MemoryStream ms = new MemoryStream(bytes);
ms.Position = 0;
Image img = Image.FromStream(ms);
ms.Close();

System.Text.UnicodeEncoding converter = new System.Text.UnicodeEncoding();
byte[] inputBytes =converter.GetBytes(inputString);
string inputString = converter.GetString(inputBytes);

string inputString = System.Convert.ToBase64String(inputBytes);
byte[] inputBytes = System.Convert.FromBase64String(inputString);
FileStream fileStream = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read);

/// 将 Stream 转成 byte[]
public byte[] StreamToBytes(Stream stream)
{
    byte[] bytes = new byte[stream.Length];
    stream.Read(bytes, 0, bytes.Length);
    // 设置当前流的位置为流的开始
    stream.Seek(0, SeekOrigin.Begin);
    return bytes;
}

/// 将 byte[] 转成 Stream
public Stream BytesToStream(byte[] bytes)
{
    Stream stream = new MemoryStream(bytes);
    return stream;
}

// 将Stream读取到文件
public void StreamToFile(Stream stream,string fileName)
{
    // 把 Stream 转换成 byte[]
    byte[] bytes = new byte[stream.Length];
    stream.Read(bytes, 0, bytes.Length);
    // 设置当前流的位置为流的开始
    stream.Seek(0, SeekOrigin.Begin);
    // 把 byte[] 写入文件
    FileStream fs = new FileStream(fileName, FileMode.Create);
    BinaryWriter bw = new BinaryWriter(fs);
    bw.Write(bytes);
    bw.Close();
    fs.Close();
}


// 从文件读取Stream
public Stream FileToStream(string fileName)
{            
    // 打开文件
    FileStream fileStream = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read);
    // 读取文件的 byte[]
    byte[] bytes = new byte[fileStream.Length];
    fileStream.Read(bytes, 0, bytes.Length);
    fileStream.Close();
    // 把 byte[] 转换成 Stream
    Stream stream = new MemoryStream(bytes);
    return stream;
}

//Bitmap 转化为 Byte[]
Bitmap BitReturn = new Bitmap();
byte[] bReturn = null;
MemoryStream ms = new MemoryStream();
BitReturn.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
bReturn = ms.GetBuffer();