Struct VNDetectTrajectoriesRequest

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#[repr(C)]
pub struct VNDetectTrajectoriesRequest { /* private fields */ }

Available on crate features VNDetectTrajectoriesRequest and VNRequest and VNStatefulRequest only.

Expand description

A request that detects trajectories of shapes (even small ones) that follow a parabolic path in a sequence of images.

This request detects objects moving and (once their path follows the constraint of a parabola), a VNTrajectoryObservation will be returned with the detected points and the equation describing the parabola.

Implementations§

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impl VNDetectTrajectoriesRequest

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pub unsafe fn initWithFrameAnalysisSpacing_completionHandler( this: Allocated<Self>, frame_analysis_spacing: CMTime, completion_handler: VNRequestCompletionHandler, ) -> Retained<Self>

Available on crate features block2 and objc2-core-media only.

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pub unsafe fn initWithFrameAnalysisSpacing_trajectoryLength_completionHandler( this: Allocated<Self>, frame_analysis_spacing: CMTime, trajectory_length: NSInteger, completion_handler: VNRequestCompletionHandler, ) -> Retained<Self>

Available on crate features block2 and objc2-core-media only.

Create a new request that will detect the trajectory of a shape in motion.

Parameter frameAnalysisSpacing: The reciprocal of the maximum rate at which buffers will be processed. The request will not process buffers that fall within the frameAnalysisSpacing after it has performed the analysis. The analysis is not done by wall time but by analysis of the time stamps of the samplebuffers being processed. This property is for instance useful to throttle the processing on slower devices. If this is set to kCMTimeZero then no frames get skipped in the analysis.

Parameter trajectoryLength: The number of points required to analyze a parabola that indicates a trajectory. Must be at least 5.

Parameter completionHandler: The block to be invoked after the request has completed its processing. The completion handler gets executed on the same dispatch queue as the request being executed.

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pub unsafe fn trajectoryLength(&self) -> NSInteger

The number of points required to analyze a parabola that indicates a trajectory.

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pub unsafe fn objectMinimumNormalizedRadius(&self) -> c_float

Specifies the minimum radius of the bounding circle of the object to be tracked. This can be used to filter out noise and small objects. The default is 0.0, which means no filtering is applied. Changing the property from frame to frame can produce eratic trajectories as objects will either disappear or be added to the tracking base on this filtering. The value is specified in normalized coordinates.

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pub unsafe fn setObjectMinimumNormalizedRadius( &self, object_minimum_normalized_radius: c_float, )

Setter for objectMinimumNormalizedRadius.

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pub unsafe fn minimumObjectSize(&self) -> c_float

👎Deprecated

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pub unsafe fn setMinimumObjectSize(&self, minimum_object_size: c_float)

👎Deprecated

Setter for minimumObjectSize.

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pub unsafe fn objectMaximumNormalizedRadius(&self) -> c_float

Specifies the maximum radius of the bounding circle of the object to be tracked. This can be used to filter out unwanted trajectories from larger objects moving through the scene. The default is 1.0, which means no filtering is applied. Changing the maximum from frame to frame can produce eratic trajectories as objects will either disappear or be added to the tracking base on this filtering. The size is specified in normalized coordinates.

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pub unsafe fn setObjectMaximumNormalizedRadius( &self, object_maximum_normalized_radius: c_float, )

Setter for objectMaximumNormalizedRadius.

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pub unsafe fn maximumObjectSize(&self) -> c_float

👎Deprecated

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pub unsafe fn setMaximumObjectSize(&self, maximum_object_size: c_float)

👎Deprecated

Setter for maximumObjectSize.

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pub unsafe fn targetFrameTime(&self) -> CMTime

Available on crate feature objc2-core-media only.

Specifies the desired target frame time for processing trajectory detection. This can be used for real-time processing of frames, which requires execution with a specific amount of time. The target frame time is evaluated from frame-to-frame. If processing takes longer than this target frame time for the currect frame, it will attempt to reduce the amount of time taken by reducing the accuracy (down to a set minimum) for the next frame. If a frame takes less time than this target, then accuracy of the next frame will be increased (up to a set maximum). The default value is kCMTimeIndefinite, meaning accuracy stays at the predefined maximum.

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pub unsafe fn setTargetFrameTime(&self, target_frame_time: CMTime)

Available on crate feature objc2-core-media only.

Setter for targetFrameTime.

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pub unsafe fn results( &self, ) -> Option<Retained<NSArray<VNTrajectoryObservation>>>

Available on crate feature VNObservation only.

Provides VNTrajectoryObservation results.

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impl VNDetectTrajectoriesRequest

Methods declared on superclass VNStatefulRequest.

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pub unsafe fn new() -> Retained<Self>

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pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>

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pub unsafe fn initWithCompletionHandler( this: Allocated<Self>, completion_handler: VNRequestCompletionHandler, ) -> Retained<Self>

Available on crate feature block2 only.

Methods from Deref<Target = VNStatefulRequest>§

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pub unsafe fn minimumLatencyFrameCount(&self) -> NSInteger

The minimum number of frames that the request has to process on before reporting back any observation. This information is provided by the request once initialized with its required paramters.

Video based request often need a minimum number of frames before they can report back any observation. An example would be that a movement detection requires at least 5 frames to be detected. The minimumLatencyFrameCount for that request would report 5 and only after 5 frames have been processed an observation would be returned in the results. This latency is indicative of how responsive a request is in respect to the incoming data.

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pub unsafe fn frameAnalysisSpacing(&self) -> CMTime

Available on crate feature objc2-core-media only.

The reciprocal of maximum rate at which buffers will be processed.

The request will not process buffers that fall within the frameAnalysisSpacing after it has performed the analysis. The analysis is not done by wall time but by analysis of of the time stamps of the samplebuffers being processed.

Methods from Deref<Target = VNImageBasedRequest>§

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pub unsafe fn regionOfInterest(&self) -> CGRect

Available on crate feature objc2-core-foundation only.

The region of the image in which the request will be performed. The rectangle is normalized to the dimensions of the image being processed and has its origin specified relative to the image’s lower-left corner.

The default value for this property is { { 0, 0 }, { 1, 1 } }. Setting this property to a rectangle that is outside of the normalized coordinate space will be accepted but result in the request failing to be performed.

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pub unsafe fn setRegionOfInterest(&self, region_of_interest: CGRect)

Available on crate feature objc2-core-foundation only.

Setter for regionOfInterest.

Methods from Deref<Target = VNRequest>§

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pub unsafe fn preferBackgroundProcessing(&self) -> bool

A hint used to minimize the resource burden of the request. Memory footprint, processing footprint and/or CPU/GPU contention will be reduced (depending on the request), at the potential cost of longer execution time. This can help, for example, with ensuring UI updates and rendering are not getting blocked by Vision processing.

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pub unsafe fn setPreferBackgroundProcessing( &self, prefer_background_processing: bool, )

Setter for preferBackgroundProcessing.

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pub unsafe fn usesCPUOnly(&self) -> bool

👎Deprecated

This property, if set to YES, signifies that the request should be performed exclusively on the CPU and not on the GPU. The default value is NO, which signifies that the request is free to leverage the GPU to accelerate any work the request may require.

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pub unsafe fn setUsesCPUOnly(&self, uses_cpu_only: bool)

👎Deprecated

Setter for usesCPUOnly.

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pub unsafe fn results(&self) -> Option<Retained<NSArray<VNObservation>>>

Available on crate feature VNObservation only.

The collection of VNObservations generated by the processing of the request.

The only valid time to access this property is after the request has been processed by a request handler. If the request failed, this property will be nil; otherwise, it will be an array of zero or more VNObservation subclasses specific to the VNRequest subclass.

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pub unsafe fn completionHandler(&self) -> VNRequestCompletionHandler

Available on crate feature block2 only.

The completion handler block that will be invoked after the request has completed processing.

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pub unsafe fn revision(&self) -> NSUInteger

The specific algorithm or implementation revision that is to be used to perform the request.

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pub unsafe fn setRevision(&self, revision: NSUInteger)

Setter for revision.

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pub unsafe fn cancel(&self)

Tries to abort the request as soon as possible. Results will be nil. The completionHandler (if present) will be called with an error of VNErrorRequestCancelled.

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pub unsafe fn supportedComputeStageDevicesAndReturnError( &self, ) -> Result<Retained<NSDictionary<VNComputeStage, NSArray<ProtocolObject<dyn MLComputeDeviceProtocol>>>>, Retained<NSError>>

Available on crate features VNTypes and objc2-core-ml only.

Obtain the collection of compute device per stage that are supported by the request.

This method’s result is based on the current state of configuration of the target request at the time of the call.

Parameter error: The address of a variable that will be populated with the error that describes the failure. If the caller does not require this information, NULL can be passed.

Returns: A dictionary of per-stage supported compute devices, or nil if an error occurs.

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pub unsafe fn computeDeviceForComputeStage( &self, compute_stage: &VNComputeStage, ) -> Option<Retained<ProtocolObject<dyn MLComputeDeviceProtocol>>>

Available on crate features VNTypes and objc2-core-ml only.

Determine what the currently configured compute device is for a specific compute stage.

Parameter computeStage: The compute stage to be introspected.

Returns: The currently assigned compute device, or nil if there is no explicit assignment.

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pub unsafe fn setComputeDevice_forComputeStage( &self, compute_device: Option<&ProtocolObject<dyn MLComputeDeviceProtocol>>, compute_stage: &VNComputeStage, )

Available on crate features VNTypes and objc2-core-ml only.

Assign a specific compute device for a compute stage.

It is important to note that any compute device can be configured for a given compute stage. Only when the request is performed is the validity of the (compute device / compute stage) assignments checked. Valid compute devices for a request’s compute stages can be obtained via -supportedComputeStageDevicesAndReturnError:.

Parameter computeDevice: The compute device to assign to the compute stage. Passing nil for this parameter will remove any explicit compute device assignment, allowing Vision to select which device to use.

Parameter computeStage: The compute stage being configured.

Methods from Deref<Target = NSObject>§

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pub fn doesNotRecognizeSelector(&self, sel: Sel) -> !

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>§

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pub fn class(&self) -> &'static AnyClass

Dynamically find the class of this object.

§Panics

May panic if the object is invalid (which may be the case for objects returned from unavailable init/new methods).

§Example

Check that an instance of NSObject has the precise class NSObject.

use objc2::ClassType;
use objc2::runtime::NSObject;

let obj = NSObject::new();
assert_eq!(obj.class(), NSObject::class());

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pub unsafe fn get_ivar<T>(&self, name: &str) -> &T
where T: Encode,

👎Deprecated: this is difficult to use correctly, use Ivar::load instead.

Use Ivar::load instead.

§Safety

The object must have an instance variable with the given name, and it must be of type T.

See Ivar::load_ptr for details surrounding this.

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pub fn downcast_ref<T>(&self) -> Option<&T>
where T: DowncastTarget,

Attempt to downcast the object to a class of type T.

This is the reference-variant. Use Retained::downcast if you want to convert a retained object to another type.

§Mutable classes

Some classes have immutable and mutable variants, such as NSString and NSMutableString.

When some Objective-C API signature says it gives you an immutable class, it generally expects you to not mutate that, even though it may technically be mutable “under the hood”.

So using this method to convert a NSString to a NSMutableString, while not unsound, is generally frowned upon unless you created the string yourself, or the API explicitly documents the string to be mutable.

See Apple’s documentation on mutability and on isKindOfClass: for more details.

§Generic classes

Objective-C generics are called “lightweight generics”, and that’s because they aren’t exposed in the runtime. This makes it impossible to safely downcast to generic collections, so this is disallowed by this method.

You can, however, safely downcast to generic collections where all the type-parameters are AnyObject.

§Panics

This works internally by calling isKindOfClass:. That means that the object must have the instance method of that name, and an exception will be thrown (if CoreFoundation is linked) or the process will abort if that is not the case. In the vast majority of cases, you don’t need to worry about this, since both root objects NSObject and NSProxy implement this method.

§Examples

Cast an NSString back and forth from NSObject.

use objc2::rc::Retained;
use objc2_foundation::{NSObject, NSString};

let obj: Retained<NSObject> = NSString::new().into_super();
let string = obj.downcast_ref::<NSString>().unwrap();
// Or with `downcast`, if we do not need the object afterwards
let string = obj.downcast::<NSString>().unwrap();

Try (and fail) to cast an NSObject to an NSString.

use objc2_foundation::{NSObject, NSString};

let obj = NSObject::new();
assert!(obj.downcast_ref::<NSString>().is_none());

Try to cast to an array of strings.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);
// This is invalid and doesn't type check.
let arr = arr.downcast_ref::<NSArray<NSString>>();

This fails to compile, since it would require enumerating over the array to ensure that each element is of the desired type, which is a performance pitfall.

Downcast when processing each element instead.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);

for elem in arr {
    if let Some(data) = elem.downcast_ref::<NSString>() {
        // handle `data`
    }
}