JP5101539B2 - Image processing apparatus, image forming apparatus, image processing method, control program, and recording medium - Google Patents

Description

  The present invention relates to an image forming apparatus having a normal mode in which printing is performed using a color material and a save mode (eco mode) in which the printing is performed while suppressing consumption of the color material as compared with the normal mode. The present invention relates to an image processing apparatus that processes image data handled as described above.

  In recent years, digital image systems have been remarkably developed, and digital image processing technology is advancing day by day. For example, in copiers and multi-function peripherals that use electrophotography, ink jet, etc., character mode, photo mode, mixed text / photo mode, etc. to perform optimal image processing according to the type of document to be printed A plurality of image processing modes are set. Further, when a plurality of image areas exist in the document, area separation processing for determining the type of each image area is performed, and image processing suitable for the type of each image area is performed on each image area. Examples of the image area include a character area having a character image and a photographic area having a photographic image.

  On the other hand, there is a printer having a normal mode for performing normal printing and an eco mode (save mode) for performing printing while suppressing the amount of toner used (toner consumption) from the normal mode for the purpose of saving toner. In such a printer, when the eco mode is set, image processing that uniformly deletes pixels from the entire area of the original image in order to reduce the amount of toner used without reducing the image quality of the printed matter below a predetermined standard (Thinning processing, etc.) is performed. Therefore, even if the document is divided into a plurality of image areas (for example, a character area and a photographic area) and the importance of a certain image area is low and the image area is low in quality, there is no problem in using toner for each image area. Since the degree of reduction of the amount is constant, there is a problem of leaving room for further reduction in the amount of toner used for an image area with low importance. The degree of reduction in the amount of toner used indicates the degree of reduction in the amount of toner used in the eco mode with respect to the amount of toner used in the normal mode.

  The following Patent Document 1 and Patent Document 2 exist as techniques for solving the above problems. The technique of Patent Document 1 discriminates a character area and a photographic area included in an input image, and when the eco mode is set, the degree of reduction in toner usage (pixel reduction rate) is separately set for the character area and the photographic area. The thinning process is performed to delete a part of the pixels constituting each image area in accordance with the set reduction degree. The technique of Patent Document 2 calculates a logical product of a specified pattern and a generated image, and performs pixel thinning from the image to reduce recording materials such as ink and toner. Patent Document 2 also shows that the reduction rate of the recording material differs for each object such as a character or a figure.

JP 2005-234391 A (publication date: September 2, 2005) JP 9-245150 A (publication date: September 19, 1997)

  In the image forming apparatus in which the degree of reduction described above is set separately for each image area, the amount of toner used is suppressed by performing image processing for each image area based on the degree of reduction for each image area in the eco mode.

  Here, if the user can control the degree of reduction with respect to the entire print image, the convenience of the image forming apparatus having the eco mode is further enhanced. In an image forming apparatus in which the degree of reduction is set separately for each image area, if the user can specify (input) the degree of reduction for each image area, the degree of reduction for the entire print image is temporarily increased. Can be changed.

  However, in the case where the user designates the reduction degree for each image area, it is difficult for the user to recognize the reduction degree of the entire print image from the reduction degree designated for each image area. That is, in this case, even if the reduction degree of the entire print image can be changed, the user cannot recognize the reduction degree of the entire print image after the change (how the change is made cannot be recognized). ), It is difficult to control the degree of reduction of the entire printed image.

  According to the present invention, even when the image forming apparatus or the image processing apparatus is configured such that the degree of reduction in the toner usage amount in the eco mode with respect to the toner usage amount in the normal mode is set separately for each image area, It is an object of the present invention to provide an image forming apparatus or an image processing apparatus capable of allowing a user to control the degree.

  In order to achieve the above object, the present invention provides a normal mode for printing an image of image data using a color material, and a save mode for printing the image while suppressing the use amount of the color material compared to the normal mode. An image processing apparatus that processes the image data handled in the image forming apparatus having the color material usage amount of the entire image in the save mode with respect to the color material usage amount of the entire image in the normal mode. When the first color material reduction degree indicating the reduction degree is designated, based on the first color material reduction degree and the image data, the target use which is the target amount of the color material usage amount for the entire image in the save mode A target usage amount determining unit for obtaining an amount; an area separating unit for separating an image of the image data into a plurality of image regions; and an image area in the save mode with respect to a color material usage amount in the image area in the normal mode. A storage device that stores in advance the second color material reduction degree indicating the degree of reduction of the color material usage amount for each image area, and the save based on the image data and the second color material reduction degree for each image area. The temporary usage amount determination unit for obtaining a temporary usage amount that is a provisional value of the color material usage amount for the image area in the mode, and the total of the temporary usage amounts determined by the temporary usage amount determination unit is less than the target usage amount If the cumulative usage is larger than the target usage, the temporary processing after the increase processing or the reduction processing is performed by performing the reduction processing to decrease the temporary usage. A usage amount adjusting unit that matches the accumulated usage amount after adjustment to the target usage amount, and for each image region, the color material usage amount in the image area in the save mode matches the adjusted usage amount. Correction for correcting the image data The usage amount adjustment unit determines an increase amount or a decrease amount for each temporary usage amount so that the increase amount or the reduction amount increases as the provisional usage amount increases in the increase process or the decrease process. It is characterized by that.

  According to the configuration of the present invention, the first color material reduction degree indicating the degree of reduction in the color material usage amount of the entire image in the save mode relative to the color material usage amount of the entire image in the normal mode is determined by the user. Can be specified. Then, in the save mode of each image area obtained based on the second color material reduction degree so that the color material usage amount for the entire print image in the save mode is adapted to the first color material reduction degree. The color material usage amount (temporary usage amount) is adjusted for each image area (the increase process or the decrease process). Therefore, according to the configuration of the present invention, even in the image forming apparatus or the image processing apparatus, the degree of reduction in the toner usage amount in the eco mode with respect to the toner usage amount in the normal mode is set separately for each image area. There is an effect that the user can control the degree of reduction with respect to the entire print image.

  Further, according to the configuration of the present invention, the increase process or the decrease process is such that the color material usage amount for the entire print image in the save mode is adapted to the first color material reduction degree. In the increase process or the decrease process, the increase amount or the decrease amount for each temporary use amount is determined so that the increase amount or the decrease amount increases as the provisional use amount increases. Therefore, an image area with a large amount of toner used has a higher degree of increase / decrease in the increase process or decrease process, and therefore the magnitude of the effect caused by the increase process or decrease process is substantially equal in all image areas. Thus, it is possible to suppress the occurrence of local image quality deterioration due to the increase process or the decrease process.

  The target usage, provisional usage, adjusted usage, and total handled by the image processing apparatus are most preferably true values (true amounts) obtained by calculation. In addition to the value, an approximate value (approximate amount) is also included. This is because some actual devices perform approximate calculation in the process of data processing (calculation). In addition, because of the processing method and the contents of the system, there are some cases where processing cannot be performed unless an allowable error range (a numerical range consisting of a true value and an approximate value) is set. Here, the approximate value means a value within a numerical range that can be equated with the true value based on the contents of the data processing executed in the actual apparatus. This numerical range is, for example, 99 to 99 of the true value. 101% is set.

  In other words, the usage adjustment unit performs processing to match the cumulative total of the adjusted usage with the target usage, but this is true when matching true values, when matching approximate values, And approximate value may be used. In addition, the correction unit performs processing to match the color material usage in the image area in the save mode with the adjusted usage, but this is done after adjusting the color material usage in the image area in the save mode. When the color material usage amount is made to coincide with the true value, the color material usage amount may be matched with the approximate value of the adjusted usage amount.

  In the image processing apparatus of the present invention, the plurality of image regions separated from the image by the region separation unit may include at least a character region and a photographic region. However, characters can often be deciphered even if the toner usage reduction level is increased, but if the toner usage reduction level is increased, the color of the photograph will be light and the image quality will appear to be extremely degraded. Things happen. Therefore, in the image processing apparatus of the present invention, when the plurality of image regions separated from the image by the region separation unit include at least a character region and a photographic region, the second color material reduction degree of the photographic region. Is set lower than the second color material reduction degree of the character area, the above situation can be suppressed.

  Furthermore, in the image processing apparatus of the present invention, the plurality of image regions separated from the image by the region separation unit may include at least a graphic region and a photographic region. However, the figure can often be deciphered even if the toner usage reduction level is increased, but if the toner usage reduction level is increased, the color of the photograph will be light and the image quality will appear to be extremely deteriorated. Things happen. Therefore, in the image processing apparatus of the present invention, when the plurality of image regions separated from the image by the region separation unit include at least a graphic region and a photographic region, the second color material reduction degree of the photographic region. Is set lower than the second color material reduction degree of the graphic area, the above situation can be suppressed.

  In the image processing apparatus of the present invention, the plurality of image regions separated from the image by the region separation unit may include at least a character region and a halftone dot region. However, characters can often be deciphered even if the toner usage reduction level is increased, but when the toner usage reduction level is increased, the halftone dot area becomes smaller and the image quality appears to be extremely deteriorated. It will happen. Therefore, in the image processing apparatus of the present invention, when at least a character region and a halftone dot region are included in the plurality of image regions separated from the image by the region separation unit, the second color material of the halftone dot region By setting the reduction degree lower than the second color material reduction degree of the character area, the above situation can be suppressed.

  Furthermore, in the image processing apparatus of the present invention, the plurality of image regions separated from the image by the region separation unit may include at least a character region and a continuous tone region. However, characters can often be deciphered even if the toner usage reduction level is increased, but if the toner usage reduction level is increased, the gradation level in the continuous tone area becomes smaller and the image quality appears to be extremely deteriorated. A situation occurs. Therefore, in the image processing apparatus of the present invention, when the plurality of image regions separated from the image by the region separation unit include at least a character region and a continuous tone region, the second of the continuous tone regions. By setting the color material reduction degree lower than the second color material reduction degree of the character region, the above situation can be suppressed.

  An image forming apparatus including the above-described image processing apparatus is also included in the scope of the present invention. Here, the image forming apparatus means an electrophotographic or inkjet printer, a copier having the printer, and a multifunction machine having the printer.

  According to another aspect of the present invention, there is provided an image forming apparatus having a normal mode for printing an image of image data using a color material and a save mode for printing the image while suppressing a use amount of the color material as compared with the normal mode. An image processing method for processing the image data to be handled, the first showing the degree of reduction of the color material usage amount of the entire image in the save mode relative to the color material usage amount of the entire image in the normal mode When a color material reduction degree is designated, target usage amount determination for obtaining a target usage amount that is a target amount of the color material usage amount for the entire image in the save mode based on the first color material reduction degree and the image data. A step of separating the image of the image data into a plurality of image regions, and a reduction of the color material usage amount of the image area in the save mode with respect to the color material usage amount of the image region in the normal mode. A step of reading out the second color material reduction degree of each image area separated in the area separation step from a storage device that stores in advance the second color material reduction degree indicating the degree for each image area; In addition, based on the image data and the second color material reduction degree read in the reading step, a provisional usage amount for obtaining a provisional usage amount that is a provisional value of the color material usage amount for the image area in the save mode. When the cumulative total of the temporary usage determined in the determining step and the temporary usage determining step is smaller than the target usage, an increase process is performed to increase each temporary usage, and the cumulative is less than the target usage A use amount adjustment step of making the cumulative amount of adjusted use amount, which is a provisional use amount after the increase process or the decrease process, coincide with the target use amount by performing a decrease process to decrease each provisional use amount when there are many; For each image area, A correction step of correcting the image data so that the amount of color material used in the image region in the mode matches the adjusted usage amount. In the usage amount adjustment step, in the increase process or the decrease process, The increase amount or the decrease amount for each temporary use amount is determined so that the increase amount or the decrease amount increases as the provisional use amount increases.

  The image processing apparatus may be realized by a computer. In this case, a control program that causes the computer to function as each unit and a computer-readable recording medium that records the control program are also included in the scope of the present invention. enter.

  According to the configuration of the present invention, even in an image forming apparatus or an image processing apparatus in which the degree of reduction in the toner usage amount in the eco mode with respect to the toner usage amount in the normal mode is set separately for each image area, the printed image There is an effect that the user can control the degree of reduction with respect to the whole.

  Further, according to the configuration of the present invention, the color material usage amount for the entire print image in the save mode is controlled by the increase process or the decrease process described above. The degree of increase / decrease in the reduction process is increased. Thereby, the magnitude of the influence caused by the increase process or the decrease process can be made substantially uniform in all the image areas, and the occurrence of local image quality deterioration due to the increase process or the decrease process can be suppressed.

1 is a block diagram illustrating a schematic configuration of a printer according to an embodiment of the present invention and a terminal device connected to the printer. It is the block diagram which showed the detail of the structure of the usage-amount calculation part shown by FIG. It is the flowchart which showed the flow of the process of the usage-amount calculation part shown by FIG. It is explanatory drawing which showed the calculation content of the usage-amount calculation part when the image of image data contains a character area, a natural image area | region, and a graphic area, and the total of all the temporary usage is less than a target usage. . It is explanatory drawing which showed the calculation content of the usage amount calculation part when the image of image data contains a character area, a natural image area | region, and a graphic area, and the total of all the temporary usage amounts is larger than a target usage amount. . It is explanatory drawing which showed the calculation content of the usage-amount calculation part in case the image of image data contains a character area | region and a natural image area | region, but does not contain a figure area | region. It is explanatory drawing which showed the calculation content of the usage-amount calculation part in case the image of image data contains a character area | region and a graphics area | region, but does not contain a natural image area | region. It is explanatory drawing which showed the calculation content of the usage-amount calculation part when the character emphasis mode is selected. It is explanatory drawing which showed the calculation content of the usage-amount calculation part when the photograph emphasis mode is selected. FIG. 6 is a block diagram showing a schematic configuration of a copying machine which is another embodiment of the present invention. It is a figure which shows an example of the image containing a character area | region, a photography area | region, and a graphic area. It is a figure which shows an example of the data structure at the time of describing the image data of the image shown by FIG. 11 by PDL.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a printer which is an embodiment of an image forming apparatus of the present invention and a terminal device connected to the printer. Note that the printer 2 of the present embodiment has a normal mode for printing an image of image data using toner, and a toner save mode for printing the image while suppressing the amount of toner used compared to the normal mode. It shall be.

  The terminal device 1 is used by a user of the printer 2 and is a personal computer in which a printer driver for operating the printer 2 is installed in addition to various application software such as image editing software. In the terminal device 1, image data created by application software such as image editing software is converted into image data described in PDL (Page Description Language) by a printer driver. Then, the image data described in PDL is transmitted to the printer 2. The image data described in PDL shows information indicating the starting position, size, and color of each image area. Further, as shown in FIG. 1, it is assumed that image data transmitted from the terminal device 1 to the printer 2 is color-specified in RGB. R is red, G is green, and B is blue.

  Further, in the present embodiment, the user can select either the normal mode or the toner save mode on the printer driver setting screen of the terminal device 1 by using a keyboard or a mouse (check each mode). Or you can check the box).

  Then, after the user selects the toner save mode by the printer driver of the terminal device 1, the toner use of the entire image in the save mode with respect to the toner use amount (color material use amount) of the entire image in the normal mode The first color material reduction degree indicating the amount reduction degree is input. That is, by this input work, the first color material reduction degree in the printer 2 is designated to the user.

The first color material reduction degree is a value indicating the reduction degree of the toner use amount of the entire image in the save mode with respect to the toner use amount (color material use amount) of the entire image in the normal mode. Any value may be used, but in the present embodiment, the first reduction rate represented by the following Equation 1 is input to the terminal device 1 as the first color material reduction degree.
First reduction rate (%) = 100 × (toner usage amount for entire print image in normal mode−toner usage amount for entire print image in toner save mode) / (toner usage amount for entire print image in normal mode) ... Formula 1
Also, the value input as the first reduction rate may be an arbitrary value set by the user, or a value selected by the user from among a plurality of preset first reduction rates. There may be. Furthermore, a printing system is constructed in which a plurality of printers 2 and control devices are connected via a network so that the control device manages the plurality of printers 2 in a unified manner. The first reduction rate may be set.

  When the first reduction rate is input to the terminal device 1, the printer driver of the terminal device 1 describes the input first reduction rate for the image data.

  The printer (image forming apparatus) 2 is an electrophotographic printing apparatus, and includes a print engine unit 4 and an image processing unit 5 as shown in FIG. The printer 2 is not limited to an electrophotographic printing apparatus, and may be an inkjet printing apparatus.

  The image processing unit (image processing apparatus) 5 is a block that performs image processing on the image data and sends the image data after the image processing to the print engine unit 4. When the image data is sent from the image processing unit 5, the print engine unit 4 forms an image corresponding to the image data on a predetermined sheet (paper, OHP, etc.).

  Next, details of the image processing unit 5 will be described. As shown in FIG. 1, the image processing unit 5 includes an area determination unit 11, a color correction unit 12, a usage amount calculation unit 13, an output tone correction unit 14, and a halftone processing unit 15.

  First, when image data described in PDL is sent to the image processing unit 5, a conversion processing unit (not shown) indicates the PDL image data, the image data indicating RGB gradation values, and the attributes of the image area. It is designed to be converted to tag data. Then, RGB image data and tag data are input to the region discriminating unit 11.

  The area discriminating unit (area separating unit) 11 discriminates the type of each image area included in the image of the image data, that is, the area separating process for separating the image of the image data sent from the terminal device 1 for each image area. The process which performs is performed. More specifically, the area discriminating unit 11 is composed of a character area composed of text data, a graphic area composed of a graphic or a graph, and photographic image data by examining the attribute information of each image area based on the tag data. A natural image area is determined.

  In addition to performing the region separation process, the region determination unit 11 transmits the image data sent from the terminal device 1 to the color correction unit 12 as it is. Further, the region discriminating unit 11 transmits a region identification signal indicating the result of the region separation processing to the subsequent use amount calculating unit 13, the output tone correcting unit 14, and the halftone processing unit 15.

  The color correction unit 12 performs processing to remove color turbidity based on the spectral characteristics of CMY (C: cyan, M: magenta, Y: yellow) color materials including unnecessary absorption components in order to realize faithful color reproduction. At the same time, black generation for generating a black (K) signal from the three color signals of CMY, that is, under color removal processing (UCR: Under Color) for generating a new CMY signal by subtracting the K signal obtained by black generation from the CMY signal. Removal). That is, as shown in FIG. 1, the color correction unit 12 converts the image data composed of RGB signals sent from the region discrimination unit 11 into image data composed of CMYK signals. Then, the color correction unit 12 transmits image data composed of CMYK signals to the usage amount calculation unit 13.

  In the toner save mode, the usage amount calculation unit 13 is based on the image data sent from the color correction unit 12 and the area identification signal sent from the area determination unit 11, and the image included in the image of the image data. For each region, a provisional usage amount that is a provisional value of the toner usage amount for each image region is calculated. Further, the usage amount calculation unit 13 adjusts each provisional usage amount calculated for each image region based on the first reduction rate described above. Then, the usage amount calculation unit 13 creates usage amount information indicating the adjusted usage amount, which is the provisional usage amount after the adjustment, for each image region, and outputs the usage amount information together with the image data to the output tone correction unit. 14 for transmission. In addition, this usage amount information also indicates a normal usage amount (see FIG. 4) described later.

  The usage amount calculation unit 13 recognizes that the toner save mode is selected when the first reduction rate is described in the input image data.

  In addition, the usage amount calculation unit 13 recognizes that the normal mode is selected when the first reduction rate is not described in the input image data. In the normal mode, the usage amount calculation unit 13 does not create the usage amount information and transmits the image data sent from the color correction unit 12 to the output gradation correction unit 14 as it is. The processing content executed by the usage amount calculation unit 13 will be described in detail later.

  The output tone correction unit (correction unit) 14 executes output tone correction processing corresponding to the output characteristic value of the print engine unit 4 for the image data sent from the usage amount calculation unit 13. The output gradation correction process is executed using an output gradation correction curve (gamma curve).

  The output tone correction unit 14 recognizes that the toner save mode is selected when the usage amount information is sent from the usage amount calculation unit 13. Then, in the toner save mode, the output tone correction unit 14 converts the image data into an image based on the usage amount information sent from the usage amount calculation unit 13 and the region identification signal sent from the region discrimination unit 11. Correction processing is performed on the image data so that the toner usage amount for each included image area matches the adjusted usage amount indicated in the usage amount information.

  Specifically, the output gradation correction unit 14 indicates, for each image region included in the image of the image data, the toner usage amount at the time of printing each image region in the usage amount information output from the usage amount calculation unit 13. A process for changing the output tone correction curve used for the output tone correction process is performed so as to match the adjusted usage amount. The method for changing the output tone correction curve will be described in detail later.

  The halftone processing unit 15 performs tone reproduction processing (halftone generation, halftone processing) on the image data sent from the output tone correction unit 14 based on the region identification signal, and finally the image Can be reproduced in a pseudo gradation.

  The image data that has been subjected to the gradation reproduction process in the halftone processing unit 15 is sent to the print engine unit 4, whereby the image indicated by the image data is printed.

  FIG. 1 shows an example in which PDL data specified by RGB color is sent from the terminal device 1 to the printer 2, but the PDL data may be color specified by CMYK. The image data input to the color correction unit 12 via the region determination unit 11 is CMYK data. In this case, the color correction unit 12 does not process the input CMYK data, and transmits the data to the usage amount calculation unit 13 as it is.

  Next, the above-described usage amount calculation unit 13 will be described in detail. As shown in FIG. 2, the usage amount calculation unit 13 includes a target amount calculation unit 101, a provisional amount calculation unit 102, an adjustment unit 103, and a storage device 34. As shown in FIG. 2, each unit included in the usage amount calculation unit 13 receives a region identification signal from the region determination unit 11, and an image of the input image data is input by the region identification signal. The type of each image area included can be recognized.

  A target amount calculation unit (target usage amount determination unit) 101 in the toner save mode, based on the image data and the first reduction rate described in the image data, a target of the toner usage amount for the entire image of the image data. This is a block for obtaining a target usage amount.

The storage device 34 is information storage means such as a ROM (Read Only Memory), and the amount of toner used in the image area in the toner save mode relative to the amount of toner used in the image area (color material usage) in the normal mode. The second color material reduction degree indicating the reduction degree is stored in each image area. The second color material reduction degree is a value set for each image area, and the reduction of the toner usage amount of the image area in the toner save mode with respect to the toner usage amount of the image area in the normal mode. Any value may be used as long as the value indicates the degree, but in the present embodiment, the second reduction rate represented by the following Expression 2 is stored in the storage device 34 for each image area as the second color material reduction degree. is doing.
Second reduction rate (%) = 100 × (toner usage for each image area in normal mode−toner usage for each image area in toner save mode) / (toner usage for each image area in normal mode) ... Formula 2
When the image data is input, the provisional amount calculation unit (provisional use amount determination unit) 102 provisionally uses the toner amount for each image region based on the second reduction rate stored in the storage device 34 and the image data. A temporary usage amount as a value is obtained for each image area.

  The adjustment unit (usage amount adjustment unit) 103 determines that each provisional use is performed when the total of all the provisional use amounts obtained by the provisional amount calculation unit 102 is smaller than the target use amount obtained by the target amount calculation unit 101. When an increase process for increasing the amount is performed and the total of all the temporary usage amounts obtained by the temporary amount calculation unit 102 is larger than the target usage amount obtained by the target amount calculation unit 101, each temporary usage amount is Decrease process to decrease. Here, the provisional use amount after the increase process or the decrease process is set as the adjusted use amount. Then, the adjustment unit 103 performs the increase process or the decrease process so that the total of all the adjusted usage amounts matches the target usage amount. Further, the adjustment unit 103 creates usage amount information indicating the adjusted usage amount and a normal usage amount, which will be described later, for each image area, and sends the usage amount information to the output tone correction unit 14 together with the image data. To transmit.

Next, the flow of processing executed by the usage amount calculation unit 13 will be described in more detail. FIG. 3 is a flowchart showing a processing flow of the usage amount calculation unit 13. As described above, the usage amount calculation unit 13 obtains the provisional usage amount and the adjusted usage amount for each image region determined by the region determination unit 11. Therefore, as shown in FIG. 3, the processing content executed by the usage amount calculation unit 13 is classified into each of Case 1 to Case 7 below.
Case 1: When the image of the image data includes a character area, a natural image area, and a graphic area (S1 to S8)
Case 2: When the image of the image data includes a character area and a natural image area but does not include a graphic area (S1 to S5, S9 to S11)
Case 3: When the image of the image data includes a character area and a graphic area but does not include a natural image area (S1 to S4, S12 to S15)
Case 4: When the image of the image data includes a graphic area and a natural image area but does not include a character area (S1 to S3, S17 to S21)
Case 5: When the image of the image data consists only of a character area (S1 to S4, S12, S16)
Case 6: When the image of the image data consists only of a natural image area (S1 to S3, S17 to S18, S22)
Case 7: When the image of the image data consists only of a graphic area (S1 to S3, S17, S23)
Below, the processing content of the usage amount calculation part 13 of case 1-case 7 is demonstrated with reference to figures.

(Case 1)
FIG. 4 shows calculation contents of the usage amount calculation unit 13 when the image of the image data includes a character area, a natural image area, and a graphic area, and the total of all the temporary usage amounts is smaller than the target usage amount. FIG. Hereinafter, the calculation contents of the usage amount calculation unit 13 in the case 1 described above will be described with reference to FIG. 4 in addition to FIG. 3.

  First, when the image data output from the color correction unit 12 is input to the usage amount calculation unit 13, the usage amount calculation unit 13 determines whether or not the first reduction rate is described in the image data (S1). . If the first reduction rate is not described in the image data (NO in S1), the usage amount calculation unit 13 sends the input image data as it is to the output tone correction unit 14, and then ends the process.

  On the other hand, when the first reduction rate is described in the image data (YES in S1), the target amount calculation unit 101 calculates the target usage amount based on the input image data and the first reduction rate (S2). ). Hereinafter, a method for calculating the target usage will be described. First, in FIG. 4, the normal usage amount means the toner usage amount of each image area in the normal mode. Further, the total normal usage amount is a toner usage amount of the entire image in the normal mode, that is, an amount corresponding to a cumulative total of the normal usage amounts. Then, the target amount calculation unit 101 calculates the normal usage amount of each image area from the input image data, and further calculates the total normal usage amount by accumulating the normal usage amount. Thereafter, the target amount calculation unit 101 obtains the target usage amount by substituting the total normal usage amount and the first reduction rate into Equation 10 of FIG. In the example of FIG. 4, the first reduction rate is 30%, and image data with the total normal usage amount being 10,000 is input, so the target usage amount is 7000.

  The target amount calculation unit 101 refers to a table showing the relationship between the density value for each pixel of the image data and the normal use amount for each image region, so that the normal use of each image region is input from the input image data. Seeking the amount. Here, the table is created by testing using a plurality of image samples in advance, and is stored in the storage device 34 of FIG. 4 indicates the ratio between the number of output pixels (number of dots) of the entire image and the number of output pixels of each image area.

  Next, the processes after S2 will be described. In case 1, since the image of the image data includes a character area, a natural image area, and a graphic area, the process proceeds to S6 (Yes in S3 to S5). In S <b> 6, the provisional amount calculation unit 102 reads out the second reduction rate of each image area included in the image of the image data from the storage device 34. Here, in the present embodiment, as shown in FIG. 4, the second reduction rate of the character region is set to 50%, the second reduction rate of the graphic region is set to 30%, and the second reduction rate of the natural image region is set. 2. The reduction rate is set to 20%.

  In S <b> 7, the provisional amount calculation unit 102 obtains a provisional usage amount for each image region. Hereinafter, a method for calculating the temporary usage amount will be described in detail. First, the provisional amount calculation unit 102 obtains the usage rate for each image region by substituting the second reduction rate into Equation 11 in FIG. Next, the provisional amount calculation unit 102 can obtain the provisional use amount for each image region by substituting the use rate and the normal use amount into Expression 12 in FIG.

  In the example of FIG. 4, the normal usage amount is 4000 and the second reduction rate is 50% in the character area, so the temporary usage amount is 2000. In the graphic area, the normal usage amount is 2000 and the second reduction rate is 30%, so the provisional usage amount is 1400. Furthermore, in the natural image area, the normal usage amount is 4000, and the second reduction rate is 20%, so that the temporary usage amount is 3200.

  After S7, the adjustment unit 103 obtains an adjusted usage amount for each image region (S8). Below, the method of calculating | requiring the usage-amount after adjustment is demonstrated in detail. First, the adjustment unit 103 substitutes the cumulative total of all the temporary usage amounts obtained in S7 and the target usage amount obtained in S2 into Equation 15 in FIG. Calculate the deficiency. Next, the adjustment unit 103 calculates the greatest common divisor of all the provisional usages obtained in S7 based on Equation 13 in FIG. Further, the adjustment unit 103 obtains the increase / decrease ratio shown in FIG. 4 by substituting the provisional usage amount and the greatest common divisor for Expression 14 in FIG. 4 for each image region. Further, the adjusting unit 103 obtains the coefficient shown in FIG. 4 by substituting the total of the obtained increase / decrease ratios and the excess / deficiency amount into the equation 16 in FIG. Thereafter, the adjustment unit 103 obtains the increase / decrease amount shown in FIG. 4 by substituting the increase / decrease ratio and the coefficient into the equation 17 in FIG. 4 for each image region. Further, the adjustment 103 calculates the adjusted usage amount for each image region by substituting the temporary usage amount and the increase / decrease amount into Equation 18 in FIG.

  In the example of FIG. 4, the provisional usage amount is 2000 in the character area, and the adjusted usage amount is 2121. Therefore, the adjustment unit 103 increases the toner usage amount by 121. In the graphic area, the provisional usage amount is 1400, and the post-adjustment usage amount is 1485, which means that the adjustment unit 103 increases the toner usage amount by 85. Further, in the natural image area, the provisional usage amount is 3200, but the adjusted usage amount is 3394, and the adjustment unit 103 increases the toner usage amount by 194.

  Thereafter, the adjustment unit 103 creates usage amount information indicating the normal usage amount of each image region and the adjusted usage amount of each image region calculated in S8, and outputs the usage amount information together with the image data to output gradation. This is sent to the correction unit 14. Thereby, the process of the usage amount calculation part 13 is complete | finished.

  In the process of FIG. 4, each value obtained by the calculation is rounded off and the decimal part is rounded down (for example, the calculation result of Expression 17 is a value including a decimal point. Each increase / decrease value shown is rounded). That is, each value handled in the processing of FIG. 4 (normal use amount, normal use total number, target use amount, provisional use amount, excess / deficiency amount, coefficient, increase / decrease rate, increase / decrease amount, greatest common divisor, adjusted use amount, Each cumulative value etc. includes not only true values but also approximate values. As described above, not only a true value but also an approximate value is allowed because an actual device often performs an approximate operation in the process of data processing, and if an approximate value is not allowed, it does not follow the actual situation. It is. Here, the approximate value means a value within a numerical range that can be equated with the true value based on the content of the data processing executed by the image processing unit 5 and the size of the true value. The numerical range is set to be variable according to the content of the data processing in which the value of the numerical range is handled and the size of the true value, for example, 95 to 105% of the true value.

  Although the processing content of the usage amount calculation unit 13 when the total of all the temporary usage amounts is larger than the target usage amount has been described above, the usage amount calculation when the total of all the temporary usage amounts is smaller than the target usage amount The processing contents of the unit 13 are also the same as the case where the total of all the temporary usage amounts is larger than the target usage amount.

  FIG. 5 shows the calculation content of the usage amount calculation unit 13 when the image of the image data includes a character area, a natural image area, and a graphic area, and the total of all the temporary usage amounts is smaller than the target usage amount. FIG. As described above, the calculation content when the total of all the temporary usage amounts is smaller than the target usage amount is the same as the case where the total of all the temporary usage amounts is larger than the target usage amount. Therefore, also in FIG. 5, various arithmetic processes are performed using the same expressions as Expressions 10 to 18 shown in FIG.

  Hereinafter, FIG. 5 will be described. Also in FIG. 5, it is assumed that, as in FIG. 4, the first reduction rate is 30%, and image data in which the total amount of normal use is 10,000 is input. However, FIG. 5 is different from FIG. 4 in that the normal use amount of the character area is 2000, the normal use amount of the graphic area is 3000, and the normal use amount of the natural image area is 5000.

  When the normal usage amount and the first reduction rate of each image region are the values shown in FIG. 5, the excess / deficiency amount calculated by Expression 15 is −100. That is, the total of all the temporary usage amounts is smaller than the target usage amount.

  Further, as shown in FIG. 5, when the cumulative total of all the temporary usage amounts is smaller than the target usage amount, the excess / deficiency amount is a negative value, so the coefficient calculated by Equation 16 is also a negative value, The increase / decrease amount calculated by Expression 17 is also a negative value. Therefore, the adjusted usage amount calculated by Equation 18 is a value that is reduced from the temporary usage amount by the absolute value of the increase / decrease amount.

  Specifically, in the character area of FIG. 5, since the temporary usage amount is 1000 and the increase / decrease amount is −14, the adjusted usage amount is 986, and the adjustment unit 103 decreases the toner usage amount by 14. It will be. Further, in the graphic area of FIG. 5, since the temporary usage amount is 2100 and the increase / decrease amount is −30, the adjusted usage amount is 2070, and the adjustment unit 103 reduces the toner usage amount by 30. . Further, in the natural image area of FIG. 5, the provisional usage amount is 4000 and the increase / decrease amount is −56. Therefore, the adjusted usage amount is 3944, and the adjustment unit 103 reduces the toner usage amount by 56. Become.

  As described above, according to the configuration of the present embodiment, the second reduction of each image area is performed so that the amount of toner used for the entire print image in the toner save mode is adapted to the first reduction rate. This means that the toner usage (provisional usage) in the toner save mode for each image area obtained based on the rate is adjusted. That is, according to the configuration of the present embodiment, in the printer 2 in which the degree of reduction in the toner usage amount in the toner save mode with respect to the toner usage amount in the normal mode is set separately for each image area, the reduction of the entire print image is performed. There is an effect that the user can control the degree.

  Also, according to the configuration of the present embodiment, the adjustment unit 103 increases or decreases the provisional usage amount of each image area using Expressions 13 to 18, and uses the adjusted provisional usage amount after the increase or decrease. It is output as a quantity. Here, as is apparent from Equations 14 and 15, since the increase / decrease amount in the increase or decrease becomes a value proportional to the provisional use amount, the adjustment unit 103 increases or decreases as the provisional use amount increases. That is, the increase amount or the decrease amount for each provisional use amount is determined so as to increase. Therefore, since the degree of increase / decrease in the increase / decrease is higher in an image area where the amount of toner used is large, the magnitude of the effect caused by the increase / decrease can be made substantially uniform in all image areas, There is an effect that it is possible to suppress the occurrence of local image quality degradation caused by the increase or decrease.

  Next, another advantage of this embodiment will be described with reference to FIG. For example, as in the example of FIG. 4, the first reduction rate is set to 30%, but unlike the example of FIG. 4, the data is used so that the toner usage is uniformly reduced by 30% for all image areas. In the case of thinning, although the data after thinning conforms to the first reduction rate, there is a difference in the degree of image quality degradation between image areas, and there is a problem that image quality degradation is noticeably caused only in certain image areas (for example, You can read the text, but the natural image disappears and disappears).

  More specifically, in the example of FIG. 4, the common reduction rate common to all image areas is set to 30%, and the “second reduction rate” in Expression 12 is replaced with “common reduction rate”. In this case, the temporary usage amount of the character region is 2800, the temporary usage amount of the graphic region is 1400, the temporary usage amount of the natural image region is 2800, and the total temporary usage amount of the entire image is 7000. Is a value adapted to the first reduction rate. However, when an image is output based on the provisional usage amount obtained from the common reduction rate as described above, characters can be read sufficiently because the contrast is high, but a natural image region having a low contrast becomes thin and blurred. .

  Therefore, the second reduction rate for each image region is determined in advance by experiments and subjective evaluation using various images. Specifically, the second reduction rate of the character region is larger than the second reduction rate of the natural image region, and the second reduction rate of the graphic region is larger than the second reduction rate of the natural image region. If the second reduction rate of the image area is determined, the above-described adverse effects can be suppressed. In the example of FIG. 4, the second reduction rate (data reduction rate) of the character area is set to 50%, the second reduction rate of the graphic area is set to 30%, and the second reduction rate of the natural image area is set to 20%. Is set. In the example of FIG. 4, the second reduction rate of the character area is higher than the second reduction rate of the graphic area, but the second reduction rate of the character area and the second reduction rate of the graphic area are They may be equal to each other.

  However, in the example of FIG. 4, the image quality level of each image area is equal only by obtaining the temporary usage amount based on the second reduction rate, but the temporary usage amount of the character area is 2000 and the graphic area is The temporary usage amount is 1400, the temporary usage amount of the natural image region is 3200, and the total toner reduction is 34%, and the output image is not adapted to the input first reduction rate (30%).

  Therefore, in the present embodiment, as shown in FIG. 4, the target usage amount (7000) is obtained from the input first reduction rate, and the cumulative value of the provisional usage amount is subtracted from the target usage amount, thereby obtaining the target usage amount. Find the excess or deficiency. Then, by assigning the excess / deficiency amount to the temporary use amount of each image area, the toner use amount of the entire output image is matched with the target use amount while varying the reduction rate for each image area. Thereby, it is possible to obtain a high-quality image while adapting the toner usage amount of the entire output image to the conditions input by the user.

  In the present embodiment, as shown in FIG. 4, the second reduction rate of the natural image region (photo region) is set lower than the second reduction rate of the character region and the second reduction rate of the graphic region. This is because, if the degree of reduction in toner usage is increased for photographs, the color becomes lighter and the image quality appears to be extremely deteriorated.

(About Case 2)
Next, the processing content of the usage amount calculation unit 13 when the image of the image data includes a character region and a natural image region but does not include a graphic region (case 2) will be described. FIG. 6 is an explanatory diagram showing calculation contents of the usage amount calculation unit 13 when an image of image data includes a character area and a natural image area but does not include a graphic area. Here, the calculation contents of case 2 are the same as the calculation contents of case 1. Therefore, also in FIG. 6, various arithmetic processes are performed using the same expressions as Expressions 10 to 18 shown in FIG. 4 or FIG.

  Hereinafter, processing of case 2 will be described based on FIGS. 3 and 6. In FIG. 6, as in FIG. 4, it is assumed that the first reduction rate is 30%, and image data whose normal usage amount is 10,000 is input. However, FIG. 6 differs from FIG. 4 in that the image data image includes a character area and a natural image area but does not include a graphic area. In FIG. 6, the normal usage amount of the character image is 4000, and the normal usage amount of the natural image area is 6000.

  Also in case 2, as in case 1, after the image data is input to the usage amount calculation unit 13, the processing of S1 and S2 in FIG. 3 is performed to calculate the target usage amount. In case 2, since the image of the image data includes the character area and the natural image area but does not include the graphic area, the process proceeds to S9 after S2 (NO in S5).

  In S9, similar to S6, the provisional amount calculation unit 102 reads the second reduction rate of each image area included in the image of the image data from the storage device 34. However, in case 2, since the image of the image data includes the character area and the natural image area but does not include the graphic area, only the second reduction ratio of the character area and the second reduction ratio of the natural image area are read in S9. It is.

  In S10, as in S7, the provisional amount calculation unit 102 obtains a provisional usage amount for each image region. In the example of FIG. 6, since the normal usage amount is 4000 and the second reduction rate is 50% in the character area, the temporary usage amount is 2000. In the natural image area, the normal usage amount is 6000, and the second reduction rate is 20%, so the provisional usage amount is 4800.

  In S <b> 11, as in S <b> 8, the adjustment unit 103 obtains an adjusted usage amount for each image area. In the example of FIG. 6, the provisional usage amount is 2000 in the character area, but the adjusted usage amount is 2059, and the adjustment unit 103 increases the toner usage amount by 59. Further, in the natural image area, the provisional usage amount is 4800, but the post-adjustment usage amount is 4941, which means that the adjustment unit 103 increases the toner usage amount by 141. That is, in Case 2, as in Case 1, the adjustment unit 103 determines an increase amount for each temporary use amount so that the increase amount increases as the provisional use amount increases.

(Case 3)
Next, processing contents of the usage amount calculation unit 13 when the image of the image data includes a character area and a graphic area but does not include a natural image area (case 3) will be described. FIG. 7 is an explanatory diagram showing calculation contents of the usage amount calculation unit 13 when an image of image data includes a character area and a graphic area but does not include a natural image area. Here, the calculation content of case 3 is the same as the calculation content of case 2. Therefore, also in FIG. 7, various arithmetic processes are performed using the same expressions as Expressions 10 to 18 shown in FIG.

  Hereinafter, processing of case 3 will be described based on FIGS. 3 and 7. In FIG. 7, as in FIG. 6, it is assumed that the first reduction rate is 30%, and image data whose normal usage amount is 10,000 is input. However, FIG. 7 differs from FIG. 6 in that the image data image includes a character area and a graphic area but does not include a natural image area. In FIG. 7, the normal usage amount of the character area is 3000, and the normal usage amount of the graphic area is 7000.

  Also in case 3, as in case 2, after the image data is input to the usage amount calculation unit 13, the processing of S1 and S2 in FIG. 3 is performed, and the target usage amount is calculated. In case 3, since the image of the image data includes the character area and the graphic area but does not include the natural image area, the process proceeds to S13 after S2 (YES in S12).

  In S <b> 13, similar to S <b> 9, the provisional amount calculation unit 102 reads out the second reduction rate of each image area included in the image of the image data from the storage device 34. However, in case 3, since the image of the image data includes a character area and a graphic area but does not include a photographic image area, only the second reduction ratio of the character area and the second reduction ratio of the graphic area are read in S13. is there.

  In S14, as in S10, the provisional amount calculation unit 102 obtains a provisional usage amount for each image region. In the example of FIG. 7, the normal usage amount is 3000 and the second reduction rate is 50% in the character area, so the temporary usage amount is 1500. In the graphic area, the normal usage amount is 7000 and the second reduction rate is 30%, so the temporary usage amount is 4900.

  In S15, as in S11, the adjustment unit 103 obtains an adjusted usage amount for each image region. In the example of FIG. 7, the temporary usage amount is 1500 in the character area, but the adjusted usage amount is 1641. Therefore, the adjustment unit 103 increases the toner usage amount by 141. . Further, in the graphic area, the temporary usage amount is 4900, but the adjusted usage amount is 5359, and the adjustment unit 103 increases the toner usage amount by 459. That is, in Case 3, as in Case 2, the adjustment unit 103 determines an increase amount for each temporary use amount so that the increase amount increases as the provisional use amount increases.

(Case 4)
When the image of the image data includes a graphic area and a natural image area but does not include a character area (case 4), the same processing as in cases 1 to 3 is performed. That is, also in Case 4, various arithmetic processes are performed using the same equations as Equations 10 to 18 shown in FIGS. However, in case 4, since the image of the image data includes the graphic area and the natural image area but does not include the character area, the process proceeds to S19 after S2 in FIG. In S <b> 19, the provisional amount calculation unit 102 reads out the second reduction rate of the graphic area and the second reduction rate of the natural image area from the storage device 34. In S20, the provisional amount calculation unit 102 obtains a provisional usage amount for the graphic area and a provisional usage amount for the natural image area. In S21, the adjustment unit 103 obtains the adjusted usage amount of the graphic area and the adjusted usage amount of the natural image area.

(About Cases 5-7)
When the image of the image data consists only of a character area (case 5), the processing of S1 and S2 in FIG. 3 is performed as in cases 1 to 4, and the target usage is calculated. However, in case 5, since the image of the image data consists of character areas, the process proceeds to S16 after S2 in FIG. 3 (NO in S12). In step S16, the usage amount calculation unit 13 determines the target usage amount as the toner usage amount of the entire print image, creates usage amount information indicating the determined toner usage amount, and uses the usage amount information as an output gradation. The data is transmitted to the correction unit 14.

  Further, when the image of the image data is composed only of the natural image area (case 6), similarly to the case 5, the processes of S1 and S2 in FIG. However, in case 6, since the image of the image data is a natural image area, the process proceeds to S22 after S2 in FIG. 3 (NO in S18). In step S22, the usage amount calculation unit 13 determines the target usage amount as the toner usage amount of the entire print image, creates usage amount information indicating the determined toner usage amount, and outputs the usage amount information as an output tone. The data is transmitted to the correction unit 14.

  Further, when the image of the image data consists only of the graphic area (case 7), the processing of S1 and S2 in FIG. 3 is performed as in case 5 to calculate the target usage. However, in case 7, since the image of the image data is made up of graphic areas, the process proceeds to S23 after S2 in FIG. 3 (NO in S17). In step S23, the usage amount calculation unit 13 determines the target usage amount as the toner usage amount of the entire print image, creates usage amount information indicating the determined toner usage amount, and outputs the usage amount information as an output tone. The data is transmitted to the correction unit 14.

(About output tone correction curve)
As described above, for each image area, the output tone correction unit 14 matches the adjusted usage amount indicated by the usage amount information output from the usage amount calculation unit 13 with the toner usage amount at the time of printing each image area. The output tone correction curve (look-up table) used in the output tone correction process is changed so as to achieve the above. Note that the “use amount information” here includes not only the true value but also an approximate value of the true value when the value obtained by the use amount calculation unit 13 is a true value. Shall.

Here, the processing for changing the output gradation correction curve (hereinafter referred to as “correction curve”) will be described in detail below. First, the correction rate of the correction curve is defined as in the following Equation 3. Then, through an experiment using a reference image for testing, correction curves of 1% correction rate, 2% correction rate, 3% correction rate,... It is stored in a storage device (not shown). That is, 70 correction curves having different correction rates are stored in the storage device.
Correction rate (%) = 100 × (toner usage when printing with uncorrected image data−toner usage when printing with corrected image data) / (toner usage when printing with uncorrected image data) ... Formula 3
When the output tone correction unit 14 receives the usage amount information indicating the normal usage amount and the adjusted usage amount for each image area from the adjustment unit 103 together with the image data, the following equation 4 is obtained for each image region. The third reduction rate shown in FIG.
Third reduction rate (%) = 100 × (normal use amount−adjusted use amount) / (normal use amount)... Formula 4
Thereafter, the output tone correction unit 14 selects a correction curve having a correction rate closest to the third reduction rate obtained by Expression 4 for each image region, and corrects the image data using the selected correction curve. Do. As a result, the amount of toner used at the time of printing in each image area can be matched with the amount of use after adjustment (true value or approximate value).

  In the above configuration, a correction curve with a correction rate of 1% to 70% is held. However, the correction curve is not particularly limited to a range of 1% to 70%, and for example, a correction rate of 1% to 60%. It may be configured to have a correction curve up to a range of%. Further, when it is difficult to hold 60 to 70 correction curves due to the capacity of the storage device, the correction curves may be held at 5% intervals. Further, correction curves may be held at 1% intervals in a frequently used correction rate range (for example, 20 to 40%), and correction curves may be held at 5% intervals in other ranges.

(Modification 1)
Further, the printer 2 described above may have a function of changing the second reduction rate of each image area in accordance with a command from the user. This point will be described below.

  The user operates the terminal device 1 to select the toner save mode and to select any one of the normal image quality mode, the character emphasis mode, and the photo emphasis mode.

  When the normal image quality mode is selected, the provisional amount calculation unit 102 reads the second reduction rate shown in FIGS. 4 to 7 from the storage device 34 and uses the read second reduction rate for each image area. Find the provisional usage of. That is, in the normal image quality mode, the second reduction rate of the character region is 50%, the second reduction rate of the graphic region is 30%, and the second reduction rate of the natural image region is 20%.

  On the other hand, when the character emphasis mode is selected, the provisional amount calculation unit 102 reads each second reduction rate shown in FIG. 8 from the storage device 34 and uses the read second reduction rate for each image area. Find the provisional usage of. That is, in the character emphasis mode, the second reduction rate of the character region is 40%, the second reduction rate of the graphic region is 35%, and the second reduction rate of the natural image region is 25%. Therefore, the second reduction rate of the character area in the normal image quality mode is 50%, and the second reduction rate of the character area in the character emphasis mode is 40%. In the character emphasis mode, the character area is more than in the normal image quality mode. The second reduction rate is suppressed. Thereby, when the character emphasis mode is selected by the user, the image quality of the character area becomes higher than when the normal image quality mode is selected.

  When the photo emphasis mode is selected, the provisional amount calculation unit 102 reads each second reduction rate shown in FIG. 9 from the storage device 34, and uses the read second reduction rate to provisionally each image area. Find usage. That is, in the photo emphasis mode, the second reduction rate of the character region is 55%, the second reduction rate of the graphic region is 35%, and the second reduction rate of the natural image region is 10%. Accordingly, the second reduction rate of the natural image area in the normal image quality mode is 20%, but the second reduction rate of the natural image area in the photo emphasis mode is 10%. The second reduction rate of the natural image area is suppressed. As a result, when the photograph-oriented mode is selected by the user, the image quality of the natural image region is higher than when the normal image quality mode is selected.

(Modification 2)
Further, the image processing apparatus provided in the copying machine may include the usage amount calculation unit of the present embodiment. This point will be described below with reference to FIG.

  As shown in FIG. 10, a copying machine (digital color copying machine, image forming apparatus) 20 includes an image input device (color image input device) 21, an image processing device (color image processing device) 22, and an image output device (color). Image output device) 23.

  The image input device 21 includes a scanner unit including a device that converts optical information, such as a CCD, into an electrical signal, and outputs a reflected light image from a document as an RGB analog signal.

  An image signal read by the image input device 21 passes through the image processing device 22 in an A / D conversion unit 24, a shading correction unit 25, an input tone correction unit 26, a region separation processing unit 27, and a usage amount calculation unit 13a. , The color correction unit 29, the black generation and under color removal unit 30, the spatial filter processing unit 31, the output tone correction unit 32, and the tone reproduction processing unit 33 in this order, and the image output device 23 as CMYK image data. Sent to.

  The A / D conversion unit 24 converts RGB analog signals into digital signals (image data). The shading correction unit 25 performs RGB image data sent from the A / D conversion unit on the RGB image data. Processing for removing various distortions generated in the illumination system, imaging system, and imaging system of the image input device 21 is performed. In addition, the shading correction unit 25 adjusts the color balance, and at the same time, performs processing for converting the signals such as density signals into signals that can be handled easily by the image processing system employed in the image processing apparatus 22. The input tone correction unit 26 performs image quality adjustment processing such as background density removal and contrast on the RGB image data from which various distortions have been removed by the shading correction unit 25.

  A region separation processing unit (region separation unit) 27 separates the input image into one of a character region, a halftone region, and a continuous tone region (printing paper region, photographic region) based on RGB image data. In addition, the region separation processing unit 27 outputs, based on the separation result, a region identification signal indicating which region the pixel belongs to, a usage amount calculation unit 13a, a black generation and under color removal unit 30, a spatial filter processing unit 31, and an output. While outputting to the gradation correction | amendment part 32 and the gradation reproduction | regeneration processing part 33, the image data sent from the input gradation correction | amendment part 26 are sent to the subsequent use amount calculation part 13a as it is.

  The usage amount calculation unit 13a has the same configuration as the usage amount calculation unit 13 in FIG. 2, and performs the same processing as the usage amount calculation unit 13 in FIG. 2 to indicate the adjusted usage amount of each image area. The used amount information is created, and this used amount information is sent to the output gradation correction unit 32. However, since the usage amount calculation unit 13a performs processing based on the image data and the region identification signal sent from the region separation processing unit 27, the normal usage amount shown in FIG. 4 and the like is calculated from the RGB image data. It is like that. Further, the usage amount calculation unit 13a stores the second reduction rate for each of the character region, the halftone dot region, and the continuous tone region, and calculates the temporary usage amount and the adjusted usage amount. Further, the usage amount calculation unit 13a sends the RGB image data to the color correction unit 29 at the subsequent stage.

  Further, the second reduction rate of the halftone dot region and the second reduction rate of the continuous tone region are set lower than the second reduction rate of the character region. This is because in the halftone area and the continuous tone area, if the degree of reduction in the toner usage is increased, the difference in density becomes smaller and the image quality appears to be extremely deteriorated.

  The color correction unit 29 performs a process of removing color turbidity based on the spectral characteristics of the CMY color material including unnecessary absorption components in order to achieve faithful color reproduction. That is, the color correction unit 29 converts the RGB image data sent from the usage amount calculation unit 13 a into CMY image data, and sends the converted CMY image data to the black generation and under color removal unit 30.

  The black generation and under color removal unit 30 generates black (K) image data from the CMY image data after color correction, and subtracts the image data obtained by black generation from the original CMY image data to create a new image data. A process for generating CMY image data is performed. As a result, the CMY image data is converted into CMYK image data.

  The spatial filter processing unit 31 performs spatial filter processing using a digital filter on the CMYK image data sent from the black generation and under color removal unit 30 to correct the spatial frequency characteristics. As a result, blurring of the output image and deterioration of graininess can be reduced.

  The output tone correction unit 32 performs output tone correction processing corresponding to the output characteristic value of the image output device 23 on the CMYK image data that has been subjected to the spatial filter processing. Similarly to the output tone correction unit 14 shown in FIG. 1, the output tone correction unit (correction unit) 32 sends the usage amount information sent from the usage amount calculation unit 13 and the spatial filter processing unit 31. Based on the received CMYK image data, correction processing is performed on the image data so that the toner usage amount for each image area included in the image data image matches the value indicated in the usage amount information. Do.

  The gradation reproduction processing unit 33 performs gradation reproduction processing on the CMYK image data based on the region identification signal so that the image can finally be reproduced in a pseudo gradation.

  Processing in the spatial filter processing unit 31 and the gradation reproduction processing unit 33 will be further described. For example, in a region separated into characters by the region separation processing unit 27, a filter having a high high-frequency component enhancement amount is used as a spatial filter in the spatial filter processing unit 31 in order to improve the reproducibility of characters. At the same time, the tone reproduction processing unit 33 performs binarization or multi-value processing using a high-resolution screen suitable for reproducing high-frequency components.

  Further, the spatial filter processing unit 31 performs low-pass filter processing for removing the input halftone component on the region separated as the halftone region by the region separation processing unit 27. The tone reproduction processing unit 33 performs binarization or multi-value processing on the halftone dot area using a screen that emphasizes tone characteristics. Further, the tone reproduction processing unit 33 performs binarization or multi-value processing on a region separated as a photographic region by the region separation processing unit 27 using a screen that emphasizes tone reproducibility.

  The image data subjected to the above-described processes is temporarily stored in a storage unit (not shown), read at a predetermined timing, and sent to the image output device 23.

  The image output device 23 prints image data on a recording medium such as paper. For example, the image output device 23 is a printer using an electrophotographic method or an inkjet method, but is not particularly limited. The above processing is controlled by a CPU (Central Processing Unit) (not shown).

As a region separation processing method in the region separation processing unit 27, for example, a method described in JP-A-2002-232232 can be used. In this method, a maximum density difference that is a difference between a minimum density value and a maximum density value in an n × m block (for example, a 15 × 15 block) including a target pixel and an absolute value of a density difference between adjacent pixels are calculated. By calculating the total density busyness, which is the sum, and comparing the maximum density difference and the total density busyness with a plurality of predetermined thresholds, the background area / continuous tone area and the character edge area / halftone area are It is to be determined. Note that the determination is made based on the characteristics shown in the following (1) to (4).
(1) In the density distribution of the base region, the density change is usually small. Therefore, both the maximum density difference and the total density busyness are very small in the base area.
(2) The density distribution in the continuous tone region has a smooth density change. Therefore, in the continuous tone region, the maximum density difference and the total density busyness are both small and slightly larger than the background region.
(3) In the halftone dot region, the maximum density difference varies, but since there are density changes as many as the number of halftone dots, the ratio of the total density busyness to the maximum density difference increases. Therefore, when the total density busyness is larger than the product of the maximum density difference and the character / halftone dot determination threshold (one of the plurality of thresholds), it can be determined that the pixel is a halftone pixel.
(4) In the density distribution of the character area, the maximum density difference is large, and the total density busyness increases accordingly. However, since the density change in the character area is less than that in the halftone area, the total density busyness of the character area is smaller than the total density busyness of the halftone area. Therefore, when the total density busyness is smaller than the product of the maximum density difference and the character / halftone dot determination threshold, it is possible to determine that the pixel is a character edge pixel.

  Next, an example of the contents of the region separation process will be described. A comparison between the calculated maximum density difference and the maximum density difference threshold and a comparison between the calculated total density busyness and the total density busyness threshold are performed. When the maximum density difference is smaller than the maximum density difference threshold and the total density busyness is smaller than the total density busyness threshold, it is determined that the target pixel is a pixel in the background area or the continuous tone area, and so on. Otherwise, it is determined that the pixel is in the character / halftone area. In addition, when it is determined that the pixel is a character / halftone area pixel, the calculated total density busyness is compared with a value obtained by multiplying the maximum density difference by the character / halftone determination threshold value to obtain the total density busyness. If it is smaller, it is determined as a pixel in the character edge region, and if the total density busyness is larger, it is determined as a pixel in the halftone dot region.

  In the above description, the usage amount calculation unit 13a is provided in the image processing device 22 of the copying machine 20, but the usage amount calculation unit 13a may be provided in the image processing device of the multifunction peripheral.

(About PDL)
FIG. 11 shows an example of an image created by the image editing software of the terminal device 1. The image in FIG. 11 is configured as a collection of various areas such as a character area, a natural image area (photo area), and a graphic area. FIG. 12 shows the data structure when the image data of the image of FIG. 11 is described in PDL. FIG. 12 shows the data structure of PDL data whose color is designated by CMYK.

  In FIG. 12, for example, reference numeral 41 is image data (print data) of a character area, reference numeral 42 is image data of a photographic area, and reference numeral 43 is image data indicating a graphic area.

  Each image data includes typeface information, region attributes, starting position information, size information, color information, and the like, and the type of each region can be determined based on such data. For example, the area discriminating unit 11 can discriminate a character area based on the typeface information shown in FIG. 12, and the graphic area can be determined based on drawing commands such as “lineto” and “closepath fill” among the information indicated by the reference mark 43. It can be determined. It is possible to determine the size of each image area based on information included in each image data.

  Further, as shown by the reference numeral 42 in FIG. 11, the photographic area shown in FIG. 11 has coordinates (50, 300) of the starting point (point A in FIG. 3) and a size (100, 200). It has become. Therefore, the coordinates of B, C, and D in the photographic image area shown in FIG. 11 are B (250, 300), C (50, 400), and D (250, 400).

  Further, “0 250 translate” of the reference mark 43 means that a point moved by 0 in the horizontal direction and 250 in the vertical direction with respect to the starting point of the photographic area is set as the starting point (point E in FIG. 11). Therefore, the coordinates of E, F, G, and H in the graphic area shown in FIG. 11 are E (50, 550), F (250, 550), G, (50, 650) H (250, 650). . In the example of FIG. 11, the origin is O (0, 0).

(About the program)
In this embodiment, a computer is recorded on a computer-readable recording medium in which program code (execution format program, intermediate code program, source program) for causing a computer to execute processing is recorded. It is also possible to record a control program for functioning. As a result, it is possible to provide a portable recording medium on which the control program is recorded. Note that a memory (not shown) such as a ROM itself may be used as a program medium for processing by the microcomputer, or a program reading device may be used as a program medium as an external storage device (not shown). It may be provided and can be read by inserting a recording medium therein.

  In any case, the stored program code may be configured to be accessed and executed by the microprocessor, or in any case, the program code is read and the read program code is the microcomputer. The program code may be downloaded to a program storage area (not shown) and executed. It is assumed that this download program is stored in the main device in advance.

  The recording medium may be a recording medium configured to be separable from the main body, such as a tape system such as a magnetic tape or a cassette tape, a magnetic disk such as a flexible disk or a hard disk, or a CD-ROM / MO / MD / Disk system including optical disk such as DVD, card system such as IC card (including memory card) / optical card, mask ROM, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), flash ROM A medium that carries a fixed program code including a semiconductor memory system such as the above may be used.

  Further, in the case of a system configuration capable of connecting a communication network including the Internet, a medium that fluidly carries the program code so as to download the program code from the communication network may be used. When the program code is downloaded from the communication network in this way, the download program may be stored in the main device in advance, or may be installed from another recording medium. The present embodiment can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission. The recording medium is read by a program reading device provided in a digital color image forming apparatus or a computer system, whereby processing of the usage amount calculation unit 13 is executed.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention is suitable for an image forming apparatus such as a printer, a copier, a multifunction peripheral, and a facsimile machine, and an image processing apparatus that processes image data handled by the image forming apparatus.

1 Terminal device 2 Printer (image forming device)
4 Print Engine Unit 5 Image Processing Unit (Image Processing Device)
11 Region discriminating unit (region separating unit)
13 Usage Calculation Unit 14 Output Tone Correction Unit (Correction Unit)
20 Copying machine (image forming device)
22 Image Processing Device 27 Region Separation Processing Unit (Region Separation Unit)
32 Output tone correction unit (correction unit)
34 Storage Device 101 Target Amount Calculation Unit (Target Usage Amount Determination Unit)
102 Provisional amount calculation unit (provisional usage determination unit)
103 Adjustment unit (Use amount adjustment unit)

Claims (9)

The image data handled in an image forming apparatus having a normal mode for printing an image of image data using a color material and a save mode for printing the image while suppressing the amount of use of the color material compared to the normal mode. An image processing apparatus for processing,
When the first color material reduction degree indicating the degree of reduction of the color material usage amount of the entire image in the save mode relative to the color material usage amount of the entire image in the normal mode is designated, the first color material reduction A target usage amount determining unit that calculates a target usage amount that is a target amount of the color material usage amount for the entire image in the save mode based on the degree and the image data;
An area separation unit for separating an image of the image data into a plurality of image areas;
A storage device that stores in advance, for each image area, a second color material reduction degree indicating a reduction degree of the color material usage amount of the image area in the save mode with respect to the color material usage amount of the image area in the normal mode;
For each image area, based on the image data and the second color material reduction degree, a provisional use amount determination unit that obtains a provisional use amount that is a provisional value of the color material use amount for the image area in the save mode;
When the cumulative amount of provisional usage determined by the provisional usage amount determination unit is smaller than the target usage amount, an increase process for increasing each temporary usage amount is performed, and when the cumulative amount is larger than the target usage amount, A use amount adjustment unit that performs a reduction process to reduce the provisional use amount, so that a cumulative amount of the adjusted use amount that is the provisional use amount after the increase process or the decrease process matches the target use amount;
A correction unit that corrects the image data so that the color material usage amount of the image region in the save mode matches the adjusted usage amount for each image region;
The usage amount adjusting unit determines an increase amount or a decrease amount for each temporary use amount so that the increase amount or the decrease amount increases as the provisional use amount increases in the increase process or the decrease process. Image processing device. The plurality of image regions separated from the image by the region separation unit includes at least a character region and a photo region,
The image processing apparatus according to claim 1, wherein the second color material reduction degree of the photographic area is set lower than the second color material reduction degree of the character area. The plurality of image regions separated from the image by the region separation unit includes at least a graphic region and a photographic region,
The image processing apparatus according to claim 1, wherein the second color material reduction degree of the photographic area is set lower than the second color material reduction degree of the graphic area. The plurality of image regions separated from the image by the region separation unit includes at least a character region and a dot region,
The image processing apparatus according to claim 1, wherein a second color material reduction degree of the halftone dot region is set lower than a second color material reduction degree of the character region. The plurality of image regions separated from the image by the region separation unit includes at least a character region and a continuous tone region,
The image processing apparatus according to claim 1, wherein a second color material reduction degree of the continuous tone area is set lower than a second color material reduction degree of the character area.   An image forming apparatus comprising the image processing apparatus according to claim 1. The image data handled in an image forming apparatus having a normal mode for printing an image of image data using a color material and a save mode for printing the image while suppressing the amount of use of the color material compared to the normal mode. An image processing method to process,
When the first color material reduction degree indicating the degree of reduction of the color material usage amount of the entire image in the save mode relative to the color material usage amount of the entire image in the normal mode is designated, the first color material reduction A target usage amount determining step for obtaining a target usage amount that is a target amount of the color material usage amount for the entire image in the save mode based on the degree and the image data;
A region separation step of separating an image of the image data into a plurality of image regions;
From a storage device that stores in advance for each image area a second color material reduction degree indicating a degree of reduction of the color material usage amount of the image area in the save mode with respect to the color material usage amount of the image area in the normal mode, A reading step of reading the second color material reduction degree of each image region separated in the region separation step;
For each image area, a provisional usage amount that is a provisional value of the color material usage amount for the image area in the save mode is obtained based on the image data and the second color material reduction degree read in the reading step. A provisional usage determination process;
When the cumulative amount of provisional usage determined in the provisional usage amount determination step is smaller than the target usage amount, an increase process for increasing each temporary usage amount is performed, and when the cumulative amount is larger than the target usage amount, A use amount adjusting step of making a cumulative amount of adjusted use amounts, which are provisional use amounts after the increase process or decrease process, coincide with the target use amount by performing a decrease process for reducing the provisional use amount;
A correction step for correcting the image data so that the amount of color material used in the image area in the save mode matches the amount of use after adjustment for each image area;
In the use amount adjustment step, an increase amount or a decrease amount for each provisional use amount is determined such that the increase amount or the decrease amount increases as the provisional use amount increases in the increase process or the decrease process. Image processing method.   A control program for controlling the image processing apparatus according to any one of claims 1 to 5, wherein the control program causes a computer to function as each of the units.   A computer-readable recording medium on which the control program according to claim 8 is recorded.

Images