在asp.net中，上传图片功能或者是常用的，生成缩略图也是常用的。baidu或者google，c#的方法也是很多的，但是一用却发现缩略图不清晰啊，缩略图片太大之类的事情，下面是我在处理图片上的代码，效果不错，所以拿出来分享，(效果能达到一些绘图软件的效果)
代码如下：
/// <summary> /// asp.net上传图片并生成缩略图 /// </summary> /// <param>HtmlInputFile控件</param> /// <param>保存的路径,些为相对服务器路径的下的文件夹</param> /// <param>缩略图的thumb</param> /// <param>生成缩略图的宽度</param> /// <param>生成缩略图的高度</param> /// <returns>缩略图名称</returns> public string UpLoadImage(HtmlInputFile upImage, string sSavePath, string sThumbExtension, int intThumbWidth, int intThumbHeight) { string sThumbFile = ""; string sFilename = ""; if (upImage.PostedFile != null) { HttpPostedFile myFile = upImage.PostedFile; int nFileLen = myFile.ContentLength; if (nFileLen == 0) return "没有选择上传图片"; //获取upImage选择文件的扩展名 string extendName = System.IO.Path.GetExtension(myFile.FileName).ToLower(); //判断是否为图片格式 if (extendName != ".jpg" && extendName != ".jpge" && extendName != ".gif" && extendName != ".bmp" && extendName != ".png") return "图片格式不正确"; byte[] myData = new Byte[nFileLen]; myFile.InputStream.Read(myData, 0, nFileLen); sFilename = System.IO.Path.GetFileName(myFile.FileName); int file_append = 0; //检查当前文件夹下是否有同名图片,有则在文件名+1 while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename))) { file_append++; sFilename = System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) + file_append.ToString() + extendName; } System.IO.FileStream newFile = new System.IO.FileStream(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename), System.IO.FileMode.Create, System.IO.FileAccess.Write); newFile.Write(myData, 0, myData.Length); newFile.Close(); //以上为上传原图 try { //原图加载 using (System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename))) { //原图宽度和高度 int width = sourceImage.Width; int height = sourceImage.Height; int smallWidth; int smallHeight; //获取第一张绘制图的大小,(比较 原图的宽/缩略图的宽 和 原图的高/缩略图的高) if (((decimal)width) / height <= ((decimal)intThumbWidth) / intThumbHeight) { smallWidth = intThumbWidth; smallHeight = intThumbWidth * height / width; } else { smallWidth = intThumbHeight * width / height; smallHeight = intThumbHeight; } //判断缩略图在当前文件夹下是否同名称文件存在 file_append = 0; sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) + extendName; while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sThumbFile))) { file_append++; sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) + file_append.ToString() + extendName; } //缩略图保存的绝对路径 string smallImagePath = System.Web.HttpContext.Current.Server.MapPath(sSavePath) + sThumbFile; //新建一个图板,以最小等比例压缩大小绘制原图 using (System.Drawing.Image bitmap = new System.Drawing.Bitmap(smallWidth, smallHeight)) { //绘制中间图 using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap)) { //高清,平滑 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; g.Clear(Color.Black); g.DrawImage( sourceImage, new System.Drawing.Rectangle(0, 0, smallWidth, smallHeight), new System.Drawing.Rectangle(0, 0, width, height), System.Drawing.GraphicsUnit.Pixel ); } //新建一个图板,以缩略图大小绘制中间图 using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight)) { //绘制缩略图 using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap1)) { //高清,平滑 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; g.Clear(Color.Black); int lwidth = (smallWidth - intThumbWidth) / 2; int bheight = (smallHeight - intThumbHeight) / 2; g.DrawImage(bitmap, new Rectangle(0, 0, intThumbWidth, intThumbHeight), lwidth, bheight, intThumbWidth, intThumbHeight, GraphicsUnit.Pixel); g.Dispose(); bitmap1.Save(smallImagePath, System.Drawing.Imaging.ImageFormat.Jpeg); } } } } } catch { //出错则删除 System.IO.File.Delete(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)); return "图片格式不正确"; } //返回缩略图名称 return sThumbFile; } return "没有选择图片"; }
HtmlInputFile控件我想大家都应该知道的，就是input type=file....
下面把调用代码也一起C上来