asp.net生成高品質縮略圖通用函數(c#代碼),支援多種生成方式

在網站開發時,生成縮略圖是一個非常常見和實用的功能.以前在asp裡隻能借助com元件實作,現在在.net裡可以利用架構的強大的類庫輕松實作.下面帖出完整的代碼(帶詳細注釋),參考了網上的一些文章及.net sdk相關内容.QQROOM網絡家園的圖檔上傳用到了所有的4種生成方式.

        /// <summary>

        /// 生成縮略圖

        /// </summary>

        /// <param name="originalImagePath">源圖路徑（實體路徑）</param>

        /// <param name="thumbnailPath">縮略圖路徑（實體路徑）</param>

        /// <param name="width">縮略圖寬度</param>

        /// <param name="height">縮略圖高度</param>

        /// <param name="mode">生成縮略圖的方式</param>    

        public static 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"://指定高寬縮放（可能變形）                

                    break;

                case "W"://指定寬，高按比例                    

                    toheight = originalImage.Height * width/originalImage.Width;

                case "H"://指定高，寬按比例

                    towidth = originalImage.Width * height/originalImage.Height;                    

                    break;        

                case "Cut"://指定高寬裁減（不變形）                

                    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 :

            }    

            //建立一個bmp圖檔

            Image bitmap = new System.Drawing.Bitmap(towidth,toheight);

            //建立一個畫闆

            Graphics g = System.Drawing.Graphics.FromImage(bitmap);

            //設定高品質插值法

            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            //設定高品質,低速度呈現平滑程度

            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

            //清空畫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繪制原圖檔的指定部分

            g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight), 

                new Rectangle(x, y, ow,oh),

                GraphicsUnit.Pixel);

            try

            {            

                //以jpg格式儲存縮略圖

                bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);

            }

            catch(System.Exception e)

            {

                throw e;

            finally

                originalImage.Dispose();

                bitmap.Dispose();                        

                g.Dispose();

        }

關鍵方法Graphics.DrawImage見ms-help://MS.NETFrameworkSDKv1.1.CHS/cpref/html/frlrfsystemdrawinggraphicsclassdrawimagetopic11.htm

本文轉自高海東部落格園部落格，原文連結：http://www.cnblogs.com/ghd258/archive/2006/02/26/337957.html，如需轉載請自行聯系原作者