将 CMSampleBuffer 转换为 UIImage

Question

我正在尝试将 sampleBuffer 转换为 UIImage 并使用 colorspaceGray 在图像视图中显示它。但它显示如下图。我认为转换有问题。如何转换 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

看起来 CMSampleBuffer 正在为您提供 RGBA 数据，然后您可以从中直接构建灰度图像。您将需要构建一个新缓冲区，在其中为每个像素执行类似 gray = (pixel.red+pixel.green+pixel.blue)/3 的操作。或者您需要根据收到的数据创建一个普通的 RGBA 图像，然后将其转换为灰度。

但是在你的代码中你根本没有做任何转换。您使用 CVPixelBufferGetBaseAddress 将原始指针指向缓冲区，而不管其中的数据类型如何。然后你只需在创建图像时传递相同的指针，假设接收到的数据是灰度的。

Answer 2

转换很简单：

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 3

现在可以使用 UIImage 上的新便捷方法进一步改进上述解决方案。我在下面概述了一个现代解决方案，也带有图像方向校正。该解决方案不使用 CGImage 转换，这提高了运行时性能。

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(cvPixelBuffer: imageBuffer)
    let image = UIImage(ciImage: ciimage, scale: 1.0, orientation: orientation())
}

将 CMSampleBuffer 转换为 UIImage

Convert CMSampleBuffer to UIImage

uiimage

ios

cmsamplebuffer

swift