JP2010074244A - Imaging apparatus, image processing method and image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To add shading to an image without changing an optical system. <P>SOLUTION: An imaging element 102 obtains image data by photoelectrically converting object light received through a photographing lens 1,010. A white balance correction part 1071 performs white balance correction to the image data. A shading processing part 118 performs the processing of adding shading emphasized more than optical characteristics of the photographing lens 1,010 is performed to the image data to which the white balance correction is performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for adding shading to an image.

  In a digital camera, shading may occur in which a peripheral portion of a photographed image becomes darker than a central portion due to characteristics of an optical system such as a lens used at the time of photographing. Some recent digital cameras, like Patent Document 1, have a function that corrects shading and corrects shading, and a lens that suppresses shading by improving the optical system. There is. When such a digital camera is used, it is possible to take an image that does not seem to show that shading has occurred.

On the other hand, the shading also produces an effect that gives the image a three-dimensional effect and an effect that emphasizes the main subject. For this reason, even when a similar subject is photographed, an image with shading may give a viewer an impression different from that of an image without shading.
JP 2005-277618 A

  In general, shading is caused by characteristics of an optical system such as a lens. Therefore, in a digital camera having an optical system that does not generate much shading, an image that does not generate much shading can be taken. However, in order to generate shading in order to capture an impressive image, it has been necessary to change the optical system, such as placing a filter in front of the lens at the time of shooting.

  An object of the present invention is to add shading to a captured image without changing the optical system.

  An imaging apparatus according to an aspect of the present invention includes an imaging unit that photoelectrically converts subject light received by an imaging element through a photographic lens, and a white balance correction unit that performs white balance correction on image data obtained from the imaging unit. The image data subjected to the white balance correction is separated into luminance component data and color component data, and the photographing of the luminance component data separated by the data separation unit And a shading processing unit that adds shading more emphasized than the optical characteristics of the lens.

  An image processing method according to another aspect of the present invention includes a step of performing white balance correction on image data obtained by photoelectrically converting subject light received by an image sensor through a photographing lens, and the white balance correction includes: Separating the performed image data into luminance component data and color component data, and adding shading that is more emphasized than the optical characteristics of the photographing lens to the separated luminance component data And.

  An image processing program according to still another aspect of the present invention includes a step of performing white balance correction on image data obtained by photoelectrically converting subject light received by an image sensor through a photographing lens, and the white balance correction Separating the image data that has been subjected to luminance component data and color component data, and adding shading that is more emphasized than the optical characteristics of the photographing lens to the separated luminance component data Is a program for causing a computer to execute steps.

  According to the present invention, it is possible to add shading to a captured image without changing the optical system.

-First embodiment-
FIG. 1 is a block diagram illustrating a configuration of a digital still camera that is an imaging apparatus according to the first embodiment. The digital still camera shown in FIG. 1 includes a camera body 1 and an interchangeable lens 2.

  The interchangeable lens 2 includes a lens 1010, a flash memory 1011, a microcomputer 1012, a driver 1013, and a diaphragm 1014. The interchangeable lens 2 is communicably connected to the camera body 1 via the I / F 999.

  The camera body 1 includes a mechanical shutter 101, an image sensor 102, an analog processing unit 103, an analog / digital conversion unit 104 (hereinafter referred to as A / D conversion unit 104), a bus 105, an SDRAM 106, and an image processing unit 107. An AE processing unit 108, an AF processing unit 109, a JPEG processing unit 110, a memory interface 111 (hereinafter referred to as a memory I / F 111), a recording medium 112, an LCD driver 113, an LCD 114, and a microcomputer 115. , An operation unit 116, a flash memory 117, and a shading processing unit 118.

  The lens 1010 focuses the optical image of the subject on the image sensor 102. The lens 1010 may be a single focus lens or a zoom lens. The flash memory 1011 stores shading characteristic information regarding the lens 1010.

  The microcomputer 1012 is connected to the I / F 999, the flash memory 1011 and the driver 1013. The microcomputer 1012 reads and writes information stored in the flash memory 1011 and controls the driver 1013. Further, the microcomputer 1012 can communicate with the microcomputer 115 via the I / F 999, transmits shading characteristics, lens focal length information, and the like to the microcomputer 115. Receive information.

  In response to an instruction from the microcomputer 1012, the driver 1013 drives the lens 1010 to change the focal length and focus position, and drives the aperture 1014. The aperture 1014 is provided in the vicinity of the lens 1010 and adjusts the amount of light of the subject.

  The mechanical shutter 101 is driven in response to an instruction from the microcomputer 115 to control the time for exposing the subject to the image sensor 102.

  The image sensor 102 is an image sensor in which a Bayer array color filter is arranged in front of a photodiode constituting each pixel. The Bayer array has a line in which R pixels and G (Gr) pixels are alternately arranged in a horizontal direction, and a line in which G (Gb) pixels and B pixels are alternately arranged, and the two lines are further divided. It is configured by alternately arranging in the vertical direction. The imaging element 102 receives the light collected by the lens 1010 by a photodiode that constitutes a pixel and performs photoelectric conversion, and outputs the amount of light to the analog processing unit 103 as a charge amount. The image sensor 102 may be a CMOS type or a CCD type.

  The analog processing unit 103 performs waveform shaping on the electrical signal (analog image signal) read from the image sensor 102 while reducing reset noise and the like, and further increases the gain so that the target brightness is obtained. . The A / D conversion unit 104 converts the analog image signal output from the analog processing unit 103 into a digital image signal (hereinafter referred to as image data).

  A bus 105 is a transfer path for transferring various data generated in the digital camera to each unit in the digital camera. The bus 105 includes an A / D conversion unit 104, an SDRAM 106, an image processing unit 107, an AE processing unit 108, an AF processing unit 109, a JPEG processing unit 110, a memory I / F 111, an LCD driver 113, The microcomputer 115 and the shading processing unit 118 are connected.

  The image data output from the A / D conversion unit 104 is temporarily stored in the SDRAM 106 via the bus 105. The SDRAM 106 is a storage unit that temporarily stores various data such as image data obtained by the A / D conversion unit 104 and image data processed by the image processing unit 107 and the JPEG processing unit 110.

  The image processing unit 107 includes a white balance correction unit 1071 (hereinafter, WB correction unit 1071), a synchronization processing unit 1072, a color reproduction processing unit 1073, and a noise reduction processing unit 1074 (hereinafter, NR processing unit 1074). Various image processing is performed on the image data read from the SDRAM 106. The WB correction unit 1071 performs processing for correcting the white balance of the image data. The synchronization processing unit 1072 performs a process of synchronizing image data based on the Bayer array into image data including R, G, and B information per pixel. The color reproduction processing unit 1073 performs color reproduction processing that changes the color of an image, and the NR processing unit 1074 performs processing to reduce noise. The image data after the noise reduction processing is stored in the SDRAM 106.

  The shading processing unit 118 performs various image processing by the image processing unit 107, reads the image data temporarily stored in the SDRAM 106, and adds shading so that the peripheral part becomes darker than the central part of the image. Perform the process.

  The AE processing unit 108 calculates subject luminance from the image data. The data for calculating the subject brightness may be an output of a dedicated photometric sensor. The AF processing unit 109 extracts a high-frequency component signal from the image data, and acquires a focus evaluation value by AF (Auto Focus) integration processing.

  When the image data is recorded, the JPEG processing unit 110 reads the image data from the SDRAM 106, compresses the read image data according to the JPEG compression method, and temporarily stores the compressed JPEG image data in the SDRAM 106. The microcomputer 115 creates a JPEG file by adding a JPEG header necessary for constructing a JPEG file to the JPEG image data stored in the SDRAM 106, and sends the created JPEG file via the memory I / F 111. To the recording medium 112. The recording medium 112 is, for example, a recording medium including a memory card that can be attached to and detached from the camera body 1, but is not limited thereto.

  The LCD driver 113 displays an image on the LCD 114. When playing back a JPEG file recorded on the recording medium 112, the JPEG processing unit 110 reads the JPEG file recorded on the recording medium 112, performs decompression processing, and temporarily stores the decompressed image data in the SDRAM 106. Let The LCD driver 113 reads the decompressed image data from the SDRAM 106, converts the read image data into a video signal, and then outputs it to the LCD 114 to display an image.

  The microcomputer 115 having a function as a control unit comprehensively controls various sequences of the digital camera body 1. An operation unit 116 and a flash memory 117 are connected to the microcomputer 115.

  The operation unit 116 is an operation member such as a power button, a release button, and various input keys. When one of the operation members of the operation unit 116 is operated by the user, the microcomputer 115 executes various sequences according to the user's operation. The power button is an operation member for instructing power on / off of the digital camera. When the power button is pressed, the microcomputer 115 turns the digital camera on or off. The release button has a two-stage switch of a first release switch and a second release switch. When the release button is pressed halfway and the first release switch is turned on, the microcomputer 115 performs a shooting preparation sequence such as AE processing and AF processing. Further, when the release button is fully pressed and the second release switch is turned on, the microcomputer 115 performs shooting by executing a shooting sequence.

  The flash memory 117 stores various parameters necessary for the operation of the digital camera, such as a white balance correction value, a low-pass filter coefficient, a shading table that determines shading characteristics, and a manufacturing number for specifying the digital still camera. . The flash memory 117 also stores various programs executed by the microcomputer 115. The microcomputer 115 reads parameters necessary for various sequences from the flash memory 117 according to a program stored in the flash memory 117, and executes each process.

  FIG. 2 is a flowchart showing a processing flow at the time of shooting and JPEG file generation according to the first embodiment.

  In step S201, shooting is performed. The shooting is the same as the conventionally used method. When the release button is pressed halfway and the first release switch is turned on, based on the AF processing that drives a lens drive mechanism (not shown) and the subject brightness so that the subject image becomes clearest, By referring to the aperture value and shutter speed determination table stored in the flash memory 117, AE processing for calculating the aperture and shutter speed is performed. When the release button is fully pressed and the second release switch is turned on, the calculated aperture value is transmitted to the microcomputer 1012 via the I / F 999. The driver 1013 drives the aperture 1014 so that the calculated aperture value is obtained based on an instruction from the microcomputer 1012. Based on the calculated shutter speed, shooting is performed by controlling the mechanical shutter 101 to obtain image data.

  In step S202, the image data obtained in step S201 is subjected to image processing such as white balance correction processing, color conversion processing, color reproduction processing, noise reduction processing, and the like in the image processing unit 107, and is synchronized. Obtained image data is obtained.

  In step S203, it is determined whether or not shading needs to be added. This determination is performed based on the operation result of the operation unit 116 by the user. That is, the user can set in advance whether or not to add shading to the image by operating the operation unit 116, and the setting result is recorded in the flash memory 117. If it is determined that it is necessary to add shading based on the setting result regarding shading addition recorded in the flash memory 117, the process proceeds to step S204. If it is determined not to add shading, the process proceeds to step S205.

  In step S204, the shading processing unit 118 performs a process of adding shading to the image data synchronized in step S202 so that the peripheral part becomes darker than the central part of the image, and the shading is added. Create image data. Details regarding the shading addition process will be described later.

  In step S205, the LCD driver 113 is controlled to display the image data on the LCD 114. This process is a process for temporarily showing the image data recorded on the recording medium 112 to the user.

  In step S 206, the image data is JPEG compressed by the JPEG processing unit 110 to obtain JPEG image data, and a JPEG header is created and stored in the SDRAM 106. In step S207, the JPEG image data and the JPEG header are configured as one file and recorded on the recording medium 112.

  FIG. 3 is a flowchart showing the processing flow when shading is added according to the first embodiment, that is, the contents of the processing in step S204 of the flowchart shown in FIG.

  In step S301, a shading table that is stored in advance in the flash memory 117 and that determines shading characteristics is read.

  For example, as shown in FIG. 4, the shading table is obtained by sampling continuous data having characteristics such that the correction coefficient gradually decreases from 1 according to the distance from the reference point at regular intervals. The reference point is, for example, a position corresponding to the center of the optical axis in the image data, and here is the center position of the image. In FIG. 4, normalization is performed so that the distance at a position farthest from the center position of the image is 1.

  As described above, the addition of shading by the shading processing unit 118 is performed after the white balance correction processing by the WB correction unit 1071 is performed. In general, captured image data often has appropriate brightness. Therefore, it is preferable to gradually darken the peripheral portion while maintaining appropriate brightness at the center serving as the reference of the image. Therefore, the correction coefficient is set to 1 or less. The correction coefficient is set to a value that adds shading more emphasized than the optical characteristics of the taking lens 1010.

  In the shading table, when the sampling interval is increased, the data amount is reduced, but the reproducibility of characteristics as shown in FIG. 4 is deteriorated. Conversely, when the sampling interval is reduced, the reproducibility of characteristics as shown in FIG. 4 is improved, but the data amount is increased.

  Here, in order to calculate the distance from the image center, it is necessary to obtain the square root. In general, since the amount of calculation increases when the square root is obtained, the shading table may be a data table storing a correction coefficient corresponding to the square of the distance from the reference point. FIG. 5 is a diagram illustrating an example of the characteristic of the correction coefficient when the horizontal axis is the square of the distance from the reference point. However, as in FIG. 4, normalization is performed so that the distance at the position farthest from the center position of the image is 1. In this case, the shading table is obtained by sampling continuous data having characteristics such that the correction coefficient gradually decreases from 1 according to the square of the distance from the reference point at regular intervals. By using the shading table having the characteristics shown in FIG. 5, it is possible to obtain the correction coefficient at a high speed with a small amount of calculation compared to the case of using the shading table having the characteristics shown in FIG.

  In step S302, based on the shading table acquired in step S301, a correction coefficient is obtained in which the center position of the image that is the reference point is 1, and the value decreases according to the distance from the center position of the image. That is, the correction coefficient at each pixel position of the image is calculated by referring to the shading table based on the distance from the center of the image.

  At this time, based on the size information of the image data to which shading is added, the point at which the distance from the center position of the image is the maximum (the point farthest from the center position) is the correction coefficient for the farthest position in the shading table. Normalize to Generally, since the four corner positions of the image are farthest from the center position, the correction coefficients at the four corner positions are the smallest correction coefficients in the shading table. Thereby, even when the aspect ratios of the image data to be recorded are different, it is possible to calculate correction coefficients that always give the same brightness to the four corners of the image.

  Further, when the data sampling interval in the shading table is large, the correction coefficient can be changed smoothly according to the distance from the center position of the image by complementing using a complementation method such as linear interpolation.

  In step S303, a process for adding shading is performed by multiplying the value of the pixel constituting the image by the correction coefficient corresponding to the pixel position calculated in step S302.

  Here, the RGB format image data is converted into image data separated into a luminance component (for example, Y) and a color difference component (for example, Cb and Cr), and only the luminance component data is multiplied by a correction coefficient to obtain luminance. To change. For example, the image processing unit 107 converts RGB format image data into luminance component and color difference component data, and temporarily stores the converted data in the SDRAM 106. The shading processing unit 118 reads the luminance component and chrominance component data stored in the SDRAM 106 and performs a process of adding shading by multiplying only the luminance component data by a correction coefficient. When the image data is RGB format data, the luminance can be changed by multiplying all of R, G, and B by the same correction coefficient. However, according to the method of multiplying only the luminance component data by the correction coefficient, , R, G, and B are multiplied by a third as compared with the case of multiplying each of the correction coefficients by R, G, and B, so that the arithmetic processing can be speeded up.

  FIG. 6A is a diagram illustrating an example of an image before shading is added, and FIG. 6B is a diagram illustrating an example of an image to which shading is added by the shading processing unit 118. As shown in FIG. 6B, the image with shading is darker as the position is farther from the center of the image. In FIGS. 6A and 6B, the subject denoted by reference numeral 61 represents the upper body of a person schematically represented.

  As described above, according to the imaging apparatus of the first embodiment, shading that is more emphasized than the optical characteristics of the photographing lens can be added by performing image processing on the image data. In particular, since processing for adding shading is performed on image data on which white balance correction has been performed, it is possible to add shading based on image data adjusted to an appropriate brightness. On the other hand, when image processing for adding shading to image data before white balance correction is performed, coloring may occur in the image after white balance correction is performed. In addition, the white balance corrected image is separated into luminance component data and color component data, and shading is added to the separated luminance component data, thereby reducing the amount of computation when adding shading. be able to.

  In addition, since it is possible to set whether or not to add shading according to user settings, image data without shading and shading are added only by changing the settings without changing the optical system. Both image data can be created.

-Second Embodiment-
The configuration of the imaging device in the second embodiment is the same as the configuration of the imaging device in the first embodiment. In the imaging apparatus according to the second embodiment, the shooting method at the time of shooting and the processing method at the time of adding shading are different from those of the first embodiment. Since the processing method at the time of adding shading is different, the code of the shading processing unit is represented as 118A.

  FIG. 7 is a flowchart showing a processing flow when shooting and JPEG file generation according to the second embodiment. Steps that perform the same processing as in the flowchart shown in FIG. 2 are given the same step numbers, and detailed descriptions thereof are omitted.

  If it is determined in step S203 that the process of adding shading to the image data is not to be performed, the process proceeds to step S201 to perform a normal photographing process. On the other hand, if it is determined in step S203 that the process of adding shading to the image data is to be performed, the process proceeds to step S701.

  In step S701, shooting is performed. Here, first, as in step S201, when the release button is pressed halfway and the first release switch is turned on, an AF process for driving a lens driving mechanism (not shown) so that the subject image becomes clearest. AE processing for calculating the aperture and shutter speed is performed by referring to the aperture value and shutter speed determination table stored in the flash memory 117 based on the subject brightness.

  Subsequently, the calculated shutter speed is corrected so that the exposure time is, for example, a quarter. When the release button is fully pressed and the second release switch is turned on, the calculated aperture value is transmitted to the microcomputer 1012 via the I / F 999. The driver 1013 drives the aperture 1014 so that the calculated aperture value is obtained based on an instruction from the microcomputer 1012. Based on the calculated shutter speed, shooting is performed by controlling the mechanical shutter 101 to obtain image data. The difference from the processing in step S201 is that the shutter speed is changed so that the under image is taken.

  When shooting is performed in step S701, the process proceeds to step S704. In step S <b> 704, the shading processing unit 118 </ b> A reads the image data that has been captured and temporarily stored in the SDRAM 106, and performs a process of adding shading. At this time, since the image processing by the image processing unit 107 is not performed, the white balance correction is not performed. Further, as described above, since the shutter speed is reduced, processing for adding shading is performed using one or more correction coefficients.

  FIG. 8 is a diagram illustrating characteristics of the shading table used in the second embodiment. The horizontal axis is the distance from the reference point (the center position of the image), and the vertical axis is the correction coefficient. Here, as in FIGS. 4 and 5, normalization is performed so that the distance at a position farthest from the center position of the image is 1. As described above, since the exposure time is controlled to be ¼, the correction coefficient at the reference position is set to 4, and the correction coefficient at the position farthest from the reference position is set to 1.

  Based on the distance from the center of the image, the shading processor 118A calculates a correction coefficient at each position of the image by referring to a shading table having characteristics as shown in FIG. 8, and uses the calculated correction coefficient. Thus, a process for correcting the pixel value of each pixel is performed. As a result, the exposure at the reference center position is appropriate, and an image that becomes darker as the distance from the center of the image increases.

  If a shooting process is performed in step S201 or a process of adding shading to image data is performed in step S704, the process proceeds to step S202. In step S202, the image processing unit 107 performs various image processes as described above on the image data. The subsequent processing is the same as the flowchart of FIG.

  According to the imaging apparatus in the second embodiment, it is possible to add shading to image data immediately after shooting.

-Third embodiment-
The configuration of the imaging device in the third embodiment is the same as the configuration of the imaging device in the first embodiment. In the imaging apparatus according to the third embodiment, the characteristics of shading added to an image are changed according to the focal length at the time of shooting. In addition, since the processing method at the time of shading addition differs, the code | symbol of a shading process part is represented as 118B.

  FIG. 9 is a flowchart showing a processing flow when shooting and JPEG file generation according to the third embodiment. Steps that perform the same processing as in the flowchart shown in FIG. 2 are given the same step numbers, and detailed descriptions thereof are omitted. What is different from the flowchart shown in FIG. 2 is a process in step S904 in which shading is added to image data that has been subjected to image processing. Details of the processing in step S904 will be described using the flowchart shown in FIG.

  FIG. 10 is a flowchart showing a processing flow when shading is added in the third embodiment, that is, a processing flow performed by the shading processing unit 118B. Steps that perform the same processing as in the flowchart shown in FIG. 3 are given the same step numbers, and detailed descriptions thereof are omitted.

  In step S <b> 1001, the focal length of the lens at the time of shooting is acquired from the microcomputer 1012 via the I / F 999 and the microcomputer 115.

  In step S1002, the shading characteristic for the focal length closest to the focal length acquired in step S1001 is acquired from the shading characteristics for the focal length previously stored in the flash memory 1011 via the I / F 999 and the microcomputer 115. To do.

  FIG. 11 is a diagram illustrating an example of shading characteristics according to different focal lengths of the lens 1010. The horizontal axis is the distance from the reference point (the center position of the image), and the vertical axis is the light amount ratio when the light amount at the reference point is 1. Here, as in FIG. 4 and the like, normalization is performed so that the distance at the position farthest from the center position of the image is 1.

  Generally, the shorter the focal length, the greater the influence of shading. That is, as shown in FIG. 11, if the distance from the center position of the image that is the reference point is the same, the light amount ratio becomes smaller as the focal length becomes shorter, and the light amount ratio becomes larger as the focal length becomes longer. In FIG. 11, only the shading characteristics corresponding to the three focal lengths of the longest focal point, the intermediate focal point, and the shortest focal point are shown, but the number of shading characteristic data stored in the flash memory 1011 is 4 according to different focal lengths. It may be more than one.

  If the shading characteristic for the focal length that matches the focal length acquired in step S1001 is not stored in the flash memory 1011, the interpolation method such as linear interpolation is used to determine the focal length at the time of shooting. The shading characteristics may be calculated.

  In step S1003, a correction coefficient is calculated. Using the reference position as the optical axis center in the image data (generally, the image center), the correction coefficient for each pixel of the image data using the distance from the reference position and the shading characteristics acquired in step S1002 Is calculated. Here, at a certain point on the image, the distance from the center position of the reference image is calculated, and the light quantity ratio corresponding to the distance is obtained from the shading characteristics. A value obtained by squaring the light amount ratio is set as a correction coefficient at that point.

  The captured image data is in a state where shading is applied due to the characteristics of shading at the focal length when the lens 1010 is captured, but by adding shading using a correction coefficient squared, the image of the lens 1010 is captured. Shading corresponding to the cube of the characteristic of shading at the focal length at that time is added.

  Note that the light amount ratio corresponding to the focal length of the lens may be used as it is as a correction coefficient. A table in which the focal length of the lens is associated with the correction coefficient may be prepared and used in advance.

  FIG. 12A shows an example of an image before shading is added, and FIGS. 12B and 12C show an example of an image to which shading is added by the shading processing unit 118B. FIG. However, FIG. 12B is an example in which shading is added on the short focus side, and FIG. 12C is an example in which shading is added on the long focus side. As described above, if the distance from the center position of the image that is the reference point is the same, the shorter the focal length, the smaller the light amount ratio, and the smaller the correction coefficient. That is, the effect of adding shading is more visually understandable when the focal length is short (see FIG. 12B) than when the focal length is long (see FIG. 12C).

  As described above, according to the imaging apparatus of the third embodiment, it is possible to add shading to captured image data using the shading characteristics of the lens used at the focal length at the time of shooting. Therefore, the shading difference due to the lens and the focal length is reflected in the amount of shading, so that more natural shading can be added.

-Fourth Embodiment-
In the imaging device according to the fourth embodiment, when trimming is performed to cut out part of an image that has undergone shading addition processing, processing for adding appropriate shading is performed again on the trimmed image. .

  FIG. 13 is a block diagram illustrating a configuration of a digital still camera that is an imaging apparatus according to the fourth embodiment. A trimming processing unit 120 is added to the configuration illustrated in FIG. The trimming processing unit 120 performs trimming processing on the image data to which shading is added by the shading processing unit 118 according to the operation of the operation unit 116 by the user.

  FIG. 14 is a flowchart showing a processing flow when shooting and JPEG file generation according to the fourth embodiment. Steps that perform the same processing as in the flowchart shown in FIG. 2 are given the same step numbers, and detailed descriptions thereof are omitted. The difference from the flowchart shown in FIG. 2 is that the process of step S1301 is added after the process of step S204 for adding shading to the image data, and step S1302 for recording the image data on the recording medium 112. It is processing of.

In step S1301, an image formed by multiplying the correction coefficient calculated when performing the shading addition process in step S204 by a value 255 for displaying with an 8-bit luminance value and disposing the image at a position corresponding to each pixel. create. Then, an image obtained by reducing the created image to, for example, one tenth size is set as a correction coefficient image. FIG. 15 is a diagram illustrating an example of a correction coefficient image created based on the correction coefficient.
In step S1302, if shading is added in the determination in step S203, the JPEG image data, JPEG header, and correction coefficient image are combined into one file. If no shading is added, the JPEG image data and JPEG header are combined into one file. Configured and recorded on the recording medium 112.

  FIG. 16 is a flowchart showing a flow in a trimming process performed by aspect conversion or the like based on an already recorded JPEG file. Note that steps that perform the same processes as those in the flowchart shown in FIG. 14 are given the same step numbers, and detailed descriptions thereof are omitted.

  In step S1501, a JPEG file to be trimmed recorded on the recording medium 112 is selected, read from the recording medium 112, necessary data such as size information is read from the JPEG header, and JPEG image data is converted into a JPEG processing unit. The image data is obtained by decompressing at 110. Here, for example, a list of JPEG files recorded on the recording medium 112 is displayed on the LCD 114, and the target JPEG file is determined by operating the operation unit 116 by the user. FIG. 17A shows an example of image data to be trimmed, and the aspect ratio of the image is, for example, 4: 3.

  In step S1502, it is determined whether or not a correction coefficient image exists in the JPEG file, that is, whether or not shading addition processing has been performed in the processing of the flowchart shown in FIG. If it is determined that there is a correction coefficient image, the process proceeds to step S1503. If it is determined that there is no correction coefficient image, the process proceeds to step S1505.

  In step S1503, the correction coefficient image data in the JPEG file read in step S1501 is enlarged so as to have the same size as the image data to obtain a correction coefficient. For example, if the size of the correction coefficient image is reduced to 1/10 in step S1301 of the flowchart shown in FIG. 14, it is enlarged 10 times. At this time, it is desirable to use a complementing method such as linear complementing as necessary. FIG. 17B is a diagram showing a correction coefficient image enlarged to have the same size as the image data.

  In step S1504, shading of image data is removed. Shading can be removed by dividing the value of each pixel by the correction coefficient obtained in step S1503 corresponding to each pixel of the image data. FIG. 17C shows an image obtained by removing shading from the image shown in FIG.

  In step S1505, the trimming processing unit 120 performs trimming processing. This process is a general process conventionally performed, and the outline is a process in which unnecessary portions in image data are deleted and only necessary portions are left. FIG. 17D shows an image that has been subjected to trimming based on the image shown in FIG.

  The processing after step S203 is the same as the flowchart shown in FIG. In step S204, processing for adding shading to the trimmed image data is performed. The processing method for adding shading is the same as the processing method for adding shading to image data before trimming. FIG. 17E shows an image obtained by adding shading to the trimmed image shown in FIG.

  In step S1301, a correction coefficient image is created. FIG. 17F shows the created correction coefficient image.

  FIG. 17G shows an image obtained by performing trimming by cutting out the central portion of the image into a square without removing shading from the image shown in FIG. Compared with the image shown in FIG. 17G in which only the trimming is performed from the image with shading, the image shown in FIG. 17E in which shading is added to the trimmed image has an effect of shading. It appears clearly.

  In step S204 in FIG. 16, the correction coefficient is calculated using a shading table stored in advance in the flash memory 117. As described in the third embodiment, the focal length of the lens 1010 at the time of shooting is calculated. The correction coefficient may be calculated using the shading characteristics in FIG.

  As described above, according to the imaging device of the fourth embodiment, when trimming processing is performed on image data to which shading has been added, before trimming is performed on image data to which shading has been added. A shading addition process different from the performed shading addition process is performed. In particular, after shading is removed from the image data with shading added, shading is added again to the trimmed image data, so appropriate shading is added according to the size of the trimmed image data. can do.

  Further, since image data to which shading is added and the correction coefficient used when performing the process for adding shading are recorded in association with each other, appropriate shading can be added and removed during trimming.

-Fifth embodiment-
The configuration of the imaging device in the fifth embodiment is the same as the configuration of the imaging device in the fourth embodiment. In the imaging device according to the fifth embodiment, when trimming is performed to cut out a part of the image subjected to the shading addition process, the trimming is performed by a method different from the method performed by the imaging device according to the fourth embodiment. The process of adding an appropriate shading is performed again on the obtained image. The processing flow at the time of shooting and JPEG file generation is the same as the processing flow of the flowchart shown in FIG.

  FIG. 18 is a flowchart illustrating a processing flow of trimming processing according to the fifth embodiment. Note that steps that perform the same processes as those in the flowcharts shown in FIGS. 3, 14, and 16 are assigned the same step numbers, and detailed descriptions thereof are omitted.

  In step S1701, which proceeds after the determination in step S1502 is denied, a correction coefficient having the same size as the image data and all 1 is created.

  In step S1702, which proceeds after the determination in step S203 is affirmed, the shading table is read from the flash memory 117 in the same manner as in step S301.

  In step S1703, a correction coefficient corresponding to the size of the trimmed image is calculated based on the shading table read in step S1702. The correction coefficient calculation method is the same as the correction coefficient calculation method in step S302 of the flowchart shown in FIG. Then, the correction coefficient obtained in the same manner as in step S302 is divided by the correction coefficient already obtained in step S1701 or step S1503. As a result, even if shading is added to the image to be trimmed, a correction coefficient comprising a difference between the shading characteristics and the shading characteristics to be added to the trimmed image can be calculated.

  The difference between the processing method of the imaging device in the fourth embodiment and the processing method of the imaging device in the fifth embodiment will be briefly summarized. In the imaging apparatus according to the fourth embodiment, the shading is removed by dividing the value of each pixel of the image with the shading by the correction coefficient used when the shading is added to the image, and then the trimmed image A process for adding shading was performed using a correction coefficient corresponding to the size of. On the other hand, in the imaging apparatus according to the fifth embodiment, the correction coefficient obtained when the shading is added to the image is divided by the correction coefficient corresponding to the size of the trimmed image, and the correction coefficient obtained by the division is obtained. Is used to further add shading to the image with the shading added.

  In step S1702 and step S1703 in FIG. 18, the correction coefficient is calculated using the shading table stored in advance in the flash memory 117. However, as described in the third embodiment, the lens 1010 is photographed. The correction coefficient may be calculated using the shading characteristic at the focal length at the time.

  As described above, according to the imaging device of the fifth embodiment, when trimming processing is performed on image data to which shading has been added, before trimming is performed on image data on which trimming processing has been performed. A shading addition process that is different from the shading addition process performed in step 1 is performed. In particular, the first correction coefficient according to the size of the image data before the trimming process is calculated, and the second correction coefficient according to the size of the image data after the trimming process is calculated, A process of adding shading to the image data after the trimming process is performed based on the calculated first correction coefficient and the second correction coefficient and the image data after the trimming process is performed. Do. Accordingly, it is possible to add appropriate shading according to the size of the trimmed image data without performing shading removal processing from the image data to which shading has been added.

-Sixth Embodiment-
The configuration of the imaging device in the sixth embodiment is the same as the configuration of the imaging device in the first embodiment. In the imaging apparatus according to the sixth embodiment, the correction coefficient used when adding shading is different. The processing flow at the time of shooting and JPEG file generation is the same as the processing flow of the flowchart shown in FIG. The processing flow when adding shading is the same as the processing flow of the flowchart shown in FIG. 3, but the correction coefficient calculation processing in step S302 is different. A method for calculating the correction coefficient will be described in detail below.

  In the first embodiment, a shading table in which a distance from a reference point (the center position of an image) is associated with a correction coefficient is prepared in advance, and the shading table is referred to based on the distance from the reference point. The correction factor was calculated. In the present embodiment, for example, shading table values for distances in the horizontal direction (x direction) and vertical direction (y direction) from the reference point on the image are obtained, and the product of the obtained values is used as the correction coefficient. At this time, normalization is performed so that the maximum distance in each direction corresponds to the value of the maximum distance in the shading table, and a correction coefficient is obtained. As a result, shading that is not concentric can be added.

  Two types of shading tables are prepared in advance: a shading table that defines a correction coefficient according to the distance in the horizontal direction from the reference point, and a shading table that defines a correction coefficient according to the distance in the vertical direction from the reference point. You may do it.

  FIG. 19A is a diagram illustrating an example of shading added using concentric correction coefficients having the same correction coefficient when the distance from the reference point is the same. FIG. 19B shows a product obtained by multiplying the horizontal correction coefficient obtained in accordance with the horizontal distance from the reference point and the vertical correction coefficient obtained in accordance with the vertical distance from the reference point. It is a figure which shows an example of the shading added using the correction coefficient obtained.

  It is also possible to use a shading table in which all correction coefficients corresponding to the distance in the horizontal direction or the vertical direction from the reference point are set to 1. FIG. 19C is a diagram illustrating an example of shading obtained when all correction coefficients corresponding to the distance in the horizontal direction from the reference point are set to 1.

  As described in the third embodiment, a shading table used for calculating the correction coefficient may be prepared and used according to the shading characteristics at the focal length when the lens 1010 is photographed.

-Seventh embodiment-
The configuration of the imaging device in the seventh embodiment is the same as the configuration of the imaging device in the first embodiment. In the imaging apparatus according to the seventh embodiment, the correction coefficient used when adding shading is different. The processing flow at the time of shooting and JPEG file generation is the same as the processing flow of the flowchart shown in FIG. The processing flow when adding shading is the same as the processing flow of the flowchart shown in FIG. 3, but the correction coefficient calculation processing in step S302 is different. A method for calculating the correction coefficient will be described in detail below.

  In the first embodiment, the correction coefficient is calculated according to the distance from the reference point. In the present embodiment, the correction coefficient is calculated by enlarging / reducing the correction coefficient calculated by the same method as in the first embodiment in the vertical and horizontal directions according to the aspect ratio of the trimmed image.

  FIG. 20A illustrates a correction coefficient obtained by enlarging or reducing a concentric correction coefficient for a 4: 3 image so as to be a correction coefficient for a 16: 9 image by the imaging apparatus according to the present embodiment. An image with shading is shown. By using an enlarged / reduced correction coefficient to correspond to a 16: 9 image, more appropriate shading can be added according to the size of the image.

  On the other hand, FIG. 20B shows the aspect of 16: 9 without changing the width after the processing for adding shading to the image data having the aspect ratio of 4: 3 is performed by the imaging apparatus according to the first embodiment. An image trimmed so as to have a ratio is shown.

  Although a plurality of embodiments have been described above, the calculated correction coefficient may be stored in the SDRAM 106, the flash memory 117, or the like and used in the second and subsequent processes. Further, when correction coefficients for image data in which the height and width of image data to which shading is added are exchanged are stored in the SDRAM 106, the flash memory 117, or the like, the correction coefficient is rotated 90 degrees right or left. The corrected coefficient may be used.

  In the first to seventh embodiments described above, the processing for adding shading is performed on the basis of the position corresponding to the optical axis center in the image data, that is, the center position of the image. However, the reference for performing the shading addition processing is used. The position can be any position on the image.

  In the description of each embodiment described above, a digital still camera has been described as an example. However, a computer may be configured to execute a program for realizing the processing described in each embodiment. That is, in a computer having a main storage device such as a CPU and a RAM, and a computer-readable storage medium storing a program for realizing all or part of the processing described in each embodiment, the CPU stores the above storage medium. Is read out, and information processing / arithmetic processing is executed to realize the same processing as that of the above-described imaging apparatus.

  Here, the computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, and the like. Further, the above-described program may be distributed to a computer via a communication line, and the computer that has received the distribution may execute the program.

  The present invention is not limited to the first to seventh embodiments described above, and various modifications and applications are possible without departing from the scope of the present invention.

It is a block diagram which shows the structure of the digital still camera which is an imaging device which concerns on 1st Embodiment. It is a flowchart which shows the process flow at the time of imaging | photography and JPEG file generation concerning 1st Embodiment. It is a flowchart which shows the processing flow at the time of the shading addition which concerns on 1st Embodiment. It is a figure which shows an example of the characteristic of the correction coefficient according to the distance from a reference point. It is a figure which shows an example of the characteristic of the correction coefficient according to the square of the distance from a reference point. FIG. 6A is a diagram illustrating an example of an image before shading is added, and FIG. 6B is a diagram illustrating an example of an image to which shading is added. It is a flowchart which shows the processing flow at the time of imaging | photography and JPEG file generation in 2nd Embodiment. It is a figure which shows the characteristic of the shading table used in 2nd Embodiment. It is a flowchart which shows the processing flow at the time of imaging | photography and JPEG file generation in 3rd Embodiment. It is a flowchart which shows the processing flow at the time of the shading addition in 3rd Embodiment. It is a figure which shows an example of the shading characteristic according to the focal distance from which a lens differs. 12A shows an example of an image before adding shading, FIG. 12B shows an example of an image added with shading on the short focus side, and FIG. It is a figure which shows an example of the image to which the shading was added by the long focus side. It is a block diagram which shows the structure of the digital still camera which is an imaging device which concerns on 4th Embodiment. It is a flowchart which shows the processing flow at the time of imaging | photography and JPEG file generation in 4th Embodiment. It is a figure which shows an example of a correction coefficient image. It is a flowchart which shows the flow in the trimming process performed by aspect conversion etc. based on the JPEG file already recorded. FIG. 17A shows an example of image data to be trimmed, FIG. 17B shows a correction coefficient image enlarged to the same size as the image data, and FIG. FIG. 17A is a diagram showing an image obtained by removing shading from the image shown in FIG. 17A. FIG. 17D is a diagram in which the center portion of the image is trimmed into a square based on the image shown in FIG. FIG. 17 (e) is a diagram showing an image performed, FIG. 17 (e) is a diagram showing an image obtained by adding shading to the trimmed image shown in FIG. 17 (d), and FIG. 17 (f) is created. FIG. 17G is a diagram showing a correction coefficient image, and FIG. 17G is a diagram showing an image that has been trimmed by cutting out the central portion of the image into a square without removing shading from the image shown in FIG. . It is a flowchart which shows the processing flow of the trimming process in 5th Embodiment. FIG. 19A is a diagram showing an example of shading added using concentric correction coefficients, and FIG. 19B is added using correction coefficients obtained according to the horizontal distance and the vertical distance. FIG. 19C is a diagram showing an example of shading, and FIG. 19C is a diagram showing an example of shading obtained when all the correction coefficients corresponding to the distance in the horizontal direction from the reference point are set to 1. FIG. 20A is a diagram showing an image obtained by adding shading using a concentric correction coefficient for a 4: 3 image and a correction coefficient enlarged or reduced so as to be a correction coefficient for a 16: 9 image. FIG. 20B shows an image trimmed so as to have an aspect ratio of 16: 9 without changing the width after the process of adding shading to the image data having the aspect ratio of 4: 3 is performed. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Camera body, 2 ... Interchangeable lens, 101 ... Mechanical shutter, 102 ... Image sensor, 103 ... Analog processing part, 104 ... Analog / digital conversion part, 105 ... Bus, 106 ... SDRAM, 107 ... Image processing part, 108 AE processing unit, 109 AF processing unit, 110 JPEG processing unit, 111 memory interface, 112 recording medium, 113 LCD driver, 114 LCD, 115 microcomputer, 116 operation unit, 117 flash memory 118 ... Shading processing unit 120 ... Trimming processing unit 999 ... I / F 1010 ... Lens 1011 ... Flash memory 1012 ... Microcomputer 1013 ... Driver 1014 ... Aperture 1071 ... White balance correction unit 1072 ... Synchronization processing unit, 1073... Color reproduction processing unit, 1074 ... Noise reduction processing unit

Claims (12)

An imaging unit that photoelectrically converts subject light received by the imaging element through the imaging lens;
A white balance correction unit that performs white balance correction on image data obtained from the imaging unit;
A data separation unit for separating the image data subjected to the white balance correction into luminance component data and color component data;
A shading processing unit that adds shading emphasized over the optical characteristics of the photographing lens to the data of the luminance component separated by the data separation unit;
An imaging apparatus comprising: A correction coefficient calculation unit that calculates a correction coefficient used in the process of adding the shading as a value of 1 or less according to the position of each pixel of the image data;
The shading processing unit obtains image data to which shading is added by multiplying the luminance component of the pixel value at the pixel position by the correction coefficient of 1 or less for each pixel position of the image data. The imaging device according to claim 1.   The imaging apparatus according to claim 2, wherein the correction coefficient calculation unit sets a value of a correction coefficient at each position on the image according to a distance from an arbitrary reference position on the image.   The correction coefficient calculation unit calculates the value of the correction coefficient at each position on the image, the distance in a first direction from an arbitrary reference position on the image, and the distance in a second direction different from the first direction. The imaging apparatus according to claim 2, wherein the imaging apparatus is set in accordance with. A trimming processing unit for performing trimming processing on the image data;
When the trimming process is performed on the image data to which the shading is added, the shading processing unit adds the shading performed before the trimming is performed on the image data to which the shading is added. The imaging apparatus according to claim 1, wherein a shading addition process different from the process is performed. A correction coefficient calculation unit for calculating a correction coefficient of 1 or less for adding the shading;
The correction coefficient calculation unit calculates a first correction coefficient according to the size of the image data before the trimming process is performed, and a second according to the size of the image data after the trimming process is performed. Calculate the correction factor for
The shading processing unit applies the image data after the trimming process is performed based on the image data after the trimming process is performed and the first correction coefficient and the second correction coefficient. The imaging apparatus according to claim 5, wherein processing for adding the shading is performed.   The shading processing unit uses the third correction coefficient obtained by dividing the second correction coefficient by the first correction coefficient to perform the shading on the image data after the trimming process is performed. The image pickup apparatus according to claim 6, wherein a process for adding the image is performed.   4. The recording apparatus according to claim 2, further comprising a recording unit that records the image data to which the shading is added and the correction coefficient used when performing the processing to add the shading in association with each other. The imaging device described in 1. A focal length acquisition unit for acquiring a focal length of the photographing lens;
The shading processing unit changes a characteristic of shading added to the image data in accordance with a focal length of the photographing lens at the time of photographing acquired by the focal length acquisition unit. The imaging device according to any one of items 8. A shading characteristic data storage unit for storing shading characteristic data according to the focal length of the photographing lens;
The shading processing unit reads out and uses shading characteristic data according to a focal length of the photographing lens at the time of photographing acquired by the focal length acquisition unit from the shading characteristic data storage unit. The imaging device described in 1. A step of performing white balance correction on image data obtained by photoelectrically converting subject light received by an image sensor through a photographing lens;
Separating the image data on which the white balance correction has been performed into luminance component data and color component data;
Adding shading emphasized over the optical characteristics of the photographing lens to the separated luminance component data;
An image processing method comprising: A step of performing white balance correction on image data obtained by photoelectrically converting subject light received by an image sensor through a photographing lens;
Separating the image data on which the white balance correction has been performed into luminance component data and color component data;
Adding shading emphasized over the optical characteristics of the photographing lens to the separated luminance component data;
An image processing program for causing a computer to execute.