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  2. Qt 5.15.17
  3. Qt Multimedia
  4. QML 类型
  5. Camera QML 类型

Camera QML 类型

访问取景器帧，并拍摄照片和影片。 更多...

import 语句： import QtMultimedia 5.15
继承：

QtObject

特性

信号

方法

详细描述

可以使用 Camera to capture images and movies from a camera, and manipulate the capture and processing settings that get applied to the images. To display the viewfinder you can use VideoOutput with the Camera set as the source. 

Item {
    width: 640
    height: 360
    Camera {
        id: camera
        imageProcessing.whiteBalanceMode: CameraImageProcessing.WhiteBalanceFlash
        exposure {
            exposureCompensation: -1.0
            exposureMode: Camera.ExposurePortrait
        }
        flash.mode: Camera.FlashRedEyeReduction
        imageCapture {
            onImageCaptured: {
                photoPreview.source = preview  // Show the preview in an Image
            }
        }
    }
    VideoOutput {
        source: camera
        anchors.fill: parent
        focus : visible // to receive focus and capture key events when visible
    }
    Image {
        id: photoPreview
    }
}

If multiple cameras are available, you can select which one to use by setting the deviceId property to a value from QtMultimedia.availableCameras . On a mobile device, you can conveniently switch between front-facing and back-facing cameras by setting the position 特性。

The various settings and functionality of the Camera stack is spread across a few different child properties of Camera.

特性 描述
imageCapture Methods and properties for capturing still images.
videoRecorder Methods and properties for capturing movies.
exposure Methods and properties for adjusting exposure (aperture, shutter speed etc).
focus Methods and properties for adjusting focus and providing feedback on autofocus progress.
flash Methods and properties for controlling the camera flash.
imageProcessing Methods and properties for adjusting camera image processing parameters.

Basic camera state management, error reporting, and simple zoom properties are available in the Camera itself. For integration with C++ code, the mediaObject property allows you to access the standard Qt Multimedia camera controls.

Many of the camera settings may take some time to apply, and might be limited to certain supported values depending on the hardware. Some camera settings may be set manually or automatically. These settings properties contain the current set value. For example, when autofocus is enabled the focus zones are exposed in the focus 特性。

For additional information, read also the 摄像头概述 .

特性文档编制

availability : enumeration

This property holds the availability state of the camera.

常量 描述
Camera.Available The camera is available for use.
Camera.Busy The camera is busy at the moment as it is being used by another process.
Camera.Unavailable The camera is not available for use (there may be no camera hardware).
Camera.ResourceMissing The camera cannot be used because of missing resources. It may be possible to try again at a later time.

cameraState : enumeration

This property holds the camera object's current state. The default camera state is ActiveState .

常量 描述
Camera.UnloadedState The initial camera state, with the camera not loaded. The camera capabilities (with the exception of supported capture modes) are unknown. This state saves the most power, but takes the longest time to be ready for capture. While the supported settings are unknown in this state, you can still set the camera capture settings like codec, resolution, or frame rate.
Camera.LoadedState The camera is loaded and ready to be configured. In this state you can query camera capabilities, set capture resolution, codecs, and so on. The viewfinder is not active in the loaded state. The camera consumes power in this state.
Camera.ActiveState In the active state, the viewfinder frames are available and the camera is ready for capture.

cameraStatus : enumeration

This property holds the camera object's current status.

常量 描述
Camera.ActiveStatus The camera has been started and can produce data, viewfinder displays video frames. Depending on backend, changing camera settings such as capture mode, codecs, or resolution in Camera.ActiveState may lead to changing the status to LoadedStatus and StartingStatus while the settings are applied, and back to ActiveStatus when the camera is ready.
Camera.StartingStatus The camera is transitioning to Camera.ActiveState . The camera service is not ready to capture yet.
Camera.StoppingStatus The camera is transitioning from Camera.ActiveState to Camera.LoadedState or Camera.UnloadedState .
Camera.StandbyStatus The camera is in the power saving standby mode. The camera may enter standby mode after some time of inactivity in the Camera.LoadedState 状态。
Camera.LoadedStatus The camera is loaded and ready to be configured. This status indicates that the camera is opened and it's possible to query for supported image and video capture settings, such as resolution, frame rate, and codecs.
Camera.LoadingStatus The camera is transitioning from Camera.UnloadedState to Camera.LoadedState or Camera.ActiveState .
Camera.UnloadingStatus The camera is transitioning from Camera.LoadedState or Camera.ActiveState to Camera.UnloadedState .
Camera.UnloadedStatus The initial camera status, with camera not loaded. The camera capabilities including supported capture settings may be unknown.
Camera.UnavailableStatus The camera or camera backend is not available.

captureMode : enumeration

This property holds the camera capture mode. The default capture mode is CaptureStillImage .

常量 描述
Camera.CaptureViewfinder Camera is only configured to display viewfinder.
Camera.CaptureStillImage Prepares the Camera for capturing still images.
Camera.CaptureVideo Prepares the Camera for capturing video.

deviceId : string

This property holds the unique identifier for the camera device being used. It may not be human-readable.

You can get all available device IDs from QtMultimedia.availableCameras . If no value is provided or if set to an empty string, the system's default camera will be used.

若可能的话， cameraState , captureMode , digitalZoom and other camera parameters are preserved when changing the camera device.

该特性在 Qt 5.4 引入。

另请参阅 displayName and position .

digitalZoom : real

This property holds the current digital zoom factor.

[read-only] displayName : string

This property holds the human-readable name of the camera.

You can use this property to display the name of the camera in a user interface.

该特性在 Qt 5.4 引入。

另请参阅 deviceId .

errorCode : enumeration

此特性保持最后错误代码。

常量 描述
Camera.NoError 没有出现错误。
Camera.CameraError 有出现错误。
Camera.InvalidRequestError System resources do not support the requested functionality.
Camera.ServiceMissingError 没有可用摄像头服务。
Camera.NotSupportedFeatureError 不支持特征。

另请参阅 errorOccurred and errorString .

errorString : string

此特性保持最后错误字符串 (若有的话)。

另请参阅 errorOccurred and errorCode .

lockStatus : enumeration

This property holds the status of all the requested camera locks.

常量 描述
Camera.Unlocked The application is not interested in camera settings value. The camera may keep this parameter without changes, which is common with camera focus, or adjust exposure and white balance constantly to keep the viewfinder image nice.
Camera.Searching The application has requested the camera focus, exposure, or white balance lock with searchAndLock() . This state indicates the camera is focusing or calculating exposure and white balance.
Camera.Locked The camera focus, exposure, or white balance is locked. The camera is ready to capture, and the application may check the exposure parameters. The locked state usually means the requested parameter stays the same, except in cases where the parameter is requested to be updated constantly. For example, in continuous focusing mode, the focus is considered locked as long as the object is in focus, even while the actual focusing distance may be constantly changing.

maximumDigitalZoom : real

This property holds the maximum digital zoom factor supported, or 1.0 if digital zoom is not supported.

maximumOpticalZoom : real

This property holds the maximum optical zoom factor supported, or 1.0 if optical zoom is not supported.

mediaObject : variant

This property holds the native media object for the camera.

It can be used to get a pointer to a QCamera object in order to integrate with C++ code. 

QObject *qmlCamera; // The QML Camera object
QCamera *camera = qvariant_cast<QCamera *>(qmlCamera->property("mediaObject"));

注意： This property is not accessible from QML.

metaData group

metaData.cameraManufacturer : variant

metaData.cameraModel : variant

metaData.dateTimeOriginal : variant

metaData.event : variant

metaData.gpsAltitude : variant

metaData.gpsImgDirection : variant

metaData.gpsLatitude : variant

metaData.gpsLongitude : variant

metaData.gpsProcessingMethod : variant

metaData.gpsSpeed : variant

metaData.gpsTimestamp : variant

metaData.gpsTrack : variant

metaData.orientation : variant

metaData.subject : variant

These properties hold the meta data for the camera captures.

  • metaData.cameraManufacturer holds the name of the manufacturer of the camera.
  • metaData.cameraModel holds the name of the model of the camera.
  • metaData.event holds the event during which the photo or video is to be captured.
  • metaData.subject holds the name of the subject of the capture or recording.
  • metaData.orientation holds the clockwise rotation of the camera at time of capture.
  • metaData.dateTimeOriginal holds the initial time at which the photo or video is captured.
  • metaData.gpsLatitude holds the latitude of the camera in decimal degrees at time of capture.
  • metaData.gpsLongitude holds the longitude of the camera in decimal degrees at time of capture.
  • metaData.gpsAltitude holds the altitude of the camera in meters at time of capture.
  • metaData.gpsTimestamp holds the timestamp of the GPS position data.
  • metaData.gpsTrack holds direction of movement of the camera at the time of capture. It is measured in degrees clockwise from north.
  • metaData.gpsSpeed holds the velocity in kilometers per hour of the camera at time of capture.
  • metaData.gpsImgDirection holds direction the camera is facing at the time of capture. It is measured in degrees clockwise from north.
  • metaData.gpsProcessingMethod holds the name of the method for determining the GPS position.

This QML property was introduced in Qt 5.4.

另请参阅 QMediaMetaData .

opticalZoom : real

This property holds the current optical zoom factor.

[read-only] orientation : int

This property holds the physical orientation of the camera sensor.

The value is the orientation angle (clockwise, in steps of 90 degrees) of the camera sensor in relation to the display in its natural orientation.

For example, suppose a mobile device which is naturally in portrait orientation. The back-facing camera is mounted in landscape. If the top side of the camera sensor is aligned with the right edge of the screen in natural orientation, orientation 返回 270 . If the top side of a front-facing camera sensor is aligned with the right edge of the screen, orientation 返回 90 .

该特性在 Qt 5.4 引入。

另请参阅 VideoOutput::orientation .

位置 : enumeration

This property holds the physical position of the camera on the hardware system.

On a mobile device, this property can be used to easily choose between front-facing and back-facing cameras. If this property is set to Camera.UnspecifiedPosition , the system's default camera is used.

若可能的话， cameraState , captureMode , digitalZoom and other camera parameters are preserved when changing the camera device.

常量 描述
Camera.UnspecifiedPosition The camera position is unspecified or unknown.
Camera.BackFace The camera is on the back face of the system hardware. For example, on a mobile device, it is on side opposite from the screen.
Camera.FrontFace The camera is on the front face of the system hardware. For example, on a mobile device, it means it is on the same side as the screen. Viewfinder frames of front-facing cameras are mirrored horizontally, so the users can see themselves as looking into a mirror. Captured images or videos are not mirrored.

该特性在 Qt 5.4 引入。

另请参阅 deviceId .

viewfinder group

viewfinder.maximumFrameRate : real

viewfinder.minimumFrameRate : real

viewfinder.resolution : size

These properties hold the viewfinder settings.

viewfinder.resolution holds the resolution of the camera viewfinder. If no resolution is given or if it is empty, the backend uses a default value.

viewfinder.minimumFrameRate holds the minimum frame rate for the viewfinder in frames per second. If no value is given or if set to 0 , the backend uses a default value.

viewfinder.maximumFrameRate holds the maximum frame rate for the viewfinder in frames per second. If no value is given or if set to 0 , the backend uses a default value.

若 viewfinder.minimumFrameRate 等于 viewfinder.maximumFrameRate , the frame rate is fixed. If not, the actual frame rate fluctuates between the two values.

Changing the viewfinder settings while the camera is in the Camera.ActiveState state may cause the camera to be restarted.

If the camera is used to capture videos or images, the viewfinder settings might be ignored if they conflict with the capture settings. You can check the actual viewfinder settings once the camera is in the Camera.ActiveStatus 状态。

Supported values can be retrieved with supportedViewfinderResolutions() and supportedViewfinderFrameRateRanges() .

This QML property was introduced in Qt 5.4.

信号文档编制

cameraStateChanged ( state )

This signal is emitted when the camera state has changed to state . Since the state changes may take some time to occur this signal may arrive sometime after the state change has been requested.

相应处理程序是 onCameraStateChanged .

注意： 相应处理程序是 onCameraStateChanged .

digitalZoomChanged ( zoom )

This signal is emitted when the digital zoom setting has changed to zoom .

相应处理程序是 onDigitalZoomChanged .

注意： 相应处理程序是 onDigitalZoomChanged .

errorOccurred ( errorCode , errorString )

This signal is emitted when an error specified by errorCode occurs. A descriptive string value is available in errorString .

相应处理程序是 onError .

注意： 相应处理程序是 onErrorOccurred .

This signal was introduced in Qt 5.15.

另请参阅 errorCode and errorString .

lockStatusChanged ()

This signal is emitted when the lock status (focus, exposure etc) changes. This can happen when locking (e.g. autofocusing) is complete or has failed.

相应处理程序是 onLockStatusChanged .

注意： 相应处理程序是 onLockStatusChanged .

manualWhiteBalanceChanged ()

此信号发射当 manualWhiteBalance 特性改变。

相应处理程序是 onManualWhiteBalanceChanged .

注意： 相应处理程序是 onManualWhiteBalanceChanged .

maximumDigitalZoomChanged ( zoom )

This signal is emitted when the maximum digital zoom setting has changed to zoom . This can occur when you change between video and still image capture modes, or the capture settings are changed.

相应处理程序是 onMaximumDigitalZoomChanged .

注意： 相应处理程序是 onMaximumDigitalZoomChanged .

maximumOpticalZoomChanged ( zoom )

This signal is emitted when the maximum optical zoom setting has changed to zoom . This can occur when you change between video and still image capture modes, or the capture settings are changed.

相应处理程序是 onMaximumOpticalZoomChanged .

注意： 相应处理程序是 onMaximumOpticalZoomChanged .

opticalZoomChanged ( zoom )

This signal is emitted when the optical zoom setting has changed to zoom .

相应处理程序是 onOpticalZoomChanged .

注意： 相应处理程序是 onOpticalZoomChanged .

whiteBalanceModeChanged ()

此信号发射当 whiteBalanceMode 特性改变。

相应处理程序是 onWhiteBalanceModeChanged .

注意： 相应处理程序是 onWhiteBalanceModeChanged .

方法文档编制

searchAndLock ()

Start focusing, exposure and white balance calculation.

This is appropriate to call when the camera focus button is pressed (or on a camera capture button half-press). If the camera supports autofocusing, information on the focus zones is available through the focus 特性。

start ()

Starts the camera. Viewfinder frames will be available and image or movie capture will be possible.

stop ()

Stops the camera, but leaves the camera stack loaded.

In this state, the camera still consumes power.

list < 对象 > supportedViewfinderFrameRateRanges ( size resolution )

Returns a list of supported viewfinder frame rate ranges.

Each range object in the list has the minimumFrameRate and maximumFrameRate 特性。

If the optional parameter resolution is specified, the returned list is reduced to frame rate ranges supported for the given resolution .

The camera must be loaded before calling this function, otherwise the returned list is empty.

该方法在 Qt 5.5 引入。

另请参阅 viewfinder .

list < size > supportedViewfinderResolutions ( real minimumFrameRate , real maximumFrameRate )

Returns a list of supported viewfinder resolutions.

If both optional parameters minimumFrameRate and maximumFrameRate are specified, the returned list is reduced to resolutions supported for the given frame rate range.

The camera must be loaded before calling this function, otherwise the returned list is empty.

该方法在 Qt 5.5 引入。

另请参阅 viewfinder .

unlock ()

Unlock focus, exposure and white balance locks.

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