Struct VNContour

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

Available on crate feature VNGeometry only.

The VNContour class describes a contour provided by a VNContoursObservation.

VNContour objects are lightweight objects that act as a façade which allows access to a small slice of the usually much larger block of data owned by a VNContoursObservation that represents all of the contours detected in an image. While the interface does present the notion of a hierarchy of parent/child contours, the implementation purposefully does not contain any explicit internal bookkeeping for this relationship. Instead, contours are uniquely identified via their indexPath property. As a side effect of this choice, repeated calls to methods that would return relational contours (e.g., -childContours or -childContourAtIndex:error:) are NOT guaranteed to return the same VNContour instances over and over again. If this kind of parent/child object stability is an absolute requirement of the client, then they are responsible for creating the necessary data structures to represent and build that instance-stable hierarchy.

See also Apple’s documentation

Implementations

impl VNContour

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

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

pub unsafe fn indexPath(&self) -> Retained<NSIndexPath>

The path to the target VNContour as it is stored in the owning VNContoursObservation’s hierarchy of contours.

pub unsafe fn childContourCount(&self) -> NSInteger

The total number of child contours in the target contour.

The use of this property is preferred over childContours.count due to the cost of building the child objects.

pub unsafe fn childContours(&self) -> Retained<NSArray<VNContour>>

The array of the contours enclosed by the target contour.

This property may come with the cost of instantiating new VNContour objects; therefore, clients are strongly encouraged to hold the results in a local variable instead of repeatedly invoking it.

pub unsafe fn childContourAtIndex_error( &self, child_contour_index: NSUInteger, ) -> Result<Retained<VNContour>, Retained<NSError>>

Returns a VNContour object that is a child of this VNContour at the specified index.

Parameter childContourIndex: The index into the childContours array.

Parameter error: The error returned if the child contour cannot be provided.

Returns: The VNContour object at the specified index path, or nil of a failure occurs.

pub unsafe fn pointCount(&self) -> NSInteger

The number of points that describe the contour.

pub unsafe fn normalizedPath(&self) -> Retained<CGPath>

Available on crate feature objc2-core-graphics only.

The contour represented as a CGPath in normalized coordinates.

The path is owned by this object and therefore will be alive as long as the the observation is alive.

pub unsafe fn aspectRatio(&self) -> c_float

The aspect ratio of the contour from the original image aspect ratio expressed as width/height

pub unsafe fn polygonApproximationWithEpsilon_error( &self, epsilon: c_float, ) -> Result<Retained<VNContour>, Retained<NSError>>

Simplifies the contour’s collection of points into a polygon using the Ramer Douglas Peucker Algorithm.

See <https ://en.wikipedia.org/wiki/Ramer–Douglas–Peucker_algorithm>

Parameter epsilon: Points that have a perpendicular distance to the line segment they are on which are greater than epsilon are kept, others are eliminated.

Parameter error: The error returned if a simplified contour cannot be created.

Returns: A new VNContour object with a simplified polygon consisting of a subset of the points that defined the original VNContour.

Methods from Deref<Target = NSObject>

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

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>

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());

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.

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`
    }
}

Trait Implementations

impl AsRef<AnyObject> for VNContour

fn as_ref(&self) -> &AnyObject

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<NSObject> for VNContour

fn as_ref(&self) -> &NSObject

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<VNContour> for VNContour

fn as_ref(&self) -> &Self

Converts this type into a shared reference of the (usually inferred) input type.

impl Borrow<AnyObject> for VNContour

fn borrow(&self) -> &AnyObject

Immutably borrows from an owned value.

impl Borrow<NSObject> for VNContour

fn borrow(&self) -> &NSObject

Immutably borrows from an owned value.

impl ClassType for VNContour

const NAME: &'static str = "VNContour"

The name of the Objective-C class that this type represents.

type Super = NSObject

The superclass of this class.

type ThreadKind = <<VNContour as ClassType>::Super as ClassType>::ThreadKind

Whether the type can be used from any thread, or from only the main thread.

fn class() -> &'static AnyClass

Get a reference to the Objective-C class that this type represents.

fn as_super(&self) -> &Self::Super

Get an immutable reference to the superclass.

impl CopyingHelper for VNContour

type Result = VNContour

The immutable counterpart of the type, or Self if the type has no immutable counterpart.

impl Debug for VNContour

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Deref for VNContour

type Target = NSObject

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl Hash for VNContour

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Message for VNContour

fn retain(&self) -> Retained<Self>

where Self: Sized,

Increment the reference count of the receiver.

impl NSCopying for VNContour

fn copy(&self) -> Retained<Self::Result>

where Self: Sized + Message + CopyingHelper,

Returns a new instance that’s a copy of the receiver.

unsafe fn copyWithZone(&self, zone: *mut NSZone) -> Retained<Self::Result>

where Self: Sized + Message + CopyingHelper,

Returns a new instance that’s a copy of the receiver.

impl NSObjectProtocol for VNContour

fn isEqual(&self, other: Option<&AnyObject>) -> bool

where Self: Sized + Message,

Check whether the object is equal to an arbitrary other object.

fn hash(&self) -> usize

where Self: Sized + Message,

An integer that can be used as a table address in a hash table structure.

fn isKindOfClass(&self, cls: &AnyClass) -> bool

where Self: Sized + Message,

Check if the object is an instance of the class, or one of its subclasses.

fn is_kind_of<T>(&self) -> bool

where T: ClassType, Self: Sized + Message,

👎Deprecated: use isKindOfClass directly, or cast your objects with AnyObject::downcast_ref

Check if the object is an instance of the class type, or one of its subclasses.

fn isMemberOfClass(&self, cls: &AnyClass) -> bool

where Self: Sized + Message,

Check if the object is an instance of a specific class, without checking subclasses.

fn respondsToSelector(&self, aSelector: Sel) -> bool

where Self: Sized + Message,

Check whether the object implements or inherits a method with the given selector.

fn conformsToProtocol(&self, aProtocol: &AnyProtocol) -> bool

where Self: Sized + Message,

Check whether the object conforms to a given protocol.

fn description(&self) -> Retained<NSObject>

where Self: Sized + Message,

A textual representation of the object.

fn debugDescription(&self) -> Retained<NSObject>

where Self: Sized + Message,

A textual representation of the object to use when debugging.

fn isProxy(&self) -> bool

where Self: Sized + Message,

Check whether the receiver is a subclass of the NSProxy root class instead of the usual NSObject.

fn retainCount(&self) -> usize

where Self: Sized + Message,

The reference count of the object.

impl PartialEq for VNContour

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl RefEncode for VNContour

const ENCODING_REF: Encoding = <NSObject as ::objc2::RefEncode>::ENCODING_REF

The Objective-C type-encoding for a reference of this type.

impl VNRequestRevisionProviding for VNContour

unsafe fn requestRevision(&self) -> NSUInteger

where Self: Sized + Message,

Available on crate feature VNRequestRevisionProviding only.

The revision of the VNRequest subclass that was used to generate the object that implements this protocol.

impl DowncastTarget for VNContour

impl Eq for VNContour