使用 AES 加密在 Swift 中加密/解密 UIImage

Question

我捎带了Encrypt/decrypt for Image on IOS UIImage 加密策略，它使用 Obj-c 来实现我在 Swift 中寻找的东西。现在，请忽略那里的“保存到库”问题，因为我在应用程序本身中解密时遇到问题。

加密步骤似乎工作正常，我确实将加密图像发送到imageView.image，但是当我尝试解密时，我得到另一个似乎已加密的图像，永远不会返回原始 .png 图像。

关于我哪里出错了有什么想法吗？ AES 加密文件在这里：https://github.com/alexeypro/EncryptDecrypt

加密/解密：

func pixelEncryptDecrypt() {

    let image = imageView.image!
    var imageRef = image.CGImage

    let width = CGImageGetWidth(imageRef)
    let height = CGImageGetHeight(imageRef)
    let colorSpace = CGColorSpaceCreateDeviceRGB()
    let bytesPerPixel: UInt = 4
    let bytesPerRow: UInt = bytesPerPixel * width
    let bitsPerComponent: UInt = 8

    let sizeOfRawDataInBytes: Int = Int(height * width * 4)
    var rawData = UnsafeMutablePointer<Void>.alloc(sizeOfRawDataInBytes)

    let context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue) | CGBitmapInfo.ByteOrder32Big)
    CGContextDrawImage(context, CGRectMake(0, 0, CGFloat(width), CGFloat(height)), imageRef)

    var data = NSData(bytes: rawData, length: sizeOfRawDataInBytes)
    data = encrypted ? data.AES256DecryptWithKey(key) : data.AES256EncryptWithKey(key)

    rawData = data.mutableCopy().mutableBytes

    let cryptContext = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue))
    imageRef = CGBitmapContextCreateImage(cryptContext);

    let encryptedImage = UIImage(CGImage: imageRef)

    imageView.image = encryptedImage

    encrypted = !encrypted

}

Answer 1

上面代码的问题是我假设了图像的 alpha 通道，经过进一步研究，这是一个愚蠢的错误。我用变量let alphaInfo = CGImageGetAlphaInfo(imageRef) 替换了假设的CGImageAlphaInfo.PremultipliedLast alpha 通道，并将该变量传递给CGBitmapContextCreate 调用。

func pixelEncryptDecrypt() {
    let image = imageView.image!
    var imageRef = image.CGImage

    let width = CGImageGetWidth(imageRef)
    let height = CGImageGetHeight(imageRef)
    let colorSpace = CGColorSpaceCreateDeviceRGB()
    let bytesPerPixel: UInt = 4
    let bytesPerRow: UInt = bytesPerPixel * width
    let bitsPerComponent: UInt = 8

    let alphaInfo = CGImageGetAlphaInfo(imageRef) // this is what solved the issue.

    let sizeOfRawDataInBytes: Int = Int(height * width * 4)
    var rawData = UnsafeMutablePointer<Void>.alloc(sizeOfRawDataInBytes)

    var context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, CGBitmapInfo(alphaInfo.rawValue) | CGBitmapInfo.ByteOrder32Big)
    CGContextDrawImage(context, CGRectMake(0, 0, CGFloat(width), CGFloat(height)), imageRef)

    var data = NSData(bytes: rawData, length: sizeOfRawDataInBytes)
    data = encrypted ? data.AES256DecryptWithKey(key) : data.AES256EncryptWithKey(key)

    rawData = data.mutableCopy().mutableBytes

    context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, CGBitmapInfo(alphaInfo.rawValue))
    imageRef = CGBitmapContextCreateImage(context);

    let encryptedImage = UIImage(CGImage: imageRef)

    imageView.image = encryptedImage

    encrypted = !encrypted
}