Why is Base64 string different in C# and Android

Question

I have convert one image into base64 string and that output same with online website.

But the same image when I convert it from Android is different.

Can you please explain why C# and Android base64 strings are different for the same image.

C#.NET Code

string cImagePath = @"G:\bg-listing.png";
byte[] imagebyte = StreamFile(cImagePath);
String result = System.Convert.ToBase64String(imagebyte);
System.IO.StreamWriter outFile;
try
{
    outFile = new System.IO.StreamWriter(Application.StartupPath + "//image2base641.txt",
                                     false,
                                     System.Text.Encoding.Default);
                outFile.Write(result.ToString());
                outFile.Close();
            }
            catch (System.Exception exp)
            {
                // Error creating stream or writing to it.
                System.Console.WriteLine("{0}", exp.Message);
            }

Android Code

Bitmap bitmapOrg = BitmapFactory.decodeResource(getResources(),  R.drawable.image);
ByteArrayOutputStream bao = new ByteArrayOutputStream();
bitmapOrg.compress(Bitmap.CompressFormat.JPEG, 100, bao);
byte [] ba = bao.toByteArray();
 String ba1=Base64.encodeToString(ba,Base64.DEFAULT);

Both image base64 are different.

Please help me.

Ted Hopp · Accepted Answer · 2013-02-08 06:04:30Z

3

There are many variants of base 64, involving line length, padding, check sums, etc. The Wikipedia article on Base64 has a nice table of variants.

My guess is that C# and Android are simply using different variants.

EDIT Based on your updated post, there are a couple of other possibilities:

Android may be modifying the .jpg file when it packages it up as a resource (however, while the resource packager is extremely aggressive regarding compression, this is probably not the case);
Android may be re-encoding the image differently than the original (two .jpg files can represent the same pixel values and not be byte-for-byte identical)

A better test would be to skip (in the Android code) the conversion from a resource to a Bitmap and back to a .jpg encoding. Just open the resource as a stream, read it directly into a byte array, and encode that in base 64.

edited Feb 8, 2013 at 6:04

answered Feb 8, 2013 at 5:45

Ted Hopp

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