validateImageData parameter and Image.FromStream()

Question

I\'m concerned about the third parameter in this overload, validateImageData. The documentation doesn\'t explain much about it, it only states that it causes the image data to b

Answer 1

From Reflector, we see:

if (validateImageData)
{
    num = SafeNativeMethods.Gdip.GdipImageForceValidation(new HandleRef(null, zero));
    if (num != 0)
    {
        SafeNativeMethods.Gdip.GdipDisposeImage(new HandleRef(null, zero));
        throw SafeNativeMethods.Gdip.StatusException(num);
    }
}

So we see that GdipImageForceValidation is called (recall, System.Drawing is just a wrapper over GDI+). The documentation for this function isn't very good:

This function forces validation of the image.

Not very useful. However, the point is made - the image file is interrogated to ensure it is safe to load. This may cause the whole image to be loaded into memory.

If you are accepting inputs from users, I certainly would set this flag to true - you never know what kind of files (malformed or otherwise) users will upload. Better safe than sorry. This is why the default is true.

Note also that GDI+ is not recommended for server environments. You're better off using System.Windows.Media.Imaging.