1.1 CoreImage的四种识别功能
1.2 边缘检测思路
1.3 用高精度边缘识别器识别特征
1.4 绘制边缘检测图层
1.5 Swift 版本
2.1 生成二维码
2.2 生成条码
2.3 读取二维码(二维码识别)
2.4 第三方框架

引言

为了提升用户体验，在OCR识别场景都将利用到边缘检测

涉及的权限

NSCameraUsageDescription

从CSDN下载Demo源码：https://download.csdn.net/download/u011018979/19260280

1、应用场景：为了提升用户体验，在OCR识别场景都将利用到边缘检测 2、原理：采用原生CoreImage框架下CIDetector可进行边缘检测，识别到边缘之后使用CAShapeLayer将边缘绘制并显示

3、原理文章：https://kunnan.blog.csdn.net/article/details/117367345

3、付费文章：iOS Document Scanner：矩形边缘识别（边缘检测） CIDetectorTypeRectangle
本文限时免费

I 、矩形边缘识别

1.1 CoreImage的四种识别功能

CoreImage下CIDetector.h自带了四种识别功能

/* 人脸识别 */
CORE_IMAGE_EXPORT NSString* const CIDetectorTypeFace NS_AVAILABLE(10_7, 5_0);
/* 矩形边缘识别 */
CORE_IMAGE_EXPORT NSString* const CIDetectorTypeRectangle NS_AVAILABLE(10_10, 8_0);
/* 二维码识别 */
CORE_IMAGE_EXPORT NSString* const CIDetectorTypeQRCode NS_AVAILABLE(10_10, 8_0);
/* 文本识别 */
#if __OBJC2__
CORE_IMAGE_EXPORT NSString* const CIDetectorTypeText NS_AVAILABLE(10_11, 9_0);

1.2 边缘检测思路

采用原生CoreImage框架下CIDetector可进行边缘检测

[CIDetector detectorOfType:CIDetectorTypeRectangle context:nil options:@{CIDetectorAccuracy : CIDetectorAccuracyHigh}];

识别到边缘之后使用CAShapeLayer将边缘绘制并显示

// 将图像空间的坐标系转换成uikit坐标系
TransformCIFeatureRect featureRect = [self transfromRealRectWithImageRect:imageRect topLeft:topLeft topRight:topRight bottomLeft:bottomLeft bottomRight:bottomRight];
// 边缘识别路径
UIBezierPath *path = [UIBezierPath new];
[path moveToPoint:featureRect.topLeft];
[path addLineToPoint:featureRect.topRight];
[path addLineToPoint:featureRect.bottomRight];
[path addLineToPoint:featureRect.bottomLeft];
[path closePath];
// 背景遮罩路径
UIBezierPath *rectPath  = [UIBezierPath bezierPathWithRect:CGRectMake(-5,
                                                                      -5,
                                                                      self.frame.size.width + 10,
                                                                      self.frame.size.height + 10)];
[rectPath setUsesEvenOddFillRule:YES];
[rectPath appendPath:path];
_rectOverlay.path = rectPath.CGPath;

边缘识别器

// 高精度边缘识别器
- (CIDetector *)highAccuracyRectangleDetector
{
    static CIDetector *detector = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^
                  {
                      detector = [CIDetector detectorOfType:CIDetectorTypeRectangle context:nil options:@{CIDetectorAccuracy : CIDetectorAccuracyHigh}];
                  });
    return detector;
}
// 低精度边缘识别器
- (CIDetector *)rectangleDetetor
{
    static CIDetector *detector = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^
                  {
                      detector = [CIDetector detectorOfType:CIDetectorTypeRectangle context:nil options:@{CIDetectorAccuracy : CIDetectorAccuracyLow,CIDetectorTracking : @(YES)}];
                  });
    return detector;
}

开启边缘检测

/// 开启边缘检测
@property (nonatomic,assign,getter=isBorderDetectionEnabled) BOOL enableBorderDetection;
// 拍照视图
@property (nonatomic, strong) KNCameraCaptureView *captureCameraView;
// 拍照视图
- (KNCameraCaptureView *)captureCameraView{
    if (!_captureCameraView) {
        _captureCameraView = [[KNCameraCaptureView alloc] initWithFrame:CGRectMake(0, 0, SCREEN_WIDTH, 300)];
                //打开边缘检测
        [_captureCameraView setEnableBorderDetection:YES];
        _captureCameraView.backgroundColor = kBlackColor;
    }
    return _captureCameraView;
}

AVCaptureVideoDataOutputSampleBufferDelegate

#pragma mark - AVCaptureVideoDataOutputSampleBufferDelegate
-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    if (self.forceStop || _isStopped || _isCapturing || !CMSampleBufferIsValid(sampleBuffer)) return;
    CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)CMSampleBufferGetImageBuffer(sampleBuffer);
    CIImage *image = [CIImage imageWithCVPixelBuffer:pixelBuffer];
    image = [self filteredImageUsingContrastFilterOnImage:image];
    if (self.isBorderDetectionEnabled)//开启了边缘检测
    {
        if (_borderDetectFrame)//开启了边缘识别
        {
            // 用高精度边缘识别器 识别特征
            NSArray <CIFeature *>*features = [[self highAccuracyRectangleDetector] featuresInImage:image];
            // 选取特征列表中最大的矩形
            _borderDetectLastRectangleFeature = [self biggestRectangleInRectangles:features];
            _borderDetectFrame = NO;
        }
        if (_borderDetectLastRectangleFeature)
        {
            _imageDedectionConfidence += .5;
//            image = [self drawHighlightOverlayForPoints:image topLeft:_borderDetectLastRectangleFeature.topLeft topRight:_borderDetectLastRectangleFeature.topRight bottomLeft:_borderDetectLastRectangleFeature.bottomLeft bottomRight:_borderDetectLastRectangleFeature.bottomRight];
            // draw border layer
            if (rectangleDetectionConfidenceHighEnough(_imageDedectionConfidence))
            {
                [self drawBorderDetectRectWithImageRect:image.extent topLeft:_borderDetectLastRectangleFeature.topLeft topRight:_borderDetectLastRectangleFeature.topRight bottomLeft:_borderDetectLastRectangleFeature.bottomLeft bottomRight:_borderDetectLastRectangleFeature.bottomRight];
            }
        }
        else
        {
            _imageDedectionConfidence = 0.0f;
            if (_rectOverlay) {
                _rectOverlay.path = nil;
            }
        }
    }
    if (self.context && _coreImageContext)
    {
        // 将捕获到的图片绘制进_coreImageContext
        [_coreImageContext drawImage:image inRect:self.bounds fromRect:image.extent];
        [self.context presentRenderbuffer:GL_RENDERBUFFER];
        [_glkView setNeedsDisplay];
    }
}

1.4 绘制边缘检测图层

// 绘制边缘检测图层
- (void)drawBorderDetectRectWithImageRect:(CGRect)imageRect topLeft:(CGPoint)topLeft topRight:(CGPoint)topRight bottomLeft:(CGPoint)bottomLeft bottomRight:(CGPoint)bottomRight
{
    if (!_rectOverlay) {
        _rectOverlay = [CAShapeLayer layer];
        _rectOverlay.fillRule = kCAFillRuleEvenOdd;
        _rectOverlay.fillColor = [UIColor colorWithRed:73/255.0 green:130/255.0 blue:180/255.0 alpha:0.4].CGColor;
        _rectOverlay.strokeColor = [UIColor whiteColor].CGColor;
        _rectOverlay.lineWidth = 5.0f;
    }
    if (!_rectOverlay.superlayer) {
        self.layer.masksToBounds = YES;
        [self.layer addSublayer:_rectOverlay];
    }
    // 将图像空间的坐标系转换成uikit坐标系
    TransformCIFeatureRect featureRect = [self transfromRealRectWithImageRect:imageRect topLeft:topLeft topRight:topRight bottomLeft:bottomLeft bottomRight:bottomRight];
    // 边缘识别路径
    UIBezierPath *path = [UIBezierPath new];
    [path moveToPoint:featureRect.topLeft];
    [path addLineToPoint:featureRect.topRight];
    [path addLineToPoint:featureRect.bottomRight];
    [path addLineToPoint:featureRect.bottomLeft];
    [path closePath];
    // 背景遮罩路径
    UIBezierPath *rectPath  = [UIBezierPath bezierPathWithRect:CGRectMake(-5,
                                                                          -5,
                                                                          self.frame.size.width + 10,
                                                                          self.frame.size.height + 10)];
    [rectPath setUsesEvenOddFillRule:YES];
    [rectPath appendPath:path];
    _rectOverlay.path = rectPath.CGPath;
}

1.5 Swift 版本

swift

//
import CoreImage
import UIKit
public final class CIImageRectangleDetector: ImageRectangleDetector {
 public func detect(image: UIImage, completion: @escaping Completion) {
  DispatchQueue.global().async {
   guard let ciImage = CIImage(image: image) else { return }
   guard let detector = CIDetector(ofType: CIDetectorTypeRectangle, context: nil, options: [CIDetectorAccuracy: CIDetectorAccuracyHigh]) else { return }
   let results = detector.features(in: ciImage)
   let sortedBySize = results.sorted { $0.bounds.area > $1.bounds.area }
   if let feature = sortedBySize.first as? CIRectangleFeature {
    let size = ciImage.extent.size
    let points = [feature.topLeft, feature.topRight, feature.bottomRight, feature.bottomLeft]
    let normalized = points.map { $0.scaledRelative(size: size) }
    let quad = Quad(clockwise: normalized)
    DispatchQueue.main.async {
     completion(quad)
    }
   } else {
    DispatchQueue.main.async {
     completion(nil)
    }
   }
  }
 }
}

II、二维码

从iOS7开始集成了二维码的生成和读取功能

2.1 生成二维码

步骤;

1.导入CoreImage框架 2.通过滤镜CIFilter生成二维码

二维码的内容(传统的条形码只能放数字)：纯文本、名片、URL

/**
 生成QR二维码
 @param text 字符串
 @param size 二维码大小
 @return 返回二维码图像
 */
+ (UIImage*)createQRWithString:(NSString*)text QRSize:(CGSize)size;
/**
 生成QR二维码
 @param text 字符串
 @param size 大小
 @param qrColor 二维码前景色
 @param bkColor 二维码背景色
 @return 二维码图像
 */
+ (UIImage*)createQRWithString:(NSString*)text QRSize:(CGSize)size QRColor:(UIColor*)qrColor bkColor:(UIColor*)bkColor;

基本用法

#pragma mark - QRCodeGenerator
+ (CIImage *)createQRForString:(NSString *)qrString {
    NSData *stringData = [qrString dataUsingEncoding:NSUTF8StringEncoding];
    // 创建filter
    CIFilter *qrFilter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    // 设置内容和纠错级别
    [qrFilter setValue:stringData forKey:@"inputMessage"];
    [qrFilter setValue:@"H" forKey:@"inputCorrectionLevel"];
    // 返回CIImage
    return qrFilter.outputImage;
}

支持二维码大小设置

+ (UIImage*)createQRWithString:(NSString*)text QRSize:(CGSize)size
{
    NSData *stringData = [text dataUsingEncoding: NSUTF8StringEncoding];
    //生成
    CIFilter *qrFilter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    [qrFilter setValue:stringData forKey:@"inputMessage"];
    [qrFilter setValue:@"H" forKey:@"inputCorrectionLevel"];
    CIImage *qrImage = qrFilter.outputImage;
    //绘制
    CGImageRef cgImage = [[CIContext contextWithOptions:nil] createCGImage:qrImage fromRect:qrImage.extent];
    UIGraphicsBeginImageContext(size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetInterpolationQuality(context, kCGInterpolationNone);
    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextDrawImage(context, CGContextGetClipBoundingBox(context), cgImage);
    UIImage *codeImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    CGImageRelease(cgImage);
    return codeImage;
}

支持二维码前/背景色设置

+ (UIImage*)createQRWithString:(NSString*)text QRSize:(CGSize)size QRColor:(UIColor*)qrColor bkColor:(UIColor*)bkColor
{
    NSData *stringData = [text dataUsingEncoding: NSUTF8StringEncoding];
    //生成
    CIFilter *qrFilter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    [qrFilter setValue:stringData forKey:@"inputMessage"];
    [qrFilter setValue:@"H" forKey:@"inputCorrectionLevel"];
    //上色
    CIFilter *colorFilter = [CIFilter filterWithName:@"CIFalseColor"
                                       keysAndValues:
                             @"inputImage",qrFilter.outputImage,
                             @"inputColor0",[CIColor colorWithCGColor:qrColor.CGColor],
                             @"inputColor1",[CIColor colorWithCGColor:bkColor.CGColor],
                             nil];
    CIImage *qrImage = colorFilter.outputImage;
    //绘制
    CGImageRef cgImage = [[CIContext contextWithOptions:nil] createCGImage:qrImage fromRect:qrImage.extent];
    UIGraphicsBeginImageContext(size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetInterpolationQuality(context, kCGInterpolationNone);
    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextDrawImage(context, CGContextGetClipBoundingBox(context), cgImage);
    UIImage *codeImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    CGImageRelease(cgImage);
    return codeImage;
}

2.2 生成条码

利用CIFilter生成条码

/**
 生成条形码
 @param text 字符串
 @param size 大小
 @return 返回条码图像
 */
+ (UIImage*)createBarCodeWithString:(NSString*)text QRSize:(CGSize)size
{
    NSData *data = [text dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:false];
    CIFilter *filter = [CIFilter filterWithName:@"CICode128BarcodeGenerator"];
    [filter setValue:data forKey:@"inputMessage"];
     CIImage *barcodeImage = [filter outputImage];
    // 消除模糊
    CGFloat scaleX = size.width / barcodeImage.extent.size.width; // extent 返回图片的frame
    CGFloat scaleY = size.height / barcodeImage.extent.size.height;
    CIImage *transformedImage = [barcodeImage imageByApplyingTransform:CGAffineTransformScale(CGAffineTransformIdentity, scaleX, scaleY)];
    return [UIImage imageWithCIImage:transformedImage];
}

2.3 读取二维码(二维码识别)

需要导入AVFoundation框架,利用摄像头识别二维码中的内容（模拟器不行）

1.输入（摄像头） 2.由会话将摄像头采集到的二维码图像转换成字符串数据 3.输出（数据） 4.由预览图层显示扫描场景

detectorOfType:CIDetectorTypeQRCode

// 声明一个 CIDetector，并设定识别类型 CIDetectorTypeQRCode
    CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeQRCode context:nil options:@{CIDetectorAccuracy: CIDetectorAccuracyHigh}];
    // 取得识别结果
    NSArray *features = [detector featuresInImage:[CIImage imageWithCGImage:image.CGImage]];

识别条码图片

#pragma mark --识别条码图片
+ (void)recognizeImage:(UIImage*)image success:(void(^)(NSArray<LBXScanResult*> *array))block;
{
    if (!image) {
        block(nil);
        return;
    }
    if (@available(iOS 8.0, *)) {
        CIImage * cimg = [CIImage imageWithCGImage:image.CGImage];
        if (!cimg) {
            block(nil);
            return;
        }
        NSArray *features = nil;
        @try {
            CIDetector*detector = [CIDetector detectorOfType:CIDetectorTypeQRCode context:nil options:@{ CIDetectorAccuracy : CIDetectorAccuracyHigh }];
            features = [detector featuresInImage:cimg];
        } @catch (NSException *exception) {
            block(nil);
            return;
        } @finally {
        }
        NSMutableArray<LBXScanResult*> *mutableArray = [[NSMutableArray alloc]initWithCapacity:1];
        for (int index = 0; index < [features count]; index ++)
        {
            CIQRCodeFeature *feature = [features objectAtIndex:index];
            NSString *scannedResult = feature.messageString;
            LBXScanResult *item = [[LBXScanResult alloc]init];
            item.strScanned = scannedResult;
            item.strBarCodeType = CIDetectorTypeQRCode;
            item.imgScanned = image;
            [mutableArray addObject:item];
        }
        if (block) {
            block(mutableArray);
        }
    }else{
        if (block) {
            LBXScanResult *result = [[LBXScanResult alloc]init];
            result.strScanned = @"只支持ios8.0之后系统";
            block(@[result]);
        }
    }
}

2.4 第三方框架

LBXZBarSDK

pod 'LBXScan/LBXNative','~> 2.5.1' #系统原生API封装库
pod 'LBXScan/LBXZXing','~> 2.5.1'
pod 'LBXScan/UI','~> 2.5.1'
#pod 'LBXZBarSDK','~> 1.3'# 删除UIWebView，相机采集分辨率设置高分辨率

iOS安全之UIWebView 被拒的解决方案：用更安全的WKWebView替代UIWebView｜蓄力计划

https://kunnan.blog.csdn.net/article/details/115673455

iOS边缘检测（Document Scanner）

引言