C#自动生成缩略图到临时文件示例

        public static void MakeThumbnail(string originalImagePath, int width, int height)
        {
            string type = Path.GetExtension(originalImagePath).ToUpper();
            MemoryStream strea = new MemoryStream();
            string path = Path.GetTempPath() + Path.GetFileNameWithoutExtension(originalImagePath) + ".tmp"; 
            System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
            int towidth = width;
            int toheight = height;
            int ow = originalImage.Width;
            int oh = originalImage.Height;
            if ((double)originalImage.Width / (double)towidth < (double)originalImage.Height / (double)toheight)
            {
                toheight = height;
                towidth = originalImage.Width * height / originalImage.Height;
            }
            else
            {
                towidth = width;
                toheight = originalImage.Height * width / originalImage.Width;
            }
            //新建一个bmp图片
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
            //新建一个画板
            System.Drawing.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(System.Drawing.Color.Transparent);