获取图片路径--生成缩略图的完整实现

在网站开发中,经常会使用一些文本编辑控件，如CuteEditor。这些控件一般都能同时输入文本和图片，并进行图文混排。如何读取该文本框中的图片路径，并生成缩略图，是很多开发者头疼的事情。本文根据网络资料进行整理，现将完整代码呈现如下：

1、获取图片地址：

       /// <summary>
        /// 通过正则表达式获取图片地址。
        /// </summary>
        /// <param name="RegExpress">正则表达式</param>
        /// <param name="InputString">源字符串</param>
        /// <returns></returns>
        //RegExpress为要匹配的正则表达式，InputString为源字符串。
        public string GetImageUrl(string RegExpress, string InputString)
        {
            //RegExpress为正则表达式，例如，获取图片URL的正则表达式为： regstring ="(?<=src=\").+?\\.(gif|jpg|bmp|png)(?=\")"
            Regex re = new Regex(RegExpress, RegexOptions.IgnoreCase|RegexOptions.Compiled);
           
            Match ma = re.Match(InputString);
            if (ma.Success)
            {
                return  ma.Value.Substring(1);
            }
            else
            {
                return "";
            }
        }

2、生成缩略图

        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImagePath">源图路径（物理路径）</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
        /// <param name="width">缩略图宽度</param>
        /// <param name="height">缩略图高度</param>
        /// <param name="mode">生成缩略图的方式</param>   
        public void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {
            Image originalImage = Image.FromFile(originalImagePath);

            int towidth = width;
            int toheight = height;

            int x = 0;
            int y = 0;
            int ow = originalImage.Width;
            int oh = originalImage.Height;

            switch (mode)
            {
                case "HW"://指定高宽缩放（可能变形）               
                    break;
                case "W"://指定宽，高按比例                   
                    toheight = originalImage.Height * width / originalImage.Width;
                    break;
                case "H"://指定高，宽按比例
                    towidth = originalImage.Width * height / originalImage.Height;
                    break;
                case "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 * height / towidth;
                        x = 0;
                        y = (originalImage.Height - oh) / 2;
                    }
                    break;
                default:
                    break;
            }

            //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();
            }
        }

3、获取缩略图相对路径

        /// <summary>
        /// 获取缩略图路径.
        /// </summary>
        /// <param name="InputString">带有图像标签的文本</param>
        /// <returns>缩略图全路径</returns>
        public string GetTitleImageUrl(string InputString)
        {
            string RegString = "(?<=src=\").+?\\.(gif|jpg|bmp)(?=\")";
            string ImageUrl = GetImageUrl(RegString, InputString);
            string ImageDirectory = System.IO.Path.GetDirectoryName(ImageUrl);
            string ImageFileName = System.IO.Path.GetFileName(ImageUrl);
            string ReturnImageUrl = ImageDirectory + "/t" + ImageFileName;//返回的缩略图的相对路径
            string InputImageUrl = System.Web.HttpContext.Current.Server.MapPath("~/"+ImageUrl);//源图物理路径
            string OutputImageUrl = System.Web.HttpContext.Current.Server.MapPath("~/"+ImageDirectory+"/t"+ImageFileName); //缩略图物理路径
            int width = 160;//缩略图宽
            int height = 190;//缩略图高
            string mode = "H";//缩放模式
            MakeThumbnail(InputImageUrl, OutputImageUrl, width, height, mode);
            return ReturnImageUrl;
        }