Trait nokhwa::camera_traits::CaptureBackendTrait

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pub trait CaptureBackendTrait {

Show 24 methods    // Required methods
    fn backend(&self) -> ApiBackend;
    fn camera_info(&self) -> &CameraInfo;
    fn refresh_camera_format(&mut self) -> Result<(), NokhwaError>;
    fn camera_format(&self) -> CameraFormat;
    fn set_camera_format(
        &mut self,
        new_fmt: CameraFormat
    ) -> Result<(), NokhwaError>;
    fn compatible_list_by_resolution(
        &mut self,
        fourcc: FrameFormat
    ) -> Result<HashMap<Resolution, Vec<u32, Global>, RandomState>, NokhwaError>;
    fn compatible_fourcc(
        &mut self
    ) -> Result<Vec<FrameFormat, Global>, NokhwaError>;
    fn resolution(&self) -> Resolution;
    fn set_resolution(&mut self, new_res: Resolution) -> Result<(), NokhwaError>;
    fn frame_rate(&self) -> u32;
    fn set_frame_rate(&mut self, new_fps: u32) -> Result<(), NokhwaError>;
    fn frame_format(&self) -> FrameFormat;
    fn set_frame_format(
        &mut self,
        fourcc: FrameFormat
    ) -> Result<(), NokhwaError>;
    fn camera_control(
        &self,
        control: KnownCameraControl
    ) -> Result<CameraControl, NokhwaError>;
    fn camera_controls(&self) -> Result<Vec<CameraControl, Global>, NokhwaError>;
    fn set_camera_control(
        &mut self,
        id: KnownCameraControl,
        value: ControlValueSetter
    ) -> Result<(), NokhwaError>;
    fn open_stream(&mut self) -> Result<(), NokhwaError>;
    fn is_stream_open(&self) -> bool;
    fn frame(&mut self) -> Result<Buffer, NokhwaError>;
    fn frame_raw(&mut self) -> Result<Cow<'_, [u8]>, NokhwaError>;
    fn stop_stream(&mut self) -> Result<(), NokhwaError>;

    // Provided methods
    fn compatible_camera_formats(
        &mut self
    ) -> Result<Vec<CameraFormat, Global>, NokhwaError> { ... }
    fn decoded_buffer_size(&self, alpha: bool) -> usize { ... }
    fn frame_texture<'a>(
        &mut self,
        device: &Device,
        queue: &Queue,
        label: Option<&'a str>
    ) -> Result<Texture, NokhwaError> { ... }

}
Expand description

This trait is for any backend that allows you to grab and take frames from a camera. Many of the backends are blocking, if the camera is occupied the library will block while it waits for it to become available.

Note:

  • Backends, if not provided with a camera format, will be spawned with 640x480@15 FPS, MJPEG CameraFormat.
  • Behaviour can differ from backend to backend. While the Camera struct abstracts most of this away, if you plan to use the raw backend structs please read the Quirks section of each backend.
  • If you call stop_stream(), you will usually need to call open_stream() to get more frames from the camera.

Required Methods§

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fn backend(&self) -> ApiBackend

Returns the current backend used.

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fn camera_info(&self) -> &CameraInfo

Gets the camera information such as Name and Index as a CameraInfo.

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fn refresh_camera_format(&mut self) -> Result<(), NokhwaError>

Forcefully refreshes the stored camera format, bringing it into sync with “reality” (current camera state)

Errors

If the camera can not get its most recent CameraFormat. this will error.

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fn camera_format(&self) -> CameraFormat

Gets the current CameraFormat. This will force refresh to the current latest if it has changed.

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fn set_camera_format( &mut self, new_fmt: CameraFormat ) -> Result<(), NokhwaError>

Will set the current CameraFormat This will reset the current stream if used while stream is opened.

This will also update the cache.

Errors

If you started the stream and the camera rejects the new camera format, this will return an error.

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fn compatible_list_by_resolution( &mut self, fourcc: FrameFormat ) -> Result<HashMap<Resolution, Vec<u32, Global>, RandomState>, NokhwaError>

A hashmap of Resolutions mapped to framerates. Not sorted!

Errors

This will error if the camera is not queryable or a query operation has failed. Some backends will error this out as a Unsupported Operation (UnsupportedOperationError).

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fn compatible_fourcc(&mut self) -> Result<Vec<FrameFormat, Global>, NokhwaError>

A Vector of compatible FrameFormats. Will only return 2 elements at most.

Errors

This will error if the camera is not queryable or a query operation has failed. Some backends will error this out as a Unsupported Operation (UnsupportedOperationError).

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fn resolution(&self) -> Resolution

Gets the current camera resolution (See: Resolution, CameraFormat). This will force refresh to the current latest if it has changed.

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fn set_resolution(&mut self, new_res: Resolution) -> Result<(), NokhwaError>

Will set the current Resolution This will reset the current stream if used while stream is opened.

This will also update the cache.

Errors

If you started the stream and the camera rejects the new resolution, this will return an error.

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fn frame_rate(&self) -> u32

Gets the current camera framerate (See: CameraFormat). This will force refresh to the current latest if it has changed.

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fn set_frame_rate(&mut self, new_fps: u32) -> Result<(), NokhwaError>

Will set the current framerate This will reset the current stream if used while stream is opened.

This will also update the cache.

Errors

If you started the stream and the camera rejects the new framerate, this will return an error.

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fn frame_format(&self) -> FrameFormat

Gets the current camera’s frame format (See: FrameFormat, CameraFormat). This will force refresh to the current latest if it has changed.

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fn set_frame_format(&mut self, fourcc: FrameFormat) -> Result<(), NokhwaError>

Will set the current FrameFormat This will reset the current stream if used while stream is opened.

This will also update the cache.

Errors

If you started the stream and the camera rejects the new frame format, this will return an error.

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fn camera_control( &self, control: KnownCameraControl ) -> Result<CameraControl, NokhwaError>

Gets the value of KnownCameraControl.

Errors

If the control is not supported or there is an error while getting the camera control values (e.g. unexpected value, too high, etc) this will error.

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fn camera_controls(&self) -> Result<Vec<CameraControl, Global>, NokhwaError>

Gets the current supported list of KnownCameraControl

Errors

If the list cannot be collected, this will error. This can be treated as a “nothing supported”.

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fn set_camera_control( &mut self, id: KnownCameraControl, value: ControlValueSetter ) -> Result<(), NokhwaError>

Sets the control to control in the camera. Usually, the pipeline is calling camera_control(), getting a camera control that way then calling value() to get a ControlValueSetter and setting the value that way.

Errors

If the control is not supported, the value is invalid (less than min, greater than max, not in step), or there was an error setting the control, this will error.

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fn open_stream(&mut self) -> Result<(), NokhwaError>

Will open the camera stream with set parameters. This will be called internally if you try and call frame() before you call open_stream().

Errors

If the specific backend fails to open the camera (e.g. already taken, busy, doesn’t exist anymore) this will error.

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fn is_stream_open(&self) -> bool

Checks if stream if open. If it is, it will return true.

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fn frame(&mut self) -> Result<Buffer, NokhwaError>

Will get a frame from the camera as a Buffer. Depending on the backend, if you have not called open_stream() before you called this, it will either return an error.

Errors

If the backend fails to get the frame (e.g. already taken, busy, doesn’t exist anymore), the decoding fails (e.g. MJPEG -> u8), or open_stream() has not been called yet, this will error.

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fn frame_raw(&mut self) -> Result<Cow<'_, [u8]>, NokhwaError>

Will get a frame from the camera without any processing applied, meaning you will usually get a frame you need to decode yourself.

Errors

If the backend fails to get the frame (e.g. already taken, busy, doesn’t exist anymore), or open_stream() has not been called yet, this will error.

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fn stop_stream(&mut self) -> Result<(), NokhwaError>

Will drop the stream.

Errors

Please check the Quirks section of each backend.

Provided Methods§

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fn compatible_camera_formats( &mut self ) -> Result<Vec<CameraFormat, Global>, NokhwaError>

Gets the compatible CameraFormat of the camera

Errors

If it fails to get, this will error.

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fn decoded_buffer_size(&self, alpha: bool) -> usize

The minimum buffer size needed to write the current frame. If alpha is true, it will instead return the minimum size of the buffer with an alpha channel as well. This assumes that you are decoding to RGB/RGBA for FrameFormat::MJPEG or FrameFormat::YUYV and Luma8/LumaA8 for FrameFormat::GRAY

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fn frame_texture<'a>( &mut self, device: &Device, queue: &Queue, label: Option<&'a str> ) -> Result<Texture, NokhwaError>

Available on crate feature wgpu-types only.

Directly copies a frame to a Wgpu texture. This will automatically convert the frame into a RGBA frame.

Errors

If the frame cannot be captured or the resolution is 0 on any axis, this will error.

Implementors§