Converting from string to Image in C#

Question

I am trying to convert a Unicode string to an image in C#. Each time I run it I get an error on this line

Image image = Image.FromStream(ms, true, true);

that says: ArgumentException was unhandled by user code. Parameter is not valid. Any ideas why this is happening? Below is the rest of the function.

public Image stringToImage(string inputString)
    {
        byte[] imageBytes = Encoding.Unicode.GetBytes(inputString);
        MemoryStream ms = new MemoryStream(imageBytes, 0, imageBytes.Length);

        ms.Write(imageBytes, 0, imageBytes.Length);
        Image image = Image.FromStream(ms, true, true);

        return image;
    }

Answer 1

Unicode doesn't encode all possible byte sequences that you'll need to represent an image.

byte[] -> String -> byte[] is a transformation that just won't work for many given sequences of bytes. You'll have to use a byte[] throughout.

For example, if you read the bytes, convert them to UTF-16 then it's possible that byte sequences will be discarded as invalid. Here's an example of an invalid byte sequence from UTF-16.

Code points U+D800 to U+DFFF[edit] The Unicode standard permanently reserves these code point values for UTF-16 encoding of the lead and trail surrogates, and they will never be assigned a character, so there should be no reason to encode them. The official Unicode standard says that all UTF forms, including UTF-16, cannot encode these code points.