C# 生成缩略图 方法

   #region -生成缩略图-
        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="orginalImagePath">原图片对象</param>
        /// <param name="thumbnailPath">缩略图的路径</param>
        /// <param name="width">指定宽度</param>
        /// <param name="heigth">指定高度</param>
        /// <param name="model">缩放类型 HW：可以变形 W:指定宽度，高安比例缩放 "H"://指定高度，宽安比例绽放 "Cut"://指定高宽，裁减（不变形）</param>
        public  void MakeThumbnail(Image orginalPric, string thumbnailPath, int width, int height, EnumThumbnailModel model)
        {
            Image originalImage = orginalPric;//获得图片对象

            int towidth = width;
            int toheight = height;

            int x = 0;
            int y = 0;

            int ow = originalImage.Width;
            int oh = originalImage.Height;

            #region -缩略图的类型-
            switch (model)
            {
                case EnumThumbnailModel.HW://指定高宽缩放（可以变形）
                    break;
                case EnumThumbnailModel.W://指定宽度，高安比例缩放
                    toheight = originalImage.Height * width / originalImage.Width;
                    break;
                case EnumThumbnailModel.H://指定高度，宽安比例绽放
                    towidth = originalImage.Width * height / originalImage.Height;
                    break;
                case EnumThumbnailModel.Cut://指定高宽，裁减（不变形）
                    if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
                    {
                        oh = originalImage.Height;
                        ow = originalImage.Height * towidth / toheight;
                        y = 0;
                        x = (originalImage.Width - ow) / 2;
                    }
                    else
                    {
                        ow = originalImage.Width;
                        oh = originalImage.Width * towidth / towidth;
                        y = 0;
                        x = (originalImage.Height - oh) / 2;
                    }

                    break;
                default:
                    break;
            }
            #endregion

            //新建一个bmp图片
            Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
            //新建一个画板
            Graphics g = System.Drawing.Graphics.FromImage(bitmap);
            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            //清空画布并以透明背景色填充
            g.Clear(Color.Transparent);
            //在指定位置并且按指定大小绘制原图片的指定部分
            g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
                new Rectangle(x, y, ow, oh),
                GraphicsUnit.Pixel);
            try
            {
                //以jpg格式保存缩略图
                bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }

        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="orginalPric">原始图片</param>
        /// <param name="thumbnailPath">缩略图路径</param>
        /// <param name="width">宽度</param>
        /// <param name="heigth">高度</param>
        /// <param name="model">类型 缩放类型 HW：可以变形 W:指定宽度，高安比例缩放 "H"://指定高度，宽安比例绽放 "Cut"://指定高宽，裁减（不变形）</param>
        /// <returns></returns>
        public void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, EnumThumbnailModel mode)
        {
            Image originalImage = Image.FromFile(originalImagePath);
            MakeThumbnail(originalImage, thumbnailPath, width, height, mode);
        }
        #endregion