JP5574015B2 - Image processing apparatus, electronic camera, and image processing program - Google Patents

Description

  The present invention relates to an image processing apparatus, an electronic camera, and an image processing program.

  2. Description of the Related Art Conventionally, a phenomenon is known in which a dark portion gradation of image data is darkened by photographing a subject having a large luminance difference. Therefore, in the invention of Patent Document 1, the tone is compressed by increasing the gain of the dark portion gradation, and the blackening of the dark portion gradation is improved.

Japanese Patent No. 2663189

  In the invention of Patent Document 1 described above, various processes for compressing gradation are performed. These processes are processes performed in addition to the normal image processing, and there is a possibility that the processing time may increase depending on the image data to be processed. Therefore, it is expected that the processing time is further shortened.

  The present invention has been made in view of the above problems, and an object of the present invention is to shorten the processing time for dark part gradation correction.

The image processing apparatus of the present invention, acquisition unit for acquiring image data and an image processing unit for performing image processing including a first gradation conversion processing on the image data acquired by the acquisition unit, the image by the image processing unit This process is performed in parallel with the process, and the image data acquired by the acquisition unit is subjected to the second gradation conversion process and the blurred image data is generated based on the image data subjected to the second gradation conversion process. and an arithmetic unit for calculating a correction value to improve the lightness of the dark area gradation of the image data to which the image processing has been performed by the image processing unit by using the blurred image data, the image processing by the image processing unit depending lightness of the dark area gradation of the image data to which the image processing has been performed by the image processing unit and the correction values calculated respectively input by the image data and the operation unit has been subjected to the correction value And a correcting unit for correcting improve.

Note that the gradation curve used in the first gradation conversion process may be different from the gradation curve used in the second gradation conversion process .

The arithmetic unit may generate the blurred image data by performing low-pass processing on the image data on which the second gradation conversion processing has been performed .

Further, the arithmetic unit, R image data based on the images data acquired by the acquisition unit, G image data, may be subjected to the second gradation conversion processing to each of the B image data.

Further, the arithmetic unit, Y image data based on the images data acquired by the acquisition unit, Cb image data may be subjected to the second gradation conversion processing to each of the Cr image data.

Further, the arithmetic unit, Y image data based on the images data acquired by the acquisition unit, Cb image data, out of the Cr image data may be subjected to the second gradation conversion processing only in the Y image data .

The calculation unit generates first image data related to brightness and second image data related to a plurality of color differences based on the image data acquired by the acquisition unit , and the first image data and the Third image data relating to brightness may be generated from the second image data, and the second gradation conversion process may be performed on the generated third image data.

  In addition, the image capturing unit that captures a subject image and generates image data, and any one of the above-described image processing apparatuses, and the acquisition unit includes an electronic camera that acquires the image data from the image capturing unit. It is effective as a specific embodiment.

  In addition, a configuration obtained by converting the configuration related to the above invention into an image processing program for realizing image processing on image data to be processed by a computer is also effective as a specific aspect of the present invention.

  According to the present invention, it is possible to shorten the processing time for dark part gradation correction.

It is a functional block diagram of the electronic camera 100 which performs the conventional gradation compression process. 3 is a functional block diagram showing details of a gradation compression processing unit 106. FIG. It is a figure explaining a low pass filter. It is a flowchart which shows the operation | movement at the time of imaging | photography of the electronic camera 100 which performs the conventional gradation compression process. It is a figure explaining the gradation curve Gm. It is a figure explaining the parameter fg of gradation compression. It is a functional block diagram of electronic camera 1 of this embodiment. 3 is a functional block diagram showing details of a low-pass calculation unit 3. FIG. It is a flowchart which shows the operation | movement at the time of imaging | photography of the electronic camera 1 of this embodiment. It is a figure explaining the gradation curves Gmcr and Gmcb. 3 is a functional block diagram showing details of a low-pass calculation unit 30. FIG. It is another flowchart which shows the operation | movement at the time of imaging | photography of the electronic camera 1 of this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, an electronic camera equipped with the image processing apparatus of the present invention will be described as an example.

  First, a conventional gradation compression process will be described for comparison.

  FIG. 1 is a diagram showing a configuration of an electronic camera 100 that performs conventional gradation compression processing. As shown in FIG. 1, an electronic camera 100 includes a photographing lens 102, an image sensor 103, an analog front end unit (hereinafter referred to as an AFE unit) 104, an image processing unit 105, and a gradation compression processing unit 106. In addition, each unit includes a compression / decompression unit 107 and a recording unit 108, and a control unit 109 that performs overall control of each unit.

  The electronic camera 100 also includes a display unit (not shown) that displays an image generated by imaging, and an operation unit (not shown) that includes a release button and a setting button. The control unit 109 includes a memory (not shown) inside, records a program for controlling each unit in advance, and detects an operation state of the operation unit.

  At the time of shooting, the control unit 109 captures a subject image via the shooting lens 102 with the image sensor 103 and generates digital image data with the AFE unit 104. The control unit 109 performs color processing and gradation conversion processing by the image processing unit 105, and then performs gradation compression processing by the gradation compression processing unit 106 to generate image data for viewing. This image data is appropriately compressed by the compression / decompression unit 107 and recorded in the recording unit 108.

  Note that the gradation compression processing unit 106 includes a low-pass calculation unit 121 and a gain addition unit 122, as shown in FIG. The low-pass calculation unit 121 performs low-pass processing using, for example, a Gaussian low-pass filter illustrated in FIG. 3 on the image data, and the gain addition unit 122 applies gain to each pixel according to the lightness of the image data subjected to low-pass processing. Is added. By such processing, it is possible to clearly reproduce a dark part that tends to be crushed normally.

  The operation at the time of shooting of the electronic camera 100 having the above-described configuration will be described with reference to the flowchart shown in FIG.

  In step S <b> 1, the control unit 109 determines whether or not the user has instructed to start shooting via an operation unit (not illustrated). If the control unit 109 determines that an instruction to start shooting is given, the process proceeds to step S2.

  In step S <b> 2, the control unit 109 controls each unit, captures a subject image with the image sensor 103 and the AFE unit 104, and generates image data.

  In step S3, the control unit 109 controls the image processing unit 105 to perform color space conversion processing on the image data generated in step S2. The color space conversion process is performed by the following equations 1 to 3.

tR [x, y] = krr · R [x, y] + krg · G [x, y] + krb · B [x, y] (Formula 1)
tG [x, y] = kgr · R [x, y] + kgg · G [x, y] + kgb · B [x, y] (Formula 2)
tB [x, y] = kbr · R [x, y] + kbg · G [x, y] + kbb · B [x, y] (Equation 3)
Note that R [x, y], G [x, y], and B [x, y] in Equations 1 to 3 indicate RGB image data, respectively, and krr, krg, and krb are predetermined coefficients. It is.

  In step S4, the control unit 109 controls the image processing unit 105 to perform gradation conversion processing on the image data subjected to the color space conversion processing in step S3. The gradation conversion processing is performed by the following equations 4 to 6.

sR [x, y] = Gm [tR [x, y]] (Formula 4)
sG [x, y] = Gm [tG [x, y]] (Formula 5)
sB [x, y] = Gm [tB [x, y]] (Expression 6)
Note that Gm in Equations 4 to 6 corresponds to, for example, the gradation curve shown in FIG.

  In step S5, the control unit 109 controls the gradation compression processing unit 106 to perform gradation compression processing on the image data subjected to the gradation conversion processing in step S4.

  First, the control unit 109 controls the low-pass calculation unit 121 to perform a low-pass calculation on the image data that has been subjected to the gradation conversion process in step S4. The low-pass calculation is performed by the following equations 7 to 11.

Y [x, y] = kr.sR [x, y] + kg.sG [x, y] + kb.sB [x, y] (Expression 7)
Cr [x, y] = kcrr · sR [x, y] + kcrg · sG [x, y] + kcrb · sB [x, y] (Equation 8)
Cb [x, y] = kcbr.sR [x, y] + kcbg.sG [x, y] + kcbb.sB [x, y] (Equation 9)
V [x, y] = ky · Y [x, y] + kcr · | Cr [x, y] | + kcb · | Cb [x, y] |

なお、式７から式９中のkr，kg，kb，kcrr，kcrg，kcrb，kcbr，kcbg，kcbbは、所定の係数である。式７から式９により、ｓＲＧＢ画像がＹＣｂＣｒ画像に変換される。また、式１０中のky，kc，kcbは、所定の係数であり、式１０により、ＹＣｂＣｒ画像からに明るさに関する画像であるＶ画像の画像データが生成される。また、式１１中のLpwは、注目画素周りのローパスフィルタであり、このローパスフィルタは、図３に示す特性を有する。そして、式１１により、Ｖ画像からローパス画像であるＬＶ画像の画像データが生成される。なお、ローパス画像は、ボケ画像の一例であり、他のローパスフィルタを用いてローパス画像を生成しても良いし、ローパス処理以外の手法を用いてボケ画像を生成しても良い。

In Expressions 7 to 9, kr, kg, kb, kcrr, kcrg, kcrb, kcbr, kcbg, and kcbb are predetermined coefficients. The sRGB image is converted into a YCbCr image by Expression 7 to Expression 9. Also, ky, kc, and kcb in Equation 10 are predetermined coefficients, and according to Equation 10, image data of a V image that is an image related to brightness is generated from a YCbCr image. Further, Lpw in Expression 11 is a low-pass filter around the target pixel, and this low-pass filter has the characteristics shown in FIG. Then, according to Expression 11, image data of an LV image that is a low-pass image is generated from the V image. The low-pass image is an example of a blurred image, and the low-pass image may be generated using another low-pass filter, or the blurred image may be generated using a method other than the low-pass processing.

  Next, the control unit 109 controls the gain adding unit 122 of the gradation compression processing unit 106 to add gain to the image data subjected to the low-pass processing. The gain is added by the following equations 12 to 14.

sRc [x, y] = sR [x, y] · fg (LV [x, y]) (Equation 12)
sGc [x, y] = sG [x, y] · fg (LV [x, y]) (Equation 13)
sBc [x, y] = sB [x, y] · fg (LV [x, y]) (Expression 14)
Note that fg in Expressions 12 to 14 is a gradation compression parameter. FIG. 6 is a diagram showing the gradation compression parameter fg. The parameter fg has a gain corresponding to the image data of the V image, as shown in FIG. The parameter fg increases as the image data of the V image is smaller (the darker the neighborhood including the processing pixel is). Conversely, the larger the image data of the V image (the brighter the neighborhood including the processing pixel), the closer the parameter fg approaches 1.
In step S6, the control unit 109 records the image data subjected to the gradation compression process in step S5 on the recording unit 108, and ends a series of processing. Note that before the image data is recorded in the recording unit 108, an image compression process (such as a JPEG compression process) may be performed as necessary via the compression / decompression unit 107.

  In contrast to the conventional gradation compression processing described above, the present embodiment performs the following processing.

  FIG. 7 is a diagram showing a configuration of the electronic camera 1 that performs the gradation compression processing of the present embodiment. As shown in FIG. 7, the electronic camera 1 according to the present embodiment is an image instead of the image processing unit 105, the gradation compression processing unit 106, and the control unit 109 of the electronic camera 100 (see FIG. 1) described in the conventional example. Each unit includes a processing unit 2, a low-pass calculation unit 3, a gain addition unit 4, and a control unit 5. Since other configurations are the same as those of the electronic camera 100 described in the conventional example, the same reference numerals are given and description thereof is omitted.

  The control unit 5 includes a memory (not shown) inside, records a program for controlling each unit in advance, and detects an operation state of the operation unit.

  At the time of shooting, the control unit 5 captures a subject image via the photographing lens 102 by the image sensor 103 and generates digital image data by the AFE unit 104. The output of the AFE unit 104 is supplied to both the image processing unit 2 and the low-pass calculation unit 3. Details of the processing will be described later.

  Note that the low-pass calculation unit 3 includes each unit of a gradation conversion processing unit 21, a V image generation unit 22, and a low-pass processing unit 23 as illustrated in FIG.

  In the electronic camera 1 having the configuration described above, the processing by the image processing unit 2 and the low-pass calculation unit 3 is performed in parallel. At the time of shooting, the image processing unit 2 performs the same processing as the steps S3 and S4 in the flowchart of FIG. 4 described in the conventional example on the output of the AFE unit 104. The operation at the time of processing in the low-pass calculation unit 3 performed in parallel with the image processing in the image processing unit 2 and the operation at the time of subsequent processing will be described with reference to the flowchart shown in FIG.

  In step S <b> 11, the control unit 5 controls the gradation conversion processing unit 21 of the low-pass calculation unit 3 to perform gradation conversion processing on the image data output from the AFE unit 104. The gradation conversion process is performed by the following equations 15 to 17.

GR [x, y] = Gm [R [x, y]] (Equation 15)
GG [x, y] = Gm [G [x, y]] (Expression 16)
GB [x, y] = Gm [B [x, y]] (Expression 17)
Note that Gm in Expressions 15 to 17 corresponds to, for example, the gradation curve shown in FIG. 5 described above. This gradation curve may be the same gradation curve as that used for the gradation conversion process (step S4 in FIG. 4) in the image processing unit 2, or may be a different gradation curve. In the present embodiment, the same gradation curve is used, and gradation conversion processing similar to the gradation conversion processing in the image processing unit 2 is performed.

  In step S12, the control unit 5 controls the V image generation unit 22 of the low-pass calculation unit 3, and based on the image data subjected to the gradation conversion process in step S11, the V image that is an image related to brightness is displayed. Generate image data. The generation of the image data of the V image is performed by the following equations 18 to 21.

Y [x, y] = kr · GR [x, y] + kg · GG [x, y] + kb · GB [x, y] (Equation 18)
Cr [x, y] = kcrr · GR [x, y] + kcrg · GG [x, y] + kcrb · GB [x, y] (Equation 19)
Cb [x, y] = kcbr · GR [x, y] + kcbg · GG [x, y] + kcbb · GB [x, y] (Equation 20)
V [x, y] = ky · Y [x, y] + kcr · | Cr [x, y] | + kcb · | Cb [x, y] |
Note that kr, kg, kb, kcrr, kcrg, kcrb, kcbr, kcbg, and kcbb in the equations 18 to 20 are predetermined coefficients. In Equation 21, ky, kc, and kcb are predetermined coefficients.

  In step S13, the control unit 5 controls the low-pass processing unit 23 of the low-pass calculation unit 3 to perform low-pass processing on the image data of the V image generated in step S12. The low-pass process is performed by the following expression 22.

なお、式２２中のLpwは、注目画素周りのローパスフィルタであり、このローパスフィルタは、上述した図３に示す特性を有する。

Note that Lpw in Expression 22 is a low-pass filter around the pixel of interest, and this low-pass filter has the characteristics shown in FIG.

  In step S <b> 14, the control unit 5 controls the gain adding unit 4 to add a gain to the image data subjected to image processing by the image processing unit 2. The gain is added by the following Expression 23 to Expression 25.

sRc [x, y] = sR [x, y] · fg (LV [x, y]) (Equation 23)
sGc [x, y] = sG [x, y] · fg (LV [x, y]) (Equation 24)
sBc [x, y] = sB [x, y] · fg (LV [x, y]) (Equation 25)
Note that fg in Expression 23 to Expression 25 is a gradation compression parameter, and has a gain corresponding to the image data of the V image, as in FIG. 6 described above.

  In step S15, the control unit 5 records the image data to which the gain is added in step S14 in the recording unit 108, and ends a series of processes. Note that before the image data is recorded in the recording unit 108, an image compression process (such as a JPEG compression process) may be performed as necessary via the compression / decompression unit 107.

  Through the series of processes described above, low-pass processing prior to gradation compression processing is executed in parallel with image processing for generating an image for viewing, and gradation is immediately obtained when the image processing is completed. A compression process can be executed. Therefore, it is possible to increase the processing speed similar to the gradation compression described in the conventional example. Therefore, the processing time can be shortened.

<Modification>
Next, a modified example of the process described using the flowchart of FIG. 9 will be described. In the example of the flowchart of FIG. 9, in step S11, gradation conversion processing (Formula 15 to Formula 17) is performed on the image data of the RGB image that is the image data output from the AFE unit 104, and in Step S12, the YCbCr image is converted. An example of generating a V image after generating (Expression 18 to Expression 20) (Expression 21) is shown. However, the processing of step S11 and step S12 may be modified as follows.

  In step S <b> 11, the control unit 5 controls the gradation conversion processing unit 21 of the low-pass calculation unit 3 to generate image data of a YCbCr image based on the image data output from the AFE unit 104. The generation of the YCbCr image is performed by the following Expressions 26 to 28.

Y [x, y] = kr.R [x, y] + kg.G [x, y] + kb.B [x, y] (Equation 26)
Cr [x, y] = kcrr · R [x, y] + kcrg · G [x, y] + kcrb · B [x, y] (Equation 27)
Cb [x, y] = kcbr · R [x, y] + kcbg · G [x, y] + kcbb · B [x, y] (Equation 28)
In Expressions 26 to 28, kr, kg, kb, kcrr, kcrg, kcrb, kcbr, kcbg, and kcbb are predetermined coefficients.

  Next, the control unit 5 controls the gradation conversion processing unit 21 of the low-pass calculation unit 3 to perform gradation conversion processing on each of the image data of the YCbCr image. The gradation conversion process is performed by the following Expressions 29 to 31.

GY [x, y] = Gmy [Y [x, y]] (Equation 29)
GCr [x, y] = Gmcr [Cr [x, y]] (Equation 30)
GCb [x, y] = Gmcb [Cb [x, y]] (Equation 31)
Note that Gmy in Expression 29 is, for example, the same gradation curve as the gradation curve Gm shown in FIG. This gradation curve may be the same gradation curve as that used for the gradation conversion process (step S4 in FIG. 4) in the image processing unit 2, or may be a different gradation curve. In the present embodiment, the same gradation curve is used, and gradation conversion processing similar to the gradation conversion processing in the image processing unit 2 is performed. Further, Gmcr and Gmcb in the expressions 30 and 31 are, for example, gradation curves shown in FIG. Gmcr and Gmcb may be the same gradation curve or different gradation curves.

  In step S12, the control unit 5 controls the V image generation unit 22 of the low-pass calculation unit 3, and based on the image data subjected to the gradation conversion process in step S11, the V image that is an image related to brightness is displayed. Generate image data. The generation of the image data of the V image is performed by the following Expression 32.

V [x, y] = ky · GY [x, y] + kcr · | GCr [x, y] | + kcb · | GCb [x, y] |
In Equation 32, ky, kc, and kcb are predetermined coefficients.

  As described above, the gradation conversion process may be performed after the YCbCr image is generated, and the V image may be generated based on the image data of the YCbCr image after the gradation conversion process. With such a configuration, low-pass processing prior to gradation compression processing is executed in parallel with image processing for generating an image for viewing, and immediately after the image processing is finished, The tone compression process can be executed. Therefore, it is possible to increase the processing speed similar to the gradation compression described in the conventional example. Therefore, the processing time can be shortened.

  In step S11, the gradation conversion process may be performed only on the image data of the Y image without performing the gradation conversion process on each of the image data of the YCbCr image. That is, in step S11, after generating the image data of the YCbCr image, the control unit 5 performs the gradation conversion process only on the image data of the Y image according to the above-described equation 29.

  In step S12, the control unit 5 determines the V image based on the image data of the Y image subjected to the gradation conversion process in step S11 and the image data of the Cr image and the Cb image not subjected to the gradation conversion process. Generate image data of an image. The generation of the image data of the V image is performed by the following Expression 33.

V [x, y] = ky · GY [x, y] + kcr · | Cr [x, y] | + kcb · | Cb [x, y] |
By adopting such a configuration, it is possible to perform the same processing as in the above-described embodiment without performing gradation conversion processing on the color difference components (Cr image and Cb image image data). Therefore, for example, it is possible to improve the lightness in an area where the dark portion is highly saturated. Therefore, the appearance color appearance can be made vivid. That is, it is possible to determine an appropriate amount of improvement in lightness according to the saturation of the dark part and the light part.

  In addition, the calculation load can be reduced as compared with the case where the gradation conversion processing is performed on each of the image data of the RGB image or each of the image data of the YCbCr image.

  Further, a configuration may be adopted in which a V image is generated first and gradation conversion processing is performed on the image data of the generated V image. In this case, a low-pass calculation unit 30 shown in FIG. 11 may be provided instead of the low-pass calculation unit 3 shown in FIGS. As illustrated in FIG. 11, the low-pass calculation unit 30 includes a V image generation unit 31, a gradation conversion processing unit 31, and a low-pass processing unit 33, and the output of the AFE unit 104 is input to the V image generation unit 31. Is done.

  Processing when the low-pass arithmetic unit 30 shown in FIG. 11 is provided will be described with reference to the flowchart of FIG.

  In step S <b> 21, the control unit 5 controls the V image generation unit 31 of the low-pass calculation unit 3 to generate image data of a V image that is an image related to brightness based on the image data output from the AFE unit 104. To do. The generation of the image data of the V image is performed by the following equations 34 to 37.

Y [x, y] = kr.R [x, y] + kg.G [x, y] + kb.B [x, y] (Formula 34)
Cr [x, y] = kcrr · R [x, y] + kcrg · G [x, y] + kcrb · B [x, y] (Formula 35)
Cb [x, y] = kcbr · R [x, y] + kcbg · G [x, y] + kcbb · B [x, y] (Equation 36)
V [x, y] = ky · Y [x, y] + kcr · | Cr [x, y] | + kcb · | Cb [x, y] |
In Expressions 34 to 36, kr, kg, kb, kcrr, kcrg, kcrb, kcbr, kcbg, and kcbb are predetermined coefficients. In Equation 37, ky, kc, and kcb are predetermined coefficients.

  In step S22, the control unit 5 controls the gradation conversion processing unit 32 of the low-pass calculation unit 30, and performs gradation conversion processing on the image data of the V image generated in step S21. The gradation conversion process is performed by the following equation 38.

GV [x, y] = Gm [V [x, y]] (Equation 38)
Note that Gm in Expression 38 corresponds to, for example, the gradation curve shown in FIG. This gradation curve may be the same gradation curve as that used for the gradation conversion process (step S4 in FIG. 4) in the image processing unit 2, or may be a different gradation curve. In the present embodiment, the same gradation curve is used, and gradation conversion processing similar to the gradation conversion processing in the image processing unit 2 is performed.

  In step S23, the control unit 5 controls the low-pass processing unit 33 of the low-pass calculation unit 30 to perform low-pass processing on the image data of the V image subjected to the gradation conversion processing in step S22. The low-pass process is performed by the following Expression 39.

なお、式３９中のLpwは、注目画素周りのローパスフィルタであり、このローパスフィルタは、上述した図３に示す特性を有する。

Note that Lpw in Equation 39 is a low-pass filter around the pixel of interest, and this low-pass filter has the characteristics shown in FIG.

  In Step S24 and Step S25, the control unit 5 performs the same processing as Step S4 and Step S5 in the flowchart of FIG. 9, and ends the series of processing.

  Through the series of processes described above, a V image can be generated in a state where gradation conversion processing has not been performed. Therefore, it is possible to determine an appropriate brightness enhancement amount that does not depend on brightness or saturation.

  In addition, the calculation load can be reduced as compared with the case where the gradation conversion processing is performed on each of the image data of the RGB image or each of the image data of the YCbCr image.

  In the present embodiment, with respect to the timing for performing gradation conversion processing prior to gradation compression processing, an example in which gradation conversion processing is performed on image data of an RGB image and gradation conversion processing is performed on image data of a YCbCr image. An example (including each YCbCr image and only the Y image) and an example in which gradation conversion processing is performed on the image data of the V image have been described. Regarding the timing of such gradation conversion processing, the gradation conversion processing may always be performed at the same timing, or the timing of gradation conversion processing may be changed as appropriate. The timing of gradation conversion processing may be determined according to a user instruction, or may be determined automatically. When determining automatically, depending on the shooting mode (for example, “Portrait Mode”, “Landscape Mode”, etc.), image contrast strength, image adjustment mode, image analysis result by scene analysis or face recognition, etc. It is good to decide.

  In this embodiment, the case where the gradation compression processing is always performed on the image generated by the imaging has been described as an example. However, the gradation compression mode in which the gradation compression processing is performed and the non-gradation compression processing is not performed. The gradation compression mode may be selectable. The selection of these modes may be performed in accordance with a user instruction or may be performed automatically. When the mode is automatically selected, the mode may be selected according to the above-described shooting mode, image contrast strength, image adjustment mode, image analysis result by scene analysis or face recognition, and the like.

  Further, the gradation curve Gm (FIG. 5) and the gradation compression parameter fg (FIG. 6) described in the present embodiment are used for the above-described shooting mode, image contrast strength, image adjustment mode, scene analysis and face recognition. It is good also as a structure changed according to the image judgment result by. As described above, by appropriately changing the gradation curve Gm and the gradation compression parameter fg, it is possible to perform gradation conversion processing optimized for an image and dark part gradation correction.

  In the present embodiment, the gradation curve Gm (FIG. 5) used for gradation conversion processing may be changed according to the influence of exposure correction. For example, when the brightness of the entire image can be maintained to some extent by exposure correction, the amount of change in the gradation curve used in the gradation compression mode may be reduced.

  In the above-described embodiment, the example in which the technique of the present invention is realized in the electronic camera 1 has been described. However, the present invention is not limited to this. For example, the present invention can be similarly applied to a compact type electronic camera, a movie camera for taking a moving image, and the like.

  Further, the image processing apparatus described in the present embodiment may be realized as software by a computer and an image processing program. In this case, the processing (steps S11 to S14 in the flowchart of FIG. 9 and steps S21 to S24 in the flowchart of FIG. 12) by the image processing unit 2, the low-pass calculation unit 3, and the gain addition unit 4 are performed. What is necessary is just to make it the structure which implement | achieves a part or all by a computer. By adopting such a configuration, it is possible to perform the same processing as in the present embodiment.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. For this reason, the above-described embodiments are merely examples in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the scope of claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Electronic camera, 2 ... Image processing part, 3 * 30 ... Low pass calculating part, 4 ... Gain addition part, 5 ... Control part, 21 * 32 ... Gradation conversion processing part, 22 * 31 ... V image generation part, 23 33: Low pass processing unit

Claims (15)

An acquisition unit for acquiring image data;
An image processing unit that performs image processing including first gradation conversion processing on the image data acquired by the acquiring unit ;
The image data to which the second gradation conversion processing has been performed with performing the second gradation conversion processing on the image data acquired by the acquisition unit to a processing performed in parallel with the image processing by the image processing unit a calculation unit which generates a blurred image data, and calculates the correction value to improve the lightness of the dark area gradation of the image data to which the image processing has been performed by the image processing unit by using the blurred image data on the basis of,
Brightness of dark area gradation of the image data to which the image processing has been performed by with the calculated correction value and the inputted each of the image processing unit wherein the image processing by the image processing section and the image data subjected to by the arithmetic unit the image processing device characterized by the Ru and a correcting unit for correcting improve in accordance with the correction value. The image processing apparatus according to claim 1.
An image processing apparatus , wherein a gradation curve used in the first gradation conversion process is different from a gradation curve used in the second gradation conversion process . The image processing apparatus according to claim 1 or 2,
The image processing apparatus, wherein the arithmetic unit performs low-pass processing on the image data on which the second gradation conversion processing has been performed to generate the blurred image data. The image processing apparatus according to any one of claims 1 to 3 ,
The arithmetic unit, the image processing apparatus characterized by R image data based on the images data acquired by the acquisition unit, G image data, the second gradation conversion processing to each of the B image data is subjected. The image processing apparatus according to any one of claims 1 to 3 ,
The arithmetic unit, the image processing apparatus characterized by Y image data based on the images data acquired by the acquisition unit, Cb image data, the second gradation conversion processing to each of the Cr image data subjected. The image processing apparatus according to any one of claims 1 to 3 ,
The arithmetic unit, Y image data based on the images data acquired by the acquisition unit, Cb image data, out of the Cr image data, and characterized by applying the second gradation conversion processing only in the Y image data Image processing device. The image processing apparatus according to any one of claims 1 to 3 ,
The calculation unit generates first image data related to brightness and second image data related to a plurality of color differences based on the image data acquired by the acquisition unit , and the first image data and the second image data An image processing apparatus, wherein third image data relating to brightness is generated from the image data and the second gradation conversion processing is performed on the generated third image data. An imaging unit that captures a subject image and generates image data;
An image processing apparatus according to any one of claims 1 to 7,
The electronic camera, wherein the acquisition unit acquires the image data from the imaging unit. An image processing program for realizing image processing on image data to be processed by a computer,
An acquisition step of acquiring the image data;
An image processing step of performing image processing including first gradation conversion processing on the image data acquired in the acquiring step ;
A process performed in parallel with the image processing in the image processing step, wherein the image data acquired in the acquisition step is subjected to a second gradation conversion process and the image data subjected to the second gradation conversion process is subjected to the second gradation conversion process. a calculating step of generating a blurred image data, and calculates the correction value to improve the lightness of the dark area gradation of the image data to the image processing has been performed in the image processing step using the blurred image data on the basis of,
The image data that has been subjected to the image processing in the image processing step and the correction value that has been calculated in the calculation step are input, respectively, and the brightness of the dark portion gradation of the image data that has been subjected to the image processing in the image processing step And a correction step for performing correction to improve the value according to the correction value. The image processing program according to claim 9.
An image processing program , wherein a gradation curve used in the first gradation conversion process and a gradation curve used in the second gradation conversion process are different . In the image processing program according to claim 9 or 10,
In the calculation step, the blurred image data is generated by performing low-pass processing on the image data on which the second gradation conversion processing has been performed . The image processing program according to any one of claims 9 to 11 ,
Wherein in the calculation step, the image processing program characterized by R image data based on the images data acquired in said acquisition step, G image data, the second gradation conversion processing to each of the B image data is subjected. The image processing program according to any one of claims 9 to 11 ,
Wherein in the calculation step, the image processing program characterized by Y image data based on the images data acquired in said acquisition step, Cb image data, the second gradation conversion processing to each of the Cr image data subjected. The image processing program according to any one of claims 9 to 11 ,
In the calculating step, Y image data based on the images data acquired in said acquisition step, Cb image data, out of the Cr image data, and characterized by applying the second gradation conversion processing only in the Y image data Image processing program. The image processing program according to any one of claims 9 to 11 ,
Wherein in the calculating step, on the basis of images data acquired in said acquiring step to generate a second image data for the first image data and a plurality of color difference relating to the brightness, the said first image data A third image data relating to brightness is generated from the second image data, and the second gradation conversion process is performed on the generated third image data.

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