IOS AVFoudation+CIRectangleFeature实时识别矩形_ios 视频流检测矩形

本文是结合IOS的Cmera和CIImage中的矩形检测器做的一个识别矩形的demo，对于简单场景效果还不错。复杂场景下检测效果还是差了点，后面会更新结合自己写的opencv算法去检测。

1.首先封装一个camera

/*
 * Camera.h
 */
#import <AVFoundation/AVFoundation.h>

@interface Camera : NSObject

@property (strong, nonatomic) AVCaptureDevice *device;
@property (strong, nonatomic) AVCaptureVideoPreviewLayer *previewLayer;
@property (strong, nonatomic) AVCaptureSession *captureSession;
@property (strong, nonatomic) AVCaptureVideoDataOutput *output;

- (void)addVideoPreviewLayer;
- (void)addVideoInputFromCamera;
- (void)addVideoOutput;

@end
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/*
 * Camera.m
 */
#import <UIKit/UIKit.h>
#import "Camera.h"

@implementation Camera

- (id)init
{
    if ((self = [super init]))
    {
        [self setCaptureSession:[[AVCaptureSession alloc] init]];
        _captureSession.sessionPreset = AVCaptureSessionPreset1920x1080;
    }
    return self;
}

- (void)addVideoPreviewLayer
{
    [self setPreviewLayer:[[AVCaptureVideoPreviewLayer alloc] initWithSession:[self captureSession]]];
    [_previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
}

- (void)addVideoInputFromCamera
{
    self.device = [[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] firstObject];

    NSError *error = nil;

    AVCaptureDeviceInput *backFacingCameraDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:self.device error:&error];
    if (!error)
    {
        if ([_captureSession canAddInput:backFacingCameraDeviceInput])
        {
            [_captureSession addInput:backFacingCameraDeviceInput];
        }
    }
}

- (void)addVideoOutput{
    [self setOutput:[[AVCaptureVideoDataOutput alloc]init]];
    [_output setAlwaysDiscardsLateVideoFrames:YES];
    [_output setVideoSettings:@{(id)kCVPixelBufferPixelFormatTypeKey:@(kCVPixelFormatType_32BGRA)}];
    if([_captureSession canAddOutput:_output]){
        [_captureSession addOutput:_output];
    }
}

- (void)dealloc {
    [[self captureSession] stopRunning];
    _previewLayer = nil;
    _captureSession = nil;
    _output = nil;
}

@end
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2.封装一个实时更新矩形的view

/*
 * RectView.h
 */
#import <UIKit/UIKit.h>

@interface RectView : UIView

@property (atomic) CGPoint point1;
@property (atomic) CGPoint point2;
@property (atomic) CGPoint point3;
@property (atomic) CGPoint point4;

- (void)drawWithPointsfirst:(CGPoint)point1 second:(CGPoint)point2 thrid:(CGPoint)point3 forth:(CGPoint)point4;

@end
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/*
 * RectView.m
 */
#import "RectView.h"

@implementation RectView

- (instancetype)init {
    if(self = [super init]) {
        self.backgroundColor = [UIColor clearColor];
    }
    return self;
}

- (void)drawRect:(CGRect)rect;
{
    [super drawRect:rect];
    CGContextRef context = UIGraphicsGetCurrentContext();
    if (context)
    {
        CGContextMoveToPoint(context, _point1.x, _point1.y);
        CGContextAddLineToPoint(context, _point2.x, _point2.y);
        CGContextAddLineToPoint(context, _point3.x, _point3.y);
        CGContextAddLineToPoint(context, _point4.x, _point4.y);
        CGContextAddLineToPoint(context, _point1.x, _point1.y);
        CGContextSetRGBStrokeColor(context, 83 /255.0, 239/255.0, 111/255.0, 1);//green
        CGContextSetLineJoin(context, kCGLineJoinRound);
        CGContextSetLineWidth(context, 3.0f);
        CGContextStrokePath(context);
    }
}

- (void)drawWithPointsfirst:(CGPoint)point1 second:(CGPoint)point2 thrid:(CGPoint)point3 forth:(CGPoint)point4 {
    _point1 = point1;
    _point2 = point2;
    _point3 = point3;
    _point4 = point4;
}

@end
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3.在检测view中添加cameraview和rectview

/*
 * 添加camera的预览view
 */
self.cameraView = [[UIView alloc] init];
self.cameraView.backgroundColor = [UIColor blackColor];
self.cameraView.frame = self.view.bounds;
[self.view addSubview:self.cameraView];
[self setCaptureManager:[[Camera alloc] init]];
[_captureManager addVideoInputFromCamera];
[_captureManager addVideoOutput];
dispatch_queue_t queue = dispatch_queue_create("VideoQueue", DISPATCH_QUEUE_SERIAL);
[_captureManager.output setSampleBufferDelegate:self queue:queue];
[_captureManager addVideoPreviewLayer];
_captureManager.previewLayer.frame = _cameraView.bounds;
[_cameraView.layer addSublayer:_captureManager.previewLayer];

/*
 * 添加实时绘制矩形的view
 */
self.rectView = [[RectView alloc] init];
self.rectView.frame = self.cameraView.frame;
self.rectView.hidden = NO;
[self.view addSubview:selfw];
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3.获取检测器

- (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;
}
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4.在每帧中检测

/*
 * samplebuffer转CIImage
 */
CVPixelBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CIImage *image = [CIImage imageWithCVPixelBuffer:imageBuffer];

/*
 * 实际图像是旋转90°的，做个旋转
 */
CIFilter *transform = [CIFilter filterWithName:@"CIAffineTransform"];
[transform setValue:image forKey:kCIInputImageKey];
NSValue *rotation = [NSValue valueWithCGAffineTransform:CGAffineTransformMakeRotation(-90 * (M_PI/180))];
[transform setValue:rotation forKey:@"inputTransform"];
image = [transform outputImage];

/*
 * 使用CIRectangleFeature检测
 */
CIRectangleFeature *rectangleFeature = [self biggestRectangleInRectangles:[[self highAccuracyRectangleDetector] featuresInImage:image]];
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5.坐标转换和实时更新view

/*
 * 坐标调整
 */
CGRect previewRect = _cameraView.frame;
CGRect imageRect = image.extent;
CGFloat deltaX = CGRectGetWidth(previewRect)/CGRectGetWidth(imageRect);
CGFloat deltaY = CGRectGetHeight(previewRect)/CGRectGetHeight(imageRect);
CGAffineTransform transform2 = CGAffineTransformMakeTranslation(0.f, CGRectGetHeight(previewRect));
transform2 = CGAffineTransformScale(transform2, 1, -1);
transform2 = CGAffineTransformScale(transform2, deltaX, deltaY);

CGPoint points[4];
points[0] = CGPointApplyAffineTransform(rectangleFeature.topLeft, transform2);
points[1] = CGPointApplyAffineTransform(rectangleFeature.topRight, transform2);
points[2] = CGPointApplyAffineTransform(rectangleFeature.bottomRight, transform2);
points[3] = CGPointApplyAffineTransform(rectangleFeature.bottomLeft, transform2);

/*
 * 实时绘图
 */
if(rectangleFeature){
    /*
     * 点给rectView
     */
    [_rectView drawWithPointsfirst:points[0]

                                    second:points[1]

                                     thrid:points[2]

                                     forth:points[3]];
    /*
     * 子线程dispatch到主线程更新view
     */
    dispatch_async(dispatch_get_main_queue(), ^{
        [self.rectView setNeedsDisplay];
    });
}
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完整代码见https://github.com/fujikoli/CIRectangleDetectDemo