GPUImage实现人脸实时识别_gpuimage 脸部贴图

最近在研究OC的生物活检方面的实现，发现SDK中自带有相应的功能类，则进行了调研与实现。

实现过程中发现一个比较坑人的一个地方，就是GPUIMAGE这个框架里面对于视频采集使用的YUV格式，而YUV格式无法与OC的类库进行配合实现实时识别。

现在我们来剖析一下GPUImageVideoCamera的实现：

@interface GPUImageVideoCamera : GPUImageOutput <AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureAudioDataOutputSampleBufferDelegate>
 
 
- (id)initWithSessionPreset:(NSString *)sessionPreset cameraPosition:(AVCaptureDevicePosition)cameraPosition;

可以看到提供了一个初始化方法，此初始化方法内部的代码如下： 

- (id)initWithSessionPreset:(NSString *)sessionPreset cameraPosition:(AVCaptureDevicePosition)cameraPosition; 
{
	if (!(self = [super init]))
    {
		return nil;
    }
    
    cameraProcessingQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,0);
	audioProcessingQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW,0);
 
    frameRenderingSemaphore = dispatch_semaphore_create(1);
 
	_frameRate = 0; // This will not set frame rate unless this value gets set to 1 or above
    _runBenchmark = NO;
    capturePaused = NO;
    outputRotation = kGPUImageNoRotation;
    internalRotation = kGPUImageNoRotation;
    captureAsYUV = YES;
    _preferredConversion = kColorConversion709;
    
	// Grab the back-facing or front-facing camera
    _inputCamera = nil;
	NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
	for (AVCaptureDevice *device in devices) 
	{
		if ([device position] == cameraPosition)
		{
			_inputCamera = device;
		}
	}
    
    if (!_inputCamera) {
        return nil;
    }
    
	// Create the capture session
	_captureSession = [[AVCaptureSession alloc] init];
	
    [_captureSession beginConfiguration];
    
	// Add the video input	
	NSError *error = nil;
	videoInput = [[AVCaptureDeviceInput alloc] initWithDevice:_inputCamera error:&error];
	if ([_captureSession canAddInput:videoInput]) 
	{
		[_captureSession addInput:videoInput];
	}
	
	// Add the video frame output	
	videoOutput = [[AVCaptureVideoDataOutput alloc] init];
	[videoOutput setAlwaysDiscardsLateVideoFrames:NO];
    
//    if (captureAsYUV && [GPUImageContext deviceSupportsRedTextures])
    if (captureAsYUV && [GPUImageContext supportsFastTextureUpload])
    {
        BOOL supportsFullYUVRange = NO;
        NSArray *supportedPixelFormats = videoOutput.availableVideoCVPixelFormatTypes;
        for (NSNumber *currentPixelFormat in supportedPixelFormats)
        {
            if ([currentPixelFormat intValue] == kCVPixelFormatType_420YpCbCr8BiPlanarFullRange)
            {
                supportsFullYUVRange = YES;
            }
        }
        
        if (supportsFullYUVRange)
        {
            [videoOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarFullRange] forKey:(id)kCVPixelBufferPixelFormatTypeKey]];
            isFullYUVRange = YES;
        }
        else
        {
            [videoOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange] forKey:(id)kCVPixelBufferPixelFormatTypeKey]];
            isFullYUVRange = NO;
        }
    }
    else
    {
        [videoOutput setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey]];
    }
    
    runSynchronouslyOnVideoProcessingQueue(^{
        
        if (captureAsYUV)
        {
            [GPUImageContext useImageProcessingContext];
            //            if ([GPUImageContext deviceSupportsRedTextures])
            //            {
            //                yuvConversionProgram = [[GPUImageContext sharedImageProcessingContext] programForVertexShaderString:kGPUImageVertexShaderString fragmentShaderString:kGPUImageYUVVideoRangeConversionForRGFragmentShaderString];
            //            }
            //            else
            //            {
            if (isFullYUVRange)
            {
                yuvConversionProgram = [[GPUImageContext sharedImageProcessingContext] programForVertexShaderString:kGPUImageVertexShaderString fragmentShaderString:kGPUImageYUVFullRangeConversionForLAFragmentShaderString];
            }
            else
            {
                yuvConversionProgram = [[GPUImageContext sharedImageProcessingContext] programForVertexShaderString:kGPUImageVertexShaderString fragmentShaderString:kGPUImageYUVVideoRangeConversionForLAFragmentShaderString];
            }
 
            //            }
            
            if (!yuvConversionProgram.initialized)
            {
                [yuvConversionProgram addAttribute:@"position"];
                [yuvConversionProgram addAttribute:@"inputTextureCoordinate"];
                
                if (![yuvConversionProgram link])
                {
                    NSString *progLog = [yuvConversionProgram programLog];
                    NSLog(@"Program link log: %@", progLog);
                    NSString *fragLog = [yuvConversionProgram fragmentShaderLog];
                    NSLog(@"Fragment shader compile log: %@", fragLog);
                    NSString *vertLog = [yuvConversionProgram vertexShaderLog];
                    NSLog(@"Vertex shader compile log: %@", vertLog);
                    yuvConversionProgram = nil;
                    NSAssert(NO, @"Filter shader link failed");
                }
            }
            
            yuvConversionPositionAttribute = [yuvConversionProgram attributeIndex:@"position"];
            yuvConversionTextureCoordinateAttribute = [yuvConversionProgram attributeIndex:@"inputTextureCoordinate"];
            yuvConversionLuminanceTextureUniform = [yuvConversionProgram uniformIndex:@"luminanceTexture"];
            yuvConversionChrominanceTextureUniform = [yuvConversionProgram uniformIndex:@"chrominanceTexture"];
            yuvConversionMatrixUniform = [yuvConversionProgram uniformIndex:@"colorConversionMatrix"];
            
            [GPUImageContext setActiveShaderProgram:yuvConversionProgram];
            
            glEnableVertexAttribArray(yuvConversionPositionAttribute);
            glEnableVertexAttribArray(yuvConversionTextureCoordinateAttribute);
        }
    });
    
    [videoOutput setSampleBufferDelegate:self queue:cameraProcessingQueue];
	if ([_captureSession