Draw a simple circle uiimage

Question

I try to make a 20x20 UIImage with a simple blue circle. I try with this function, but the result is a blue circle in a black square. How do I remove the black square around

Answer 1

A custom initializer for creating a circle with a specific diameter and color:

extension UIImage {
    convenience init?(diameter: CGFloat, color: UIColor) {
        let size = CGSize(width: diameter, height: diameter)
        UIGraphicsBeginImageContextWithOptions(size, false, 0)
        guard let contex = UIGraphicsGetCurrentContext() else {
            return nil
        }

        contex.saveGState()
        let rect = CGRect(origin: .zero, size: size)
        contex.setFillColor(color.cgColor)
        contex.fillEllipse(in: rect)
        contex.restoreGState()

        guard let image = UIGraphicsGetImageFromCurrentImageContext(),
        let cgImage = image.cgImage else {
            return nil
        }
        UIGraphicsEndImageContext()

        self.init(cgImage: cgImage)
    }
}