C#更改gif图片大小后仍然保持动画效果

先声明，不是我原创的，我也是借鉴别人的方法。

        public Form1()
        {
            InitializeComponent();

            PictureBox picImg = new PictureBox();
            int width = 100;
            int height = 60;
            picImg.Width = width;
            picImg.Height = height;
            Image res = Image.FromFile("01.gif");
            Image gif = new Bitmap(width, height);
            Image frame = new Bitmap(width, height);
            Graphics g = Graphics.FromImage(gif);
            Rectangle rg = new Rectangle(0, 0, width, height);
            Graphics gFrame = Graphics.FromImage(frame);
            MemoryStream ms = new MemoryStream();

            foreach (Guid gd in res.FrameDimensionsList)
            {
                FrameDimension fd = new FrameDimension(gd);
                FrameDimension f = FrameDimension.Time;
                int count = res.GetFrameCount(fd);
                ImageCodecInfo codecInfo = GetEncoder(ImageFormat.Gif);
                System.Drawing.Imaging.Encoder encoder = System.Drawing.Imaging.Encoder.SaveFlag;
                EncoderParameters eps = null;

                for (int i = 0; i < count; i++)
                {
                    res.SelectActiveFrame(f, i);
                    if (i == 0)
                    {

                        g.DrawImage(res, rg);

                        eps = new EncoderParameters(1);

                        //第一帧需要设置为MultiFrame 

                        eps.Param[0] = new EncoderParameter(encoder, (long)EncoderValue.MultiFrame);
                        bindProperty(res, gif);
                        gif.Save(ms, codecInfo, eps);
                    }
                    else
                    {

                        gFrame.DrawImage(res, rg);

                        eps = new EncoderParameters(1);

                        //如果是GIF这里设置为FrameDimensionTime，如果为TIFF则设置为FrameDimensionPage 

                        eps.Param[0] = new EncoderParameter(encoder, (long)EncoderValue.FrameDimensionTime);

                        bindProperty(res, frame);
                        gif.SaveAdd(frame, eps);
                    }
                }

                eps = new EncoderParameters(1);
                eps.Param[0] = new EncoderParameter(encoder, (long)EncoderValue.Flush);
                gif.SaveAdd(eps);
            }
            picImg.Image = Image.FromStream(ms);
            this.Controls.Add(picImg);
        }

        private void bindProperty(Image a, Image b)
        {

            //这个东西就是每一帧所拥有的属性，可以用GetPropertyItem方法取得这里用为完全复制原有属性所以直接赋值了 

            //顺便说一下这个属性里包含每帧间隔的秒数和透明背景调色板等设置，这里具体那个值对应那个属性大家自己在msdn搜索GetPropertyItem方法说明就有了 

            for (int i = 0; i < a.PropertyItems.Length; i++)
            {
                b.SetPropertyItem(a.PropertyItems[i]);
            }
        }

        private ImageCodecInfo GetEncoder(ImageFormat format)
        {

            ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();

            foreach (ImageCodecInfo codec in codecs)
            {
                if (codec.FormatID == format.Guid)
                {
                    return codec;
                }
            }
            return null;
        }