Convert colours of every pixel in video preview - Swift - ios

Question

I have the following code which displays a camera preview, retrieves a single pixel's colour from the UIImage and converts this value to a 'filtered' colour.
func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
connection.videoOrientation = orientation
let videoOutput = AVCaptureVideoDataOutput()
videoOutput.setSampleBufferDelegate(self, queue: DispatchQueue.main)
let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
let cameraImage = CIImage(cvImageBuffer: pixelBuffer!)
let typeOfColourBlindness = ColourBlindType(rawValue: "deuteranomaly")
/* Gets colour from a single pixel - currently 0,0 and converts it into the 'colour blind' version */
let captureImage = convert(cmage: cameraImage)
let colour = captureImage.getPixelColour(pos: CGPoint(x: 0, y: 0))
var redval: CGFloat = 0
var greenval: CGFloat = 0
var blueval: CGFloat = 0
var alphaval: CGFloat = 0
_ = colour.getRed(&redval, green: &greenval, blue: &blueval, alpha: &alphaval)
print("Colours are r: \(redval) g: \(greenval) b: \(blueval) a: \(alphaval)")
let filteredColour = CBColourBlindTypes.getModifiedColour(.deuteranomaly, red: Float(redval), green: Float(greenval), blue: Float(blueval))
print(filteredColour)
/* #################################################################################### */
DispatchQueue.main.async {
// placeholder for now
self.filteredImage.image = self.applyFilter(cameraImage: cameraImage, colourBlindness: typeOfColourBlindness!)
}
}
Here is where the x: 0, y: 0 pixel value is converted:
import Foundation
enum ColourBlindType: String {
case deuteranomaly = "deuteranomaly"
case protanopia = "protanopia"
case deuteranopia = "deuteranopia"
case protanomaly = "protanomaly"
}
class CBColourBlindTypes: NSObject {
class func getModifiedColour(_ type: ColourBlindType, red: Float, green: Float, blue: Float) -> Array<Float> {
switch type {
case .deuteranomaly:
return [(red*0.80)+(green*0.20)+(blue*0),
(red*0.25833)+(green*0.74167)+(blue*0),
(red*0)+(green*0.14167)+(blue*0.85833)]
case .protanopia:
return [(red*0.56667)+(green*0.43333)+(blue*0),
(red*0.55833)+(green*0.44167)+(blue*0),
(red*0)+(green*0.24167)+(blue*0.75833)]
case .deuteranopia:
return [(red*0.625)+(green*0.375)+(blue*0),
(red*0.7)+(green*0.3)+(blue*0),
(red*0)+(green*0.3)+(blue*0.7)]
case .protanomaly:
return [(red*0.81667)+(green*0.18333)+(blue*0.0),
(red*0.33333)+(green*0.66667)+(blue*0.0),
(red*0.0)+(green*0.125)+(blue*0.875)]
}
}
}
The placeholder for now comment refers to the following function:
func applyFilter(cameraImage: CIImage, colourBlindness: ColourBlindType) -> UIImage {
//do stuff with pixels to render new image
/* Placeholder code for shifting the hue */
// Create a place to render the filtered image
let context = CIContext(options: nil)
// Create filter angle
let filterAngle = 207 * Double.pi / 180
// Create a random color to pass to a filter
let randomColor = [kCIInputAngleKey: filterAngle]
// Apply a filter to the image
let filteredImage = cameraImage.applyingFilter("CIHueAdjust", parameters: randomColor)
// Render the filtered image
let renderedImage = context.createCGImage(filteredImage, from: filteredImage.extent)
// Return a UIImage
return UIImage(cgImage: renderedImage!)
}
And here is my extension for retrieving a pixel colour:
extension UIImage {
func getPixelColour(pos: CGPoint) -> UIColor {
let pixelData = self.cgImage!.dataProvider!.data
let data: UnsafePointer<UInt8> = CFDataGetBytePtr(pixelData)
let pixelInfo: Int = ((Int(self.size.width) * Int(pos.y)) + Int(pos.x)) * 4
let r = CGFloat(data[pixelInfo]) / CGFloat(255.0)
let g = CGFloat(data[pixelInfo+1]) / CGFloat(255.0)
let b = CGFloat(data[pixelInfo+2]) / CGFloat(255.0)
let a = CGFloat(data[pixelInfo+3]) / CGFloat(255.0)
return UIColor(red: r, green: g, blue: b, alpha: a)
}
}
How can I create a filter for the following colour range for example?
I want to take in the camera input, replace the colours to be of the Deuteranopia range and display this on the screen, in real time, using Swift.
I am using a UIImageView for the image display.

Answer 1

To learn how to perform filtering of video capture and real-time display of the filtered image, you may want to study the AVCamPhotoFilter sample code from Apple, and other sources such as this objc.io tutorial
In short, using a UIImage for real-time rendering is not a good idea - it's too slow. Use a OpenGL (e.g. GLKView) of Metal (e.g. MTKView). The AVCamPhotoFilter code uses MTKView and renders to intermediate buffers, but you can also render a CIImage directly using the appropriate CIContext methods, e.g. for metal https://developer.apple.com/documentation/coreimage/cicontext/1437835-render
In addition, regarding your color filter - you may want to look at the CIColorCube core image filter as shown here.

Answer 2

let filterName = "CIColorCrossPolynomial"
//deuteronomaly
let param = ["inputRedCoefficients" : CIVector(values: [0.8, 0.2, 0, 0, 0, 0, 0, 0, 0, 0], count: 10),
"inputGreenCoefficients" : CIVector(values: [0.25833, 0.74167, 0, 0, 0, 0, 0, 0, 0, 0], count: 10),
"inputBlueCoefficients" : CIVector(values: [0, 0.14167, 0.85833, 0, 0, 0, 0, 0, 0, 0], count: 10)]
let filter = CIFilter(name: filterName, parameters: param)
let startImage = CIImage(image: image!)
filter?.setValue(startImage, forKey: kCIInputImageKey)
let newImage = UIImage(ciImage: ((filter?.outputImage)!))
filter result:
filter result 2: