<System.Runtime.InteropServices.DllImport("gdiplus.dll", ExactSpelling:=True, CharSet:=System.Runtime.InteropServices.CharSet.Unicode)>
Friend Shared Function GdipSaveImageToFile(image As IntPtr, filename As String, <System.Runtime.InteropServices.[In]> ByRef clsid As Guid, encparams As IntPtr) As Integer
End Function

Sub test(hbmp as IntPtr, filename as String, clsid as Guid)
    Dim status as Integer = GdipSaveImageToFile(hbmp, filename, clsid, IntPtr.Zero)
    If status <> 0 Then
        MessageBox.Show("Error status = " & status)
    End If
End Sub

<System.Runtime.InteropServices.DllImport("gdiplus.dll", ExactSpelling:=True, CharSet:=System.Runtime.InteropServices.CharSet.Unicode)>
Friend Shared Function GdipSaveImageToFile(image As IntPtr, filename As String, <System.Runtime.InteropServices.[In]> ByRef clsid As Guid, ByRef encparams As cEncoderParameters) As Integer
End Function

<StructLayout(LayoutKind.Sequential, Pack:=2, CharSet:=CharSet.Ansi)>
Friend Structure cEncoderParameter
    Public GUID As Guid
    Public NumberOfValues As UInt32
    Public type As UInt32
    Public Value As IntPtr
End Structure

<StructLayout(LayoutKind.Sequential, Pack:=2)>
Friend Class cEncoderParameters
    Public Count As UInt32
    Public Parameter As cEncoderParameter
End Class
Friend Enum cEncoderParameterType As UInt32
    EncoderParameterValueTypeByte = 1      ' 8-bit unsigned int
    EncoderParameterValueTypeASCII = 2     ' 8-bit byte containing one 7-bit ASCII code. NULL terminated.
    EncoderParameterValueTypeShort = 3     ' 16-bit unsigned int
    EncoderParameterValueTypeLong = 4      ' 32-bit unsigned int
    EncoderParameterValueTypeRational = 5  ' Two Longs. The first Long Is the numerator, the second Long expresses the denomintor.
    EncoderParameterValueTypeLongRange = 6     ' Two longs which specify a range of integer values. The first Long specifies the
    '                                            lower end And the second one  specifies the higher end. All values are inclusive at both ends
    EncoderParameterValueTypeUndefined = 7     ' 8-bit byte that can take any value depending on field definition
    EncoderParameterValueTypeRationalRange = 8 ' Two Rationals. The first Rational specifies the lower end And the second specifies
    '                                            the higher end. All values are inclusive at both ends
    EncoderParameterValueTypePointer = 9       ' A pointer to a parameter defined data.
End Enum

Sub b(hbmp As IntPtr, filename As String, clsid As Guid)
    Dim eps As New cEncoderParameters
    eps.Count = 1
    eps.Parameter.GUID = Encoder.Quality.Guid
    eps.Parameter.NumberOfValues = 1
    eps.Parameter.type = cEncoderParameterType.EncoderParameterValueTypeLong
    eps.Parameter.Value = New IntPtr(10)

    If GdipSaveImageToFile(hbmp, filename, clsid, eps) <> 0 Then
        MessageBox.Show("Error")
    End If
End Sub

Dim pEnc As IntPtr = Marshal.AllocHGlobal(Marshal.SizeOf(eps))
Marshal.StructureToPtr(eps, pEnc, False)

status = GdipSaveImageToFile(hbmp, filename, clsid, pEnc)

Marshal.FreeHGlobal(pEnc)

class EncoderParameter
{
public:
    GUID    Guid;               // GUID of the parameter
    ULONG   NumberOfValues;     // Number of the parameter values
    ULONG   Type;               // Value type, like ValueTypeLONG  etc.
    VOID*   Value;              // A pointer to the parameter values
};

class EncoderParameters
{
public:
    UINT Count;                      // Number of parameters in this structure
    EncoderParameter Parameter[1];   // Parameter values
};

GpStatus WINGDIPAPI
GdipSaveImageToFile(GpImage *image, GDIPCONST WCHAR* filename,
                GDIPCONST CLSID* clsidEncoder,
                GDIPCONST EncoderParameters* encoderParams);