Struct CNObjectTracker

Source

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

Available on crate feature CNObjectTracker only.

Expand description

Converts a normalized point or rectangle into a detection track that tracks an object over time.

Implementations§

Source §

impl CNObjectTracker

Source

pub unsafe fn isSupported() -> bool

Indicates whether the current device supports object detection and tracking.

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pub unsafe fn initWithCommandQueue( this: Allocated<Self>, command_queue: &ProtocolObject<dyn MTLCommandQueue>, ) -> Retained<Self>

Available on crate feature objc2-metal only.

Create a new detection track builder.

Parameters:
commandQueue: the command queue of a metal device to which commands should be submitted to perform work

Source

pub unsafe fn findObjectAtPoint_sourceImage( &self, point: CGPoint, source_image: &CVPixelBuffer, ) -> Option<Retained<CNBoundsPrediction>>

Available on crate features objc2-core-foundation and objc2-core-video only.

Find the bounds of an object at the given point. Can be used to convert a normalized point in an image to a rectangle that can be used to start tracking.

Parameters:
point: location of object in image in normalized coordinates where (0.0, 0.0) is the upper left corner, and (1.0, 1.0) is the lower right
sourceImage: pixel buffer containing the image
Returns: A prediction, which includes bounds that can be used to start tracking, or nil if no discernible object is detected.

Source

pub unsafe fn startTrackingAt_within_sourceImage_sourceDisparity( &self, time: CMTime, normalized_bounds: CGRect, source_image: &CVPixelBuffer, source_disparity: &CVPixelBuffer, ) -> bool

Available on crate features objc2-core-foundation and objc2-core-media and objc2-core-video only.

Start creating a detection track to track an object within the given bounds.

Parameters:
time: the presentation time of the first frame in the detection track
normalizedBounds: the bounds of the object to track in normalized coordinates where (0.0, 0.0) is the upper left corner, and (1.0, 1.0) is the lower right
sourceImage: image buffer containing the image
sourceDisparity: disparity buffer containing depth information
Returns: whether the object can be tracked
Note: if the object can be tracked, a detection is added to the detection track being built

Source

pub unsafe fn continueTrackingAt_sourceImage_sourceDisparity( &self, time: CMTime, source_image: &CVPixelBuffer, source_disparity: &CVPixelBuffer, ) -> Option<Retained<CNBoundsPrediction>>

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

Continue tracking an object for which tracking has started, and add a new detection to the detection track being built.

Parameters:
time: the presentation time of the frame to be added to the detection track
Returns: a prediction of where the object is in the source image

Source

pub unsafe fn finishDetectionTrack(&self) -> Retained<CNDetectionTrack>

Available on crate feature CNDetectionTrack only.

Finish constructing the detection track and return it.

Returns: a detection track which tracks the object

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pub unsafe fn resetDetectionTrack(&self)

Reset the builder to construct a new detection track.

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

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

Methods from Deref<Target = NSObject>§

Source

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());

Source

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.

Source

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`
    }
}