Image capturing apparatus, method of controlling image capturing apparatus, and storage medium

An image capturing apparatus includes an image capturing unit configured to capture an image of an object and generate image data, a compression unit configured to compress the image data generated by the image capturing unit, a display control unit configured to decode the image data compressed by the compression unit and display the decoded image data on a display unit, and an instruction unit configured to issue an instruction to magnify an image to be displayed on the display unit, wherein, in a case where the instruction unit issues the instruction to magnify the image to be displayed on the display unit, the compression unit reduces a compression rate of the image data.

BACKGROUND

Field of the Disclosure

The present disclosure relates to an image capturing apparatus, a method of controlling the image capturing apparatus, and a storage medium.

Description of the Related Art

In recent years, an increasing amount of data is output from a sensor of an image capturing apparatus, such as a digital camera or digital camcorder, due to an increased resolution, an increased frame rate, and an increased number of bits, and this results in a tight transmission bandwidth. Accordingly, a technique for easing a bandwidth by encoding data output from a sensor has been discussed (refer to, for example, Japanese Patent Application Laid-Open No. 2016-213527).

Further, in recent years, many image capturing apparatuses are equipped with an electronic viewfinder (EVF) or a monitor so that a user can capture an image while checking the image with the EVF or the monitor. However, it is often difficult to check whether an image is in focus using a monitor that has a small screen size. Thus, a technique for magnifying a region of interest to check whether an image is in focus is also discussed (refer to, for example, Japanese Patent Application Laid-Open No. 2009-267893).

The conventional techniques can ease a bandwidth by encoding data output from a sensor. However, when a user performs a magnification operation to check whether an image is in focus, an encoding distortion becomes visible, if the encoding is applied to an image to be displayed on an EVF or a monitor.

SUMMARY

Embodiments of the present disclosure are directed to a technique for reducing visibility of an encoding distortion in a magnified image display while preventing an increase in data amount.

According to embodiments of the present disclosure, an image capturing apparatus includes an image capturing unit configured to capture an image of an object and generate image data, a compression unit configured to compress the image data generated by the image capturing unit, a display control unit configured to decode the image data compressed by the compression unit and display the decoded image data on a display unit, and an instruction unit configured to issue an instruction to magnify an image to be displayed on the display unit, wherein, in a case where the instruction unit issues the instruction to magnify the image to be displayed on the display unit, the compression unit reduces a compression rate of the image data.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a block diagram illustrating an example of a configuration of an image capturing apparatus100according to the present exemplary embodiment.

As illustrated inFIG. 1, the image capturing apparatus100includes an image capturing element111and an image processing unit112. The image capturing element111includes an image capturing unit101and an encoding unit102. The image processing unit112includes a decoding unit103, a development processing unit104, a display unit105, an operation unit106, and a control unit107.

A configuration of the image capturing element111will be described below.

The image capturing unit101includes a lens optical system and an image sensor, such as a charge-coupled device (CCD) image sensor or complementary metal oxide semiconductor (CMOS) sensor. The lens optical system includes an optical lens, a diaphragm, a focus control unit, and a lens driving unit, and is able to perform optical zooming. The image sensor converts optical information from the lens optical system into an electric signal. The image capturing unit101generates image data by converting the electric signal acquired by the image sensor into a digital signal.

The encoding unit102encodes the image data generated by the image capturing unit101to reduce a data amount and outputs the encoded data to the image processing unit112via a sensor interface (sensor I/F).

A configuration of the image processing unit112will be described below.

The control unit107controls the entire image capturing apparatus100. The decoding unit103decodes the encoded data input from the image capturing element111via the sensor I/F. The development processing unit104performs development processing, such as demosaicing processing, noise reduction processing, optical distortion correction processing, and color correction processing, on the decoded image data.

The display unit105is a display apparatus attached to the image capturing apparatus100, such as a monitor or electronic viewfinder (EVF), and displays an image developed by the development processing unit104. The display unit105displays an image so that a user can check an image to be captured. The operation unit106is a user interface via which the user inputs an instruction to the image capturing apparatus100. In a case where a touch panel is mounted on the display unit105, the user can input an instruction via a button displayed on the monitor of the display unit105. Further, physical buttons, a stick, a shutter button, and a menu button attached to the image capturing apparatus100are also part of the operation unit106.

A process that is performed by the control unit107of the image capturing apparatus100will be described below based on a flowchart illustrated inFIG. 2with reference toFIGS. 1, 3A, 3B, and 3C. Specifically, a control process that is performed when the image capturing apparatus100is turned on and the display unit105displays an object to be captured and the image is magnified and displayed based on a user operation will be described below.

FIG. 2is a flowchart illustrating an example of a process of displaying a magnified image of an object according to the present exemplary embodiment.

In step S201, the control unit107sets an initial setting of a reading region for image capturing from an effective pixel region of the image sensor of the image capturing unit101. In the initial setting, a maximum recording pixel region is set as the reading region.

In step S202, the control unit107sets an initial setting of a compression rate of the encoding unit102. In this processing, the compression rate is determined so that a data amount of output data from the image capturing element111, which is determined based on the reading region determined in step S201and a frame rate read from the image capturing unit101, becomes a data amount that can be transmitted from the sensor I/F.

For example, in a case where an image is displayed at a high frame rate on the monitor or the EVF, the displayed image is not likely to appear unnatural to the user. To realize such a display, however, a significant amount of data is transmitted via the sensor I/F, and if the amount exceeds the transmission capacity of the sensor I/F, an adequate frame rate is no longer maintained. Thus, the compression rate is set to, for example, ½ to reduce the data amount, so that data can be transmitted while a high frame rate is maintained.

In step S203, the control unit107determines whether a current mode is a live view (LV) mode in which the user can check an object from the monitor or the EVF. In a case where the control unit107determines that the current mode is not the LV mode (e.g., the current mode is a reproduction mode) (NO in step S203), the process ends. On the other hand, in a case where the control unit107determines that the current mode is the LV mode (YES in step S203), the processing proceeds to step S204. The process also ends when a power source of the image capturing apparatus100is turned off.

In step S204, the image capturing unit101generates image data in the reading region set in step S201or a reading region set in step S210described below. Then, in step S205, the encoding unit102encodes the generated image data at the compression rate set in step S202or a compression rate set in step S211described below, and outputs the encoded data to the image processing unit112via the sensor I/F.

In step S206, the decoding unit103decodes the encoded data output via the sensor I/F. In step S207, the development processing unit104develops the image data decoded in step S206. In step S208, the control unit107performs display control to display the image data developed in step S207on the monitor or the EVF that is the display unit105.

FIG. 3Aillustrates a state where an image including an object is displayed without being magnified on the monitor that is the display unit105of the image capturing apparatus100. A magnification (+) button and a reduction (−) button are provided at an upper right portion of the image capturing apparatus100as part of the operation unit106. When a magnification operation is not performed by the user, an image including an object is displayed without being magnified.

In step S209, the control unit107determines whether an instruction to magnify the image is received from the operation unit106based on the magnification operation by the user.FIG. 3Billustrates a state where the magnification operation is performed by the user. In a state where the image including the object is displayed on the display unit105, the user may perform an operation to magnify the image in order to, for example, check whether the object is in focus. The user operates the magnification (+) button to transmit an instruction to magnify the image from the operation unit106to the control unit107. In step S209, in a case where the control unit107determines that an instruction to magnify the image is received from the operation unit106(YES in step S209), the processing proceeds to step S210. On the other hand, in a case where the control unit107determines that an instruction to magnify the image is not received from the operation unit106(NO in step S209), the processing returns to step S203to process the next frame.

In step S210, the control unit107re-sets a reading region of the image sensor of the image capturing unit101based on a magnification rate specified by the operation unit106. In a case where the magnification operation is performed, the reading region becomes smaller than the reading region set in step S201. Consequently, the amount of data output from the image capturing unit101of the image capturing element111decreases. Further, the magnification rate is determined based on the magnification operation by the user. For example, the control unit107determines the magnification rate based on the length of time when the magnification (+) button is operated.

In step S211, the control unit107re-sets a compression rate of the encoding unit102. In a case where the magnification operation is performed by the user, an encoding distortion may be visible in the magnified image if the image is magnified at the high compression rate set in step S202. Thus, the compression rate is reduced in step S211to thereby reduce the encoding distortion in the magnified image. Since the amount of data output from the image capturing unit101decreases as a result of the processing in step S210, the high frame rate is maintained even if a lower compression rate than the compression rate set in step S202is set.

FIG. 3Cillustrates a state where the magnified image is displayed after the reading region of the image sensor is re-set in step S210and the compression rate is changed in step S211. Since a low compression rate is set in step S211, the encoding distortion originating from the encoding unit102in the image capturing element111is reduced even in the magnified image.

A control process of changing the compression rate of the encoding unit102based on the magnification rate to maintain a constant amount of data transmission from the sensor I/F and to reduce visibility of an encoding distortion in a magnified image display will be described below with reference toFIGS. 4A, 4B, and 5.

FIG. 4Aillustrates a relationship between a maximum recording pixel region401that is recordable by the image sensor of the image capturing unit101and a magnification display region402. In a normal display when no magnification operation is performed by the user, the control unit107displays an image captured by the maximum recording pixel region401in full screen on the display unit105. In a case where, for example, the magnification operation is performed by the user, the magnification display region402having a size that is ¼ the size of the maximum recording pixel region401is magnified to be displayed in full screen on the display unit105.

FIG. 4Billustrates a relationship between a reading region of the image sensor and a magnification display region in a magnified image display. A shaded portion inFIG. 4Bindicates a sensor reading region of the image capturing unit101in a case where the magnification display region402is magnified and displayed. Even in a case where the length and the width of the magnification display region402are respectively ½ the length and the width of the maximum recording pixel region401, the lengthwise direction needs to be entirely read since the length of a reading region403of the image sensor is the same as the length of the maximum recording pixel region401.

FIG. 5illustrates a relationship between a data amount in data transmission from the image capturing element111to the image processing unit112and a magnification rate in a case where the magnification operation is performed via the operation unit106. A point501specifies a transmission data amount in a case where the magnification rate is 1, i.e., an image is not magnified, and the transmission data amount is defined as 1 in the present exemplary embodiment. This is a data amount in a case where an image of the entire maximum recording pixel region401inFIG. 4Ais captured and the captured image is transmitted at a predetermined frame rate (e.g., 60 fps). Descriptions of a data amount hereinafter are based on the above-described data amount.

In the present exemplary embodiment, the amount of data that can be transmitted from the image capturing element111to the image processing unit112is limited, and a maximum transmission data amount510, which is a limit value of the amount of data that can be transmitted per unit time, is 0.5, as illustrated inFIG. 5. The maximum transmission data amount510varies, for example, depending on whether power saving is intended or depending on a hardware specification. In the example illustrated inFIG. 5, in order to transmit data from the image capturing element111to the image processing unit112at the above-described frame rate in a case where no magnification operation is performed, the data amount needs to be compressed to ½. Thus, the compression rate is set to ½ in the initial setting of the compression rate in step S202inFIG. 2.

Thereafter, in a case where the magnification operation is performed by the user to change the magnification rate to 1.2 times specified by a point502, the transmission data amount is changed to 0.8, so that the compression rate is re-set to ⅝ in step S211. Further, in a case where the magnification operation is performed by the user to change the magnification rate to 1.6 times specified by a point503, the transmission data amount is changed to 0.6, so that the compression rate is re-set to ⅘ in step S211.

As described above, according to the present exemplary embodiment, the amount of data transmission (frame rate) from the image capturing element111to the image processing unit112is set to be constant, and in a case where the magnification rate is increased, the compression rate is correspondingly reduced. Therefore, in a case where an image is magnified, the compression rate is reduced, so that the encoding distortion is less likely to occur and less likely to become visible.

A second exemplary embodiment of the present disclosure will be described below with reference to the drawings.

FIG. 6is a block diagram illustrating an example of a configuration of an image capturing apparatus600according to the present exemplary embodiment. Only different configurations from those of the image capturing apparatus100illustrated inFIG. 1will be described below, and descriptions of similar elements are omitted.

As illustrated inFIG. 6, the image capturing apparatus600includes an image capturing element611and an image processing unit612. The image capturing element611includes the image capturing unit101and a first encoding unit102. The image processing unit612includes the decoding unit103, the display unit105, the operation unit106, the control unit107, a development processing unit601, a second encoding unit602, a memory interface (memory I/F)603, a memory604, and a recording unit605.

The development processing unit601performs basically the same processing as that of the development processing unit104inFIG. 1and outputs developed image data to the display unit105and the second encoding unit602. The second encoding unit602performs high efficiency encoding, such as H.264 or H.265, on input image data and outputs the encoded data to the memory I/F603. The memory I/F603adjusts a request to access the memory604from the respective processing units and controls reading and writing of data from and to the memory604. The memory604is a memory configured to store various types of data output from the processing units of the image capturing apparatus600and is, for example, a volatile memory. The recording unit605reads the encoded data stored in the memory604and records the read data on a recording medium606. The recording medium606is an external recording medium configured to record data captured and encoded by the image capturing apparatus600and is, for example, a secure digital (SD) card.

A process that is performed by the control unit107of the image capturing apparatus600will be described below with reference to a flowchart illustrated inFIG. 7. Descriptions of the processing that is also illustrated in the flowchart inFIG. 2are omitted.

In step S701, the control unit107determines whether a shutter button of the operation unit106is fully pressed and a recording instruction is thereby received. In a case where the control unit107determines that a recording instruction is not received (NO in step S701), the processing proceeds to step S208. On the other hand, in a case where the control unit107determines that a recording instruction is received (YES in step S701), the processing proceeds to step S702.

In step S702, the second encoding unit602encodes the developed image data. Then, in step S703, the memory OF603stores the encoded data in the memory604. Then, the recording unit605records the encoded data (image data) on the recording medium606.

As described above, in a case where a magnification operation is performed by the user, the compression rate of the first encoding unit102is changed based on the magnification rate as in the first exemplary embodiment. Thus, in a case where a recording instruction is received after a magnification operation is performed, image data on a magnified image is stored in the memory604, and thereafter the recording unit605records the image data on the recording medium606.

As described above, according to the present exemplary embodiment, in a case where a magnified image is to be recorded, a magnified image that is less likely to cause an encoding distortion is recorded. While steps S702and S703are performed prior to step S208in the present exemplary embodiment, step S208can be performed prior to or in parallel with steps S702and S703.

Embodiments of the present disclosure reduce visibility of an encoding distortion in a magnified image display while preventing an increase in data amount.

OTHER EMBODIMENTS

This application claims the benefit of Japanese Patent Application No. 2019-151862, filed Aug. 22, 2019, which is hereby incorporated by reference herein in its entirety.