according to claim 1, further comprising control means for controlling the temperature of the fixing unit based on the maximum loading amount per page image. A minimum detection size is defined in advance to determine whether the object is an object for which the amount of data described above is to be obtained.
The image forming apparatus according to claim 1, wherein the minimum detection size is equal to the size of a rectangle having a horizontal length of M pixels and a vertical length of N pixels.   The color line detection means determines whether a number of colors greater than a predetermined threshold is used in each divided area obtained by dividing the target line, and a number of colors greater than the predetermined threshold is used in any of the divided areas. The image forming apparatus according to claim 3, wherein the flag line is determined to be the target line by determining the target line as the color line.   The color line detection means sequentially determines whether each of the divided areas uses the number of colors greater than the predetermined threshold in each of the divided areas, and determines whether the number of colors is greater than the predetermined threshold. 5. The image forming apparatus according to claim 4, wherein processing for the remaining divided areas is skipped when the result of the determination for one becomes true.   The image forming apparatus according to claim 4, wherein the predetermined threshold value is determined by the lowest temperature of the temperature that the fixing unit can take when fixing the color material. It also has a CPU
The image forming apparatus according to any one of claims 4 to 6, wherein the divided area has a predetermined size enabling high-speed access by the CPU.   The continuous color line detection means determines whether or not the color line detected by the color line detection means is continuous in the longitudinal direction N or more, which is the number of pixels in the vertical direction of the detection minimum size, The image forming apparatus according to any one of claims 4 to 7, wherein only a color line continuous in a direction is detected as the continuous color line.   The image forming apparatus according to any one of claims 4 to 8, wherein a horizontal length of the unit area is equal to M pixels which is a horizontal length of the minimum detection size. The maximum loading amount deriving unit per page image sets 0 as an initial value of the maximum loading amount per page image,
Setting a search window in the column of the maximum applied amount per line corresponding to each line, calculating an average value of the maximum applied amount in the set search window, and calculating the average value of the calculated average value When the value of the maximum loading amount per page image is updated and made to be the calculated average value when the loading amount per image is larger than the maximum loading amount, the page is repeatedly executed while moving the search window. The image forming apparatus according to any one of claims 4 to 9, wherein the maximum amount of application per image is derived.   11. The image forming apparatus according to claim 10, wherein the length in the vertical direction of the search window is equal to N pixels which is the length in the vertical direction of the minimum detection size. The color line detection means notifies the position of the search window set when finding the divided area in which the number of colors larger than the predetermined threshold is used, to the maximum applied amount deriving means per line.
12. The image forming apparatus according to claim 10, wherein the means for deriving the maximum applied amount per line skips processing on an area from the top of the line to the position. An image forming apparatus that controls the temperature of a fixing unit based on the amount of applied color material of an object in a page image.
A determination unit that determines whether one or more colors are used for each line constituting the page image;
A determination unit that determines whether the determined color line is a color line that appears continuously in the vertical direction;
Deriving means for counting the applied amount per unit area in the color lines appearing continuously in the vertical direction, and deriving the maximum applied amount per color line;
Maximum value per page image derived Maximum value per page image based on the average value of maximum amount per color line corresponding to each of a plurality of color lines appearing continuously in the longitudinal direction including the color line An image forming apparatus comprising: a loading amount deriving means. A control method of an image forming apparatus, which controls a temperature of a fixing unit based on an applied amount of a coloring material of an object in a page image.
Detecting a color line in which one or more colors are used out of a plurality of lines constituting the page image;
Detecting continuous color lines appearing continuously in the vertical direction out of the detected color lines;
Counting the applied amount per unit area in each of the detected continuous color lines, and deriving the maximum applied amount per line constituting the page image;
And D. deriving the maximum loading amount per page image based on the derived maximum loading amount per line.   The program for making a computer perform the control method of Claim 14.

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