This is my code and I tried lot of code varieties already...
public String getStringImage(Bitmap bmp){
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bmp.compress(Bitmap.CompressFormat.JPEG, 100, baos);
byte[] imageBytes = baos.toByteArray();
String encodedImage = Base64.encodeToString(imageBytes,Base64.DEFAULT);
return encodedImage;
}