How to write AES cipher text to an image

问题

In the process of image encryption using AES, when the pixel values are read and when the AES encryption applied, the cipher text results in some negative values. How is it possible to frame an encrypted image from these kind of negative values i.e., cipher text?

来源：https://stackoverflow.com/questions/33776494/how-to-write-aes-cipher-text-to-an-image