斯威夫特5。

class ImageConverter {

    func base64ToImage(_ base64String: String) -> UIImage? {
        guard let imageData = Data(base64Encoded: base64String) else { return nil }
        return UIImage(data: imageData)
    }

    func imageToBase64(_ image: UIImage) -> String? {
        return image.jpegData(compressionQuality: 1)?.base64EncodedString()
    }

}

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)
    }
}

@implementation UIImage (Extended)

- (NSString *)base64String {
    NSData * data = [UIImagePNGRepresentation(self) base64EncodedDataWithOptions:NSDataBase64Encoding64CharacterLineLength];
    return [NSString stringWithUTF8String:[data bytes]];
}

@end

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!

}

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];

我尝试了所有的解决方案，没有一个对我有效(使用Swift 4)，这是对我有效的解决方案，如果将来有人面临同样的问题。

let temp = base64String.components(separatedBy: ",")
let dataDecoded : Data = Data(base64Encoded: temp[1], options: 
 .ignoreUnknownCharacters)!
let decodedimage = UIImage(data: dataDecoded)

yourImage.image = decodedimage