"The pixel format not supported" error

            Aurigma.GraphicsMill.Drawing.GdiGraphics graphics = bitmap.GetGdiGraphics();

        private void button1_Click(object sender, EventArgs e)
        {
            try { 
            const int centerX = 150;
            const int centerY = 150;
            const int radius = 110;

                //Create Bitmap object
            Aurigma.GraphicsMill.Bitmap bitmap =
                new Aurigma.GraphicsMill.Bitmap(300, 150, Aurigma.GraphicsMill.PixelFormat.Format24bppRgb);
            bitmap.Load(@"C:\Temp\Test.png");

            Aurigma.GraphicsMill.Drawing.GdiGraphics graphics = bitmap.GetGdiGraphics();

            //Adjust font settings
            Aurigma.GraphicsMill.Drawing.Font font =
                new Aurigma.GraphicsMill.Drawing.Font("Times New Roman", 37, false, false);
            font.VerticalAlignment = Aurigma.GraphicsMill.Drawing.VerticalAlignment.Bottom;
            font.HorizontalAlignment = Aurigma.GraphicsMill.Drawing.HorizontalAlignment.Center;

            string text = "Rounded sample text";

            //Get characters positions
            float[] positions = font.GetCharacterPositions(text, 0);
            //Get string width
            float strWidth = font.MeasureString(text).Width;
            //Get string height
            float strHeight = font.MeasureString(text).Height;

            Aurigma.GraphicsMill.Drawing.SolidBrush brush =
                new Aurigma.GraphicsMill.Drawing.SolidBrush(Aurigma.GraphicsMill.RgbColor.Black);

            //Draw character by character
            for (int i = 0; i < text.Length; i++)
            {
                float charWidth = font.GetBlackBox(text[i]).Width;

                //Compute angle to which rotate current character. Rotation will be
                //performed relative to the middle of the bottom side of the character.
                float angle = (float)(Math.PI - (positions[i] + charWidth / 2.0f) * Math.PI / strWidth);

                //Compute the x and y coordinate of the bottom/top* middle* of the character
                float x = (float)(centerX + radius * Math.Cos(angle));
                float y = (float)(centerY - radius * Math.Sin(angle));

                System.Drawing.Drawing2D.Matrix rotateMatrix = new System.Drawing.Drawing2D.Matrix();

                //Convert angle from radians to degrees
                float degAngle = (float)(angle / Math.PI * 180);

                rotateMatrix.RotateAt(90 - degAngle, new System.Drawing.PointF(x, y));

                graphics.Transform = rotateMatrix;

                graphics.DrawString(text[i].ToString(), font, brush, x, y);

            }
                
            bitmap.Save(@"C:\Temp\NewImage.png");
            MessageBox.Show("done");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            
        }