当前swift 2代码：

编辑：添加了CIAreaAverage的实现，如Simon所示。它被useGPU布尔分开。

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)")

Answer 1

CIAreaAverage过滤器性能不佳的问题和原因是缺少输入范围的定义。因此，滤镜的输出与输入图像的大小相同，因此您可以在完整的图像上循环而不是1×1像素的图像。因此，执行所需的时间与初始版本相同。

如CIAreaAverage文档中所述，您可以指定 inputExtent 参数。如何在swift中完成此操作可以在类似问题的this answer中找到：

    let cameraImage = CIImage(CVPixelBuffer: pixelBuffer!)
    let extent = cameraImage.extent
    let inputExtent = CIVector(x: extent.origin.x, y: extent.origin.y, z: extent.size.width, w: extent.size.height)
    let filter = CIFilter(name: "CIAreaAverage", withInputParameters: [kCIInputImageKey: cameraImage, kCIInputExtentKey: inputExtent])!
    let outputImage = filter.outputImage!

如果您希望获得更高的性能，可以确保重复使用CIContext，而不是为每个捕获的帧重新创建它。

Answer 2

核心图像过滤器可以完成这项工作CIAreaAverage，它会返回包含感兴趣区域的平均颜色的单像素图像（您感兴趣的区域将是整个图像）。

仅供参考，我有一篇讨论applying Core Image filters to a live camera feed here的博客文章。简而言之，过滤器需要一个CIImage，您可以根据captureImage在sampleBuffer内创建：

let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
let cameraImage = CIImage(CVPixelBuffer: pixelBuffer!)

...而且cameraImage您需要传递给CIAreaAverage。

干杯，

西蒙

Answer 3

如果您将数据作为浮点值，则可以使用

func vDSP_meanv

如果这不是一个选项，请尝试以某种方式处理数据，以便优化程序可以使用SIMD指令。我没有任何好的配方，对我来说这是一次试错练习，但代码的某些重新排列可能比其他人提供更好的机会。例如，我会尝试从循环中删除开关。 SIMD将对您的计算进行矢量化，此外，您可以通过GCD使用多线程处理，在单独的核心上处理每一行图像数据......

计算AVCaptureVideoDataOutput Feed的平均RGB像素值的最快方法 - CPU / GPU

当前swift 2代码：

3 个答案: