Swift meetup question. Got stumbled with this Swift extension (below) where convenience failable initializer is implemented. At the very bottom there’s image which is what is needed. How to use this image to init self. Assignment to self in initializers only allowed for value types. To complete initialization here some self.init should be called (for not convenience initializers it will be super.init). But there’s no initializer for UIImage with UIImage parameter. As a workaround I use one with CGImage parameter. But it isn’t good solution as cgImage getter is failable. Nicer solution should exist!

extension UIImage {

    public convenience init?(from buffer: UnsafeMutablePointer<Double>, rows: Int, cols: Int, toRange0_1: Bool) {
        if toRange0_1 {
            let size: vDSP_Length = vDSP_Length(rows * cols)
            var min: Double = 0.0
            vDSP_minvD(buffer, 1, &min, size)
            min *= -1.0
            vDSP_vsaddD(buffer, 1, &min, buffer, 1, size)
            var max: Double = 0.0
            vDSP_maxvD(buffer, 1, &max, size)
            if max != 0 {
                vDSP_vsdivD(buffer, 1, &max, buffer, 1, size)
            } else {
                print("🔥 can't proceed with division by 0")
                return nil
        // TODO: do it with data provider!
        let size = CGSize(width: rows, height: cols)
        UIGraphicsBeginImageContextWithOptions(size, true, 1.0 /* we need just single resolution */)
        defer { UIGraphicsEndImageContext() }
        for r in 0..<rows {
            for c in 0..<cols {
                let pixelValue = buffer[r * cols + c]
                UIColor(red: CGFloat(pixelValue), green: 0.0, blue: 0.0, alpha: 1.0).setFill()
                UIRectFill(CGRect(x: CGFloat(r), y: CGFloat(c), width: CGFloat(1.0), height: CGFloat(1.0))) // Draw just one pixel in r,c
        guard let image = UIGraphicsGetImageFromCurrentImageContext(),
              let cgImage = image.cgImage
        else {
            return nil
        // TODO: What a way to do this without cgImage?
        // cgImage is workaround here to build UIImage with existing initializer.
        self.init(cgImage: cgImage)