Hjælp til at resize

Jeg bruger følgende til at resize mine jpg billeder:

        public static Bitmap resizeImage(string filePath, int width, int height)
        {
            System.Drawing.Bitmap bmpOut = null;

            try
            {
                Bitmap bmp = new Bitmap(filePath);
               
                if(height == 0)
                {
                    double tmpHeight = ((double)bmp.Height/(double)bmp.Width) * width;
                    height = (int)tmpHeight;
                }   

                if(width == 0)
                {
                    double tmpWidth = ((double)bmp.Width/(double)bmp.Height) * height;
                    width = (int)tmpWidth;
                }

                bmpOut = new Bitmap(width, height);
                Graphics g = Graphics.FromImage(bmpOut);
                g.CompositingQuality =  System.Drawing.Drawing2D.CompositingQuality.HighQuality;
                g.SmoothingMode =  System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
//                g.FillRectangle(Brushes.White, 0, 0, width, height);
                g.DrawImage(bmp, 0, 0, width, height);
                bmp.Dispose();
                GC.Collect();
            }
            catch
            {
                return null;
            }

            return bmpOut;
        }

Men den laver ikke nogle særlige flotte billeder. Hvad kan jeg gøre for at optimere den funktion?