JP2021078051A - Image processing device and image control method, program, and storage medium - Google Patents

Abstract

To make it possible to generate an image having appropriate lightness and gradation on a high brightness side when developing the image captured according to an exposure reference value of a gamma characteristic set at the time of photographing.SOLUTION: An image processing device includes: input means for inputting an image; setting means for acquiring an exposure reference value corresponding to a first gamma characteristic set at the time of photographing; selection means for acquiring an exposure reference value of a second gamma characteristic selected from a plurality of preset gamma characteristics; difference means for obtaining difference between the exposure reference value of the first gamma characteristic and the exposure reference value of the second gamma characteristic; and control means for changing the second gamma characteristic based on the difference so that lightness of the image is maintained.SELECTED DRAWING: Figure 2

Description

The present invention relates to a RAW image development processing technique.

In recent years, the performance of hardware has improved, and a RAW video workflow for developing a RAW video recorded by a camera on a workstation, a personal computer (PC), or the like has been utilized. By utilizing the RAW video workflow, it is possible to adjust the color, white balance (WB), and contrast without degrading the image quality during color grading. In order to utilize the RAW video workflow, it is important to shoot RAW video with high materiality. For example, in a scene with a large difference in brightness, it is difficult to recover a RAW moving image in which the image signal is saturated by color grading, so it is necessary to shoot the RAW moving image with underexposure giving priority to the bright part.

In this case, the problem is the appearance of the monitoring image at the time of shooting. If a gamma curve that presupposes a RAW movie with proper exposure is applied to a RAW movie that gives priority to bright areas, an underexposed image will be developed. If this is monitored on the rear monitor of the camera or an external monitor output by HDMI, etc., it will be difficult to identify the subject and the convenience of shooting will be impaired. Gamma characteristics are suitable (Non-Patent Document 1).

NLE applications used for color grading processing are also premised on Log workflow, which is widely used in video workflows premised on post production. Therefore, in the color grading process of the RAW video workflow, when the RAW video is input to the NLE application, the image developed by the Log curve is first displayed, and the user performs the color grading process in the same procedure as the Log workflow. become.

White Paper: Canon-Log Cine Optoelectronic Transfer Function Function

The color grading process based on the Log workflow is premised on having the equipment, knowledge, and experience of the Log workflow, which makes it difficult for a cinematographer who is good at still images, for example. On the other hand, it is conceivable to construct a new workflow using the RAW still image development workflow for the color grading process of the RAW moving image workflow.

However, the RAW still image development workflow is provided with only a gamma curve having a gradation characteristic close to that of the completed image, and there is no log curve that is premised on color grading processing in a subsequent process. Therefore, when a RAW movie shot with an exposure setting that prioritizes bright areas is applied to a new workflow, an under (dark) image far from the completed image is displayed.

The present invention has been made in view of the above problems, and an object of the present invention is to obtain appropriate brightness and gradation on the high luminance side when developing an image taken according to an exposure reference value of gamma characteristics set at the time of shooting. It is to realize a technique capable of generating a retained image.

In order to solve the above problems and achieve the object, the image processing apparatus of the present invention has an input means for inputting an image and a setting means for acquiring an exposure reference value according to a first gamma characteristic set at the time of shooting. A selection means for acquiring an exposure reference value of a second gamma characteristic selected from a plurality of predetermined gamma characteristics, an exposure reference value of the first gamma characteristic, and an exposure reference of the second gamma characteristic. It has a difference means for obtaining a difference between values, and a control means for changing the second gamma characteristic based on the difference so that the brightness of the image is maintained.

According to the present invention, when developing an image taken according to the exposure reference value of the gamma characteristic set at the time of shooting, it is possible to generate an image in which appropriate brightness and gradation on the high luminance side are maintained. Become.

The block diagram which shows the structure of the image pickup apparatus of Embodiment 1. The block diagram which shows the structure of the image processing part of Embodiment 1. The block diagram which shows the structure of the gamma generation part of Embodiment 1. The figure which illustrates the gamma table at the time of photography and the gamma table at the time of development of Embodiment 1. The figure which illustrates the gamma characteristic used for the gamma generation processing of Embodiments 1 and 2. The flowchart which shows the gamma generation processing of Embodiment 1.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiment, not all of the plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the attached drawings, the same or similar configurations are designated by the same reference numbers, and duplicate explanations are omitted.

[Embodiment 1] The first embodiment will be described below.

Hereinafter, an example in which the image processing device of the present embodiment is applied to an information processing device such as a personal computer (PC) or a workstation (WS) to process image data captured by an imaging device such as a digital camera will be described. .. The image processing device of the present embodiment is not limited to these, and includes imaging devices such as digital cameras, communication devices such as mobile phones and smartphones which are one of them, portable information devices such as tablet terminals and PDAs, and scanners. It can also be applied to image readers, image forming devices such as printers, and other devices.

<Configuration of imaging device>
First, the configuration and function of the image pickup apparatus 100 of the present embodiment will be described with reference to FIG.

The optical system 1 includes a lens group including a zoom lens and a focus lens, and a shutter having an aperture function, and forms a subject image on an imaging surface of an imaging unit 2.

The image pickup unit 2 has an image pickup device composed of a CCD, CMOS, or the like that converts a subject image into an electric signal. The image sensor is, for example, a single-plate color image sensor provided with a general primary color filter. The primary color filters consist of three types of color filters having transmission main wavelength bands near 650 nm, 550 nm, and 450 nm, respectively, and color planes corresponding to the R (red), G (green), and B (blue) bands, respectively. To shoot. In the single-plate color image sensor, color filters are spatially arranged in a mosaic pattern for each pixel, and each pixel obtains the intensity in a single color plane. Therefore, a color mosaic image is output from the image sensor. ..

The A / D conversion unit 3 converts the analog image signal output from the imaging unit 2 into a digital signal, performs noise reduction processing, and outputs the image data composed of the digital signal to the development processing unit 4 and the output unit 7. To do. In this embodiment, 14-bit image data is generated for each pixel.

The development processing unit 4 performs development processing such as pixel interpolation processing, luminance signal processing, and color signal processing on the image data output from the A / D conversion unit 3. By the development process of this embodiment, the color space of R, G, and B is converted into the color space of 8-bit luminance (Y) data and color difference (U, V) data, and is output from the development processing unit 4 as YUV data. It shall be. In the present embodiment, the case where the captured image is recorded as a RAW image will be described, but even if the recording format is a RAW image, it is possible to set “at the time of photographing γ” as the setting of the image pickup apparatus 100. This shooting γ is, for example, a parameter when generating a display image (shooting monitoring image) for confirming the shot image at the shooting site. The development processing unit 4 develops the RAW image with parameters suitable for the monitoring image at the time of shooting, and displays the developed image on the display unit 12, for example. In the present embodiment, as one of the gamma characteristics (γ curve) that can be set as γ at the time of photographing, a predetermined Log characteristic (hereinafter, Logγ) having a dynamic range (D range) of 800% is used. As other shooting γ, standard γ and high-luminance gradation priority γ can also be used. These shooting γs are selected by, for example, a user operation. Unless otherwise specified, in this embodiment, it is assumed that Logγ is set as γ at the time of photographing.

The signal processing unit 6 performs resizing processing or the like on the developed image data and outputs the image data to the output unit 7.

The metadata processing unit 5 processes metadata related to RAW images. The metadata is information indicating a setting at the time of shooting a RAW image, such as a shooting γID that uniquely indicates the shooting γ. The metadata processing unit 5 generates metadata in cooperation with the control unit 10 and outputs the metadata to the output unit 7. In the present embodiment, a value of "5" indicating Logγ with a D range of 800% is described in the metadata as a γID at the time of photographing. The γID at the time of shooting will be described later.

The output unit 7 performs at least one of output to a communication interface such as HDMI (registered trademark: High-Definition Multimedia Interface), recording to a recording medium such as a semiconductor memory card, and output to the display unit 12. .. In the present embodiment, the output unit 7 adds the metadata generated by the metadata processing unit 5 to the image data output from the A / D conversion unit 3 and outputs the RAW image file to the recording medium. Further, the shooting monitoring image output from the signal processing unit 6 is output to the display unit 12.

The operation unit 9 includes at least one of various switches, buttons, a touch panel, and the like that accept various operations from the user. The touch panel is integrally formed with the display unit 12. When the operation unit 9 receives a user operation, the operation unit 9 outputs an operation signal to a control unit 10 described later, and the control unit 10 performs various arithmetic processes based on the operation signal and controls each unit.

The control unit 10 includes a CPU and an MPU that control the entire image pickup apparatus 100, and executes a program stored in the memory 11 described later to realize the processing of the flowchart described later. The memory 11 stores programs read from constants, variables, recording media, and the like for the operation of the control unit 10. Further, the memory 11 contains image data, an aperture value, a shutter speed, an ISO sensitivity, a white balance gain value, and a BT. Data of shooting information such as color gamut settings such as 709 is stored.

Each component of the image pickup apparatus 100 is connected by a bus 8 so that various data and signals can be exchanged.

<Configuration of image processing device>
Next, the configuration and function of the image processing device 200 of the present embodiment will be described with reference to FIG. The image processing device 200 is a device that develops RAW images, and a PC, workstation, tablet device, or the like in which applications for developing and editing are installed can be used.

The input unit 20 performs processing such as input of RAW image data output from the output unit 27 of the image pickup apparatus 100 through an HDMI (registered trademark) cable or the like, input of a RAW image file stored in a recording medium, and the like. The input unit 20 outputs RAW image data to the perspective unit 21. In this embodiment, a RAW image file is input from the semiconductor memory card.

The parse unit 21 analyzes the data structure of the RAW image file acquired from the input unit 20 and acquires the information described in the RAW image data and the metadata. The perspective unit 21 outputs RAW image data to the development processing unit 24. Of the information described in the metadata, the perspective unit 21 outputs the γID at the time of shooting to the γ generation unit 25, and stores other information in the memory 31.

The γ generation unit 25 performs a γ generation process for generating γ characteristics for developing RAW image data by using the information described in the metadata of the RAW image file and the information stored in advance in the memory 31 described later. Then, the generated modified γ characteristic is output to the developing processing unit 24. The details of this process will be described later.

The development processing unit 24 performs development processing such as pixel interpolation processing, luminance signal processing, and color signal processing on the RAW image data. By the development processing of this embodiment, the color space of R, G, and B is converted into the color space of 8-bit luminance (Y) data and color difference (U, V) data, and is output from the development processing unit 24 as YUV data. It shall be.

The signal processing unit 26 performs resizing processing or the like on the developed image data and outputs the image data to the output unit 27. The output unit 27 is at least one of output to a communication interface such as HDMI (registered trademark), recording to a recording medium such as a semiconductor memory card, and output to a display device (not shown) of the image processing device 200. Perform processing.

The operation unit 29 includes at least one of various switches, buttons, a touch panel, and the like that accept various operations from the user. The touch panel is integrally formed with a display device (not shown). When the operation unit 29 receives the user operation, the operation unit 29 outputs an operation signal to the control unit 30, which will be described later, and the control unit 10 performs various arithmetic processes based on the operation signal and controls each unit.

The control unit 30 includes a CPU and an MPU that control the entire image processing device 200, and executes a program stored in the memory 31 described later to realize the processing of the flowchart described later. The memory 31 stores programs read from constants, variables, recording media, and the like for the operation of the control unit 30. Further, in the memory 31, the image data, the aperture value, the shutter speed, the ISO sensitivity, the white balance gain value, and the BT. Data of shooting information such as color gamut settings such as 709 is stored.

Each component of the image processing device 200 is connected by a bus 28 so that various data and signals can be exchanged.

<Γ generation process>
Next, with reference to FIG. 3, the configuration and function of the image processing apparatus 200 and the γ generation processing will be described.

The image processing device 200 of the present embodiment has a function of developing a RAW image by using a RAW still image development workflow. Therefore, it is assumed that only the γ characteristic of the gradation characteristic close to the completed image is retained in the memory 31, and the γ characteristic having a low exposure reference value premised on the color grading process in the subsequent process is not retained unlike Logγ. To do.

FIG. 5A illustrates the relationship between the γ characteristic at the time of photographing and the exposure reference value. 501 is an input / output characteristic of Logγ having a D range of 800%. The input value 502 is a signal value 300 in the 14-bit digital image signal (0-16383). Here, in Logγ501 of the present embodiment, an exposure reference value of a signal value of 300 (14 bits) is defined. This means that the exposure at the time of shooting is controlled so that the subject having a reflectance of 18% has a signal value of 300. Therefore, when shooting is performed with Logγ501 set as γ at the time of shooting, shooting is performed with an exposure such that a subject having a reflectance of 18% has a signal value of 300. Further, in Logγ501, the output value 503 corresponding to the input value 502 becomes a signal value 88 in the 8-bit digital image signal. This is output to the display unit 12 as a monitoring image at the time of shooting.

Returning to the description of FIG. When the γ generation unit 25 develops a RAW image taken by adjusting the exposure to the exposure reference value of γ at the time of shooting with the γ characteristic of the gradation characteristic having a higher exposure reference value, the γ generation unit 25 has an appropriate brightness and a high brightness side. It has a function of changing the γ characteristic at the time of development in order to generate an image in which the gradation of is maintained.

The exposure reference value setting unit 301 sets the shooting γ exposure reference value by using the shooting γ ID acquired from the perspective unit 21 and the shooting γ table 305 read from the memory 11. FIG. 4A illustrates the γ table 305 at the time of photographing. The shooting γ table 305 is registered in association with the shooting setting for specifying the shooting γ characteristic, the γID that can uniquely specify the shooting γ characteristic, the γ name, and the exposure reference value defined by the γ characteristic. There is. In the present embodiment, as a shooting setting for specifying the shooting γ, a flag indicating whether or not a mode using Logγ is set, a flag indicating whether or not the high-brightness side / gradation priority mode is set, and shooting The ISO sensitivity of the time is associated and registered.

The exposure reference value setting unit 301 searches the shooting γ table 305, sets the exposure reference value corresponding to the shooting γID acquired from the perspective unit 21 to the shooting γ exposure reference value, and sets the γ selection unit 302 and the difference unit. Output to 303. The exposure reference value setting unit 301 does not use the shooting γID, but uses the shooting setting for specifying the shooting γ characteristic to specify the shooting γ characteristic, and sets the corresponding exposure reference value to the shooting γ exposure. It may be set as a reference value.

The γ selection unit 302 selects and sets the development γ ID using the shooting γ exposure reference value output from the exposure reference value setting unit 301 and the development γ table 306 read from the memory 11. Here, the criteria for selecting which developing γ is selected will be described later with reference to FIG. FIG. 4B illustrates the γ table 306 during development. In the developing γ table 306, the γID, the γ name, and the exposure reference value defined by the γ characteristic, which can uniquely identify the developing γ characteristic, are registered in association with each other. In the present embodiment, for example, the image processing apparatus 200 is provided with two types of γ characteristics during development, standard γ and high-luminance side gradation priority γ, and information on the two types of γ characteristics is also registered in the γ table during development. ing.

FIG. 5B illustrates the relationship between the γ characteristic during development and the exposure reference value. The characteristics of the standard γ504 are close to those of γ2.2, and are suitable for images intended for viewing on an SDR (Standard Dynamic Range) monitor or print output. The input value 505 is, for example, a signal value 1200 in a 14-bit digital image signal. Since the signal value 1200 is an exposure reference value defined by the standard γ characteristic 504 as shown in FIG. 4, the exposure is controlled so that a subject having a reflectance of 18% has this value at the time of shooting. In this case, the output value 508 corresponding to the reflectance 18% input value 505 becomes the signal value 123 in the 8-bit digital image signal. Further, in the high-luminance side gradation priority γ506, when a digital signal having a size half the size of the standard γ is input, the input below the exposure reference value becomes the same output as the standard γ, and the signal larger than the exposure reference value is more than the standard γ. It has a characteristic that the gradation of the bright part is extended by applying a strong knee characteristic. The input value 507 is, for example, a signal value 600 in a 14-bit digital image signal. Since this value is the exposure reference value of the high-luminance side gradation priority γ, this value is used for a subject having a reflectance of 18%. The output value 508 corresponding to the reflectance 18% input value 507 is the same value as the standard γ. Here, the γ selection unit 302 outputs the selected development γ exposure reference value to the difference unit 303.

The difference unit 303 obtains the difference value between the shooting γ exposure reference value output from the exposure reference value setting unit 301 and the developing γ exposure reference value output from the γ selection unit 302, and causes the brightness control unit 304 to obtain the difference value. Output.

The brightness control unit 304 reads from the difference value of the exposure reference value output from the difference unit 303, the developing γ ID set by the γ selection unit 302, the developing γ table 306 read from the memory 11, and the memory 11. The brightness of the input image is controlled by using the γ characteristic table 307. In the present embodiment, the brightness control unit 304 changes the developing γ characteristics set by, for example, the γ selection unit 302. The brightness control unit 304 outputs the changed γ characteristic to the development processing unit 24.

<Γ generation process>
Next, the γ generation process by the γ generation unit 25 of the present embodiment will be described with reference to FIG.

The process of FIG. 6 is realized by the control unit 30 of the image processing device 200 executing the program and controlling the γ generation unit 25.

In S601, the exposure reference value setting unit 301 acquires the shooting γID output from the perspective unit 21. It is assumed that the γID at the time of photographing of this embodiment is 5 set in the image pickup apparatus 100.

In S602, the exposure reference value setting unit 301 refers to the shooting γ table 305 read from the memory 11 and obtains the shooting γ exposure reference value corresponding to the shooting γ ID. In the present embodiment, the shooting γID is “5”, and from FIG. 4A, the shooting γ exposure reference value corresponding to the shooting γID “5” is 300. The exposure reference value setting unit 301 outputs the γ exposure reference value at the time of shooting to the γ selection unit 302 and the difference unit 303.

In S603, the γ selection unit 302 refers to the exposure reference value of the developing γ table 306 read from the memory 11, and is equal to or higher than the shooting γ exposure reference value and closest to the shooting γ exposure reference value. To explore. In the present embodiment, the γ exposure reference value at the time of shooting is 300, and the exposure reference value described in the γ table at the time of development in FIG. 4B is 1200 of the standard γ and 600 of the gradation priority γ on the high luminance side. is there. All of them satisfy the condition of being equal to or higher than the γ exposure reference value at the time of shooting, but in S606 described later, the γ characteristic is changed according to the difference between the γ exposure reference value at the time of shooting and the γ exposure reference value at the time of development. Therefore, the closer the γ-exposure reference value during development is to the γ-exposure reference value during shooting, the more the amount of change in the γ characteristic read from the memory 11 can be suppressed. In the present embodiment, since the γ characteristics during development are changed by changing the white point and the midpoint together, the larger the amount of change in the γ characteristics during development, the faster the output signal reaches the signal value 255, which is the upper limit of 8 bits. It becomes the γ characteristic that hits. Therefore, in the present embodiment, 600 of the high-luminance side gradation priority γ, which is closer to the γ exposure reference value at the time of shooting, is selected and set as the γ exposure reference value at the time of development.

In S604, the γ selection unit 302 refers to the exposure reference value of the γ table 306 during development and selects the γID corresponding to the γ exposure reference value during development. In the present embodiment, the development γ exposure reference value is 600, and “2” is selected as the corresponding development γ ID. The γ selection unit 302 outputs the γID during development to the brightness control unit 304, and outputs the γ exposure reference value during development to the difference unit 303.

In S605, the difference unit 303 obtains the difference value between the shooting γ exposure reference value output from the exposure reference value setting unit 301 and the developing γ exposure reference value output from the γ selection unit 302. The difference value of the exposure reference value in this embodiment is 300. The difference unit 303 outputs the difference value of the exposure reference value to the brightness control unit 304, and proceeds to S606.

In S606, the brightness control unit 304 determines the developing γ characteristic selected by the γ selection unit 302 according to the difference value between the shooting γ exposure reference value and the developing γ exposure reference value output from the difference unit 303. change.

FIG. 5C illustrates the relationship between the developed γ characteristic and the changed γ characteristic in the present embodiment. The brightness control unit 304 reads the γ characteristic table 307 from the memory 11 and sets the high-luminance side gradation priority γ506 as the development γ characteristic according to the development γID set by the γ selection unit 302. However, as for the characteristic of the high-luminance side gradation priority γ506, since the output value 509 corresponding to the γ exposure reference value 502 at the time of shooting becomes the signal value 73, an image underexposed than the proper exposure is output. Therefore, the brightness control unit 304 changes the white point and the midpoint of the γ characteristic during development by the difference between the γ exposure reference value during shooting and the γ exposure reference value during development.

As for the characteristics of the changed γ510, the output value 508 corresponding to the γ exposure reference value 502 at the time of shooting becomes the signal value 123, and an image with proper exposure can be output. The brightness control unit 304 outputs the changed γ characteristic to the development processing unit 24. Here, changing the white point and midpoint of γ during development is equivalent to multiplying by digital gain. In the present embodiment, for example, an appropriate brightness can be obtained by applying the digital gain for one step to the input image and then applying the γ characteristic at the time of development. Therefore, the brightness control unit 304 may output the digital gain amount and the developing γ characteristic to the developing processing unit 24 instead of the changed γ characteristic.

In S603, the γ selection unit 302 cannot fixedly select the γ characteristic having a low exposure reference value. For example, in a scene where the difference between the bright part and the dark part is small and the dynamic range is narrow, a RAW image having a high γ exposure reference value at the time of shooting may be taken in order to emphasize the dark part S / N.

In the present embodiment, for example, if the ISO sensitivity of the image pickup apparatus 100 is lowered from 400 to 100, the gain increase amount during development can be reduced by two steps, and the γ exposure reference value at the time of photographing is raised from 300 to 1200. In this case, a standard γ having an exposure reference value of 1200 or a Log γ having a D range of 200% is used as the shooting γ, and the imaging device 100 records a shooting γ ID showing these γ characteristics in a RAW image file. In the image processing apparatus 200 that has received this RAW image file, the γ exposure reference value at the time of shooting is set to 1200 by the above-mentioned S601 and S602. The γ selection unit 302 selects the standard γ exposure reference value 1200 from the developing γ table 306 read from the memory 11 and sets it as the developing γ exposure reference value according to the condition that it is equal to or higher than the shooting γ exposure reference value.

According to the first embodiment, in the process of developing a RAW image taken by adjusting the exposure to the γ exposure reference value at the time of shooting, when developing with the γ characteristic of the gradation characteristic whose exposure reference value is higher than the γ characteristic at the time of shooting, First, the difference between the exposure reference value of the γ characteristic at the time of shooting and the γ characteristic at the time of development is obtained. Then, the developing γ characteristic that minimizes the difference is selected, and the white point and the midpoint of the developing γ characteristic are changed according to the difference. As a result, it is possible to generate an image in which appropriate brightness and gradation on the high luminance side are maintained.

[Embodiment 2]
In the first embodiment, an example in which the brightness control unit 304 changes the white point and the mid point of the γ characteristic at the time of development has been described. On the other hand, in the second embodiment, an example will be described in which the brightness control unit 304 changes only the midpoint while maintaining the white point of the γ characteristic during development. The configuration of the image processing circuit that realizes the second embodiment is the same as that of the first embodiment.

FIG. 6 is a flowchart showing the γ generation process of the γ generation unit 25 of the present embodiment. In the present embodiment, since the brightness control unit 304 changes only the midpoint while maintaining the white point of the γ characteristic during development, the larger the amount of change in the γ characteristic during development, the more the color reproducibility obtained deviates from the design time. Therefore, there is a high possibility that color bending and tone jumping will occur. Therefore, in S603, the γ selection unit 302 selects 600 of the high-luminance side gradation priority γ that is closer to the γ exposure reference value at the time of shooting, and sets it as the γ characteristic exposure reference value at the time of development.

The processing in S601, S602, S604, and S605 is the same as that in the first embodiment.

In S606, the brightness control unit 304 determines the developing γ characteristic selected by the γ selection unit 302 according to the difference value between the shooting γ exposure reference value and the developing γ exposure reference value output from the difference unit 303. change. FIG. 5D illustrates the relationship between the developed γ characteristic and the changed γ characteristic in the present embodiment.

The brightness control unit 304 reads the γ characteristic table 307 from the memory 11 and sets the high-luminance side gradation priority γ506 as the development γ characteristic according to the development γID set by the γ selection unit 302. However, as for the characteristic of the high-luminance side gradation priority γ506, since the output value 509 corresponding to the γ exposure reference value 502 at the time of shooting becomes the signal value 73, an image underexposed than the proper exposure is output. Therefore, the brightness control unit 304 changes the midpoint by the difference between the γ exposure reference value during shooting and the γ exposure reference value during development while maintaining the white point of the γ characteristic during development. As for the characteristics of the changed γ511, the output value 509 corresponding to the γ exposure reference value 502 at the time of shooting becomes the signal value 123, and an image with proper exposure can be output. The brightness control unit 304 outputs the changed γ characteristic to the development processing unit 24.

According to the second embodiment, in the process of developing a RAW image taken by adjusting the exposure to the γ-exposure reference value at the time of shooting, when developing with the γ characteristic of gradation characteristics having a high γ-exposure reference value at the time of shooting, first shooting Obtain the difference between the exposure reference value of the time γ characteristic and the time γ characteristic during development. Then, the development γ characteristic that minimizes the difference is selected, and only the midpoint is changed according to the difference while maintaining the white point of the development γ characteristic. As a result, it is possible to generate an image in which the gradation on the higher luminance side than that of the first embodiment is maintained while maintaining an appropriate brightness and minimizing the risk of color bending.

In each of the above-described embodiments, the hardware configuration of each block of the γ generation unit 25 has also been described, but since the operation of each block is a process that can be realized by software, a part of each operation of the γ generation unit 25. Alternatively, all may be implemented by software processing. Further, with respect to the other blocks in the image processing apparatus 200 of FIG. 2, a part or all of them may be similarly implemented by software processing.

[Other Embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

The invention is not limited to the above embodiments, and various modifications and modifications can be made without departing from the spirit and scope of the invention. Therefore, a claim is attached to make the scope of the invention public.

100 ... Imaging device, 200 ... Image processing device, 4, 24 ... Development processing unit, 10, 30 ... Control unit, 25 ... γ generation unit, 301 ... Exposure reference value setting unit, 302 ... γ selection unit, 303 ... Difference unit , 304 ... Brightness control unit

Claims (9)

Input means for inputting images and
A setting means for acquiring an exposure reference value according to the first gamma characteristic set at the time of shooting, and
A selection means for acquiring an exposure reference value of a second gamma characteristic selected from a plurality of predetermined gamma characteristics, and
A difference means for obtaining the difference between the exposure reference value of the first gamma characteristic and the exposure reference value of the second gamma characteristic, and
An image processing apparatus comprising: a control means for changing the second gamma characteristic based on the difference so that the brightness of the image is maintained. Claim 1 is characterized in that the selection means selects the second gamma characteristic having an exposure reference value closest to the exposure reference value corresponding to the first gamma characteristic among the plurality of gamma characteristics. The image processing apparatus according to. The image processing apparatus according to claim 1 or 2, wherein the control means changes the white point and the mid point of the second gamma characteristic based on the difference. The image processing apparatus according to any one of claims 1 to 3, wherein the control means gains up with respect to a gamma characteristic applied to the input image based on the difference. Any one of claims 1 to 4, wherein the control means changes the midpoint of the second gamma characteristic while maintaining the white point of the second gamma characteristic based on the difference. The image processing apparatus according to. The second gamma characteristic has a gradation characteristic having a higher exposure reference value than the first gamma characteristic.
The image processing according to any one of claims 1 to 5, wherein the input image is a RAW image taken by an imaging device with an exposure reference value corresponding to the first gamma characteristic. apparatus. Steps to enter the image and
The step of acquiring the exposure reference value according to the first gamma characteristic set at the time of shooting, and
A step of acquiring an exposure reference value of a second gamma characteristic selected from a plurality of predetermined gamma characteristics, and
The step of obtaining the difference between the exposure reference value of the first gamma characteristic and the exposure reference value of the second gamma characteristic, and
An image processing method performed by an image processing apparatus, which comprises a step of changing the second gamma characteristic based on the difference so that the brightness of the image is maintained. A program for causing a computer to function as each means of the image processing apparatus according to any one of claims 1 to 6. A computer-readable storage medium containing a program for causing the computer to function as each means of the image processing apparatus according to any one of claims 1 to 6.

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