通过颜色生成图片

UIImage+Extensions.swift

extension UIImage {
    class func imageWithColor(color: UIColor) -> UIImage {
        let rect: CGRect = CGRect(x: 0, y: 0, width: 1, height: 1)
        UIGraphicsBeginImageContextWithOptions(CGSize(width: 1, height: 1), false, 0)
        color.setFill()
        UIRectFill(rect)
        let image: UIImage? = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        return image!
    }
}

Usage：

let image = UIImage.imageWithColor(color: UIColor.red)