I assume this question came to be because you looked at the doc of xor in matlab and saw that it only applied to logical (binary / boolean) values. That's because xor is a logical operator.
It would be a bit pointless to have to binarise an image to be able to encrypt it. It certainly wouldn't be reversible anyway.
What you are looking for is the bit-wise xor, bitxor which can xor two integer bit xoring their corresponding bits.
encimage = bitxor(rawimage, somevalue)
%or
encimage = bitxor(rawimage, someotherimagethesamesize)
