Struct VNGeometryUtils

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

Available on crate feature VNGeometryUtils only.

Expand description

Apple’s documentation

Implementations§

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impl VNGeometryUtils

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pub unsafe fn boundingCircleForContour_error( contour: &VNContour, ) -> Result<Retained<VNCircle>, Retained<NSError>>

Available on crate feature VNGeometry only.

Calculates a bounding circle that includes a collection of points or a VNContour object. Note that because this is based on a geometric shape the aspect ratio is important when using normalized points. This takes the aspect ratio of the contour into account when using a VNContour as an input. boundingCircleForPoints and boundingCircleForSIMDPoints assume that the aspect ratio is correctly applied to the points.

Parameter contour: A contour around which to find the bounding circle.

Parameter points: A collection of points around which to find the bounding circle.

Parameter pointCount: Number of points in points

Parameter contour: VNContour object whose bounding circle needs to be calculated

Parameter error: An output parameter, populated only in case of algorithmic failure

Returns: the VNCircle object describing the bounding circle or nil, if the algorithm failed. The latter case is accompanied by populating an ‘error’ output parameter

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pub unsafe fn boundingCircleForPoints_error( points: &NSArray<VNPoint>, ) -> Result<Retained<VNCircle>, Retained<NSError>>

Available on crate feature VNGeometry only.

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pub unsafe fn calculateArea_forContour_orientedArea_error( area: NonNull<c_double>, contour: &VNContour, oriented_area: bool, ) -> Result<(), Retained<NSError>>

Available on crate feature VNGeometry only.

Calculates a closed contour area using Green’s theorem. The contour is represented by a set of points in VNContour object, It’s important to note that a random set of points, or a contour with self-crossing edges will likely produce undefined results Note that because this is based on a geometric shape the aspect ratio is important when using normalized points. This takes the aspect ratio of the contour into account when using a VNContour as an input.

Parameter area: Output parameter to be populated with calculated contour area

Parameter contour: A VNContour object whose area is being calculated

Parameter orientedArea: If true, returns signed area - positive for CCW oriented contours and negative for CW oriented contours. If false, returned area is always positive.

Parameter error: An output parameter, populated only in case of algorithmic failure

Returns: Area calculation status, YES indicates success, NO - failure. The failure case is accompanied by populating an ‘error’ output parameter

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pub unsafe fn calculatePerimeter_forContour_error( perimeter: NonNull<c_double>, contour: &VNContour, ) -> Result<(), Retained<NSError>>

Available on crate feature VNGeometry only.

Calculates perimeter, or a sum of all arc-lengths (edges), of a closed contour. The contour is represented by a set of points in VNContour object. Note that because this is based on a geometric shape the aspect ratio is important when using normalized points. This takes the aspect ratio of the contour into account when using a VNContour as an input.

Parameter perimeter: Output parameter to be populated with calculated contour perimeter

Parameter contour: A VNContour object whose perimeter is being calculated

Parameter error: An output parameter, populated only in case of algorithmic failure

Returns: Perimeter calculation status, YES indicates success, NO - failure. The failure case is accompanied by populating an ‘error’ output parameter

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impl VNGeometryUtils

Methods declared on superclass NSObject.

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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>§

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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`
    }
}