channelDescription(bufferType:)
Returns the range and clamp limits for a specified channel in a Core Video image format.
Declaration
func channelDescription(bufferType: vImage.BufferType) -> vImageChannelDescription?Parameters
- bufferType:
The source buffer type.
Return Value
A vImageChannelDescription structure that describes the range and clamp limits for the specified channel.
Discussion
Use this function to return the vImageChannelDescription description for a specified channel in a Core Video format.
For example, the following code prints the description of each channel in a kCVPixelFormatType_420YpCbCr8Planar Core Video image format:
let cvImageFormat = vImageCVImageFormat.make(
format: .format420YpCbCr8Planar,
matrix: kvImage_ARGBToYpCbCrMatrix_ITU_R_709_2.pointee,
chromaSiting: .center,
colorSpace: CGColorSpace(name: CGColorSpace.sRGB)!,
alphaIsOpaqueHint: true)!
// Prints:
// luminance vImageChannelDescription(min: 0.0, zero: 16.0, full: 235.0, max: 255.0)
// Cb vImageChannelDescription(min: 0.0, zero: 128.0, full: 240.0, max: 255.0)
// Cr vImageChannelDescription(min: 0.0, zero: 128.0, full: 240.0, max: 255.0)
for channel in cvImageFormat.channels {
let desc = cvImageFormat.channelDescription(bufferType: channel)!
print("\(channel) \t\t \(desc)")
}