Need MD5 hash for an in memory System.Drawing.Image

Question

Need MD5 hash for an in memory System.Drawing.Image

Answer 1

A simple sample, based on the sample in MSDN; note that this hash is dependent on the internal representation of the image and will not correspond to the hash created from a file.

using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Security.Cryptography;
using System.Text;

class Program
{
    static string getMd5Hash(byte[] buffer)
    {
        MD5 md5Hasher = MD5.Create();

        byte[] data = md5Hasher.ComputeHash(buffer);

        StringBuilder sBuilder = new StringBuilder();
        for (int i = 0; i < data.Length; i++)
        {
            sBuilder.Append(data[i].ToString("x2"));
        }
        return sBuilder.ToString();
    }

    static byte[] imageToByteArray(Image image)
    {
        MemoryStream ms = new MemoryStream();
        image.Save(ms, ImageFormat.Bmp);
        return ms.ToArray();
    }

    static void Main(string[] args)
    {
        Image image = Image.FromFile(@"C:\tmp\Jellyfish.jpg");
        byte[] buffer = imageToByteArray(image);
        string md5 = getMd5Hash(buffer);
    }
}

To be able to use the MD5 class you need to add a reference to System.Security.

Depending on what you are going to use the hash for you should consider the fact that MD5 is no longer state of the art and that there are better hash functions available if you need a strong hash.