how to display MTKView with rgba16Float MTLPixelFormat

Question

I have an MTKView set to use MTLPixelFormat.rgba16Float. I\'m having display issues which can be best described with the following graphic:

So the intended UIC

Answer 1

The key turned out to be in undoing the gamma correction that is inherently embedded in a UIColor

let colorSRGB = UIColor(red: 0.92, green: 0.79, blue: 0.18, alpha: 1.0)
let rgbaSRGB = colorSRGB.getRGBAComponents()!
let gammapower : CGFloat = 2.2

let r = pow(rgbaSRGB.red, gammapower)
let g = pow(rgbaSRGB.green, gammapower)
let b = pow(rgbaSRGB.blue, gammapower)
let a = pow(rgbaSRGB.alpha, gammapower)

let colorNoGamma: UIColor = UIColor(red: CGFloat(r), green: CGFloat(g), blue: CGFloat(b), alpha: CGFloat(a))

Once I pass colorNoGamma to be applied in an MKTView with MTLPixelFormat.rgba16Float, the results will match a UIView displaying colorSRGB. It makes sense once you think through it...Thanks to @MoDJ for leading me in the right path.

Note that, on the MTKView side, I can keep the texture settings as originally defined, namely:

let texDescriptor = MTLTextureDescriptor.texture2DDescriptor(pixelFormat: MTLPixelFormat.rgba8Unorm, width: Int(width), height: Int(height), mipmapped: isMipmaped)
target = texDescriptor.textureType

And, if I want to convert the currentDrawable into a texture to be displayed in a UIImageView, then I want to make sure I don't apply ANY colorspace settings. I.e:

let strokeCIImage = CIImage(mtlTexture: metalTextureComposite, options: [:])!.oriented(CGImagePropertyOrientation.downMirrored)
let imageCropCG = cicontext.createCGImage(strokeCIImage, from: box, format: kCIFormatABGR8, colorSpace: colorSpace)  // kCIFormatRGBA8 gives same result. Not sure what's proper
let layerStroke = CALayer()
layerStroke.frame = bbox
layerStroke.contents = imageCropCG

Note the argument options: [:] means I pass no colorspace/premultiplication/renderer settings as I did in the original post where I defined kciOptions