Which type of Charset suitable for image encoding ? [Kotlin] - arrays

Question

I had tried to convert btye array to string in charset-8, but it's not working. Can someone guide me please.
Here is how I convert Bitmap to bytearray
private fun BitmapToByteArray(): ByteArray
{
val stream = ByteArrayOutputStream()
btm1!!.compress(Bitmap.CompressFormat.PNG, 100, stream)
val bitmapdata: ByteArray = stream.toByteArray()
return bitmapdata
}
Here is how I encrypt the data
private fun encrypting_data(bitmapdata: ByteArray): String {
val key = secretkey!!.text.toString()
val btm1 = bitmapdata.toString(Charsets.UTF_8)
val s = btm1
//generating key from given secret key
val skey: Key = SecretKeySpec(key.toByteArray(), "AES")
print(skey.toString())
val c: Cipher = Cipher.getInstance("AES")
c.init(Cipher.ENCRYPT_MODE, skey)
//encrypting text string
val re = c.doFinal(s.toByteArray())
//converting encrypted string to base64
val re_base64 = Base64.encodeToString(re, Base64.NO_WRAP or Base64.NO_PADDING)
Log.e("aaAA", re_base64.toString())
//converting each chr of base64 string to binary and combining it
for (i in re_base64) {
var single_b_string = Integer.toBinaryString((i.toInt()))
//if binary str is less than 8 bit then making it 8 bit by adding 0's
if (single_b_string.length < 8) {
for (j in 1..(8 - single_b_string.length)) {
single_b_string = "0" + single_b_string
}
}
//final binary string to hide in image
b_string = b_string + single_b_string
}
Log.e("barraylength", b_string.toString())
Log.e("barray", b_string!!.length.toString())
return b_string.toString()
}
please guide me, thank you

Answer 1

Short answer: none.
Charsets are used to map characters to binary and vice-versa. It doesn't make sense to decode the bytes of an image into a string using a character encoding. There is even a chance that you find sequences of bytes that are not valid sequences in the character encoding that you choose, so they will not be converted to characters correctly.
Sometimes it's necessary to use text to represent binary data (e.g. when using text-only transports/media to store it).
In these cases, you can use other kinds of encodings, for instance Base64, but I guess you know about it because you're already sort of using base64 here as well.
Note that, in your current code, you are converting a ByteArray (bitmapdata) into a String (btm1/s) only to convert it back into a ByteArray (s.toByteArray()). Why do you even need to do so?