Struct CIQRCodeFeature

Source

pub struct CIQRCodeFeature { /* private fields */ }

Available on crate feature CIFeature only.

Expand description

Information about a Quick Response code detected in a still or video image.

Note: In macOS 10.13, iOS 11, and tvOS 11 or later, the Vision framework replaces these classes for identifying and analyzing image features. See <doc ://com.apple.documentation/documentation/vision/vndetectbarcodesrequest>)

A QR code is a two-dimensional barcode using the ISO/IEC 18004:2006 standard. The properties of a CIQRCodeFeature object identify the corners of the barcode in the image perspective and provide the decoded message.

To detect QR codes in an image or video, choose CIDetectorTypeQRCode type when initializing a CIDetector object.

Implementations§

Source §

impl CIQRCodeFeature

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pub unsafe fn bounds(&self) -> CGRect

Available on crate feature objc2-core-foundation only.

A rectangle that indicates the position and extent of the QR code feature in image coordinates.

This property identifies the rectangular region of the image containing the detected QR code, not necessarily the shape of the QR code. A detected feature is square in space, but may appear as a four-sided polygon in the image. Use the properties listed in CIQRCodeFeature to find the corners of the QR code as it appears in perspective.

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pub unsafe fn topLeft(&self) -> CGPoint

Available on crate feature objc2-core-foundation only.

The image coordinate of the upper-left corner of the detected QR code.

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pub unsafe fn topRight(&self) -> CGPoint

Available on crate feature objc2-core-foundation only.

The image coordinate of the upper-right corner of the detected QR code.

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pub unsafe fn bottomLeft(&self) -> CGPoint

Available on crate feature objc2-core-foundation only.

The image coordinate of the lower-left corner of the detected QR code.

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pub unsafe fn bottomRight(&self) -> CGPoint

Available on crate feature objc2-core-foundation only.

The image coordinate of the lower-right corner of the detected QR code.

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pub unsafe fn messageString(&self) -> Option<Retained<NSString>>

The string decoded from the detected barcode.

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pub unsafe fn symbolDescriptor(&self) -> Option<Retained<CIQRCodeDescriptor>>

Available on crate feature CIBarcodeDescriptor only.

An abstract representation of a QR Code symbol.

The property is a CIQRCodeDescriptor instance that contains the payload, symbol version, mask pattern, and error correction level, so the QR Code can be reproduced.

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impl CIQRCodeFeature

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 = CIFeature>§

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pub unsafe fn type(&self) -> Retained<NSString>

The type of feature that was discovered.

The type can be one of:

CIFeatureTypeFace
CIFeatureTypeRectangle
CIFeatureTypeQRCode
CIFeatureTypeText

Source

pub unsafe fn bounds(&self) -> CGRect

Available on crate feature objc2-core-foundation only.

The rectangle that bounds the location of discovered feature.

The rectangle is in the cartesian coordinate system of the image.

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());

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`
    }
}