获取AVCaptureSession samplebuffer 一像素的 rgb值

typedef unsigned char byte;
typedef struct RGBPixel{
    byte red, green, blue;
} RGBPixel;

- (void)captureOutput:(AVCaptureOutput *)captureOutput 
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer 
       fromConnection:(AVCaptureConnection *)connection 
{ 
    
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    CVPixelBufferLockBaseAddress(imageBuffer,0);
    
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);
    uint8_t *src_buff = (uint8_t*)CVPixelBufferGetBaseAddress(imageBuffer);
    
    CVPixelBufferUnlockBaseAddress(imageBuffer, 0);
    RGBPixel *pixelData = (RGBPixel *)src_buff;

    int len = bytesPerRow * height;
    for(int i=0; i<len; i+=4){
        
        RGBPixel pixel = pixelData[i/4];
        
        int a = 0;
        int r = pixel.red;
        int g = pixel.green;
        int b = pixel.blue;

        NSLog(@"first values = r:%d g:%d b:%d", r, g, b);
        
        a = src_buff[i+3];
        r = src_buff[i+2];
        g = src_buff[i+1];
        b = src_buff[i];

        NSLog(@"second values = r:%d g:%d b:%d", r, g, b);
 
    }

}

typedef struct RGBPixel{
    byte blue, green, red;
} RGBPixel;