Question

昨天我为此编写了一个工作代码，但是我删除了它，当写一个新的东西时真的很奇怪：

我用这种方式对它进行编码：

let pictureData = UIImagePNGRepresentation(picture!)
let pictureToString64 = pictureData?.base64EncodedStringWithOptions(NSDataBase64EncodingOptions.Encoding64CharacterLineLength)

（之前我有JPEGRepresentation，但它没有工作，所以我尝试使用JPEG）我通过获取pic 64来解码，我认为它具有正确的值。它以iVBORw0KGgoAAAANSUhEUgAAAUAA（...）

开头

 let decodedData = NSData(base64EncodedString: pic64, options:NSDataBase64DecodingOptions(rawValue: 0))
 let decodedImage = UIImage(data: decodedData!)
 let pictureDataLocal = UIImageJPEGRepresentation(decodedImage!, 100)
                defaults.setObject(pictureDataLocal, forKey: "profilePicture")

问题是decodeData总是为零。为什么会这样？

Answer 1

我认为这与NSDataBase64DecodingOptions有关。

使用NSDataBase64DecodingOptions.IgnoreUnknownCharacters代替NSDataBase64DecodingOptions(rawValue: 0)，我能够将Base64编码的字符串解码回NSData，并从该数据创建UIImage：

let picture = UIImage(named: "myImage")

let pictureData = UIImagePNGRepresentation(picture!)

let pictureToString64 = pictureData?.base64EncodedStringWithOptions(NSDataBase64EncodingOptions.Encoding64CharacterLineLength)

let decodedData = NSData(base64EncodedString: pictureToString64!, options:NSDataBase64DecodingOptions.IgnoreUnknownCharacters)
let decodedImage = UIImage(data: decodedData!)
let pictureDataLocal = UIImageJPEGRepresentation(decodedImage!, 100)

NSDataBase64DecodingOptions继承自OptionSetType，这就是你获得rawValue初始化程序的原因。最好使用其中一种类型，而不是传入一个值。我在标题中看到NSDataBase64DecodingOptions是结构中唯一的公共变量，所以我尝试了它。

@available(iOS 7.0, *)
public struct NSDataBase64DecodingOptions : OptionSetType {
    public init(rawValue: UInt)

    // Use the following option to modify the decoding algorithm so that it ignores unknown non-Base64 bytes, including line ending characters.
    public static var IgnoreUnknownCharacters: NSDataBase64DecodingOptions { get }
}

编码/解码base64 decodingData = nil

1 个答案: