JP2008124890A - Exposure discrimination apparatus and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately discriminate whether image exposure is adequate. <P>SOLUTION: A thumbnail image capturing unit 111 and a feature amount calculation area setting unit 112 cooperatively capture/generate a thumbnail image by analyzing producer note information or the like and in the thumbnail image, an effective image data area (exposure related area) as an area occupied by image data obtained while being affected by exposure in image capturing is defined as a feature amount calculation area. Namely, in a case where black bar images are added to above and under the image for size adjustment, an area other than the portion occupied by the black bar images is defined as a feature amount calculation area. For each of a plurality of blocks produced by dividing the feature amount calculation area, an average value of reference maximum brightness values of the blocks is derived from brightness values of pixels belonging to each block and on the basis of the reference maximum brightness average value, it is discriminated whether image exposure is adequate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for determining whether or not the exposure of an image represented by image data is appropriate, and more specifically, a technique for determining the exposure of an image through exposure determination with a thumbnail image representing an outline of the image. It is about.

  When printing an image (photograph image) taken by a digital camera or the like using a printer or a multifunction machine, it is wasteful to print all the taken images. That is, the captured images include underexposed images and overexposed images, and it is meaningless to print these images.

  FIG. 11 is an explanatory diagram showing an example of an image with proper exposure and an image with insufficient exposure. In FIG. 11, (a) is an image of fireworks that have risen in the night sky. The background is dark, but the entire image is dotted with bright portions, and the exposure is appropriate, meaning that printing is also effective. It can be said that there is an image. On the other hand, in (b), only a part of the image is bright, but the other part is dark, so the image is underexposed, and it can be said that the image does not make much sense even if it is printed.

  As described above, in general, an image obtained by shooting fireworks, a night view, and the like is an image with appropriate exposure, whereas a part of the image is bright, but the other part is a dark image with insufficient exposure.

  Therefore, if an image with an appropriate exposure can be determined from a large number of captured images, for example, only an image that the user originally desires to print can be automatically printed.

  By the way, as a method for determining whether the exposure of an image is excessive or insufficient, for example, a method described in the following patent document is known.

  Specifically, for example, with respect to an image to be determined, an average value of luminance values of each pixel is obtained, and based on the value, it is determined whether the exposure of the image is excessive or insufficient. Yes.

JP-A-9-68764 JP 2002-281337 A

  However, as described above, an average value of luminance values of each pixel (hereinafter, sometimes referred to as a luminance average value) is obtained for an image to be discriminated, and whether or not the exposure of the image is appropriate based on the value. When trying to discriminate, there is a problem that some images are misjudged.

  FIG. 12 is an explanatory diagram showing a histogram of luminance values and an average luminance value for each image in FIG. In FIG. 12, (a) is a histogram of luminance values for an image with appropriate exposure in FIG. 11 (a), and (b) is a luminance value for an image with insufficient exposure in FIG. 11 (b). It is a histogram. In (a) and (b), Av indicates the average value (luminance average value) of the luminance values of the pixels in the image.

  As shown in FIG. 12, when the average exposure value Av of each pixel is compared between the image with the appropriate exposure shown in FIG. 11A and the image with the insufficient exposure shown in FIG. Therefore, only by using this luminance average value Av, the image shown in FIG. 11A is an image with appropriate exposure, and the image shown in FIG. 11B is an image with insufficient exposure. It can be understood that it is difficult to discriminate.

  An object of the present invention is to solve the above-described problems of the prior art and provide a technique capable of appropriately determining whether or not an image is properly exposed.

In order to achieve at least a part of the above object, an exposure determination apparatus of the present invention is an exposure determination apparatus for determining whether or not the exposure of an image represented by image data is appropriate,
A feature amount calculation region setting unit that sets a feature amount calculation region as a region for calculation of the feature amount affected by the exposure in a thumbnail image that represents an outline of the image corresponding to the image;
Dividing the set feature amount calculation region into a plurality of blocks, and comparing the brightness index value indicating the brightness of each pixel belonging to the divided block from the thumbnail image data representing the thumbnail image in the divided block A brightness contrast reference index value that is a reference value is derived for each of the divided blocks, and an average value of the brightness contrast reference index values for each of the divided blocks is a first evaluation value that is one of the feature values. A first evaluation value derivation unit,
Based on the first evaluation value, it is determined whether or not the exposure of the thumbnail image is appropriate. When it is determined that the exposure of the thumbnail image is appropriate, the exposure of the image is also appropriate. An exposure discriminating unit for discriminating,
The feature amount calculation area setting unit includes:
In setting the feature amount calculation region in the thumbnail image, the feature amount calculation region is set by extracting from the thumbnail image an exposure-related region occupied by the image data obtained by the influence of exposure at the time of image acquisition. The gist is to do.

  As described above, in the exposure determination apparatus according to the present invention, when determining appropriateness of exposure of an image, a thumbnail image representing an image outline corresponding to the image is used. Since the thumbnail image has a smaller image size than the original image (hereinafter, this image will be referred to as the main image for convenience of explanation), the number of thumbnail image data representing the thumbnail image is the main image. Compared to data representing For this reason, the processing speed can be increased and the processing time can be shortened by reducing the number of data to be processed later.

In this case, the main image that is subject to exposure appropriateness must be provided as a Jpeg file (DCF basic file) that conforms to the file format standard (DCF standard) for digital camera images established by the Japan Electronics Manufacturers Association (JEIDA). For example, a thumbnail image (DCF basic thumbnail) usually exists in the DCF basic file. Therefore, in this case, the thumbnail image may be subjected to processing described later. A thumbnail image conforming to the DCF file has an aspect ratio of 4: 3. In this case, the thumbnail image is usually 160 × 120 pixels in size, and the image size is much larger than that of the main image. small. Therefore, the processing time can be greatly shortened by reducing the processing load. In the case of an Exif file that does not conform to the DCF standard, the presence or absence of a thumbnail image is checked from the tag information. If a thumbnail image exists, the processing time can be shortened using the thumbnail image.

  On the other hand, if there is no thumbnail image in the Exif file, or if the main image to be determined for proper exposure is a file that does not have a thumbnail image (for example, a JPEG (Joint Photographic Experts Group) file), thinning is performed from the main image. A thumbnail image may be generated by processing or the like, and the generated thumbnail image may be used. In this case, the image size of the thumbnail image and the configuration of the thumbnail image data are determined by the processing contents to be thinned out. Therefore, the image size of the thumbnail image and the configuration of the thumbnail image data are ascertained from the processing process of the thinning processing employed. Can be processed.

  In the exposure determination device of the present invention using a thumbnail image, first, a feature as a region for calculating a feature amount affected by the exposure in a thumbnail image representing an outline of the image corresponding to the main image. Set the amount calculation area. Since this feature amount calculation area is a target area for determining appropriateness of exposure using thumbnail image data included in the area, when setting this feature amount calculation area in a thumbnail image, the influence of exposure at the time of image acquisition is determined. An exposure-related area occupied by the image data obtained by receiving the image data is extracted from the thumbnail image, and the feature amount calculation area is set.

  Here, the exposure-related area is an area occupied by the image data obtained by the influence of exposure at the time of image acquisition. The thumbnail image obtained from the image is not uniform and relates to the aspect ratio of the main image. Therefore, it is also possible to set the feature amount calculation area by determining the exposure involved area according to the aspect ratio of the image. Specifically, if the aspect ratio of the main image is 4: 3, the thumbnail image based on the main image will remain at 4: 3 according to the DCF standard. Since the above-described exposure-related area (that is, the entire area of the main image) changes as it is in the thumbnail image, the entire area of the thumbnail image is set as the exposure-related area, and the area is set as a feature amount calculation area.

  On the other hand, if the aspect ratio of the main image is an aspect ratio other than 4: 3, the thumbnail image having the aspect ratio of 4: 3 conforming to the DCF standard is generated in the process of generating the thumbnail image from the main image having the aspect ratio. Although converted, data unrelated to exposure (for example, data representing black bars added for size adjustment above and below the image) is usually added in this conversion process. The data area occupied by data unrelated to exposure (thumbnail image data) is not affected by the exposure in the thumbnail image corresponding to the main image as well as the main image. Therefore, by excluding the data area irrelevant to the exposure from the thumbnail image, the exposure-related area is extracted from the thumbnail image and the feature amount calculation area is set. In this way, data (thumbnail image data) included in an area that is not affected by the exposure in the thumbnail image can be excluded from the processing described later, so that the reliability of the processing described later for determining the appropriateness of exposure can be improved. Can improve the accuracy of exposure determination.

  When setting the feature amount calculation region after extracting the exposure-related region, in addition to the setting according to the aspect ratio as described above, the thumbnail image is scanned and the exposure is performed according to the transition state of the thumbnail image data. It is also possible to define the area of involvement. That is, in the area occupied by the black bars above and below the image for size adjustment described above, the thumbnail image data is almost completely uniform in the data scanning column, but in the area reflecting the original image, the data scanning column is usually used. Since the data value (e.g., luminance) changes at, the exposure-related area can be extracted by excluding the area occupied by the data irrelevant to the exposure, and the feature amount calculation area can be set. .

  The exposure discriminating apparatus of the present invention divides the feature amount calculation region in the thumbnail image set in this way into a plurality of blocks, and from the thumbnail image data representing the thumbnail image in the divided block, each pixel belonging to the divided block. A brightness contrast reference index value, which is a contrast reference value of a brightness index value indicating brightness, is derived for each of the divided blocks, and an average value of the brightness contrast reference index values for each of the divided blocks is calculated based on the feature amount. The first evaluation value is one. In this case, as the brightness index value indicating the brightness of each pixel, a brightness value or brightness determined by the influence of exposure can be used, and the brightness index value is set as the brightness value as the comparison reference index value. In addition to the maximum luminance value in the case, a value corresponding to the maximum luminance value, for example, the n-th value from the larger side, or the value of the histogram cumulative m% from the larger side can be adopted. The same applies to the brightness.

  Then, the exposure determination device of the present invention determines whether the thumbnail image is exposed based on the first evaluation value (average value of the brightness contrast reference index value), which is one of the feature quantities affected by exposure. It is determined whether or not the thumbnail image is appropriate, and when it is determined that the exposure of the thumbnail image is appropriate, the exposure of the image is also determined to be appropriate.

  Therefore, for thumbnail images corresponding to images obtained by shooting fireworks or night views, that is, images (main images) in which the background is dark but bright portions are scattered throughout the image, each of the feature amount calculation areas Since each block can obtain a certain value as the brightness comparison reference index value, the first evaluation value, which is the average value of the brightness comparison reference index values, is used as an exposure determination index. Thus, it can be determined that the exposure is an appropriate image. On the other hand, for an image in which only a part is bright but other parts are dark, only a part of the blocks can obtain a large value as the brightness contrast reference index value. By using the first evaluation value as the average value of the above as an index for determining exposure, it can be determined that the image is insufficiently exposed.

  Therefore, according to the exposure determination apparatus of the present invention, the first evaluation value, which is the average value of the brightness comparison reference index values for each block in the feature amount calculation region in the thumbnail image corresponding to the main image, is determined as the exposure determination. Therefore, it is possible to appropriately determine whether the exposure of the main image corresponding to the thumbnail image is appropriate as well as the thumbnail image. In addition, since the thumbnail image is used as described above, there is an advantage that it is possible to determine the appropriateness of exposure within a short time. In addition, since the first evaluation value is the average value of the brightness contrast reference index values, it is possible to more appropriately determine whether or not the exposure of the image is appropriate without complicating the calculation process.

  The above-described exposure determination apparatus of the present invention can take various forms. For example, the exposure determination unit determines whether the thumbnail image is exposed when the first evaluation value exceeds a first threshold. It is preferable to determine that the exposure is appropriate for the image as appropriate. In this way, it is possible to determine whether or not the exposure of the image is appropriate by a simple method of comparing the first evaluation value and the first threshold value.

Further, based on the thumbnail image data belonging to the set feature quantity calculation area, an average value of the brightness index values in the feature quantity calculation area is derived as a second evaluation value that is one of the feature quantities. A second evaluation value deriving unit;
The exposure determination unit determines whether or not the thumbnail image is properly exposed based on a threshold function equation having the first and second evaluation values as variables, and the thumbnail image is appropriately exposed. If it is determined that there is an image, it may be determined that the exposure of the image is also appropriate.

  In this way, together with the first evaluation value derived from the thumbnail image data belonging to each block obtained by dividing the feature amount calculation region, the second evaluation value that is the feature amount of the entire feature amount calculation region is used as an index for determining exposure. Therefore, it is possible to more appropriately determine whether or not the exposure of the image is appropriate.

In this way, when using the first and second evaluation values, the average value of the brightness comparison reference index value, which is the first evaluation value, is divided from the luminance value of each pixel belonging to the divided block. The average value AvRmax of the maximum luminance values derived for each of the blocks, and the average value of the brightness index value as the second evaluation value is determined from the luminance values of the pixels belonging to the set feature amount calculation area. When the average value Av of the derived luminance values is set to a and b (where a and b are positive numbers), the threshold function equation is
AvRmax> −a · Av + b
And
When the threshold function formula is satisfied, it may be determined that the exposure of the thumbnail image is appropriate, assuming that the exposure of the thumbnail image is appropriate.

  With this configuration, it can be determined with higher accuracy whether or not the exposure of the image is appropriate.

  As described above, when using the average value AvRmax of the maximum luminance value or the average value Av of the luminance value, when the image is a JPEG image compressed by JPEG (Joint Photographic Experts Group), the luminance value of each pixel is The average value Av may be obtained as an average value of DC components of a discrete cosine transform (DCT) obtained for each 8 × 8 pixel block of the JPEG image.

  With this configuration, the processing time can be significantly shortened as compared with the case of obtaining the average of the luminance values of the pixels for the entire image. Further, since the maximum luminance value is an easily obtainable value, further reduction in processing time can be expected.

  The present invention is not limited to a device invention such as the above-described exposure discriminating apparatus, but can also be realized as a method invention such as an exposure discriminating method. Further, aspects as a computer program for constructing those methods and apparatuses, aspects as a recording medium recording such a computer program, data signals embodied in a carrier wave including the computer program, etc. It can also be realized in various ways.

Hereinafter, embodiments of the present invention will be described in the following order based on examples.
A. First embodiment:
A-1. Example configuration:
A-2. Example operation:
A-3. Effects of the embodiment:
B. Second embodiment:
B-1. Example configuration:
B-2. Example operation:
B-3. Effects of the embodiment:
C. Variation:

A. First embodiment:
A-1. Example configuration:
FIG. 1 is a block diagram showing a multi-function machine equipped with an exposure discriminating apparatus as a first embodiment of the present invention. A multifunction device 10 shown in FIG. 1 functions as an exposure determination device, and also includes a control circuit 100 that performs control and the like on various components described later, and a scanner unit 140 that reads an image from a photograph and converts it into image data. The memory card slot 150 for reading / writing image data and the like to / from the inserted memory card 150a is connected to a digital camera (not shown) via a USB cable (not shown) to read / write image data and the like. A USB interface unit 160, a liquid crystal display 170 for displaying images and various messages, an operation unit 180 for receiving various instructions from the user, and for printing an image on paper based on the image data. The printer unit 190 is mainly provided.

  Among these, the control circuit 100 includes a CPU 110 that performs various processes and controls according to a computer program, a RAM 120 that temporarily stores data obtained during the processes and controls by the CPU 110, the computer program used by the CPU 110, and the like. ROM 130 for storing the data. In addition, the CPU 110 executes the above computer program to thereby perform a thumbnail image acquisition unit 111, a feature amount calculation area setting unit 112, a maximum luminance average value calculation unit 113, an exposure determination unit 114, an image correction unit 116, , Functions as the print control unit 118. Among these, in particular, the feature amount calculation area setting unit 112, the maximum luminance average value calculation unit 113, the exposure determination unit 114, and the like constitute an exposure determination device.

  In FIG. 1, a feature amount calculation region setting unit 112 corresponds to a feature amount calculation region setting unit in the present invention, and a maximum luminance average value calculation unit 113 corresponds to a first evaluation value deriving unit in the present invention. The exposure determination unit 114 corresponds to the exposure determination unit in the present invention.

A-2. Example operation:
Next, regarding the operation of the multifunction machine 10 of the present embodiment, the user instructs the multifunction machine 10 shown in FIG. 1 to execute “automatic printing” for all image data recorded on the memory card 150a. The case will be described as an example.

  Here, “automatic printing” is a process in which the multi-function peripheral 10 automatically selects and prints several images suitable for printing from among a large number of images. As part of such “automatic printing”, when an image suitable for printing is selected, an image discrimination process is performed by the exposure discrimination apparatus of the present embodiment.

  FIG. 2 is a flowchart showing a processing procedure of an exposure determination processing routine in the first embodiment.

  When the user gives an instruction to execute “automatic printing” to all image data recorded on the memory card 150a via the operation unit 180, the CPU 110 sequentially displays the image data as shown in FIG. An exposure determination processing routine is executed.

  When the exposure determination processing routine shown in FIG. 2 is started, first, the thumbnail image acquisition unit 111 functioning by the CPU 110 accesses the memory card 150a via the memory card slot 150, and a plurality of recordings recorded on the memory card 150a. One piece of image data is read out and acquired from the image data, and is written in the RAM 120 (step S102). This image data is data about a main image with respect to a thumbnail image to be described later. Next, the feature amount calculation region setting unit 112 functioning by the CPU 110 cooperates with the thumbnail image acquisition unit 111 to perform a feature amount calculation region setting process (step S103). The feature amount calculation area setting process includes a plurality of processes as shown in the figure, and it is determined whether or not there is a thumbnail image for the main image by analyzing the acquired image data (for example, file information analysis, tag information analysis, etc.) Step S131).

  If it is determined in step S131 that there is no thumbnail image, in the subsequent step S132, a thumbnail image and its thumbnail image are obtained from the image data acquired in step S102 in accordance with a predetermined thumbnail image creation process including data thinning. Create data. In this case, since the processing procedure of the thumbnail image creation process is stored in the ROM 130 in advance, a thumbnail image is created by the processing procedure.

  Following the affirmative determination (with thumbnail image) in step S131 and the thumbnail image creation in step S132, it is determined whether or not the aspect ratio of the main image is 4: 3 (step S133). Also in step S133, the determination can be made by the file information analysis or the manufacturer note information analysis as described above. If it is determined that the aspect ratio of the main image is 4: 3, if the aspect ratio is this aspect ratio, not only the main image but also the thumbnail image corresponding to the main image, the entire image is the original image at the time of image acquisition. Since the image data represents the entire thumbnail image, the entire thumbnail image is set as a feature amount calculation region to be processed later (step S134). In this case, the whole area of the thumbnail image, which is a feature amount calculation area, is an area occupied by image data obtained by the influence of exposure at the time of image acquisition, and thus corresponds to an exposure-related area according to the present invention.

  On the other hand, if a negative determination is made that the aspect ratio of the main image is other than 4: 3, the following is performed. Regardless of whether the image data of the main image is a DCF file, if the main image has an aspect ratio other than 4: 3, the thumbnail image is sized to fit the aspect ratio of 4: 3. Since adjustment is performed, image data (thumbnail image data) corresponding to an image as a black bar is included above and below the image. Further, even in the thumbnail image created in step S132, if the aspect ratio of the main image is an aspect ratio other than 4: 3, the size is adjusted so as to conform to the aspect ratio of 4: 3 during the thumbnail image creation process. Since the adjustment is made, image data (thumbnail image data) corresponding to an image as a black bar is added above and below the image. In other words, black bar images are added above and below the image for size adjustment. FIG. 3 is an explanatory diagram showing the relationship between the aspect ratio and the thumbnail image. As shown in FIG. 3, if it is determined in step S133 that the aspect ratio of the main image is other than 4: 3, an effective image data area corresponding to the image data representing the original image at the time of image acquisition is determined. It is set in a feature amount calculation area to be processed later (step S135). That is, the image data (thumbnail image data) corresponding to the black bars above and below the image shown in FIG. 3 is not valid image data corresponding to the image data representing the original image at the time of image acquisition. The effective image data area is extracted by excluding the image area including the image data corresponding to (thumbnail image data) from the thumbnail image, and is set as the feature amount calculation area. The effective image data area, which is a feature amount calculation area in this case, is an area occupied by image data obtained by the influence of exposure at the time of image acquisition, and thus corresponds to an exposure-related area according to the present invention.

  By the way, in determining the effective image data area in step S135, various methods can be taken. For example, if the aspect ratio (for example, the aspect ratio such as 3: 2 or 16: 9) included in the main image is found by file information analysis or manufacturer note information analysis, the contrast with the aspect ratio of 4: 3 described above can be obtained. After that, the area occupied by the black bars added above and below the thumbnail image is found. Therefore, the effective image data area can be determined by excluding the occupied areas of the black bars above and below the image thus obtained from the thumbnail images. In addition, it is possible to take a method of scanning a thumbnail image that exists in advance corresponding to the provided main image or a thumbnail image created in step S132 in the horizontal direction from the upper end to the lower end of the image. In this method, the difference in data properties between the occupied area of the black bars above and below the image for size adjustment and the effective image data area other than the occupied area is used as follows. In other words, in the area occupied by the black bars above and below the image for size adjustment, the thumbnail image data is almost completely uniform in the data scanning column, but in the effective image data area, the original state of the image at the time of image acquisition is the thumbnail. Since it is reflected in the image data, the data value (for example, brightness, etc.) usually changes in the data scanning column. Therefore, there is a difference in the scanning situation between the scanning of the black bar occupied area and the scan of the effective image data area. Therefore, the black bar occupied area above and below the image is obtained from the difference in the scanning situation, and the occupied area is defined as the thumbnail. An effective image data area is extracted from the image and set as a feature amount calculation area.

  When the feature amount calculation area is set in this way, the maximum luminance average value calculation unit 113 functioning by the CPU 110 divides the set feature amount calculation area into M × N (M and N are integers of 1 or more) blocks. (Step S104). Specifically, the block size, the position of each block, and the like are calculated from the thumbnail image data belonging to the set feature amount calculation area. Next, the maximum luminance average value calculation unit 113 obtains the maximum luminance value Bmax from the luminance values of the pixels belonging to the block for each block based on the thumbnail image data (step S106).

  FIG. 4 is an explanatory diagram schematically showing how the maximum luminance value Bmax is obtained for each block. In the example shown in FIG. 4, assuming that M = 5 and N = 5, the maximum value degree value Bmax (m, n) is obtained for a total of 25 blocks (where m = 1,... 5, n = 1,..., 5).

  Subsequently, the maximum luminance average value calculation unit 113 calculates the maximum luminance average value AvBmax by calculating the average of the calculated maximum luminance values Bmax for each block (step S108).

For example, in the case of the example shown in FIG. 4, the maximum luminance average value AvBmax is as shown in Expression (1).

  Next, the exposure determination unit 114 functioned by the CPU 110 determines whether or not the calculated maximum luminance average value AvBmax exceeds a predetermined threshold Th2 (step S110). A thumbnail image corresponding to the set feature amount calculation area is determined to be an image with an appropriate exposure, and a main image corresponding to the thumbnail image is selected as a print target image (step S112). Then, the image correction unit 116 functioned by the CPU 110 performs image correction processing including various image quality corrections such as contrast, brightness, color balance, and noise removal on the image data of the main image selected as the print target image. (Step S114), the exposure determination processing routine is terminated. On the other hand, if the calculated maximum luminance average value AvBmax does not exceed the threshold Th2, the exposure determination unit 114 determines that the thumbnail image corresponding to the set feature amount calculation area is an image with insufficient exposure. The main image corresponding to the thumbnail image is not selected as the print target image (step S116), and the exposure determination processing routine is terminated.

  In this way, the CPU 110 sequentially executes the exposure determination processing routine shown in FIG. 2 on the image data of all the main images recorded on the memory card 150a, so that each image indicated by the image data is exposed. Depending on the appropriateness / insufficiency, the image to be printed is divided into the image that is not to be printed, and desired image correction is performed on the image to be printed.

  Then, the print control unit 118 functioning by the CPU 110 controls the printer unit 190 to sequentially print the print target images that have been determined to be appropriate for exposure and have undergone image correction.

  As described above, it is possible to automatically select and print an appropriate image having an exposure suitable for printing from among a large number of images recorded on the memory card 150a. It should be noted that for the main image excluded from the print target image because the thumbnail image corresponding to the set feature amount calculation area is underexposed in step S116, the main image can be deleted from the memory card 150a. Further, the main image to be printed through steps S112 to S114 can be updated and stored in the memory card 150a as image data reflecting the correction result in step S114.

A-3. Effects of the embodiment:
FIG. 5 is an explanatory diagram showing a histogram of luminance values and a maximum average luminance value for each image in FIG. In FIG. 5, as in FIG. 12, (a) is a histogram of luminance values for the image with the appropriate exposure in FIG. 11 (a), and (b) is insufficient in the exposure of FIG. 11 (b). It is a histogram of the luminance value about an image. In (a) and (b), AvBmax indicates the maximum average brightness value in the image. Since the thumbnail image is created by decimation of the image data of the main image, there is a difference in the number of data between the luminance value distribution of the pixels in the thumbnail image and the luminance value distribution of the pixels in the main image. Since there is only one, FIG. 5 shows the distribution of image data in the main image in comparison with FIG. 11 which is a luminance value distribution diagram of the main image.

  As shown in FIG. 5, in the image with the appropriate exposure shown in FIG. 11A, the maximum brightness average value AvBmax exceeds the threshold Th2, whereas the image shown in FIG. In this case, the maximum average brightness value AvBmax is significantly lower than the threshold value Th2, and thus the maximum average brightness value AvBmax, which is the average of the maximum brightness values for each block in the image, is used as an index for determining exposure. Accordingly, it is possible to appropriately determine that the image illustrated in FIG. 11A is an image with appropriate exposure and the image illustrated in FIG. 11B is an image with insufficient exposure.

  FIG. 6 is a graph showing the distribution of each image using a luminance average value and a maximum luminance average value as parameters for a large number of images, together with a threshold value for the luminance average value. FIG. It is the graph shown with the threshold value about a luminance average value. FIG. 6 and FIG. 7 also show the luminance value distribution in the main image, but are included in the thumbnail image that is the target for determining the appropriateness of exposure in this embodiment, specifically, in the feature amount calculation area set as described above. It can be said that the luminance value distribution in the thumbnail image data is also the distribution shown in FIGS. Therefore, unless otherwise specified, in the following description, the luminance value distribution in the main image will be described.

  6 and 7, the horizontal axis represents the average luminance value Av, and the vertical axis represents the maximum average luminance value AvBmax, which can take a value of 0 to 255. Further, since the maximum luminance average value AvBmax and the luminance average value Av are in a relationship of AvBmax ≧ Av, each image is positioned above the straight line of AvBmax = Av on the graph. At this time, a circle indicates an image with proper exposure, and a cross indicates an image with insufficient exposure. Furthermore, the group of images located at the center and the upper right are respectively normal images, and the group of images located at the lower left are respectively brighter by a part, represented by the image shown in FIG. The other part is a dark image, and the group of images located between these groups is an image of fireworks, a night view, etc. represented by the image shown in FIG.

  Conventionally, as described above, the average luminance value Av in the image is used as an index for determining exposure. For example, as illustrated in FIG. 6, when the threshold Th1 for the average luminance value Av is “64”, , It can be determined that the exposure is appropriate, and for images that are only partially bright, it can be determined that the exposure is insufficient, but for images such as fireworks and night views, the exposure is appropriate. In spite of the fact that the image should be determined to be a correct image, it was erroneously determined that the image was insufficiently exposed, and there was a problem.

  In contrast, in the present embodiment, as described above, the maximum luminance average value AvBmax in the image (specifically, the thumbnail image of the set feature amount calculation area) is used as an index for exposure determination. As described above, when the threshold Th2 for the maximum average brightness value AvBmax is “64”, not only normal images but also most images of fireworks, night scenes, and the like are images whose exposure is appropriate. Can be determined. Further, with respect to an image that is only partially bright, it is possible to determine that all the images are images that are underexposed.

  As described above, according to the present embodiment, whether the exposure of an image is appropriate by using the maximum luminance average value AvBmax in an image (specifically, a thumbnail image of a set feature amount calculation area) as a discrimination index. It is possible to appropriately determine whether or not. When determining the appropriateness of exposure, a simple calculation of calculating an average value (maximum luminance average value AvBmax) from the maximum luminance value for each block and comparing the maximum luminance average value AvBmax with the threshold Th2 may be performed. Therefore, it is possible to determine whether the image is suitable for exposure without complicating the calculation process.

  In addition, in the present embodiment, since the image to be subjected to exposure suitability determination is a thumbnail image corresponding to the main image, the number of data to be subjected to the processing for exposure suitability determination in steps S104 to S108 described above can be reduced. . Therefore, it is possible to increase the processing speed, to shorten the processing time, and to quickly print the main image with proper exposure.

  Further, in this embodiment, in setting the feature amount calculation area of the image composed of the data affected by the exposure in the thumbnail image that is the subject of the exposure appropriateness determination, the aspect ratio of the main image is 4: 3. If there is an aspect ratio other than 4: 3, the entire area of the thumbnail image is set as a feature amount calculation area (step S134). The effective image data area is extracted by exclusion and set as the feature amount calculation area (step S135). Therefore, the feature amount calculation area for determining the appropriateness of exposure can be an image area composed of image data (thumbnail image data) affected by the exposure at the time of image acquisition, so that the accuracy of exposure determination can be improved.

B. Second embodiment:
B-1. Example configuration:
FIG. 8 is a block diagram showing a multi-function machine equipped with an exposure discriminating apparatus as a second embodiment of the present invention. The MFP 20 shown in FIG. 8 is structurally different from the MFP 10 shown in FIG. 1 in that the CPU 110 executes a computer program so that the maximum luminance average value calculation unit 113, the exposure determination unit 114, and the image correction unit. 116 and the print control unit 118, and further functions as a luminance average value calculation unit 119. Since the other configuration is the same as that of the multifunction machine 10 shown in FIG. 1, the description thereof is omitted. In FIG. 8, the luminance average value calculation unit 119 corresponds to a second evaluation value deriving unit in the present invention.

B-2. Example operation:
As for the operation of this embodiment, as in the case of the first embodiment, the user selects all the image data recorded on the memory card 150a for the multifunction device 20 shown in FIG. A case where an instruction to execute “print” is given will be described as an example.

  The operation of this embodiment is different from the operation of the first embodiment in that the average brightness value Av and the maximum brightness average value AvBmax are used as indicators for determining appropriateness of exposure, and a threshold function equation using both average values as variables. It is a point which performs exposure discrimination based on this.

  FIG. 9 is a flowchart showing a processing procedure of an exposure determination processing routine in the second embodiment.

  When the user instructs execution of “automatic printing” for all image data recorded in the memory card 150a via the operation unit 180, the CPU 110 sequentially displays the image data as shown in FIG. An exposure determination processing routine is executed.

  When the exposure determination processing routine shown in FIG. 9 is started, first, the thumbnail image acquisition unit 111 functioning by the CPU 110 accesses the memory card 150a via the memory card slot 150, similarly to step S102 shown in FIG. Then, one image data is read out and acquired from the plurality of image data recorded in the memory card 150a, and is written in the RAM 120 (step S302). Next, the feature amount calculation region setting unit 112 functioning by the CPU 110 cooperates with the thumbnail image acquisition unit 111 to perform the above-described series of feature amount calculation region setting processing (step S103 / steps S131 to 135).

  Next, based on the thumbnail image data belonging to the set feature amount calculation area, the average brightness value of each pixel constituting the thumbnail image is obtained, thereby obtaining the average brightness of the thumbnail images corresponding to the set feature amount calculation area. The value Av is calculated (step S304).

  In calculating the luminance average value Av, if the main image is a JPEG image compressed by JPEG (Joint Photographic Experts Group), the following processing is performed by paying attention to the data structure of the JPEG image. Decided to do. That is, the image data type is determined at the time of data acquisition in step S302, and if it is a JPEG image, the following processing is performed. If the image is not a JPEG image, the luminance average value Av is calculated by various methods from the thumbnail image data of the thumbnail image corresponding to the set feature amount calculation area.

  1. Since a JPEG image has an 8 × 8 pixel block in one processing size, when the maximum luminance value for each block is obtained in the exposure determination process, the maximum size of the 8 × 8 pixel block is used as a unit. Find the luminance value. In this way, the process of dividing the image into M × N blocks can be omitted, and the maximum luminance value for each block can be combined when decoding the JPEG image in units of 8 × 8 pixels. Efficient processing is possible.

  2. In a JPEG image, an 8 × 8 pixel block is subjected to discrete cosine transform (DCT) and expressed as 8 × 8 frequency components. Therefore, when calculating the luminance average value Av of the image in step S304, the DC component of the DCT in that block is acquired for each block of 8 × 8 pixels, the average value of those DC components is obtained, and the image The average luminance value Av may be used. Since the average value of the DC component of the DCT in each block is the same as the average luminance value of the entire image, even if the average value of the DC component is the average luminance value Av of the image, the accuracy of exposure determination is not impaired. It is. For example, the luminance value is a scale of 0 to 256, and the DC component is a scale of -1024 to 1023. By adopting such a method, the processing time can be significantly shortened compared to the case of obtaining the average of the luminance values of the pixels for the entire image.

  Next, the maximum luminance average value calculation unit 113 performs the same processing as steps S104 to S108 shown in FIG. In other words, the maximum luminance average value calculation unit 113 divides the set feature amount calculation region into M × N blocks (step S306), and then, based on the thumbnail image data belonging to the set feature amount calculation region. For each block, the maximum luminance value Bmax in the block is obtained (step S308), and the maximum luminance average value AvBmax is calculated from the obtained maximum luminance value Bmax (step S310).

  In this case, if the image data is JPEG data, when obtaining the maximum luminance value Bmax for each block, the DC component of the DCT in the block and the AC component up to the third coefficient are obtained for each block of 8 × 8 pixels. And the maximum luminance value of the block may be obtained. This is because the value of the high frequency component of the AC components of the DCT in each block is usually very small, and even if these values are ignored, the accuracy of exposure determination is not impaired. By adopting such a method, the processing time can be significantly reduced as compared with the case where the maximum luminance value is obtained from the luminance values of the pixels belonging to the block.

Subsequently, the exposure determination unit 114 determines whether or not the calculated luminance average value Av and maximum luminance average value AvBmax satisfy a threshold function equation represented by equation (2) (step S312).
AvBmax> −a · Av + b (2)
However, in Formula (2), a and b are positive constants, respectively.

  When the threshold function equation is satisfied, the exposure determination unit 114 determines that the thumbnail image corresponding to the set feature amount calculation area is an image with appropriate exposure, and prints the main image corresponding to the thumbnail image. It selects as a target image (step S314). Then, the image correction unit 116 performs image correction processing including various image quality corrections on the image selected as the print target image (step S316), and ends the exposure determination processing routine.

  On the other hand, when the threshold function equation is not satisfied, the exposure determination unit 114 determines that the thumbnail image corresponding to the set feature amount calculation area is an image with insufficient exposure, and the book corresponding to the thumbnail image. The image is not selected as an image to be printed (step S318), and the exposure determination processing routine is terminated.

  In this way, the CPU 110 sequentially executes the exposure determination processing routine shown in FIG. 9 for all the image data recorded on the memory card 150a, so that each image indicated by the image data is appropriately / insufficiently exposed. Accordingly, the image to be printed is classified into an image that is not to be printed and a desired image correction is performed on the image to be printed. Then, the print control unit 118 controls the printer unit 190 to sequentially print the print target images subjected to the image correction.

  As described above, it is possible to automatically select and print an appropriate image having an exposure suitable for printing from among a large number of images recorded on the memory card 150a.

B-3. Effects of the embodiment:
FIG. 10 is a graph showing the distribution of each image using the average brightness value and the maximum average brightness parameter as parameters for a large number of images, together with a threshold function expression. The description of the horizontal and vertical axes, the range of values, the distribution state of each image, the circle and cross marks, the group of each image, and the like are the same as in FIG. 6 and FIG. To do. Further, FIG. 10 also shows the luminance value distribution in the main image as in FIGS. 6 and 7, but the thumbnail image that is a target for determining the appropriateness of exposure in this embodiment, specifically, as described above. Since the luminance value distribution in the thumbnail image data included in the feature amount calculation area is also the distribution shown in FIG. 10, unless otherwise specified, the following description will be made with the luminance value distribution in the main image.

  In the present embodiment, as described above, the threshold function equation represented by equation (2) is used as an index for determining exposure. For example, as shown in FIG. 10, the constant a is “1” and the constant b is “80”. Then, from the straight line AvBmax = −Av + 80, all the images located in the upper right are determined to be images with appropriate exposure, and all the images located in the lower left are determined to be images with insufficient exposure. Will be. As a result, not only normal images, but also images such as fireworks and night scenes, all the images can be determined to be images with appropriate exposure. Further, even for a partially bright image, it is possible to determine that almost all images are images that are underexposed.

  As described above, according to the present embodiment, whether the exposure of the image is appropriate with higher accuracy by using the threshold function equation having the luminance average value Av and the maximum luminance average value AvBmax as variables. It can be determined whether or not.

C. Variation:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the scope of the invention.

C-1. Modification 1:
In the second embodiment described above, the brightness average value Av of the image is used to perform the exposure determination. However, the present invention is not limited to this, and other feature values of the image are used. You may make it use. For example, the following feature amounts may be used instead of the luminance average value Av.

1. 1. Pixel ratio of blackout pixels: ratio of the number of pixels having a luminance value of 0 to the number of pixels of the entire image Pixel number ratio of dark pixels: Ratio of the number of pixels having a luminance value of 0 to i to the number of pixels of the entire image (where i is an integer of 1 or more)
3. 3. Cumulative histogram: luminance value of histogram cumulative a% from dark side or bright side Pixel number ratio of bright pixels: Ratio of the number of pixels having a luminance value of i to 255 with respect to the number of pixels of the entire image (where i is an integer of 1 or more)
5. Standard deviation: Standard deviation of luminance value (in the case of JPEG image, standard deviation of DC component of DCT in 8 × 8 pixel block)

C-2. Modification 2:
In the embodiment described above, the image data recorded on the memory card 150a is the subject of exposure discrimination, but a digital camera or the like is connected to the USB interface unit 160, and the image data recorded on the digital camera is targeted. Alternatively, the image data read by the scanner unit 140 may be the target.

C-3. Modification 3:
In the second embodiment described above, the average brightness value Av and the maximum average brightness value AvBmax are calculated and exposure determination is performed using the threshold function formula shown in formula (2). Thus, exposure determination may be performed using a lookup table.

  That is, a look-up table is prepared in advance, in which the luminance average value Av and the maximum luminance average value AvBmax are input, and the determination result is output, and the calculated luminance average value Av and maximum luminance average value AvBmax are looked up. By inputting into the table, a discrimination result corresponding to the combination of the values is obtained from the lookup table.

C-4. Modification 4:
In the above-described embodiment, the case where the present invention is applied at the time of performing “automatic printing” has been described as an example. However, for example, the present invention may be applied at the time of performing “assist printing”. That is, in “automatic printing”, an image that is determined to be an image with insufficient exposure as a result of exposure determination is not subjected to printing and printing is not executed, whereas in “assist printing”, for example, printing is performed. Prior to this, only the image whose exposure is determined to be an appropriate image by the exposure determination is displayed as a print candidate on the liquid crystal display 170 to ask for the user's permission. Alternatively, the result of exposure determination may be displayed to indicate which image is suitable for printing.

C-5. Modification 5:
In the above-described embodiment, as the image exposure determination, it is determined whether the exposure is an appropriate image or an underexposure image. However, the exposure is an appropriate image or the exposure is excessive. It is also possible to determine whether the image is a processed image. For example, it is easily realized by performing the same exposure determination process after inverting the luminance value of each pixel itself (that is, replacing luminance value 0 with luminance value 255 and luminance value 255 with luminance value 0). can do.

C-6. Modification 6:
In the above-described embodiment, the maximum brightness value Bmax for each block is used in the exposure determination process, but the present invention is not limited to this. That is, instead of the maximum luminance value, a value according to it may be used. For example, the nth largest value among the luminance values of the pixels belonging to the block may be used. Alternatively, the histogram cumulative m% value may be used from the larger side. Further, the brightness can be used instead of the luminance value.

C-7. Modification 7:
In the above-described embodiments, the range that the luminance value of the pixel can take is 0 to 255, but the present invention is not limited to this, and may be a wider range or a narrow range. There may be.

C-8. Modification 8:
In the above-described embodiments, the case where the exposure determination apparatus of the present invention is applied to a multifunction peripheral has been described. However, the exposure determination apparatus may be applied to various devices such as a printer, a digital camera, an image viewer, a scanner, and a projector. You may make it apply to a computer.

1 is a block diagram illustrating a multi-function peripheral including an exposure determination apparatus as a first embodiment of the present invention. It is a flowchart which shows the process sequence of the exposure discrimination | determination process routine in 1st Example. It is explanatory drawing which shows the relationship between an aspect-ratio and a thumbnail image. It is explanatory drawing which shows typically a mode that the maximum luminance value Bmax was calculated | required for every block. It is explanatory drawing which showed the histogram of the luminance value, and the maximum luminance average value about each image in FIG. It is the graph which showed distribution of each image which used the luminance average value and the maximum luminance average value as parameters for a large number of images together with a threshold value for the luminance average value. It is the graph which showed distribution of each image which used the luminance average value and the maximum luminance average value as parameters for a large number of images together with a threshold value for the maximum luminance average value. It is a block diagram which shows the multifunctional machine provided with the exposure determination apparatus as 2nd Example of this invention. It is a flowchart which shows the process sequence of the exposure discrimination | determination process routine in a 2nd Example. It is the graph which showed distribution of each image which used the luminance average value and the maximum luminance average value as parameters for a large number of images together with a threshold function equation. It is explanatory drawing which shows the example of the image with appropriate exposure, and the image with insufficient exposure, respectively. It is explanatory drawing which showed the histogram of the luminance value, and the luminance average value about each image in FIG.

Explanation of symbols

10 ... MFP 20 ... MFP 100 ... Control circuit 110 ... CPU
DESCRIPTION OF SYMBOLS 111 ... Thumbnail image acquisition part 112 ... Feature-value calculation area setting part 113 ... Maximum luminance average value calculation part 114 ... Exposure discrimination part 116 ... Image correction part 118 ... Print control part 119 ... Brightness average value calculation unit 120 ... RAM
130 ... ROM
DESCRIPTION OF SYMBOLS 140 ... Scanner part 150 ... Memory card slot 150a ... Memory card 160 ... USB interface part 170 ... Liquid crystal display 180 ... Operation part 190 ... Printer part

Claims (12)

An exposure determination device for determining whether or not exposure of an image represented by image data is appropriate,
A feature amount calculation region setting unit that sets a feature amount calculation region as a region for calculation of the feature amount affected by the exposure in a thumbnail image that represents an outline of the image corresponding to the image;
Dividing the set feature amount calculation region into a plurality of blocks, and comparing the brightness index value indicating the brightness of each pixel belonging to the divided block from the thumbnail image data representing the thumbnail image in the divided block A brightness contrast reference index value that is a reference value is derived for each of the divided blocks, and an average value of the brightness contrast reference index values for each of the divided blocks is a first evaluation value that is one of the feature values. A first evaluation value derivation unit,
Based on the first evaluation value, it is determined whether or not the exposure of the thumbnail image is appropriate. When it is determined that the exposure of the thumbnail image is appropriate, the exposure of the image is also appropriate. An exposure discriminating unit for discriminating,
The feature amount calculation area setting unit includes:
In setting the feature amount calculation area in the thumbnail image, the feature amount calculation area is set by extracting from the thumbnail image the exposure-related area occupied by the image data obtained by the influence of exposure at the time of image acquisition. Yes Exposure discrimination device. The exposure determination device according to claim 1,
The feature amount calculation area setting unit includes:
An exposure determination apparatus that sets the feature amount calculation area by determining the exposure involved area according to an aspect ratio of the image represented by the image data. The exposure determination device according to claim 1,
The feature amount calculation area setting unit includes:
An exposure determination device that scans the thumbnail image, determines the exposure-related region according to a transition state of the thumbnail image data, and sets the feature amount calculation region. An exposure determination apparatus according to any one of claims 1 to 3,
The exposure determination unit determines that the exposure of the thumbnail image is appropriate when the first evaluation value exceeds a first threshold value, and that the exposure of the image is also appropriate. An exposure determination apparatus according to any one of claims 1 to 3,
A second value for deriving an average value of the brightness index values of the feature quantity calculation area as a second evaluation value as one of the feature quantities based on the thumbnail image data belonging to the set feature quantity calculation area. Evaluation value deriving unit
The exposure determination unit
When it is determined whether or not the thumbnail image is properly exposed based on a threshold function equation having the first and second evaluation values as variables, and when it is determined that the thumbnail image is appropriately exposed An exposure discrimination device that discriminates that the exposure of the image is also appropriate. The exposure determination device according to claim 5,
The average value AvRmax of the maximum luminance value derived for each of the divided blocks from the luminance value of each pixel belonging to the divided block is the average value of the brightness contrast reference index value that is the first evaluation value. The average value of the brightness index values as the second evaluation value is the average value Av of the luminance values derived from the luminance values of the pixels belonging to the set feature amount calculation area, and the constants are a and b. (Where a and b are positive numbers), the threshold function equation is
AvRmax> −a · Av + b
And
An exposure discriminating apparatus that discriminates that the exposure of the thumbnail image is appropriate when the threshold function equation is satisfied, and that the exposure of the thumbnail image is appropriate. The exposure determination device according to claim 6,
When the image is a JPEG image compressed by JPEG (Joint Photographic Experts Group), the average value Av of the luminance value of each pixel is a discrete cosine transform obtained for each 8 × 8 pixel block of the JPEG image ( An exposure discriminating apparatus that calculates the average value of DC components of DCT (discrete cosine transform). An exposure determination method for determining whether or not exposure of an image represented by image data is appropriate,
(A) a step of setting a feature amount calculation region as a region for calculating a feature amount affected by exposure in a thumbnail image representing an outline of the image corresponding to the image;
(B) A brightness index indicating the brightness of each pixel belonging to the divided block from the thumbnail image data representing the thumbnail image in the divided block, by dividing the set feature amount calculation region into a plurality of blocks. A brightness contrast reference index value that is a contrast reference value of values is derived for each of the divided blocks, and an average value of the brightness contrast reference index values for each of the divided blocks is one of the feature quantities. (C) based on the first evaluation value, it is determined whether or not the exposure of the thumbnail image is appropriate, and when it is determined that the exposure of the thumbnail image is appropriate, A step of determining that the exposure of the image is also appropriate,
In the step (a) of setting the feature amount calculation area,
In setting the feature amount calculation region in the thumbnail image, the feature amount calculation region is set by extracting from the thumbnail image an exposure-related region occupied by the image data obtained by the influence of exposure at the time of image acquisition. Yes Exposure discrimination method. The exposure determination method according to claim 8,
In the step (a) in which the average value of the brightness contrast reference index value is set as a first evaluation value that is one of the feature amounts,
Based on the thumbnail image data belonging to the set feature quantity calculation area in addition to the first evaluation value, an average value of the brightness index values in the feature quantity calculation area is one of the feature quantities. Derived as the second evaluation value,
In the step (C) of determining the appropriateness of the exposure,
When it is determined whether or not the thumbnail image is properly exposed based on a threshold function equation having the first and second evaluation values as variables, and when it is determined that the thumbnail image is appropriately exposed An exposure determination method for determining that the exposure of the image is also appropriate. A computer program for determining whether exposure of an image represented by image data is appropriate,
(A) a procedure for setting a feature quantity calculation region as a target area for calculating a feature quantity affected by exposure in a thumbnail image representing an outline of the image corresponding to the image;
(B) A brightness index indicating the brightness of each pixel belonging to the divided block from the thumbnail image data representing the thumbnail image in the divided block, by dividing the set feature amount calculation region into a plurality of blocks. A brightness contrast reference index value that is a contrast reference value of values is derived for each of the divided blocks, and an average value of the brightness contrast reference index values for each of the divided blocks is one of the feature quantities. (C) Based on the first evaluation value, it is determined whether or not the exposure of the thumbnail image is appropriate, and when it is determined that the exposure of the thumbnail image is appropriate, And causing the computer to execute a procedure for determining that the exposure of the image is also appropriate,
In the procedure (a) for setting the feature amount calculation area,
In setting the feature amount calculation region in the thumbnail image, the feature amount calculation region is set by extracting from the thumbnail image an exposure-related region occupied by the image data obtained by the influence of exposure at the time of image acquisition. A computer program for causing a computer to execute the procedure to be executed. A computer program according to claim 10,
In the procedure (a) in which the average value of the brightness contrast reference index value is the first evaluation value that is one of the feature amounts,
Based on the thumbnail image data belonging to the set feature quantity calculation area in addition to the first evaluation value, an average value of the brightness index values in the feature quantity calculation area is one of the feature quantities. Causing the computer to execute a procedure derived as the second evaluation value;
In the procedure (C) for determining the appropriateness of exposure,
When it is determined whether or not the thumbnail image is properly exposed based on a threshold function equation having the first and second evaluation values as variables, and when it is determined that the thumbnail image is appropriately exposed A computer program for causing a computer to execute a procedure for determining that the exposure of the image is also appropriate.   The computer-readable recording medium which recorded the computer program of Claim 10 or Claim 11.

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