For all of you that want to hide text in your data arrays, I have created Steganography.jl.
Right now, it works reliably only for ASCII text (7-bits) being embedded into arrays of any of the built-in UInt, Int, Float and Complex types. It shouldn’t be hard to extend it to other character sets. Obviously the data type you embed into should be larger than 8 bits.
To get an idea of what is possible with this package, consider that all five books of A Song of Ice and Fire by George R. R. Martin comprise about 10 MB of text. I was able to use this package to embed all five books into a typical 3D brain MRI data set with no noticeable effect on the image quality.
To install, Pkg.update(); Pkg.add("Steganography").
Hope you enjoy!