Can be as easy as:
var ms = new MemoryStream(imageData);
System.Drawing.Image image = Image.FromStream(ms);
image.Save("c:\\image.jpg");
Testing it out:
byte[] imageData;
// Create the byte array.
var originalImage = Image.FromFile(@"C:\original.jpg");
using (var ms = new MemoryStream())
{
originalImage.Save(ms, ImageFormat.Jpeg);
imageData = ms.ToArray();
}
// Convert back to image.
using (var ms = new MemoryStream(imageData))
{
Image image = Image.FromStream(ms);
image.Save(@"C:\newImage.jpg");
}