如何获取kCVPixelFormatType_DepthFloat16（半点浮点数）的值？

Question

我正在使用 swift 处理 iOS 前置深度相机的项目。根据 Apple 文档，媒体类型为 kCVPixelFormatType_DepthFloat16，半点浮动，尺寸为 640*360，帧率为 30fps。我被困在如何进一步逐个像素地检索和处理值。

let buffer:CVPixelBuffer = depthData.depthDataMap //depthData is AVDepthData type
CVPixelBufferLockBaseAddress(buffer, CVPixelBufferLockFlags(rawValue: 0))
let width = CVPixelBufferGetWidth(buffer)
let height = CVPixelBufferGetHeight(buffer)
for y in 0 ..< height {
  for x in 0 ..< width {
    let pixel = ?? //what should I do here?
  }
}

Answer 1

我已经解决了我的问题。这可以通过两种方式完成。

使用kCVPixelFormatType_DepthFloat32而不是kCVPixelFormatType_DepthFloat16，它将具有与之前的深度图相同的维度和fps。然后你可以将其转换为 Swift Float 类型，如下所示：

let width = CVPixelBufferGetWidth(buffer)
let height = CVPixelBufferGetHeight(buffer)

CVPixelBufferLockBaseAddress(buffer, CVPixelBufferLockFlags(rawValue: 0))
let floatBuffer = unsafeBitCast(CVPixelBufferGetBaseAddress(buffer), to: UnsafeMutablePointer<Float>.self)

for y in 0 ..< height {
    for x in 0 ..< width {
        let pixel = floatBuffer[y*width+x]
    }
}
CVPixelBufferUnlockBaseAddress(self, CVPixelBufferLockFlags(rawValue: 0))

第二种方式是先转成UInt16，再在前面加两个零字节

// to access the point height = y, width = x, thanks to this project https://github.com/edvardHua/Articles/tree/master/%5BAR:MR%20%E5%9F%BA%E7%A1%80%5D%20%E5%88%A9%E7%94%A8%20iPhone%20X%20%E7%9A%84%E6%B7%B1%E5%BA%A6%E7%9B%B8%E6%9C%BA(TruthDepth%20Camera)%E8%8E%B7%E5%BE%97%E5%83%8F%E7%B4%A0%E7%82%B9%E7%9A%84%E4%B8%89%E7%BB%B4%E5%9D%90%E6%A0%87/Obtain3DCoordinate
let rowData = CVPixelBufferGetBaseAddress(buffer)! + Int(y) *  CVPixelBufferGetBytesPerRow(buffer)
var f16Pixel = rowData.assumingMemoryBound(to: UInt16.self)[x]
var f32Pixel = Float(0.0)
var src = vImage_Buffer(data: &f16Pixel, height: 1, width: 1, rowBytes: 2)
var dst = vImage_Buffer(data: &f32Pixel, height: 1, width: 1, rowBytes: 4)
vImageConvert_Planar16FtoPlanarF(&src, &dst, 0)
let depth = f32Pixel //depth in cm

如何获取kCVPixelFormatType_DepthFloat16（半点浮点数）的值？

How to get the value of kCVPixelFormatType_DepthFloat16 (half-point float)?

ios

swift

half-precision-float