C# 改变图片width height dpi 方法

  if (this.pbMain.Image.VerticalResolution < 200 || this.pbMain.Image.HorizontalResolution < 200)
                    {
                        //System.Drawing.Image img = System.Drawing.Image.FromHbitmap(((Bitmap)this.images[0]).GetHbitmap());
                        //float x = img.VerticalResolution;
                        //float y = img.HorizontalResolution;
                        int width = ((Bitmap)this.images[0]).Width;
                        int height = ((Bitmap)this.images[0]).Height;
                        if (height > width)
                        {
                            height = 2338;
                            width = 1653;

                        }
                        else if (width > height)
                        {
                            height = 1653;
                            width = 2338;
                        }
                        Bitmap bmpSource = new Bitmap(((Bitmap)this.images[0]), width, height);
                        //Bitmap bmpSource = new Bitmap(((Bitmap)this.images[0]));
                        int iSourceWidth = bmpSource.Width;
                        int iSourceHeight = bmpSource.Height;
                        float fSourceHorResolution = bmpSource.HorizontalResolution;
                        float fSourceVerResolution = bmpSource.VerticalResolution;
                        //图象dpi
                        float fTargetHorResolution = 200;
                        float fTargetVerResolution = 200;
                        Bitmap bmpTarget = new Bitmap(width, height);
                        Graphics g = Graphics.FromImage(bmpTarget);
                        g.DrawImage(bmpSource, 0, 0, iSourceWidth, iSourceHeight);
                        bmpTarget.SetResolution(fTargetHorResolution, fTargetVerResolution);
                        bmpTarget = TiffManager.KiSharpen(bmpTarget, (float)0.7);
                        bmpTarget = TiffManager.ConvertTo1bbpIndexed(bmpTarget, (float)0.8);
                        bmpTarget.Save(filename, info, ep);
                    }