將 CMSampleBuffer 轉換為 UIImage

Question

我正在嘗試將 sampleBuffer 轉換為 UIImage 並使用 colorspaceGray 在圖像視圖中顯示它。 但它顯示為下圖。 我認為轉換存在問題。 如何轉換 CMSampleBuffer？

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
    print("buffered")
    let imageBuffer: CVImageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!
    CVPixelBufferLockBaseAddress(imageBuffer, CVPixelBufferLockFlags(rawValue: 0))
    let width: Int = CVPixelBufferGetWidth(imageBuffer)
    let height: Int = CVPixelBufferGetHeight(imageBuffer)
    let bytesPerRow: Int = CVPixelBufferGetBytesPerRow(imageBuffer)
    let lumaBuffer = CVPixelBufferGetBaseAddress(imageBuffer)

    //let planeCount : Int = CVPixelBufferGetPlaneCount(imageBuffer)
    let grayColorSpace: CGColorSpace = CGColorSpaceCreateDeviceGray()
    let context: CGContext = CGContext(data: lumaBuffer, width: width, height: height, bitsPerComponent: 8, bytesPerRow: bytesPerRow , space: grayColorSpace, bitmapInfo: CGImageAlphaInfo.none.rawValue)!
    let dstImageFilter: CGImage = context.makeImage()!
    let imageRect : CGRect = CGRect(x: 0, y: 0, width: width, height: height)
    context.draw(dstImageFilter, in: imageRect)
    let image = UIImage(cgImage: dstImageFilter)
    DispatchQueue.main.sync(execute: {() -> Void in
        self.imageTest.image = image
    })
}

Answer 1

轉換很簡單：

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
     let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!
     let ciimage = CIImage(cvPixelBuffer: imageBuffer)   
     let image = self.convert(cmage: ciimage) 
}

// Convert CIImage to UIImage
func convert(cmage: CIImage) -> UIImage {
     let context = CIContext(options: nil)
     let cgImage = context.createCGImage(cmage, from: cmage.extent)!
     let image = UIImage(cgImage: cgImage)
     return image
}

Answer 2

看起來CMSampleBuffer正在為您提供 RGBA 數據，然后您可以從中直接構建灰度圖像。 您要么需要構建一個新的緩沖區，其中為每個像素執行類似gray = (pixel.red+pixel.green+pixel.blue)/3 。 或者您需要根據您收到的數據創建一個普通的 RGBA 圖像，然后將其轉換為灰度。

但是在您的代碼中，您根本沒有過渡。 您使用CVPixelBufferGetBaseAddress將原始指針指向緩沖區，而不管那里有什么類型的數據。 然后您只需在創建圖像時傳遞相同的指針，假設接收到的數據是灰度的。

Answer 3

現在可以使用UIImage上的新便利方法進一步改進上述解決方案。 我在下面概述了一個帶有圖像方向校正的現代解決方案。 該解決方案不使用CGImage轉換，這提高了運行時性能。

func orientation() -> UIImage.Orientation {
    let curDeviceOrientation = UIDevice.current.orientation
    var exifOrientation: UIImage.Orientation
    switch curDeviceOrientation {
        case UIDeviceOrientation.portraitUpsideDown:  // Device oriented vertically, Home button on the top
            exifOrientation = .left
        case UIDeviceOrientation.landscapeLeft:       // Device oriented horizontally, Home button on the right
            exifOrientation = .upMirrored
        case UIDeviceOrientation.landscapeRight:      // Device oriented horizontally, Home button on the left
            exifOrientation = .down
        case UIDeviceOrientation.portrait:            // Device oriented vertically, Home button on the bottom
            exifOrientation = .up
        default:
            exifOrientation = .up
    }
    return exifOrientation
}

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
    guard let imageBuffer: CVPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return }
    let ciimage : CIImage = CIImage(cvPixelBuffer: imageBuffer)
    let image = UIImage.init(ciImage: ciimage, scale: 1.0, orientation: orientation())
}