iOS live video face masking demo. For more details see http://chriscavanagh.wordpress.com/2013/11/12/live-video-face-masking-on-ios/

CJCAnonymousFacesFilter.h

//
//  CJCAnonymousFacesFilter.h
//  CJC.FaceMaskingDemo
//
//  Created by Chris Cavanagh on 11/9/13.
//  Copyright (c) 2013 Chris Cavanagh. All rights reserved.
//

#import <CoreImage/CoreImage.h>

@interface CJCAnonymousFacesFilter : CIFilter
{
	CIImage *inputImage;
}

@property (nonatomic) CIImage *inputImage;
@property (nonatomic) NSArray *inputFacesMetadata;

@end

CJCAnonymousFacesFilter.m

//
//  CJCAnonymousFacesFilter.m
//  CJC.FaceMaskingDemo
//
//  Created by Chris Cavanagh on 11/9/13.
//  Copyright (c) 2013 Chris Cavanagh. All rights reserved.
//

#import "CJCAnonymousFacesFilter.h"
#import <AVFoundation/AVFoundation.h>

@interface CJCAnonymousFacesFilter ()

@property (nonatomic) CIFilter *anonymize;
@property (nonatomic) CIFilter *blend;
@property (atomic) CIImage *maskImage;

@end

@implementation CJCAnonymousFacesFilter
@synthesize inputImage;
@synthesize inputFacesMetadata;

- (CIImage *)outputImage
{
	// Create a pixellated version of the image
	[self.anonymize setValue:inputImage forKey:kCIInputImageKey];

	CIImage *maskImage = self.maskImage;
	CIImage *outputImage = nil;

	if ( maskImage )
	{
		// Blend the pixellated image, mask and original image
		[self.blend setValue:_anonymize.outputImage forKey:kCIInputImageKey];
		[_blend setValue:inputImage forKey:kCIInputBackgroundImageKey];
		[_blend setValue:self.maskImage forKey:kCIInputMaskImageKey];

		outputImage = _blend.outputImage;

		[_blend setValue:nil forKey:kCIInputImageKey];
		[_blend setValue:nil forKey:kCIInputBackgroundImageKey];
		[_blend setValue:nil forKey:kCIInputMaskImageKey];
	}
	else
	{
		outputImage = _anonymize.outputImage;
	}

	[_anonymize setValue:nil forKey:kCIInputImageKey];

	return outputImage;
}

- (CIFilter *)anonymize
{
	if ( !_anonymize )
	{
//		_anonymize = [CIFilter filterWithName:@"CIGaussianBlur"];
//		[_anonymize setValue:@( 40 ) forKey:kCIInputRadiusKey];

		_anonymize = [CIFilter filterWithName:@"CIPixellate"];
		[_anonymize setValue:@( 40 ) forKey:kCIInputScaleKey];
	}

	return _anonymize;
}

- (CIFilter *)blend
{
	if ( !_blend )
	{
		_blend = [CIFilter filterWithName:@"CIBlendWithMask"];
	}

	return _blend;
}

- (void)setInputFacesMetadata:(NSArray *)theInputFacesMetadata
{
	inputFacesMetadata = theInputFacesMetadata;

	self.maskImage = theInputFacesMetadata ? [self createMaskImageFromMetadata:theInputFacesMetadata] : nil;
}

- (CIImage *) createMaskImageFromMetadata:(NSArray *)metadataObjects
{
	CIImage *maskImage = nil;

	for ( AVMetadataObject *object in metadataObjects )
	{
		if ( [[object type] isEqual:AVMetadataObjectTypeFace] )
		{
			AVMetadataFaceObject* face = (AVMetadataFaceObject*)object;
			CGRect faceRectangle = [face bounds];
			CGFloat height = inputImage.extent.size.height;
			CGFloat width = inputImage.extent.size.width;

			CGFloat centerY = ( height * ( 1 - ( faceRectangle.origin.x + faceRectangle.size.width / 2.0 ) ) );
			CGFloat centerX = width * ( 1 - ( faceRectangle.origin.y + faceRectangle.size.height / 2.0 ) );
			CGFloat radiusX = width * ( faceRectangle.size.width / 1.5 );
			CGFloat radiusY = height * ( faceRectangle.size.height / 1.5 );

			CIImage *circleImage = [self createCircleImageWithCenter:CGPointMake( centerX, centerY )
															  radius:CGVectorMake( radiusX, radiusY )
															   angle:0];

			maskImage = [self compositeImage:circleImage ontoBaseImage:maskImage];
		}
	}

	return maskImage;
}

- (CIImage *) createCircleImageWithCenter:(CGPoint)center
								   radius:(CGVector)radius
									angle:(CGFloat)angle
{
	CIFilter *radialGradient = [CIFilter filterWithName:@"CIRadialGradient" keysAndValues:
								@"inputRadius0", @(radius.dx),
								@"inputRadius1", @(radius.dx + 1.0f ),
								@"inputColor0", [CIColor colorWithRed:0.0 green:1.0 blue:0.0 alpha:1.0],
								@"inputColor1", [CIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.0],
								kCIInputCenterKey, [CIVector vectorWithX:0 Y:0],
								nil];

	CGAffineTransform transform = CGAffineTransformMakeTranslation( center.x, center.y );
	transform = CGAffineTransformRotate( transform, angle );
	transform = CGAffineTransformScale( transform, 1.2, 1.6 );

	CIFilter *maskScale = [CIFilter filterWithName:@"CIAffineTransform" keysAndValues:
						   kCIInputImageKey, radialGradient.outputImage,
						   kCIInputTransformKey, [NSValue valueWithBytes:&transform objCType:@encode( CGAffineTransform )],
						   nil];

	return [maskScale valueForKey:kCIOutputImageKey];
}

- (CIImage *) compositeImage:(CIImage *)ciImage
			   ontoBaseImage:(CIImage *)baseImage
{
	if ( nil == baseImage ) return ciImage;

	CIFilter *filter = [CIFilter filterWithName:@"CISourceOverCompositing" keysAndValues:
						kCIInputImageKey, ciImage,
						kCIInputBackgroundImageKey, baseImage,
						nil];

	return [filter valueForKey:kCIOutputImageKey];
}

@end

CJCViewController.h

//
//  CJCViewController.h
//  CJC.FaceMaskingDemo
//
//  Created by Chris Cavanagh on 11/9/13.
//  Copyright (c) 2013 Chris Cavanagh. All rights reserved.
//

#import <UIKit/UIKit.h>
#import <GLKit/GLKit.h>
#import <AVFoundation/AVFoundation.h>

@interface CJCViewController : GLKViewController <AVCaptureMetadataOutputObjectsDelegate, AVCaptureVideoDataOutputSampleBufferDelegate>

@end

CJCViewController.m

//
//  CJCViewController.m
//  CJC.FaceMaskingDemo
//
//  Created by Chris Cavanagh on 11/9/13.
//  Copyright (c) 2013 Chris Cavanagh. All rights reserved.
//

#import "CJCViewController.h"
#import <AVFoundation/AVFoundation.h>
#import "CJCAnonymousFacesFilter.h"

@interface CJCViewController ()
{
	dispatch_queue_t _serialQueue;
}

@property (strong, nonatomic) EAGLContext *eaglContext;
@property (strong, nonatomic) CIContext *ciContext;
@property (strong, nonatomic) CJCAnonymousFacesFilter *filter;
@property (strong, nonatomic) AVCaptureSession *captureSession;
@property (strong, nonatomic) NSArray *facesMetadata;

@end

@implementation CJCViewController

- (void)viewDidLoad
{
	[super viewDidLoad];

	self.eaglContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];

	if ( !_eaglContext )
	{
		NSLog(@"Failed to create ES context");
	}

	self.ciContext = [CIContext contextWithEAGLContext:_eaglContext];

	GLKView *view = (GLKView *)self.view;
	view.context = _eaglContext;
	view.drawableDepthFormat = GLKViewDrawableDepthFormat24;

	_serialQueue = dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0 );

	self.filter = [CJCAnonymousFacesFilter new];
}

- (void)viewWillAppear:(BOOL)animated
{
	[super viewWillAppear:animated];

	[self setupAVCapture];
}

- (void)viewWillDisappear:(BOOL)animated
{
	[self tearDownAVCapture];

	[super viewWillDisappear:animated];
}

- (void)dealloc
{    
	[self tearDownAVCapture];
	
	if ([EAGLContext currentContext] == _eaglContext)
	{
		[EAGLContext setCurrentContext:nil];
	}
}

- (void)setupAVCapture
{
	AVCaptureSession *captureSession = [AVCaptureSession new];

	[captureSession beginConfiguration];

	NSError *error;

	// Input device

	AVCaptureDevice *captureDevice = [self frontOrDefaultCamera];
	AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:captureDevice error:&error];

	if ( [captureSession canAddInput:deviceInput] )
	{
		[captureSession addInput:deviceInput];
	}

	if ( [captureSession canSetSessionPreset:AVCaptureSessionPresetHigh] )
	{
		captureSession.sessionPreset = AVCaptureSessionPresetHigh;
	}

	// Video data output

	AVCaptureVideoDataOutput *videoDataOutput = [self createVideoDataOutput];

	if ( [captureSession canAddOutput:videoDataOutput] )
	{
		[captureSession addOutput:videoDataOutput];

		AVCaptureConnection *connection = videoDataOutput.connections[ 0 ];

		connection.videoOrientation = AVCaptureVideoOrientationPortrait;
	}

	// Metadata output

	AVCaptureMetadataOutput *metadataOutput = [self createMetadataOutput];

	if ( [captureSession canAddOutput:metadataOutput] )
	{
		[captureSession addOutput:metadataOutput];

		metadataOutput.metadataObjectTypes = [self metadataOutput:metadataOutput allowedObjectTypes:self.faceMetadataObjectTypes];
	}

	// Done

	[captureSession commitConfiguration];

	dispatch_async( _serialQueue,
				   ^{
					   [captureSession startRunning];
				   });

	_captureSession = captureSession;

//	[self updateVideoOrientation:self.interfaceOrientation];
}

- (void)tearDownAVCapture
{
	[_captureSession stopRunning];

	_captureSession = nil;
}

- (AVCaptureMetadataOutput *)createMetadataOutput
{
	AVCaptureMetadataOutput *metadataOutput = [AVCaptureMetadataOutput new];

	[metadataOutput setMetadataObjectsDelegate:self queue:_serialQueue];

	return metadataOutput;
}

- (NSArray *)metadataOutput:(AVCaptureMetadataOutput *)metadataOutput
		 allowedObjectTypes:(NSArray *)objectTypes
{
	NSSet *available = [NSSet setWithArray:metadataOutput.availableMetadataObjectTypes];

	[available intersectsSet:[NSSet setWithArray:objectTypes]];

	return [available allObjects];
}

- (NSArray *)barcodeMetadataObjectTypes
{
	return @
	[
	 AVMetadataObjectTypeUPCECode,
	 AVMetadataObjectTypeCode39Code,
	 AVMetadataObjectTypeCode39Mod43Code,
	 AVMetadataObjectTypeEAN13Code,
	 AVMetadataObjectTypeEAN8Code,
	 AVMetadataObjectTypeCode93Code,
	 AVMetadataObjectTypeCode128Code,
	 AVMetadataObjectTypePDF417Code,
	 AVMetadataObjectTypeQRCode,
	 AVMetadataObjectTypeAztecCode
	 ];
}

- (NSArray *)faceMetadataObjectTypes
{
	return @
	[
	 AVMetadataObjectTypeFace
	 ];
}

- (AVCaptureVideoDataOutput *)createVideoDataOutput
{
	AVCaptureVideoDataOutput *videoDataOutput = [AVCaptureVideoDataOutput new];

	[videoDataOutput setSampleBufferDelegate:self queue:_serialQueue];

	return videoDataOutput;
}

- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
//	[self updateVideoOrientation:toInterfaceOrientation];
}

- (void)updateVideoOrientation:(UIInterfaceOrientation)orientation
{
	AVCaptureConnection *connection = ( (AVCaptureOutput *)_captureSession.outputs[ 0 ] ).connections[ 0 ];

	if ( [connection isVideoOrientationSupported] )
	{
		connection.videoOrientation = [self videoOrientation:orientation];
	}
}

- (AVCaptureVideoOrientation)videoOrientation:(UIInterfaceOrientation)orientation
{
	switch ( orientation )
	{
		case UIDeviceOrientationPortrait: return AVCaptureVideoOrientationPortrait;
		case UIDeviceOrientationPortraitUpsideDown: return AVCaptureVideoOrientationPortraitUpsideDown;
		case UIDeviceOrientationLandscapeLeft: return AVCaptureVideoOrientationLandscapeRight;
		case UIDeviceOrientationLandscapeRight: return AVCaptureVideoOrientationLandscapeLeft;
		default: return AVCaptureVideoOrientationPortrait;
	}
}

- (AVCaptureDevice *)frontOrDefaultCamera
{
	NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];

	for ( AVCaptureDevice *device in devices )
	{
		if ( device.position == AVCaptureDevicePositionFront )
		{
			return device;
		}
	}

	return [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
}

- (void)didReceiveMemoryWarning
{
	[super didReceiveMemoryWarning];
	
	if ( [self isViewLoaded] && [[self view] window] == nil )
	{
		self.view = nil;
	
		[self tearDownAVCapture];
	
		if ( [EAGLContext currentContext] == _eaglContext )
		{
			[EAGLContext setCurrentContext:nil];
		}
	
		self.eaglContext = nil;
	}
	
	// Dispose of any resources that can be recreated.
}

#pragma mark - GLKView and GLKViewController delegate methods

- (void)update
{
}

- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect
{
}

#pragma mark Metadata capture

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
	_facesMetadata = metadataObjects;
}

#pragma mark Video data capture

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
	CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer( sampleBuffer );

	if ( pixelBuffer )
	{
		CFDictionaryRef attachments = CMCopyDictionaryOfAttachments( kCFAllocatorDefault, sampleBuffer, kCMAttachmentMode_ShouldPropagate );
		CIImage *ciImage = [[CIImage alloc] initWithCVPixelBuffer:pixelBuffer options:(__bridge NSDictionary *)attachments];

		if ( attachments ) CFRelease( attachments );

		CGRect extent = ciImage.extent;

		_filter.inputImage = ciImage;
		_filter.inputFacesMetadata = _facesMetadata;

		CIImage *output = _filter.outputImage;

		_filter.inputImage = nil;
		_filter.inputFacesMetadata = nil;

		dispatch_async( dispatch_get_main_queue(),
					   ^{
						   UIView *view = self.view;
						   CGRect bounds = view.bounds;
						   CGFloat scale = view.contentScaleFactor;

						   CGFloat extentFitWidth = extent.size.height / ( bounds.size.height / bounds.size.width );
						   CGRect extentFit = CGRectMake( ( extent.size.width - extentFitWidth ) / 2, 0, extentFitWidth, extent.size.height );

						   CGRect scaledBounds = CGRectMake( bounds.origin.x * scale, bounds.origin.y * scale, bounds.size.width * scale, bounds.size.height * scale );

						   [_ciContext drawImage:output inRect:scaledBounds fromRect:extentFit];
						   // [_ciContext render:output toCVPixelBuffer:pixelBuffer];

						   [_eaglContext presentRenderbuffer:GL_RENDERBUFFER];
						   [(GLKView *)self.view display];
					   });
	}
}

- (BOOL)shouldAutorotate
{
	return NO;
}

@end