The BITMAPINFOHEADER contains information about the color space and dimensions of a DIB.

C# Definition:

[StructLayout(LayoutKind.Sequential)]
public struct BITMAPINFOHEADER
{
    public uint  biSize;
    public int   biWidth;
    public int   biHeight;
    public ushort   biPlanes;
    public ushort   biBitCount;
    public BitmapCompressionMode  biCompression;
    public uint  biSizeImage;
    public int   biXPelsPerMeter;
    public int   biYPelsPerMeter;
    public uint  biClrUsed;
    public uint  biClrImportant;

    public void Init()
    {
        biSize = (uint)Marshal.SizeOf(this);
    }
}

VB Definition:

Public Structure BITMAPINFOHEADER
     Public biSize As Int32
     Public biWidth As Int32
     Public biHeight As Int32
     Public biPlanes As Int16
     Public biBitCount As Int16
     Public biCompression As BitmapCompressionMode
     Public biSizeImage As Int32
     Public biXPelsperMeter As Int32
     Public biYPelsPerMeter As Int32
     Public biClrUsed As Int32
     Public biClrImportant As Int32
End Structure

User-Defined Field Types:

None.

Notes:

The unmanaged size of the structure must be set before the structure can be used by the API. This can be done by using the Init() call which uses the Marshal.SizeOf(this) method to get the appropriate size.

(Thanks to Mike I for the VB.NET definition).

http://msdn.microsoft.com/en-us/library/dd183376