WO2019129020A1

WO2019129020A1 - Automatic focusing method of camera, storage device and mobile terminal

Info

Publication number: WO2019129020A1
Application number: PCT/CN2018/123725
Authority: WO
Inventors: 许玉新; 张刘哲
Original assignee: 捷开通讯(深圳)有限公司
Priority date: 2017-12-26
Filing date: 2018-12-26
Publication date: 2019-07-04
Also published as: CN107911616A

Abstract

Disclosed are an automatic focusing method of a camera, a storage device and a mobile terminal. The method comprises the steps of: when detecting that a camera is started, judging whether there is a human face in a current picture in the camera; and if there is a human face in the current picture, then controlling the camera to focus so that a proportion occupied by the human face in a screen is a pre-set value. The present invention solves the problem in the prior art that, when photographing a figure, a mobile terminal cannot automatically focus so the size of the photographed figure is appropriate.

Description

Camera automatic focusing method, storage device and mobile terminal

This application claims the priority of the Chinese patent application filed on December 26, 2017, the Chinese Patent Office, application number 201711431427.7, the invention titled "a camera automatic focusing method, storage device and mobile terminal", the entire content of which is The citations are incorporated herein by reference.

Technical field

The present invention relates to the field of mobile terminal technologies, and in particular, to a camera automatic focusing method, a storage device, and a mobile terminal.

Background technique

With the popularity of smart phones, taking photos or taking pictures with smartphones has become a habit in people's daily lives. Whether it is a friend meeting or a parent-child interaction moment, take out a smart phone and leave a photo or a video to record the beautiful. Memory. People often use smart phones to shoot close-up characters. When shooting close-up characters, the proportion of characters in the whole picture is very important for the formed picture. If the ratio is too big or too small, it is not convenient to watch the memories. Therefore, when performing character shooting, it is often necessary to manually adjust the focal length of the camera according to the distance between the lens and the person being photographed to maintain the proportion of the person in the screen. When the person being photographed keeps moving, such as when the child is playing, the camera has to be repeatedly zoomed to capture the desired character size effect, which obviously causes great inconvenience to the shooting.

Therefore, the prior art has yet to be improved and developed.

technical problem

The embodiment of the invention provides a camera automatic focusing method, a storage device and a mobile terminal, which can solve the problem that the existing mobile terminal cannot automatically adjust the focus when the person is photographing, so that the size of the captured person is suitable.

Technical solution

The technical solution of the present invention is as follows:

In a first aspect, an embodiment of the present invention provides a camera automatic focusing method, which includes the steps of:

When it is detected that the camera is turned on, it is determined whether the current picture in the camera has a face;

If there is a face in the current picture, control the camera to focus to the proportion of the face on the screen as a preset value.

The camera auto-focusing method, wherein the step of controlling the camera to focus to a ratio of a face to a screen is a preset value, comprising:

Frame the face in the current picture, and control the camera to focus to the frame area to the screen area as the default value.

Frame the face in the current picture and calculate the ratio of the frame selection area to the screen area;

When the ratio is greater than the preset value, controlling the focal length of the camera to be reduced to a ratio of the frame selection area to the screen is a preset value;

When the ratio is less than the preset value, the camera focal length is controlled to be enlarged until the ratio of the frame selection area to the screen is a preset value.

The camera auto-focusing method, after the step of calculating the ratio of the frame selection area to the screen area, further includes:

When the ratio is equal to the preset value, there is no need to adjust the camera.

The camera automatic focusing method, wherein the frame used for the frame selection is a rectangular frame.

The control camera automatically adjusts the focal length to control the distance between the lens and the subject, so that the proportion of the face in the screen is a preset value.

The camera auto-focusing method, wherein the step of selecting a face in the current picture, and controlling the camera to focus to a ratio of the frame-selected area to the screen area is a preset value, including:

After the face of the current picture is selected in the frame, the ratio of the pixel points in the area selected by the control camera to the total pixel of the screen is preset.

The camera auto-focusing method, wherein before the step of determining whether the current picture in the camera is a human face when the camera is detected to be turned on, the method further includes:

Set an auto focus function;

After the auto focus function is turned on, the step of determining whether the current picture in the camera has a face is detected when the camera is detected to be turned on.

In a second aspect, an embodiment of the present invention provides a storage device, where a plurality of instructions are stored, where the instructions are suitable for being loaded by a processor and performing the following steps:

The storage device, wherein the instructions are adapted to be loaded by a processor and executed specifically:

In the current picture, there is a face, and the face in the current picture is selected, and the ratio of the camera to the area of the screen to the screen area is preset.

The face of the current picture is framed, and the face in the current picture is selected, and the ratio of the frame selection area to the screen area is calculated;

When the ratio is less than the preset value, the focal length of the camera is controlled to be enlarged until the ratio of the frame selection area to the screen is a preset value.

The storage device, wherein the instructions are adapted to be loaded by a processor and continue to execute:

When the ratio is equal to the preset value, the camera is controlled to maintain the current focal length.

In a third aspect, an embodiment of the present invention provides a mobile terminal, where the mobile terminal includes:

a processor adapted to implement each instruction;

A storage device having stored thereon a plurality of instructions adapted to be loaded by the processor and to perform the following steps:

The mobile terminal, wherein the step of controlling the camera to focus to a ratio of a face to a screen is a preset value, comprising:

The mobile terminal, after the step of calculating a ratio of a frame selection area to a screen area, further includes:

The mobile terminal, wherein the frame used for the frame selection is a rectangular frame.

In the mobile terminal, the step of selecting a face in the current picture, and controlling the camera to focus to a ratio of the frame selection area to the screen area is a preset value, including:

The mobile terminal, wherein before the step of determining whether the current picture in the camera is a human face when the camera is detected to be turned on, the method further includes:

Set an auto focus function;

Beneficial effect

The camera automatically adjusts the focus method, when the camera is turned on, by acquiring the current picture in the camera whether there is a human face, if the face is face, the camera automatically controls the focus to the proportion of the face to the screen as a preset value, thereby controlling the person The size of the face in the picture is fixed, so that the size of the captured person in the captured picture is appropriate and remains unchanged, so that no matter whether the character moves or not, the size of the character in the picture is not affected, thereby solving the prior art movement. The terminal cannot automatically adjust the focus when shooting a character to make the size of the captured person suitable.

DRAWINGS

FIG. 1 is a schematic flow chart of a method for automatically focusing a camera according to the present invention.

2 is a structural block diagram of a preferred embodiment of a mobile terminal provided by the present invention.

FIG. 3 is a schematic structural diagram of a mobile terminal according to an embodiment of the present invention.

Embodiments of the invention

The present invention provides a camera automatic focusing method, a storage device, and a mobile terminal. The present invention will be further described in detail below in order to make the objects, technical solutions and effects of the present invention more clear and clear. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention provides a camera automatic focusing method, wherein, as shown in FIG. 1, the steps include:

S1, when detecting that the camera is turned on, determining whether the current picture in the camera has a human face;

S2. If there is a face in the current picture, control the camera to focus to the proportion of the face on the screen as a preset value.

The camera automatic focusing method according to the present invention is suitable for mobile terminals such as smart phones and tablet computers. In the camera auto-focusing method, when the camera is turned on, it is detected whether a face exists in the current picture of the camera, and if a human face exists, the camera is automatically adjusted to adjust the focal length to control the distance between the lens and the object. , the proportion of the face in the screen is a preset value, so that the proportion of the face in the camera in the screen is always fixed, that is, the size of the captured person in the screen is kept constant, the user There is no need to manually adjust the focal length of the camera repeatedly, which can bring great convenience to the user. The preset value is an empirical value. When the proportion of the face on the screen is the preset value, the size of the character is suitable, which can satisfy the better subject viewing and the overall proportion of the screen is coordinated.

Preferably, in the step S1, whether the camera is turned on in real time is detected. When the camera is turned on, whether the camera mode or the camera mode is used at this time, the face recognition technology can be used to determine whether the current picture in the camera exists. Thereby, the mobile terminal automatically enters the steps of face capture and size adjustment.

Of course, before the step S1, an auto focus function opening step can also be set. Turning on the auto focus function means that the user is going to use the mobile terminal for person shooting and needs to ensure that the proportion of the captured face in the screen is a preset value, then the mobile terminal is only after the auto focus function is turned on. It is required to detect whether the camera is turned on and when detecting that the camera is turned on, determine whether there is a face in the current picture and adjust the focal length of the camera to achieve a predetermined shooting effect (ie, the face occupies the screen ratio to a preset value); and if the automatic adjustment If the focus function is not turned on, it means that the user needs to perform only regular shooting. Therefore, when the camera is turned on, there is no need to detect whether the current picture in the camera has a human face, but only conventional photography or imaging is required.

In the step S2, the step of controlling the camera to adjust the ratio of the face to the screen as a preset value includes:

Because of the irregularity of the face, it is relatively difficult to calculate the area. When the presence of a human face in the current picture is detected, the face pattern can be selected by using the regular pattern frame, and the camera can be adjusted to focus on the face selection. The area of the regular pattern (ie, the selected area of the frame) occupies the ratio of the screen area to a preset value, thereby achieving the purpose of adjusting the size ratio of the subject in the picture more quickly. Preferably, the regular pattern is displayed in a transparent line manner so as not to affect the user's shooting and real-time observation of the shooting effect.

More preferably, after the face in the current picture is selected in the frame, the ratio of the pixel point in the frame selection area to the total pixel point of the screen is controlled to be a preset value, and the face is adjusted during the camera focusing process. As the size changes, the frame selection area also becomes larger or smaller.

Preferably, the regular pattern is rectangular, the area calculation is convenient and the human face is relatively close. In the frame selection, the sides of the rectangle are tangent to the edge of the face.

Specifically, the step of controlling the camera to focus to a ratio of the face to the screen is a preset value, including:

S201, selecting a face in the current picture, and calculating a ratio of a frame selection area to a screen area;

S202. When the ratio is greater than a preset value, controlling a focal length of the camera to be reduced to a ratio of a frame selection area to a screen is a preset value;

S203. When the ratio is less than a preset value, controlling the focal length of the camera to be enlarged to a ratio of the frame selection area to the screen is a preset value.

After selecting a face in the frame, compare the area of the frame selection area with the area of the entire screen, and calculate the ratio of the area of the frame selection area to the area of the entire screen. If the calculated ratio is greater than the preset value, it indicates that the camera is in the camera. If the face is too large in the current picture and the camera is too close to the character, the focal length of the camera is reduced until the ratio of the frame selection area to the screen is a preset value; and if the calculated ratio is less than the preset value, it indicates that the current picture in the camera is in the current picture. If the face is too small and the camera is too far away from the character, the focal length of the camera is controlled until the ratio of the frame selection area to the screen is the preset value.

Preferably, when controlling the focus of the camera, the camera increases the focal length or reduces the focal length by a preset step value, and after the current focus adjustment, calculates whether the frame selection area accounts for the preset value of the screen ratio, and if so, ends. Focusing, otherwise continue to focus until the frame selection area is the preset value.

Based on the above method, the present invention also provides a storage device having stored thereon a plurality of instructions, wherein the instructions are adapted to be loaded by a processor and perform the following steps:

Based on the foregoing method, the present invention further provides a mobile terminal, as shown in FIG. 2, including:

The processor 100 is adapted to implement each instruction;

The storage device 200 is adapted to store a plurality of instructions adapted to be loaded by the processor and to perform the camera autofocus method as described above.

The technical details and benefits of the above mobile terminal and storage device have been elaborated in the above methods, and are not described herein again.

FIG. 3 is a block diagram showing a specific structure of a mobile terminal according to an embodiment of the present invention. The mobile terminal can be used to implement the camera auto-focusing method provided in the foregoing embodiment. The mobile terminal 1200 can be a smartphone or a tablet.

As shown in FIG. 3, the mobile terminal 1200 may include an RF (Radio Frequency) circuit 110, a memory 120 including one or more (only one shown) computer-readable storage medium, an input unit 130, and a display unit. 140, sensor 150, audio circuit 160, transmission module 170, including processor 180 having one or more processing cores (only one shown) and power supply 190 and the like. It will be understood by those skilled in the art that the structure of the mobile terminal 1200 shown in FIG. 3 does not constitute a limitation of the mobile terminal 1200, and may include more or less components than those illustrated, or combine some components or different components. Arrangement. among them:

The RF circuit 110 is configured to receive and transmit electromagnetic waves, and realize mutual conversion between electromagnetic waves and electrical signals, thereby communicating with a communication network or other devices. The RF circuit 110 may include various existing circuit elements for performing these functions, such as an antenna, a radio frequency transceiver, a digital signal processor, an encryption/decryption chip, a Subscriber Identity Module (SIM) card, a memory, and the like. The RF circuit 110 can communicate with various networks such as the Internet, an intranet, a wireless network, or communicate with other devices over a wireless network. The wireless network described above may include a cellular telephone network, a wireless local area network, or a metropolitan area network. The above wireless networks may use various communication standards, protocols and technologies, including but not limited to global mobile communication systems (Global System for Mobile Communication, GSM), Enhanced Mobile Communication Technology (Enhanced Data GSM Environment, EDGE), Wideband Code Division Multiple Access (Wideband Code) Division Multiple Access, WCDMA), Code Division Multiple Access (Code Division) Access, CDMA), Time Division Multiple Access (TDMA), Wireless Fidelity (Wireless Fidelity, Wi-Fi) (such as the Institute of Electrical and Electronics Engineers Standard IEEE 802.11a, IEEE 802.11b, IEEE 802.11g and / or IEEE 802.11n), VoIP (Voice) Over Internet Protocol, VoIP), Worldwide Interoperability for Microwave Access (Worldwide Interoperability for Microwave Access, Wi-Max, other protocols for mail, instant messaging, and short messages, as well as any other suitable communication protocol, may even include protocols that are not currently being developed.

The memory 120 can be used to store software programs and modules, such as program instructions/modules corresponding to the camera autofocus method in the above embodiment, and the processor 180 executes various functional applications by running software programs and modules stored in the memory 120. Data processing, that is, the function of automatic focusing of the camera. Memory 120 may include high speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid state memory. In some examples, memory 120 can further include memory remotely located relative to processor 180, which can be connected to mobile terminal 1200 via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

The input unit 130 can be configured to receive input numeric or character information and to generate keyboard, mouse, joystick, optical or trackball signal inputs related to user settings and function controls. In particular, input unit 130 can include touch-sensitive surface 131 as well as other input devices 132. Touch-sensitive surface 131, also referred to as a touch display or trackpad, can collect touch operations on or near the user (such as a user using a finger, stylus, etc., on any suitable object or accessory on touch-sensitive surface 131 or The operation near the touch-sensitive surface 131) and driving the corresponding connecting device according to a preset program. Alternatively, the touch-sensitive surface 131 can include two portions of a touch detection device and a touch controller. Wherein, the touch detection device detects the touch orientation of the user, and detects a signal brought by the touch operation, and transmits the signal to the touch controller; the touch controller receives the touch information from the touch detection device, converts the touch information into contact coordinates, and sends the touch information. The processor 180 is provided and can receive commands from the processor 180 and execute them. In addition, the touch-sensitive surface 131 can be implemented in various types such as resistive, capacitive, infrared, and surface acoustic waves. In addition to the touch-sensitive surface 131, the input unit 130 can also include other input devices 132. Specifically, other input devices 132 may include, but are not limited to, one or more of a physical keyboard, function keys (such as volume control buttons, switch buttons, etc.), trackballs, mice, joysticks, and the like.

The display unit 140 can be used to display information input by the user or information provided to the user and various graphical user interfaces of the mobile terminal 1200, which can be composed of graphics, text, icons, video, and any combination thereof. The display unit 140 may include a display panel 141, and optionally, an LCD (Liquid may be used) The display panel 141 is configured in the form of a Crystal Display (LCD) or an OLED (Organic Light-Emitting Diode). Further, the touch-sensitive surface 131 may cover the display panel 141, and when the touch-sensitive surface 131 detects a touch operation thereon or nearby, it is transmitted to the processor 180 to determine the type of the touch event, and then the processor 180 according to the touch event The type provides a corresponding visual output on display panel 141. Although in FIG. 3, touch-sensitive surface 131 and display panel 141 are implemented as two separate components to implement input and output functions, in some embodiments, touch-sensitive surface 131 can be integrated with display panel 141 for input. And output function.

Mobile terminal 1200 may also include at least one type of sensor 150, such as a light sensor, motion sensor, and other sensors. Specifically, the light sensor may include an ambient light sensor and a proximity sensor, wherein the ambient light sensor may adjust the brightness of the display panel 141 according to the brightness of the ambient light, and the proximity sensor may close the display panel 141 when the mobile terminal 1200 moves to the ear. And / or backlight. As a kind of motion sensor, the gravity acceleration sensor can detect the magnitude of acceleration in all directions (usually three axes). When it is stationary, it can detect the magnitude and direction of gravity. It can be used to identify the gesture of the mobile phone (such as horizontal and vertical screen switching, related Game, magnetometer attitude calibration), vibration recognition related functions (such as pedometer, tapping), etc.; as for the mobile terminal 1200 can also be configured with gyroscopes, barometers, hygrometers, thermometers, infrared sensors and other sensors, here No longer.

The audio circuit 160, the speaker 161, and the microphone 162 can provide an audio interface between the user and the mobile terminal 1200. The audio circuit 160 can transmit the converted electrical data of the received audio data to the speaker 161 for conversion to the sound signal output by the speaker 161; on the other hand, the microphone 162 converts the collected sound signal into an electrical signal by the audio circuit 160. After receiving, it is converted into audio data, and then processed by the audio data output processor 180, transmitted to the mobile terminal 110 via the RF circuit 110, or outputted to the memory 120 for further processing. The audio circuit 160 may also include an earbud jack to provide communication of the peripheral earphones with the mobile terminal 1200.

The mobile terminal 1200 can help the user to send and receive emails, browse web pages, access streaming media, etc. through the transmission module 170 (eg, Wi-Fi module), which provides wireless broadband Internet access to the user. Although FIG. 3 shows the transmission module 170, it can be understood that it does not belong to the essential configuration of the mobile terminal 1200, and may be omitted as needed within the scope of not changing the essence of the invention.

The processor 180 is a control center of the mobile terminal 1200 that connects various portions of the entire handset with various interfaces and lines, by running or executing software programs and/or modules stored in the memory 120, and recalling data stored in the memory 120. The various functions and processing data of the mobile terminal 1200 are executed to perform overall monitoring of the mobile phone. Optionally, the processor 180 may include one or more processing cores; in some embodiments, the processor 180 may integrate an application processor and a modem processor, wherein the application processor mainly processes an operating system, a user interface, and For applications, etc., the modem processor primarily handles wireless communications. It can be understood that the above modem processor may not be integrated into the processor 180.

The mobile terminal 1200 also includes a power source 190 (such as a battery) that powers the various components. In some embodiments, the power source can be logically coupled to the processor 180 through a power management system to manage charging, discharging, and power consumption through the power management system. Management and other functions. Power supply 190 may also include any one or more of a DC or AC power source, a recharging system, a power failure detection circuit, a power converter or inverter, a power status indicator, and the like.

Although not shown, the mobile terminal 1200 may further include a camera (such as a front camera, a rear camera), a Bluetooth module, and the like, and details are not described herein. Specifically, in this embodiment, the display unit of the mobile terminal is a touch screen display, the mobile terminal further includes a memory, and one or more programs, wherein one or more programs are stored in the memory and configured to be one or one The above processor executes one or more programs that include instructions for performing the following operations:

In some embodiments, the step of controlling the camera to focus to a ratio of the face to the screen is a preset value, including:

In some embodiments, after the step of calculating the ratio of the area of the screen to the screen area, the method further includes:

In some embodiments, the frame used for the frame selection is a rectangular frame.

In some embodiments, the step of selecting a face in the current picture, and controlling the camera to focus to a ratio of the frame selection area to the screen area is a preset value, including:

In some embodiments, before the step of determining whether the current picture in the camera is a human face when the camera is detected to be turned on, the method further includes:

Set an auto focus function;

In summary, the present invention provides a camera auto-focusing method, a storage device, and a mobile terminal. The camera automatically adjusts a focus method according to the present invention. When the camera is turned on, the current picture in the camera is obtained by a face. If there is a human face, the camera automatically controls the focal length to the proportion of the face to the screen as a preset value, thereby controlling the size of the face in the picture to be fixed, so that the size of the captured person in the captured picture is appropriate and remains unchanged. Therefore, no matter whether the character moves or not, the size of the character in the screen is not affected, thereby solving the problem that the mobile terminal in the prior art cannot automatically adjust the focus when shooting the character so that the size of the captured person is appropriate.

It is to be understood that the application of the present invention is not limited to the above-described examples, and those skilled in the art can make modifications and changes in accordance with the above description, all of which are within the scope of the appended claims.

Claims

A camera automatic focusing method, comprising the steps of:

When it is detected that the camera is turned on, it is determined whether the current picture in the camera has a face;

If there is a face in the current picture, control the camera to focus to the proportion of the face on the screen as a preset value.
The camera auto-focusing method according to claim 1, wherein the step of controlling the camera to focus to a ratio of a face to a screen is a preset value, comprising:

Frame the face in the current picture, and control the camera to focus to the frame area to the screen area as the default value.
The camera auto-focusing method according to claim 1, wherein the step of controlling the camera to focus to a ratio of a face to a screen is a preset value, comprising:

Frame the face in the current picture and calculate the ratio of the frame selection area to the screen area;

When the ratio is greater than the preset value, controlling the focal length of the camera to be reduced to a ratio of the frame selection area to the screen is a preset value;

When the ratio is less than the preset value, the focal length of the camera is controlled to be enlarged until the ratio of the frame selection area to the screen is a preset value.
The camera auto-focusing method according to claim 3, wherein after the step of calculating the ratio of the frame selection area to the screen area, the method further comprises:

When the ratio is equal to the preset value, the camera is controlled to maintain the current focal length.
The camera autofocus method according to claim 2, wherein the frame used for the frame selection is a rectangular frame.
The camera auto-focusing method according to claim 1, wherein the step of controlling the camera to focus to a ratio of a face to a screen is a preset value, comprising:

The control camera automatically adjusts the focal length to control the distance between the lens and the subject, so that the proportion of the face in the screen is a preset value.
The camera auto-focusing method according to claim 2, wherein the step of selecting a face in the current picture, and controlling the camera to focus to a ratio of the frame-selected area to the screen area is a preset value, comprising:

After the face of the current picture is selected in the frame, the ratio of the pixel points in the area selected by the control camera to the total pixel of the screen is preset.
The camera auto-focusing method according to claim 1, wherein before the step of determining whether the current picture in the camera is a human face when the camera is detected to be turned on, the method further includes:

Set an auto focus function;

After the auto focus function is turned on, the step of determining whether the current picture in the camera has a face is detected when the camera is detected to be turned on.
A storage device having stored thereon a plurality of instructions, wherein the instructions are adapted to be loaded by a processor and perform the following steps:

When it is detected that the camera is turned on, it is determined whether the current picture in the camera has a face;

If there is a face in the current picture, control the camera to focus to the proportion of the face on the screen as a preset value.
The storage device of claim 9 wherein said instructions are adapted to be loaded by a processor and executed specifically:

In the current picture, there is a face, and the face in the current picture is selected, and the ratio of the camera to the area of the screen to the screen area is preset.
The storage device of claim 9 wherein said instructions are adapted to be loaded by a processor and executed specifically:

The face of the current picture is framed, and the face in the current picture is selected, and the ratio of the frame selection area to the screen area is calculated;

When the ratio is greater than the preset value, controlling the focal length of the camera to be reduced to a ratio of the frame selection area to the screen is a preset value;

When the ratio is less than the preset value, the focal length of the camera is controlled to be enlarged until the ratio of the frame selection area to the screen is a preset value.
The storage device of claim 11 wherein the instructions are adapted to be loaded by the processor and continue to execute:

When the ratio is equal to the preset value, there is no need to adjust the camera.
A mobile terminal, wherein the mobile terminal comprises:

a processor adapted to implement each instruction;

A storage device having stored thereon a plurality of instructions adapted to be loaded by the processor and to perform the following steps:

When it is detected that the camera is turned on, it is determined whether the current picture in the camera has a face;

If there is a face in the current picture, control the camera to focus to the proportion of the face on the screen as a preset value.
The mobile terminal of claim 13, wherein the step of controlling the camera to focus to a ratio of the face to the screen is a preset value, comprising:

Frame the face in the current picture, and control the camera to focus to the frame area to the screen area as the default value.
The mobile terminal of claim 13, wherein the step of controlling the camera to focus to a ratio of the face to the screen is a preset value, comprising:

Frame the face in the current picture and calculate the ratio of the frame selection area to the screen area;

When the ratio is greater than the preset value, controlling the focal length of the camera to be reduced to a ratio of the frame selection area to the screen is a preset value;

When the ratio is less than the preset value, the focal length of the camera is controlled to be enlarged until the ratio of the frame selection area to the screen is a preset value.
The mobile terminal of claim 15, wherein the step of calculating a ratio of the area of the screen to the screen area further comprises:

When the ratio is equal to the preset value, the camera is controlled to maintain the current focal length.
The mobile terminal of claim 14, wherein the frame used for the frame selection is a rectangular frame.
The mobile terminal of claim 13, wherein the step of controlling the camera to focus to a ratio of the face to the screen is a preset value, comprising:

The control camera automatically adjusts the focal length to control the distance between the lens and the subject, so that the proportion of the face in the screen is a preset value.
The mobile terminal of claim 14, wherein the step of selecting a face in the current picture, controlling the camera to focus to a ratio of the frame selection area to the screen area is a preset value, comprising:

After the face of the current picture is selected in the frame, the ratio of the pixel points in the area selected by the control camera to the total pixel of the screen is preset.
The mobile terminal according to claim 13, wherein before the step of determining whether the current picture in the camera is a human face when the camera is detected to be turned on, the method further includes:

Set an auto focus function;

After the auto focus function is turned on, the step of determining whether the current picture in the camera has a face is detected when the camera is detected to be turned on.