ASP.NET中生成缩略图的代码
先必须导入 using System.Drawing;
- // <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="mode">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)
- {
- 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, System.Drawing.Imaging.ImageFormat.Gif);
- break;
- case "jpg":
- bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
- break;
- case "bmp":
- bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp);
- break;
- case "png":
- bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png);
- break;
- default:
- bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
- break;
- }
- }
- catch (System.Exception e)
- {
- throw e;
- }
- finally
- {
- originalImage.Dispose();
- bitmap.Dispose();
- g.Dispose();
- }
- }