''' <summary>
''' Returns a 4 times downscaled image of left-top rectangle of JPEG2000 image.
''' </summary>
Public Shared Function GetJpeg2000RectangleDownscaled4(filename As String) As Vintasoft.Imaging.VintasoftImage
    Using stream As System.IO.Stream = New System.IO.FileStream(filename, System.IO.FileMode.Open, System.IO.FileAccess.Read)
        Using decoder As New Vintasoft.Imaging.Codecs.Decoders.Jpeg2000Decoder(stream)
            ' check available scales
            Dim scales As Integer() = decoder.GetImageRectScales(0, decoder.GetDefaultDecodingSettings(0))
            For i As Integer = 0 To scales.Length - 1
                If scales(i) = 4 Then
                    ' get top-left rectangle of raster grid with scale 4
                    Return decoder.GetImageRect(0, 0, 4, Nothing, Nothing, Nothing)
                End If
            Next

            Throw New System.Exception("Scale 4 is not available for specified JPEG2000 file.")
        End Using
    End Using
End Function

/// <summary>
/// Returns a 4 times downscaled image of left-top rectangle of JPEG2000 image.
/// </summary>
public static Vintasoft.Imaging.VintasoftImage GetJpeg2000RectangleDownscaled4(string filename)
{
    using (System.IO.Stream stream =
        new System.IO.FileStream(filename, System.IO.FileMode.Open, System.IO.FileAccess.Read))
    {
        using (Vintasoft.Imaging.Codecs.Decoders.Jpeg2000Decoder decoder =
            new Vintasoft.Imaging.Codecs.Decoders.Jpeg2000Decoder(stream))
        {
            // check available scales
            int[] scales = decoder.GetImageRectScales(0, decoder.GetDefaultDecodingSettings(0));
            for (int i = 0; i < scales.Length; i++)
            {
                if (scales[i] == 4)
                {
                    // get top-left rectangle of raster grid with scale 4
                    return decoder.GetImageRect(0, 0, 4, null, null, null);
                }
            }

            throw new System.Exception("Scale 4 is not available for specified JPEG2000 file.");
        }
    }
}