vImageCVImageFormat_GetChromaSiting(_:)
Returns the chrominance siting of a Core Video image format.
Declaration
func vImageCVImageFormat_GetChromaSiting(_ format: vImageConstCVImageFormat) -> Unmanaged<CFString>!Parameters
- format:
The Core Video image format to query.
Return Value
A CFString that describes the positioning of the chrominance samples.
Discussion
4:2:0 and 4:2:0 YpCbCr image formats that have subsampled chrominance require the position of the chrominance samples relative to the luminance samples.
The functions that create Core Video image formats, such as vImageCVImageFormat_CreateWithCVPixelBuffer(_:), return a vImageCVImageFormat. The following code shows how you create a vImageConstCVImageFormat representation of a vImageCVImageFormat instance to pass to vImageCVImageFormat_GetChromaSiting(_:):
let chromaSiting = withUnsafeBytes(of: cvImageFormat) { bytes in
let format = bytes.assumingMemoryBound(
to: vImageConstCVImageFormat.self).first!
return vImageCVImageFormat_GetChromaSiting(format)
}