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引言

从CSDN下载Demo源码：download.csdn.net/download/u0…

1. 应用场景：证件扫描、文字辨认
2. 原理：利用iOS13 VNDocumentCameraViewController的证件扫描和VNRecognizeTextRequest文字辨认功能进行完成
3. 原理文章：kunnan.blog.csdn.net/article/det…

I 、 iOS13 证件扫描API

VisionKit的VNDocumentCameraViewController

API_AVAILABLE(ios(13.0)) API_UNAVAILABLE(macos, tvos, watchos)
@interface VNDocumentCameraViewController : UIViewController

II、iOS13 文字辨认API

Vision的 VNRecognizeTextRequest

API_AVAILABLE(macos(10.15), ios(13.0), tvos(13.0))
@interface VNRecognizeTextRequest : VNImageBasedRequest <VNRequestProgressProviding>

效果图：

III 事例

#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
NSArray<VNRequest *> *requests;
dispatch_queue_t textRecognitionWorkQueue;
NSString *resultingText;
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    // Parar e esconder o Indicador de atividade do OCR
    [self->activityIndicator stopAnimating];
    self->activityIndicator.hidden = YES;
    // Solicitar que o Vision seja executado em cada pgina do documento digitalizado.
    requests = [[NSArray<VNRequest *> alloc] init];
    // Cria a fila de expedio para executar solicitaes do Vision.
    dispatch_queue_attr_t qos = dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, QOS_CLASS_USER_INITIATED, -1);
    textRecognitionWorkQueue = dispatch_queue_create("TextRecognitionQueue", qos);
    resultingText = @"";
    [self setupVision];
}
// Solicita o Setup do Vision, pois a solicitao pode ser reutilizada
- (void)setupVision {
    VNRecognizeTextRequest *textRecognitionRequest = [[VNRecognizeTextRequest alloc] initWithCompletionHandler:^(VNRequest * _Nonnull request, NSError * _Nullable error) {
        NSMutableArray *observations;
        @try {
            observations  = [[NSMutableArray alloc] init];
            for (VNRecognizedTextObservation *obs in request.results) {
                [observations addObject:(VNRecognizedTextObservation *)obs];
            }
        }
        @catch (NSException *exception) {
            NSLog(@"As observaes so de um tipo inesperado.");
        }
        @finally {
            //NSLog(@"Condio final");
        }
        // Concatena o texto reconhecido de todas as observaes.
        NSInteger maximumCandidates = 1;
        for (VNRecognizedTextObservation *observation in observations) {
            VNRecognizedText *candidate = [observation topCandidates:maximumCandidates].firstObject;
            resultingText = [NSString stringWithFormat:@"%@%@",
                             resultingText,
                             candidate.string];
        }
    }];
    // Especifica o nvel de reconhecimento
    textRecognitionRequest.recognitionLevel = VNRequestTextRecognitionLevelAccurate;
    requests = @[textRecognitionRequest];
}
- (IBAction)scanReceipts:(id)sender {
    //Cria uma instancia da Classe de Leitura de Docs da Vision, e abre ela
    VNDocumentCameraViewController *documentCameraViewController = [[VNDocumentCameraViewController alloc] init];
    documentCameraViewController.delegate = self;
    [self presentModalViewController:documentCameraViewController animated:YES];
}
// MARK: VNDocumentCameraViewControllerDelegate
- (void)documentCameraViewController:(VNDocumentCameraViewController *)controller didFinishWithScan:(VNDocumentCameraScan *)scan {
    // Limpe qualquer texto existente.
    self->textView.text = @"";
    // Descartar a cmera de documentos
    [controller dismissModalViewControllerAnimated:YES];
    self->activityIndicator.hidden = NO;
    [self->activityIndicator startAnimating];
    dispatch_async(textRecognitionWorkQueue, ^{
        resultingText = @"";
        for (int pageIndex=0; pageIndex<scan.pageCount; pageIndex++) {
            struct CGImage *image = [scan imageOfPageAtIndex:pageIndex].CGImage;
            NSDictionary *d = [[NSDictionary alloc] init];
            VNImageRequestHandler *requestHandler = [[VNImageRequestHandler alloc] initWithCGImage:image options:d];
            NSError *error = nil;
            @try {
                [requestHandler performRequests:requests error:&error];
            }
            @catch (NSException *exception) {
                NSLog(@"%@", exception);
            }
            @finally {
                NSLog(@"Condio final");
            }
        }
        dispatch_async(dispatch_get_main_queue(), ^{
            self->textView.text = resultingText;
            [self->activityIndicator stopAnimating];
            self->activityIndicator.hidden = YES;
        });
    });
}
@end

see also

iOS13扫描证件&银行卡信息辨认；身份证辨认 (正反) ；矩形边际辨认 ；自定义证件相机 （含demo源码）

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