JP4333016B2 - Image forming apparatus, image data processing method, and recording medium recording image data processing program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a technique for correcting digital image data obtained by a scanner or a digital camera so that its main subject has an appropriate density.
[0002]
[Prior art]
  As a density correction method for color digital image data, there is known a method for correcting a histogram of each RGB color component so that the color (density) of all the image data for each RGB color is gray (gray). . This method is based on Evans' theorem that "when a general outdoor landscape is photographed, all the colors recorded in the image are combined to become gray".
[0003]
[Problems to be solved by the invention]
  For example, image data with a biased density on the entire screen, such as an image of a person photographed without a flash on a bright background or an image of a person photographed with a flash on a dark background, is obtained by the above method. When corrected, there is a problem that the person who is the main subject is not corrected properly due to the influence of the background.
[0004]
  The present invention has been made to solve the above-described problems of the conventional example, and an image forming apparatus, an image data processing method, and an image data processing program capable of appropriately correcting the density of a main subject in an image. An object of the present invention is to provide a recording medium on which is recorded.
[0005]
[Means for Solving the Problems]
  In order to achieve the above object, the present inventionRelated to one aspectThe image forming apparatusImage data dividing means for dividing image data composed of a plurality of pixel data into a plurality of groups so as to correspond to each region when an image formed using the image data is divided into a plurality of regions; Among the divided areas, the color of the pixel is specified from each pixel data included in a group corresponding to one or more previously selected areas, and the largest number of pixels among the pixels included in the group Color specifying means for specifying the color shared by the group as the color of the area corresponding to the group, color comparing means for comparing the color of the specified area with a predetermined color set in advance, and the color of the area When the predetermined color is included in the image, the average luminance calculation means for calculating the average value of the luminance of the region using the pixel data included in the region, and the average value of the calculated luminance Correction amount calculation means for calculating a correction amount for correcting to a predetermined luminance value set in advance, image data correction means for correcting all pixel data using the calculated correction amount, and corrected image data An image forming means for forming an image usingIt is characterized by comprising.
[0006]
  UpStructurePreferably, the correction amount is a value obtained by multiplying a difference between the predetermined luminance value and the average value of the luminance by a predetermined coefficient.
[0007]
  Furthermore, the predetermined color is preferably a color relating to human skin.
[0008]
  Also,Of the present inventionAccording to other aspectsThe image data processing method isAn image data dividing step of dividing image data composed of a plurality of pixel data into a plurality of groups so as to correspond to each region when an image formed using the image data is divided into a plurality of regions; Among the divided areas, the color of the pixel is specified from each pixel data included in a group corresponding to one or more previously selected areas, and the largest number of pixels among the pixels included in the group A color specifying step for specifying a color shared by the group as a color of an area corresponding to the group, a color comparing step for comparing the color of the specified area with a predetermined color set in advance, and a color of the area An average luminance calculation step for obtaining an average value of luminance of the area using pixel data included in the area when the predetermined color is included in A correction amount calculation step for calculating a correction amount for correcting the average value of the obtained luminance to a predetermined luminance value set in advance, and an image data correction step for correcting all pixel data using the determined correction amount; A corrected image data output step for outputting corrected image data;It is characterized by comprising.
[0009]
  UpNotationIn the method, the correction amount is preferably a value obtained by multiplying a difference between the predetermined luminance value and the average value of the luminance by a predetermined coefficient.
[0010]
  Furthermore, the predetermined color is preferably a color relating to human skin.
[0011]
  further,Of the present inventionAccording to other aspectsThe recording medium on which the image data processing program is recorded isImage data division processing for dividing image data composed of a plurality of pixel data into a plurality of groups so as to correspond to each region when an image formed using the image data is divided into a plurality of regions; Among the divided areas, the color of the pixel is specified from each pixel data included in a group corresponding to one or more previously selected areas, and the largest number of pixels among the pixels included in the group A color specifying process for specifying a color shared by the group as a color of the area corresponding to the group, a color comparing process for comparing the color of the specified area with a predetermined color, and a color of the area When the predetermined color is included in the image, the average luminance calculation processing for obtaining the average value of the luminance of the region using the pixel data included in the region, and the average value of the obtained luminance Correction amount calculation processing for calculating a correction amount for correcting to a predetermined luminance value set in advance, image data correction processing for correcting all pixel data using the calculated correction amount, and corrected image data Corrected image data output processing for outputtingIs recorded to make the computer execute.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  First embodiment
  The first embodiment of the present invention will be described by taking a digital printer as an example. FIG. 1 shows the external configuration of a digital printer (digital photographic processing apparatus) according to this embodiment. The same applies to the second and third embodiments described later.
[0013]
  The digital printer is for directly printing an image captured by a digital camera on a piece of photographic paper, or for reading an image formed on a silver salt film with a scanner and printing it on the piece of photographic paper. As shown in FIG. 1, a digital printer has a small area on a photographic paper corresponding to each pixel of an image sensor of a digital camera or a scanner as R (red), G (green) and B (blue) or Y (yellow), An image forming unit 100 that forms an image by exposing to light of one of the three primary colors of M (magenta) and C (cyan), and developing the exposed photographic paper; The image data processing unit 200 performs processing and outputs it to the image forming unit 100.
[0014]
  The image forming unit 100 cuts magazines 101 and 102 in which a plurality of types (for example, two types) of long photographic paper having different widths are wound and stored, and the photographic paper drawn from the magazine 101 or 102 into a predetermined size, and cuts the paper. An exposure unit 103 that exposes an image transmitted from the image data processing unit 200 on the printed photographic paper piece; a development processing unit 104 that develops, bleaches, fixes, and stabilizes the exposed photographic paper piece; and a developed print A drying unit 105 that dries the paper pieces and a sorter unit 106 that sorts the dried photographic paper pieces into, for example, a film unit. The image forming unit 100 does not include a light source, a lens, a shutter, and the like for enlarging and exposing an image on a film in a conventional analog photographic processing apparatus on a photographic paper piece.
[0015]
  The image data processing unit 200 reads image data recorded on a recording medium such as a memory card or a CD-R, or a data recording / reading device 201 for recording corrected image data on these recording media. A scanner 202 for directly reading an image formed on film or photographic paper, a display 203 for displaying the read image on a monitor, a keyboard 204 for inputting instructions for predetermined image processing and print processing, The image data to be printed is subjected to predetermined processing, converted into control data for controlling the exposure unit, and output to the image forming unit 100. The control circuit (not shown) is configured. Further, the image data may be directly transmitted / received to / from another apparatus via a modem, a LAN board, a communication line, or the like.
[0016]
  Next, FIG. 2 shows a block configuration for explaining the functions of the digital printer of the first embodiment.
[0017]
  The image data input unit 210 includes, for example, an input / output interface, a CPU, a ROM, and a RAM. The image data input unit 210 takes in digital image data output from the data recording / reading apparatus 201 and the scanner 202, temporarily stores the data in a RAM, and saves it. To do. Here, the digital image data is an output signal relating to the luminance of each color component of R (red), G (green), and B (blue) from each pixel of an image sensor such as a digital camera or a scanner that images the image data. (RGB data) are serially arranged and input / output serially via an interface.
[0018]
  The image reproduction unit 211 includes a display 203, a CPU, a ROM, a RAM, and the like, and reproduces a prescan image on the monitor screen of the display 203 using the input image data.
[0019]
  The range selection unit 212 includes a mouse, a keyboard 204, a CPU, a ROM, a RAM, and the like. Among prescan images reproduced on the display 203, an operator or a user is a main subject (for example, a human face). Specify the range to recognize.
[0020]
  The average luminance calculation unit 213 includes a CPU, a ROM, a RAM, and the like. The average luminance calculation unit 213 performs predetermined processing on input image data, particularly image data included in a range selected by the range selection unit 212, and applies each pixel to each pixel. The corresponding luminance is calculated, a luminance histogram is created, and the average value of the luminance in the selected range is calculated. The RGB data is information relating to color and luminance (brightness), and the arithmetic processing shown in the following equation 1 is performed on the RGB data, and YCC data (C2, YY, C1) representing luminance information and color difference information is converted into YCC data. Convert. YY represents luminance information, and C1 and C2 represent color difference information. With this conversion, only information relating to luminance can be extracted from the RGB data.
[0021]
[Expression 1]
[0022]
  The correction amount calculation unit 214 includes a CPU, a ROM, a RAM, and the like, and compares the calculated average luminance of the main subject portion with a predetermined luminance value corresponding to a preset appropriate luminance, In order to make the portion have appropriate luminance (appropriate density), a correction amount necessary to match the average value of luminance with a predetermined luminance value is calculated and stored in a RAM or the like.
[0023]
  The image data correction unit 215 includes a CPU, a ROM, a RAM, and the like, and corrects the luminance (RGB data) of the image data regarding all pixels using the calculated correction amount.
[0024]
  Similar to the image data input unit 210, the corrected image data output unit 216 includes an input / output interface, a CPU, a ROM, a RAM, and the like, and outputs corrected image data to the image forming unit 100.
[0025]
  The image forming unit 100 forms an image on the photographic paper using the corrected image data. The CPU, ROM, and RAM may be the same as each other, or different ones may be used as appropriate according to the configuration of each unit.
[0026]
  Next, flowcharts of image data processing in the first embodiment are shown in FIGS. First, when image data is read by the image data input unit 200 (step S1), the image reproduction unit 211 reads the image data from the RAM of the image data input unit 210 and displays a pre-scan image on the display 203 (step S1). S3). In this state, the user or the operator determines whether or not luminance correction is necessary for the displayed pre-scan image (step S5). If luminance correction is not necessary, the user or operator moves to step S1 using a mouse or a keyboard. Return and display the next pre-scanned image.
[0027]
  On the other hand, when luminance correction is necessary, a range that the user or operator recognizes as a main subject in the pre-scan image displayed on the display 203 using the mouse or keyboard of the range selection unit 212, for example, a person's A main subject region is selected for a face portion or the like (step S7).
[0028]
  When the main subject area is selected, the average luminance calculation unit 213 reads out the image data included in the selected range from the RAM of the image data input unit 210 (step S9), and the luminance for each pixel according to the above equation (1). Information YY is extracted (step S11). Further, a luminance histogram of each pixel included in the selected range is created (step S13), and an average value of the luminance in the selected range is calculated (step S15).
[0029]
  The correction amount calculation unit 214 compares the calculated average value of luminance with a predetermined luminance value corresponding to preset appropriate luminance, and calculates a luminance correction amount (step S17). When the luminance correction amount is calculated, the luminance correction amount is stored in the RAM of the image data input unit 210 together with, for example, a film frame number for specifying the image data (step S19).
[0030]
  When the brightness correction amount is saved, the image reproduction unit 211 determines whether or not a pre-scan image is displayed on the display 203 for all the image data stored in the RAM of the image data input unit 210 (step S21). ) If the pre-scan is not completed, steps S1 to S21 are repeated.
[0031]
  When the pre-scan is completed for all the image data (YES in step S21), the image data correction unit 215 sequentially reads out each image data and the luminance correction amount related to the image data (step S23), and uses the luminance correction amount. The image data is corrected (step S25), and the corrected image data is stored in a RAM or the like (step S27). Further, the image data correction unit 215 determines whether or not the luminance correction has been performed on all the image data targeted for luminance correction (step S29). If the correction has not been completed, steps S23 to S29 are performed. repeat.
[0032]
  When the correction of all the image data is completed, the corrected image data output unit 216 determines whether to output the corrected image data to the image forming unit 100 (step S31). That is, when an image is formed using the corrected image data, the corrected image data output unit 216 outputs the corrected image data to the image forming unit 100 (step S33). Then, the image forming unit 100 forms an image on the photographic paper piece using the corrected image data output from the image data processing unit 200 (step S35), and ends this flow.
[0033]
  Next, the effect of correcting image data according to the first embodiment will be described with reference to FIG. For example, as shown in FIG. 5B, an image captured by a digital camera or the like is a “backlight scene” in which the luminance of the background is high (the density is low and bright) and the luminance of the main subject is low (the density is high and dark). And
[0034]
  When this image data is used as it is without correction, an image of a backlight scene is obtained as shown in FIG. 5B. On the other hand, according to Evans' theorem, when the RGB color components are corrected so that the color of all the image data for each RGB color becomes gray, the background becomes gray as shown in FIG. The person who is the main subject with originally low brightness (high density and darkness) is corrected to be darker and its details are almost completely destroyed.
[0035]
  In contrast, when the main subject portion is extracted and all the image data is corrected so that the luminance (density) of the main subject portion is appropriate as in the present embodiment, as shown in FIG. In addition, although the background with originally high luminance (low density and light) is corrected to be brighter, the person who is the main subject is corrected to appropriate luminance (proper density) so that the details can be clearly identified. As a result, an appropriate correction can be performed even for an image with a biased density, such as a backlight scene. Contrary to the example shown in FIG. 5, even when the main subject has a high brightness and the background brightness is low, as in the case of flash photography in a dark place, an appropriate correction can be similarly performed. it can.
[0036]
  Second embodiment
  Next, a second embodiment of the present invention will be described. In the first embodiment, the pre-scan image is temporarily displayed on the display 203 using the input image data, and the user or operator is configured to specify the range of the main subject to be subjected to luminance correction. In the second embodiment, the color information of the image data is analyzed, and the portion that seems to be the main subject is automatically recognized using the color information.
[0037]
  A block configuration for explaining the functions of the digital printer of the second embodiment is shown in FIG.
[0038]
  As in the case of the first embodiment, the image data input unit 220 includes, for example, an input / output interface, a CPU, a ROM, a RAM, and the like, takes in digital image data output from the data recording / reading device 201 and the scanner 202, It is temporarily stored in a RAM or the like and saved.
[0039]
  The color specifying unit 221 includes a CPU, a ROM, a RAM, and the like. The color specifying unit 221 performs predetermined processing on the input image data, and the color corresponding to each pixel (hereinafter simply referred to as “pixel color”). ). The RGB data is information relating to color and luminance (brightness), and the arithmetic processing shown in Equation 1 is performed on the RGB data to convert it into YCC data (C2, YY, C1) representing luminance information and color difference information. To do. By this conversion, it is possible to extract only information about color from RGB data.
[0040]
  FIG. 7 is a two-dimensional representation of color information with C1 as the vertical axis and C2 as the horizontal axis. The area shown by hatching in FIG. 7 represents an average skin color range of Japanese when a person is photographed as a main subject.
[0041]
  The pixel data extraction unit 222 includes a CPU, a ROM, a RAM, and the like. The pixel data extraction unit 222 is a predetermined color that represents a main subject in which the color of each pixel specified by the color specification unit 221 is set in advance, for example, the skin color of a person All the image data corresponding to the main subject and corresponding to the pixels having a predetermined color or a color included in the predetermined range are extracted and stored in the RAM or the like. Specifically, for all the pixels, the values of C1 and C2 calculated by the color specifying unit 221 are compared with the values of the LUT (lookup table) stored in advance in the ROM, and the values of C1 and C2 are compared. Is determined to be equal to the predetermined value or within a predetermined range. As a result, image data relating to the main subject is extracted from all the pixel data.
[0042]
  The average luminance calculation unit 223 includes a CPU, a ROM, a RAM, and the like, and calculates the average value of the luminance of the portion corresponding to the main subject using all the extracted image data. The present embodiment aims to correct the main subject in the image to an appropriate luminance (density) without being affected by the luminance of other parts such as the background. Luminance information for only the portion of the subject can be obtained.
[0043]
  The correction amount calculation unit 224 includes a CPU, a ROM, a RAM, and the like, and compares the calculated average luminance of the main subject portion with a predetermined luminance value corresponding to a preset appropriate luminance, In order to make the portion have appropriate luminance (appropriate density), a correction amount necessary to match the average value of luminance with a predetermined luminance value is calculated and stored in a RAM or the like.
[0044]
  The image data correction unit 225 includes a CPU, a ROM, a RAM, and the like, and corrects the luminance (RGB data) of the image data regarding all pixels using the calculated correction amount.
[0045]
  The corrected image data output unit 226 includes an input / output interface, a CPU, a ROM, a RAM, and the like, like the image data input unit 220, and outputs corrected image data to the image forming unit 100.
[0046]
  Next, flowcharts of image data processing in the second embodiment are shown in FIGS. In the second embodiment, first, color information for specifying a main subject area, for example, the color of a person's skin is selected from a color chart or the like displayed on a display using a mouse or a keyboard, Set (step S51).
[0047]
  When the image data is read by the image data input unit 220 (step S53), the color specifying unit 221 reads the image data from the RAM of the image data input unit 210, and the color information C1 and C2 for each pixel according to Equation 1 above. Is extracted (step S55), and the color of the pixel is specified for each pixel. Then, the pixel data extraction unit 222 compares the color of each identified pixel with the color of the main subject set in step S51 (step S57), and pixel data or luminance of a pixel having the same color as the color of the main subject. Only the information YY is extracted and stored in the RAM or the like (step S59). Further, the color identification unit 221 or the pixel data extraction unit 222 determines whether or not the pixel color identification, comparison, and pixel data extraction have been completed for all the pixels (step S61), and is completed for all the pixels. Steps S55 to S61 are repeated until the above.
[0048]
  When the pixel color specification, comparison, and pixel data extraction are completed for all the pixels, the average luminance calculation unit 223 has the same color as the color of the main subject using the pixel data or luminance information YY extracted in step S59. A luminance histogram of all pixels is created, and an average luminance value is calculated (step S63).
[0049]
  The correction amount calculation unit 224 compares the calculated average value of luminance with a predetermined luminance value corresponding to preset appropriate luminance, and calculates a luminance correction amount (step S65). When the brightness correction amount is calculated, the brightness correction amount is stored in the RAM of the image data input unit 210 together with, for example, a film frame number for specifying the image data (step S67).
[0050]
  When the luminance correction amount is stored, for example, the correction amount calculation unit 224 determines whether or not the luminance correction amount has been calculated for all the image data (step S69), and the calculation of the luminance correction amount has been completed for all the image data. If not, steps S53 to S69 are repeated.
[0051]
  When the brightness correction amount is calculated for all image data (YES in step S69), the image data correction unit 225 sequentially reads each image data and the brightness correction amount related to the image data (step S71), and uses the brightness correction amount. Each image data is corrected (step S73), and the corrected image data is stored in a RAM or the like (step S75). Further, the image data correction unit 225 determines whether or not the luminance correction has been performed on all the image data to be subjected to the luminance correction (step S77). If the correction has not been completed, steps S71 to S77 are performed. repeat.
[0052]
  When the correction of all the image data is completed, the corrected image data output unit 226 determines whether to output the corrected image data to the image forming unit 100 (step S79). That is, when an image is formed using the corrected image data, the corrected image data output unit 226 outputs the corrected image data to the image forming unit 100 (step S81). Then, the image forming unit 100 forms an image on the photographic paper piece using the corrected image data output from the image data processing unit 200 (step S83), and ends this flow.
[0053]
  Third embodiment
  Next, a third embodiment of the present invention will be described. In the second embodiment, the color of each pixel is specified using all the pixel data in the image data, and the luminance average is calculated using the pixel data of the pixel having the same color as the color of the main subject set in advance. It was configured to calculate the brightness correction amount by obtaining the value,BookIn the embodiment, the image is divided into a plurality of areas, and pixel data of the color information of the image data is used by using pixel data of one or more preselected areas, for example, a part of the area located in the center of the screen. Analysis, calculation of average value of luminance and calculation of luminance correction amount are performed.
[0054]
  FIG. 10 shows a block configuration for explaining the functions of the digital printer of the third embodiment.
[0055]
  As in the first and second embodiments, the image data input unit 230 includes, for example, an input / output interface, a CPU, a ROM, a RAM, and the like, and digital image data output from the data recording / reading device 201 or the scanner 202. Is temporarily stored in a RAM or the like and stored.
[0056]
  The image data dividing unit 231 includes a CPU, a ROM, a RAM, and the like. When it is assumed that an image is formed using any one of the captured image data, the image data dividing unit 231 is divided into a plurality of areas. Correspondingly, the image data is divided into a plurality of groups according to the address of the pixel.
[0057]
  The color specifying unit 232 includes a CPU, a ROM, a RAM, and the like. Among the regions divided by the image data dividing unit 231, one or two or more previously selected regions, for example, a plurality of regions near the center of the screen Using each pixel data included in a group corresponding to a region or the like, the arithmetic processing shown in Equation 1 above is performed on the RGB data to convert it into YCC data (C2, YY, C1) representing luminance information and color difference information. . By this conversion, only information relating to the color is extracted from the RGB data, and the color of each pixel is specified. Furthermore, the color shared by the largest number of pixels in the groupTheSpecified as the color of the area corresponding to the group.
[0058]
  The color comparison unit 233 includes a CPU, a ROM, a RAM, and the like, and is specified by the color specification unit 232.TerritoryThe color of the area is compared with a predetermined color set in advance, for example, the color of the main subject arbitrarily set by the user or operator such as the skin color of a person,This areaThe specified color is included in the colors ofOrJudge whether or not.
[0059]
  The average luminance calculation unit 234 includes a CPU, a ROM, a RAM, and the like.Specified by the color specifying unit 232When it is determined that a predetermined color is included in the color of the area, the average value of the luminance of the area is calculated using the pixel data of the area. In the present embodiment, luminance correction processing is performed using only the image data of a portion where the possibility that a main subject is likely to exist, so that the number of data to be processed is reduced, and the time required for calculation processing is reduced. Is possible.
[0060]
  The correction amount calculation unit 235 includes a CPU, a ROM, a RAM, and the like. The correction amount calculation unit 235 compares the calculated average luminance of the main subject portion with a predetermined luminance value corresponding to a preset appropriate luminance, In order to make the portion have appropriate luminance (appropriate density), a correction amount necessary to match the average value of luminance with a predetermined luminance value is calculated and stored in a RAM or the like.
[0061]
  The image data correction unit 236 includes a CPU, a ROM, a RAM, and the like, and corrects the luminance (RGB data) of the image data regarding all the pixels using the calculated correction amount.
[0062]
  The corrected image data output unit 237 includes an input / output interface, a CPU, a ROM, a RAM, and the like, like the image data input unit 220, and outputs corrected image data to the image forming unit 100.
[0063]
  Next, flowcharts of image data processing in the third embodiment are shown in FIGS.
[0064]
  When the image data is read by the image data input unit 230 (step S101), the image data dividing unit 231 assumes that the virtual image is formed vertically using the image data as shown in FIG. The image data is divided into a plurality (for example, 5 × 5 = 25) in the horizontal direction and the horizontal direction (step S103), and the image data is divided into a plurality of groups according to the pixel addresses and the like so as to correspond to the divided areas.
[0065]
  The color specifying unit 232 reads out from the RAM of the image data input unit 210 pixel data of a group corresponding to one or more pre-selected regions among the regions divided by the image data dividing unit 231 (step S1). S105), color information C1 and C2 for each pixel is extracted according to the above equation 1 (step S107), and the color of the pixel is specified for each pixel. In addition, create a histogram for each pixel color,The groupThe color shared by the largest number of pixels included inThe groupIs specified as the color of the region corresponding to (step S109).
[0066]
  Next, the color comparison unit 233 is identified.TerritoryThe color of the area is compared with the color of the main subject set in advance (step S111),In the color of the areaSame color as main subjectWhether or not is included(Step S113). The same color as the main subjectincludeIn this case, the average luminance calculation unit 234 creates a luminance histogram of all the pixels included in the area using the pixel data or luminance information YY of the area, and calculates the average value of the luminance (step S115). The same color as the main subjectContainsIf not (NO in step S113), the process proceeds to step S121 to perform brightness correction of the next image data.
[0067]
  The correction amount calculation unit 235 compares the calculated average value of luminance with a predetermined luminance value corresponding to preset appropriate luminance, and calculates a luminance correction amount (step S117). When the luminance correction amount is calculated, the luminance correction amount is stored in the RAM or the like of the image data input unit 230 together with, for example, the film frame number for specifying the image data (step S119).
[0068]
  When the luminance correction amount is stored, for example, the correction amount calculation unit 235 determines whether or not the luminance correction amount has been calculated for all image data (step S121), and the calculation of the luminance correction amount has been completed for all image data. If not, steps S101 to S121 are repeated.
[0069]
  When the luminance correction amount is calculated for all the image data (YES in step S121), the image data correction unit 236 sequentially reads each image data and the luminance correction amount related to the image data (step S123), and uses the luminance correction amount. Each image data is corrected (step S125), and the corrected image data is stored in a RAM or the like (step S127). Further, the image data correction unit 236 determines whether or not the luminance correction has been performed on all the image data to be subjected to the luminance correction (step S129). If the correction has not been completed, steps S123 to S129 are performed. repeat.
[0070]
  When the correction of all the image data is completed, the corrected image data output unit 237 determines whether to output the corrected image data to the image forming unit 100 (step S131). That is, when an image is formed using the corrected image data, the corrected image data output unit 237 outputs the corrected image data to the image forming unit 100 (step S133). Then, the image forming unit 100 forms an image on a piece of photographic paper using the corrected image data output from the image data processing unit 200 (step S135), and this flow ends.
[0071]
  Other embodiments
  In each of the above embodiments, the main subject region is specified, and the luminance correction amount is determined so that the average luminance value of the main subject region becomes a predetermined luminance value corresponding to the appropriate luminance. However, the present invention is not limited to this. Instead, a value obtained by multiplying the difference between the average luminance value and the predetermined luminance value by a predetermined coefficient (for example, an arbitrary value between 60% and 80%) may be used as the luminance correction amount. good. That is, as shown in FIG. 7, even if the color of a person's skin is taken as an example of the color of the main subject, the color of the main subject may not be a single color but may have a certain color range. If the luminance is corrected only for a region having (for example, the color of a person's skin), the correction is excessive for other color regions similar to that color, and the image quality after correction may be deteriorated. . Also, if the brightness of the main subject before correction is extremely high or low compared to the appropriate brightness, if the brightness of the main subject area is completely corrected to the proper brightness, the brightness of the parts other than the main subject will be abnormal. May become low or high. Therefore, in these cases, it is preferable not to completely correct the luminance of the main subject area to the appropriate luminance, but to correct the luminance close to the appropriate luminance. Further, in each of the above embodiments, the color of the main subject area is treated as a single color, but the present invention is not limited to this, and a plurality of colors included in a predetermined range may be used.
[0072]
  In the first embodiment, the pre-correction image is displayed on the monitor screen of the display 203 as a pre-scan image. However, the print image is further displayed on the display 203 using the corrected image data. You may display on a monitor screen. Further, when displaying a pre-scan image on the monitor screen of the display 203 and when calculating the luminance correction amount of the main subject area, the number of pixels of the image data may be thinned. The latter is the same in the second and third embodiments.
[0073]
  Furthermore, in each of the above-described embodiments, the digital printer is described as an example of the image forming apparatus. However, the present invention is not limited to this, and the personal computer and a color printer connected thereto, for example, a thermal transfer color printer, an ink jet color printer, and the like. A printer, a laser color printer, or the like may be used.
[0074]
  Furthermore, the present invention is not limited to an image forming apparatus, but also includes an image data correction method executed by a personal computer and a recording medium on which a program for executing the method is recorded.
[0075]
【The invention's effect】
  As explained above, the present inventionDrawings related toAccording to the image forming apparatus,Image data dividing means for dividing image data composed of a plurality of pixel data into a plurality of groups so as to correspond to each region when an image formed using the image data is divided into a plurality of regions; Among the divided areas, the color of the pixel is specified from each pixel data included in a group corresponding to one or more previously selected areas, and the largest number of pixels among the pixels included in the group Color specifying means for specifying the color shared by the group as the color of the area corresponding to the group, color comparing means for comparing the color of the specified area with a predetermined color set in advance, and the color of the area When the predetermined color is included in the image, the average luminance calculation means for calculating the average value of the luminance of the region using the pixel data included in the region, and the average value of the calculated luminance Correction amount calculation means for calculating a correction amount for correcting to a predetermined luminance value set in advance, image data correction means for correcting all pixel data using the calculated correction amount, and corrected image data An image forming means for forming an image usingIt comprises.
[0076]
  In addition, the present inventionPertaining toAccording to the image data processing method,An image data dividing step of dividing image data composed of a plurality of pixel data into a plurality of groups so as to correspond to each region when an image formed using the image data is divided into a plurality of regions; Among the divided areas, the color of the pixel is specified from each pixel data included in a group corresponding to one or more previously selected areas, and the largest number of pixels among the pixels included in the group A color specifying step for specifying a color shared by the group as a color of an area corresponding to the group, a color comparing step for comparing the color of the specified area with a predetermined color set in advance, and a color of the area An average luminance calculation step for obtaining an average value of luminance of the area using pixel data included in the area when the predetermined color is included in A correction amount calculation step for calculating a correction amount for correcting the average value of the obtained luminance to a predetermined luminance value set in advance, and an image data correction step for correcting all pixel data using the determined correction amount; A corrected image data output step for outputting corrected image data;It comprises.
[0077]
  Furthermore, the present inventionPertaining toAccording to the recording medium on which the image data processing program is recorded,Image data division processing for dividing image data composed of a plurality of pixel data into a plurality of groups so as to correspond to each region when an image formed using the image data is divided into a plurality of regions; Among the divided areas, the color of the pixel is specified from each pixel data included in a group corresponding to one or more previously selected areas, and the largest number of pixels among the pixels included in the group A color specifying process for specifying a color shared by the group as a color of the area corresponding to the group, a color comparing process for comparing the color of the specified area with a predetermined color, and a color of the area When the predetermined color is included in the image, the average luminance calculation processing for obtaining the average value of the luminance of the region using the pixel data included in the region, and the average value of the obtained luminance Correction amount calculation processing for calculating a correction amount for correcting to a predetermined luminance value set in advance, image data correction processing for correcting all pixel data using the calculated correction amount, and corrected image data Corrected image data output processing for outputtingIs recorded to make the computer execute.
[0078]
  That is, according to these inventions, PaintingSince the brightness of the image data is automatically corrected without displaying the image once on the monitor screen, the total processing time can be shortened. If it is assumed that an image is formed using image data, the image is divided into a plurality of areas, and one or more areas that the user or operator thinks that the main subject is likely to exist are selected. Since the luminance correction is performed using only the pixel data included in the selected area, the number of pixel data used for calculating the luminance correction amount can be greatly reduced, and the time required for calculating the luminance correction amount can be reduced. It can be shortened.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an external configuration of a digital printer according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a digital printer according to the first embodiment of the present invention.
FIG. 3 is a flowchart of image data processing in the first embodiment.
FIG. 4 is a continuation of the flowchart of FIG.
FIG. 5 is a diagram for explaining an effect of luminance correction of image data according to the present invention.
FIG. 6 is a block diagram of a digital printer according to a second embodiment of the present invention.
FIG. 7 is a diagram two-dimensionally representing color information.
FIG. 8 is a flowchart of image data processing in the second embodiment.
9 is a continuation of the flowchart of FIG.
FIG. 10 is a block diagram of a digital printer according to a third embodiment of the present invention.
FIG. 11 is a flowchart of image data processing in the third embodiment.
FIG. 12 is a continuation of the flowchart of FIG.
FIG. 13 is a diagram illustrating a state in which a virtual image is divided into a plurality of regions in the third embodiment.
[Explanation of symbols]
100: Image forming unit
200: Image data processing unit
210: Image data input unit
211: Image playback unit
212: Range selection unit
213: Average luminance calculation unit
214: Correction amount calculation unit
215: Image data correction unit
216: Corrected image data output unit
220: Image data input unit
221: Color identification part
222: Pixel data extraction unit
223: Average luminance calculation unit
224: Correction amount calculation unit
225: Image data correction unit
226: Corrected image data output unit
230: Image data input unit
231: Image data dividing unit
232: Color specifying part
233: Color comparison unit
234: Average luminance calculation unit
235: Correction amount calculation unit
236: Image data correction unit
237: corrected image data output unit

Claims (7)

Image data dividing means for dividing image data composed of a plurality of pixel data into a plurality of groups so as to correspond to each region when an image formed using the image data is divided into a plurality of regions;
Among the divided areas, the color of the pixel is specified from each pixel data included in a group corresponding to one or more previously selected areas, and the largest number of pixels among the pixels included in the group a color identification means but be specified as a color of the region corresponding to that group the color to be shared,
Color comparing means for comparing the color of the identified area with a predetermined color set in advance;
If it contains the predetermined color in the color before Symbol area, the average luminance calculating means for calculating an average value of luminance of the region using the pixel data included in the region,
A correction amount calculation means for calculating a correction amount for correcting the average value of the determined luminance to a predetermined luminance value set in advance;
Image data correction means for correcting all pixel data using the determined correction amount;
Image forming means for forming an image using the corrected image data;
An image forming apparatus comprising: The image forming apparatus according to claim 1 , wherein the correction amount is a value obtained by multiplying a difference between the predetermined luminance value and the average value of the luminance by a predetermined coefficient. The predetermined color image forming apparatus according to claim 1 or claim 2, characterized in that the color of human skin. An image data dividing step of dividing image data composed of a plurality of pixel data into a plurality of groups so as to correspond to each region when an image formed using the image data is divided into a plurality of regions;
Among the divided areas, the color of the pixel is specified from each pixel data included in a group corresponding to one or more previously selected areas, and the largest number of pixels among the pixels included in the group a color specifying step but be specified as a color of the region corresponding to that group the color to be shared,
A color comparison step of comparing the predetermined color that has been previously set the color of the identified said region,
If it contains the predetermined color in the color before Symbol area, the average luminance calculating step of obtaining an average value of the luminance of the region using the pixel data included in the region,
A correction amount calculating step for calculating a correction amount for correcting the average value of the determined luminance to a predetermined luminance value set in advance;
An image data correction step for correcting all pixel data using the determined correction amount;
A corrected image data output step for outputting the corrected image data;
An image data processing method comprising: The image data processing method according to claim 4 , wherein the correction amount is a value obtained by multiplying a difference between the predetermined luminance value and the average value of the luminance by a predetermined coefficient. Image data processing method according to claim 4 or claim 5, wherein the predetermined color is the color of human skin. Image data division processing for dividing image data composed of a plurality of pixel data into a plurality of groups so as to correspond to each region when an image formed using the image data is divided into a plurality of regions;
Among the divided areas, the color of the pixel is specified from each pixel data included in a group corresponding to one or more previously selected areas, and the largest number of pixels among the pixels included in the group color specifying process but be specified as a color of the region corresponding to that group the color to be shared,
Color comparing process for comparing the predetermined color that has been previously set the color of the identified said region,
If it contains the predetermined color in the color before Symbol area, the average luminance calculation process for obtaining the average value of the luminance of the region using the pixel data included in the region,
A correction amount calculation process for calculating a correction amount for correcting the average value of the calculated luminance to a predetermined luminance value set in advance;
Image data correction processing for correcting all pixel data using the obtained correction amount;
A corrected image data output process for outputting the corrected image data;
A recording medium on which an image data processing program for causing a computer to execute is recorded.