C# GDI畫圖改變圖像大小

  private void Create_Validate_Image()
    {
      

        System.Drawing.Bitmap validate_image = new System.Drawing.Bitmap(width, height);

        System.Drawing.Image image11 = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Request.MapPath("42.jpg"));

        var image112 = image11.GetThumbnailImage(image11.Width / 2, image11.Height / 2, () => { return false; }, IntPtr.Zero);

        Graphics g = Graphics.FromImage(validate_image);
    
        g.Clear(Color.White);
        g.DrawImage(image112, 0, 0);

           System.IO.MemoryStream ms = new System.IO.MemoryStream();

           validate_image.Save(ms, ImageFormat.Gif);
          Response.ClearContent();
           Response.ContentType = "image/GIF";

           Response.BinaryWrite(ms.ToArray());

    
           g.Dispose();
          validate_image.Dispose();
     
    }

//翻轉

imgPng.RotateFlip(RotateFlipType.Rotate180FlipX);

截取
 
Rectangle
 rect = new

Rectangle(0, 0, imgPng.Width / 2, imgPng.Height);

Bitmap
 clipPng = new

Bitmap(imgPng).Clone(rect, imgPng.PixelFormat);

摘自 Bychentufeiyang的專欄