Struct VNRecognizeTextRequest

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

Available on crate features VNRecognizeTextRequest and VNRequest only.

A request that will detect regions of text and recognize the containing text in an image.

This request will generate VNRecognizedTextObservation objects describing the locations of text and the actual text recognized.

See also Apple’s documentation

Implementations

impl VNRecognizeTextRequest

pub unsafe fn supportedRecognitionLanguagesForTextRecognitionLevel_revision_error( recognition_level: VNRequestTextRecognitionLevel, request_revision: NSUInteger, ) -> Result<Retained<NSArray<NSString>>, Retained<NSError>>

👎Deprecated

Returns all the supported languages for a given text recognition level. Note that a language supported in one recognition level might not be available in another.

pub unsafe fn supportedRecognitionLanguagesAndReturnError( &self, ) -> Result<Retained<NSArray<NSString>>, Retained<NSError>>

Obtain the collection of supported recognition languages.

This method will return the collection of all possible language identifiers that are recognized by the target request based on its current state of configuration at the time of the call.

Parameter error: The address of the variable that will be populated with the error if the call fails.

Returns: The collection of language identifiers, or nil if a failure occurs.

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

Specify the languages used for the detection. The order of the languages in the array defines the order in which languages will be used during the language processing. The languages are specified as ISO language codes.

pub fn setRecognitionLanguages(&self, recognition_languages: &NSArray<NSString>)

Setter for recognitionLanguages.

pub fn customWords(&self) -> Retained<NSArray<NSString>>

An array of strings that will be used at the word recognition stage in addition to the recognition languages. The customWords list takes precedence over the standard lexicon.

pub fn setCustomWords(&self, custom_words: &NSArray<NSString>)

Setter for customWords.

pub fn recognitionLevel(&self) -> VNRequestTextRecognitionLevel

The recognition level selects which techniques will be used during the text recognition. There are trade-offs between performance and accuracy.

pub fn setRecognitionLevel( &self, recognition_level: VNRequestTextRecognitionLevel, )

Setter for recognitionLevel.

pub fn usesLanguageCorrection(&self) -> bool

Determines whether language correction should be applied during the recognition process. Disabling this will return the raw recognition results providing performance benefits but less accurate results.

pub fn setUsesLanguageCorrection(&self, uses_language_correction: bool)

Setter for usesLanguageCorrection.

pub fn automaticallyDetectsLanguage(&self) -> bool

Language detection will try to automatically identify the script/langauge during the detection and use the appropiate model for recognition and language correction. This can be particularly helpful, if the nature of the content is unkown and with this flag being set it will for instance determine if text is latin vs chinese so you don’t have to pick the language model in the first case. But as the language correction cannot always guarantee the correct detection, it is advisable to set the languages, if you have domain knowledge of what language to expect. The default value is NO. Also note that this feature is only available since VNRecognizeTextRequestRevision3 and is a no-op before that.

pub fn setAutomaticallyDetectsLanguage( &self, automatically_detects_language: bool, )

Setter for automaticallyDetectsLanguage.

pub fn minimumTextHeight(&self) -> c_float

pub fn setMinimumTextHeight(&self, minimum_text_height: c_float)

Setter for minimumTextHeight.

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

Available on crate feature VNObservation only.

VNRecognizedTextObservation results.

impl VNRecognizeTextRequest

Methods declared on superclass VNRequest.

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

Creates a new VNRequest with no completion handler.

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

Available on crate feature block2 only.

Creates a new VNRequest with an optional completion handler.

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.

impl VNRecognizeTextRequest

Methods declared on superclass NSObject.

pub fn new() -> Retained<Self>

Methods from Deref<Target = VNImageBasedRequest>

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.

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>

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.

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

Setter for preferBackgroundProcessing.

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.

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

👎Deprecated

Setter for usesCPUOnly.

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.

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.

pub unsafe fn revision(&self) -> NSUInteger

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

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

Setter for revision.

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.

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.

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.

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>

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 VNRecognizeTextRequest

fn as_ref(&self) -> &AnyObject

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

impl AsRef<NSObject> for VNRecognizeTextRequest

fn as_ref(&self) -> &NSObject

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

impl AsRef<VNImageBasedRequest> for VNRecognizeTextRequest

fn as_ref(&self) -> &VNImageBasedRequest

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

impl AsRef<VNRecognizeTextRequest> for VNRecognizeTextRequest

fn as_ref(&self) -> &Self

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

impl AsRef<VNRequest> for VNRecognizeTextRequest

fn as_ref(&self) -> &VNRequest

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

impl Borrow<AnyObject> for VNRecognizeTextRequest

fn borrow(&self) -> &AnyObject

Immutably borrows from an owned value.

impl Borrow<NSObject> for VNRecognizeTextRequest

fn borrow(&self) -> &NSObject

Immutably borrows from an owned value.

impl Borrow<VNImageBasedRequest> for VNRecognizeTextRequest

fn borrow(&self) -> &VNImageBasedRequest

Immutably borrows from an owned value.

impl Borrow<VNRequest> for VNRecognizeTextRequest

fn borrow(&self) -> &VNRequest

Immutably borrows from an owned value.

impl ClassType for VNRecognizeTextRequest

const NAME: &'static str = "VNRecognizeTextRequest"

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

type Super = VNImageBasedRequest

The superclass of this class.

type ThreadKind = <<VNRecognizeTextRequest 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 VNRecognizeTextRequest

type Result = VNRecognizeTextRequest

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

impl Debug for VNRecognizeTextRequest

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

Formats the value using the given formatter.

impl DefaultRetained for VNRecognizeTextRequest

fn default_retained() -> Retained<Self>

The default Retained for a type.

impl Deref for VNRecognizeTextRequest

type Target = VNImageBasedRequest

The resulting type after dereferencing.

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

Dereferences the value.

impl Hash for VNRecognizeTextRequest

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 VNRecognizeTextRequest

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

where Self: Sized,

Increment the reference count of the receiver.

impl NSCopying for VNRecognizeTextRequest

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 VNRecognizeTextRequest

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 VNRecognizeTextRequest

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 VNRecognizeTextRequest

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

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

impl VNRequestProgressProviding for VNRecognizeTextRequest

unsafe fn progressHandler(&self) -> VNRequestProgressHandler

where Self: Sized + Message,

Available on crate features VNRequest and block2 only.

Requests that support the VNRequestProgressProviding protocol would periodically call the progressHandler to report progress on longer running tasks.

unsafe fn setProgressHandler(&self, progress_handler: VNRequestProgressHandler)

where Self: Sized + Message,

Available on crate features VNRequest and block2 only.

Setter for progressHandler.

unsafe fn indeterminate(&self) -> bool

where Self: Sized + Message,

Available on crate feature VNRequest only.

If a request cannot determine its progress in fractions completed, this property will be set.

impl DowncastTarget for VNRecognizeTextRequest

impl Eq for VNRecognizeTextRequest