ios – 计算AVCaptureVideoDataOutput feed的平均RGB像素值的最快方法 – CPU / GPU

我想知道是否有更有效的方法来执行GPU / openGL,因为这是一个可并行化的图像处理任务. (也许是一个沉重的高斯模糊,并读取中心像素值？)

一个特定的要求是使用高水平的平均值来获得高精度结果.请注意下面的CGFloat结果.

目前swift 2代码：

编辑：添加了CIAreaAverage的实现,如Simon所示.它由useGPU bool分隔.

func captureOutput(captureOutput: AVCaptureOutput!,didOutputSampleBuffer sampleBuffer: CMSampleBuffer!,fromConnection connection: AVCaptureConnection!) {

    var redmean:CGFloat = 0.0;
    var greenmean:CGFloat = 0.0;
    var bluemean:CGFloat = 0.0;

    if (useGPU) {
            let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
            let cameraImage = CIImage(CVPixelBuffer: pixelBuffer!)
            let filter = CIFilter(name: "CIAreaAverage")
            filter!.SETVALue(cameraImage,forKey: kCIInputImageKey)
            let outputImage = filter!.valueForKey(kCIoUtputImageKey) as! CIImage!

            let ctx = CIContext(options:nil)
            let cgImage = ctx.createCGImage(outputImage,fromRect:outputImage.extent)

            let rawData:NSData = CGDataProviderCopyData(CGImageGetDataProvider(cgImagE))!
            let pixels = UnsafePointer<UInt8>(rawData.bytes)
            let bytes = UnsafeBufferPointer<UInt8>(start:pixels,count:rawData.length)
            var BGRA_index = 0
            for pixel in UnsafeBufferPointer(start: bytes.baseAddress,count: bytes.count) {
                switch BGRA_index {
                case 0:
                    bluemean = CGFloat (pixel)
                case 1:
                    greenmean = CGFloat (pixel)
                case 2:
                    redmean = CGFloat (pixel)
                case 3:
                    break
                default:
                    break
                }
                BGRA_index++

            }
     } else {
            let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
            CVPixelBufferLockBaseAddress(imageBuffer!,0)

            let baseAddress = CVPixelBufferGetBaseAddressOfPlane(imageBuffer!,0)
            let bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer!)
            let width = CVPixelBufferGetWidth(imageBuffer!)
            let height = CVPixelBufferGetHeight(imageBuffer!)
            let colorSpace = CGColorSpaceCreateDeviceRGB()

            let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawvalue).rawValue | CGBitmapInfo.byteOrder32Little.rawValue

            let context = CGBitmapContextCreate(baseAddress,width,height,8,bytesPerRow,colorSpace,bitmapInfo)
            let imageRef = CGBitmapContextCreateImage(context)
            CVPixelBufferUnlockBaseAddress(imageBuffer!,0)
            let data:NSData = CGDataProviderCopyData(CGImageGetDataProvider(imageRef))!
            let pixels = UnsafePointer<UInt8>(data.bytes)
            let bytes = UnsafeBufferPointer<UInt8>(start:pixels,count:data.length)
            var redsum:CGFloat = 0
            var greensum:CGFloat  = 0
            var bluesum:CGFloat  = 0
            var BGRA_index = 0
            for pixel in UnsafeBufferPointer(start: bytes.baseAddress,count: bytes.count) {
            switch BGRA_index {
            case 0:
                bluesum += CGFloat (pixel)
            case 1:
                greensum += CGFloat (pixel)
            case 2:
                redsum += CGFloat (pixel)
            case 3:
                //alphasum += UInt64(pixel)
                break
            default:
                break
            }

            BGRA_index += 1
            if BGRA_index == 4 { BGRA_index = 0 }
        }
        redmean = redsum / CGFloat(bytes.count)
        greenmean = greensum / CGFloat(bytes.count)
        bluemean = bluesum / CGFloat(bytes.count)            
        }

print("R:\(redmean) G:\(greenmean) B:\(bluemean)")