将基础64解码为图像

Question

我在一个数组中有一个base64字符串，我可以把它拉出来但是当我尝试解码时，str已满但decodeData是零？我不知道为什么

let str = values[0]["image"] as? String
            let decodedData = Data(base64Encoded: str!)
            let decodedImage = UIImage(data: decodedData!)
            let pictureDataLocal = UIImageJPEGRepresentation(decodedImage!, 100)
            self.profileImage.image =  UIImage(data: pictureDataLocal!)