ASP 生成缩略图

来源：互联网发布：知乎保存的图片在哪编辑：程序博客网时间：2024/05/29 02:31

站点首页需要加载图书的封面，但是所有封面资源都过于“庞大”，导致首页加载速度灰常慢，所以直接在资源批量上传的时候对封面图片生成缩略图，在网上看到一段非常不错的代码段，摘取并测试，是可以用的，自己又对部分进行了修改，优化了点点。。。

下面是方法代码：

        /// <summary>        /// 生成缩略图         /// </summary>        /// <param name="originalImagePath">源图路径</param>        /// <param name="thumbnailPath">缩略图路径</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:HW指定高宽缩放(可能变形);W指定宽，高按比例 H指定高，宽按比例 Cut指定高宽裁减(不变形)</param>        /// <param name="imageType">要缩略图保存的格式(gif,jpg,bmp,png) 为空或未知类型都视为jpg</param>        public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode, string imageType)        {            string imageName = originalImagePath.Substring(originalImagePath.LastIndexOf("\\")+1);            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                 switch (imageType.ToLower())                {                    case "gif":                        bitmap.Save(thumbnailPath + "\\" + imageName, System.Drawing.Imaging.ImageFormat.Gif);                        break;                    case "jpg":                        bitmap.Save(thumbnailPath + "\\" + imageName, System.Drawing.Imaging.ImageFormat.Jpeg);                        break;                    case "bmp":                        bitmap.Save(thumbnailPath + "\\" + imageName, System.Drawing.Imaging.ImageFormat.Bmp);                        break;                    case "png":                        bitmap.Save(thumbnailPath + "\\" + imageName, System.Drawing.Imaging.ImageFormat.Png);                        break;                    default:                        bitmap.Save(thumbnailPath + "\\" + imageName, System.Drawing.Imaging.ImageFormat.Jpeg);                        break;                }            }            catch (System.Exception e)            {                throw e;            }            finally            {                originalImage.Dispose();                bitmap.Dispose();                g.Dispose();            }        }

下面是简单的调用

 <span style="white-space:pre"></span>private void button1_Click(object sender, EventArgs e)        {            string filepath = @"D:\Work\JL_Resource\JL_Image\Source\Image\骑扁马的扁人_c1.jpg";            string cutpath = @"D:\Work\JL_Resource\JL_Image\Source\CutImage";            MakeThumbnail(filepath,cutpath,12,12,"H","");        }

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