在网站开发时,生成缩略图是一个非常常见和实用的功能.以前在asp里只能借助com组件实现,现在在.net里可以利用框架的强大的类库轻松实现.下面帖出完整的代码(带详细注释),参考了网上的一些文章及.net sdk相关内容.QQROOM网络家园的图片上传用到了所有的4种生成方式.
        /// <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 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 > (do