对于Base64代码，例如:

"data:image/jpg;base64,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"

使用Swift5.0代码如下:

func imageFromBase64(_ base64: String) -> UIImage? {
    if let url = URL(string: base64), let data = try? Data(contentsOf: url) {
        return UIImage(data: data)
    }
    return nil
}

斯威夫特iOS8

// prgm mark ---- 

// convert images into base64 and keep them into string

func convertImageToBase64(image: UIImage) -> String {

    var imageData = UIImagePNGRepresentation(image)
    let base64String = imageData.base64EncodedStringWithOptions(.allZeros)

    return base64String

}// end convertImageToBase64


// prgm mark ----

// convert images into base64 and keep them into string

func convertBase64ToImage(base64String: String) -> UIImage {

    let decodedData = NSData(base64EncodedString: base64String, options: NSDataBase64DecodingOptions(rawValue: 0) )

    var decodedimage = UIImage(data: decodedData!)

    return decodedimage!

}// end convertBase64ToImage

Swift版本-创建base64镜像

在我看来，在UIImagePNGRepresenatation()的情况下隐式Unwrapped Optional是不安全的，所以我建议使用扩展如下:

extension UIImage {

    func toBase64() -> String? {
        let imageData = UIImagePNGRepresentation(self)
        return imageData?.base64EncodedStringWithOptions(NSDataBase64EncodingOptions.Encoding64CharacterLineLength)
    }
}

Swift 3.0和Xcode 8.0

let imageData = UIImageJPEGRepresentation(imageView.image!, 1)

    let base64String = (imageData! as Data).base64EncodedString(options: NSData.Base64EncodingOptions(rawValue: 0))
    print(base64String)

对于iOS 7+， Objective-C，下面是如何从一个图像URL开始转换:

NSURL *url = [NSURL URLWithString:self.groove.thumbnailURL];

UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:url]];

NSString *base64String = [UIImagePNGRepresentation(image)
base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];

在Swift 3.0中

func decodeBase64(toImage strEncodeData: String) -> UIImage {

    let dataDecoded  = NSData(base64Encoded: strEncodeData, options: NSData.Base64DecodingOptions.ignoreUnknownCharacters)!
    let image = UIImage(data: dataDecoded as Data)
    return image!

}