asp.net上传图片生成缩略图-优快云博客

本文介绍了一个ASP.NET中的图片上传功能及生成高质量缩略图的方法。通过使用C#代码，确保了缩略图既清晰又不会过大，并且能够适应多种常见的图片格式。

asp.net上传图片生成缩略图

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：

 
      001/// <summary>  

      002    /// asp.net上传图片并生成缩略图  

      003    /// </summary>  

      004    /// <param name="upImage">HtmlInputFile控件</param>  

      005    /// <param name="sSavePath">保存的路径,些为相对服务器路径的下的文件夹</param>  

      006    /// <param name="sThumbExtension">缩略图的thumb</param>  

      007    /// <param name="intThumbWidth">生成缩略图的宽度</param>  

      008    /// <param name="intThumbHeight">生成缩略图的高度</param>  

      009    /// <returns>缩略图名称</returns>  

      010    public string UpLoadImage(HtmlInputFile upImage, string sSavePath, string sThumbExtension, int intThumbWidth, int intThumbHeight)  

      011    {  

      012        string sThumbFile = "";  

      013        string sFilename = "";         

      014        if (upImage.PostedFile != null)  

      015        {  

      016            HttpPostedFile myFile = upImage.PostedFile;  

      017            int nFileLen = myFile.ContentLength;  

      018            if (nFileLen == 0)  

      019                return "没有选择上传图片";             

      020            //获取upImage选择文件的扩展名  

      021            string extendName = System.IO.Path.GetExtension(myFile.FileName).ToLower();  

      022            //判断是否为图片格式  

      023            if (extendName != ".jpg" && extendName != ".jpge" && extendName != ".gif" && extendName != ".bmp" && extendName != ".png")  

      024                return "图片格式不正确";  

      025              

      026            byte[] myData = new Byte[nFileLen];  

      027            myFile.InputStream.Read(myData, 0, nFileLen); 

      028            sFilename = System.IO.Path.GetFileName(myFile.FileName);  

      029            int file_append = 0;  

      030            //检查当前文件夹下是否有同名图片,有则在文件名+1  

      031            while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))  

      032            {  

      033                file_append++;  

      034                sFilename = System.IO.Path.GetFileNameWithoutExtension(myFile.FileName)  

      035                    + file_append.ToString() + extendName;  

      036            }  

      037            System.IO.FileStream newFile  

      038                = new System.IO.FileStream(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename),  

      039                System.IO.FileMode.Create, System.IO.FileAccess.Write);  

      040            newFile.Write(myData, 0, myData.Length);  

      041            newFile.Close(); 

      042            //以上为上传原图 

      043            try 

      044            {  

      045                //原图加载  

      046                using (System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))  

      047                {  

      048                    //原图宽度和高度  

      049                    int width = sourceImage.Width;  

      050                    int height = sourceImage.Height;  

      051                    int smallWidth;  

      052                    int smallHeight; 

      053                    //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)  

      054                    if (((decimal)width) / height <= ((decimal)intThumbWidth) / intThumbHeight)  

      055                    {  

      056                        smallWidth = intThumbWidth;  

      057                        smallHeight = intThumbWidth * height / width;  

      058                    }  

      059                    else 

      060                    {  

      061                        smallWidth = intThumbHeight * width / height;  

      062                        smallHeight = intThumbHeight;  

      063                    } 

      064                    //判断缩略图在当前文件夹下是否同名称文件存在  

      065                    file_append = 0;  

      066                    sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) + extendName; 

      067                    while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sThumbFile)))  

      068                    {  

      069                        file_append++;  

      070                        sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) +  

      071                            file_append.ToString() + extendName;  

      072                    }  

      073                    //缩略图保存的绝对路径  

      074                    string smallImagePath = System.Web.HttpContext.Current.Server.MapPath(sSavePath) + sThumbFile; 

      075                    //新建一个图板,以最小等比例压缩大小绘制原图  

      076                    using (System.Drawing.Image bitmap = new System.Drawing.Bitmap(smallWidth, smallHeight))  

      077                    {  

      078                        //绘制中间图  

      079                        using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap))  

      080                        {  

      081                            //高清,平滑  

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

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

      084                            g.Clear(Color.Black);  

      085                            g.DrawImage(  

      086                            sourceImage,  

      087                            new System.Drawing.Rectangle(0, 0, smallWidth, smallHeight),  

      088                            new System.Drawing.Rectangle(0, 0, width, height),  

      089                            System.Drawing.GraphicsUnit.Pixel  

      090                            );  

      091                        }  

      092                        //新建一个图板,以缩略图大小绘制中间图  

      093                        using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight))  

      094                        {  

      095                            //绘制缩略图  

      096                            using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap1))  

      097                            {  

      098                                //高清,平滑  

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

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

      101                                g.Clear(Color.Black);  

      102                                int lwidth = (smallWidth - intThumbWidth) / 2;  

      103                                int bheight = (smallHeight - intThumbHeight) / 2;  

      104                                g.DrawImage(bitmap, new Rectangle(0, 0, intThumbWidth, intThumbHeight), lwidth, bheight, intThumbWidth, intThumbHeight, GraphicsUnit.Pixel);  

      105                                g.Dispose();  

      106                                bitmap1.Save(smallImagePath, System.Drawing.Imaging.ImageFormat.Jpeg);  

      107                            }  

      108                        }  

      109                    }  

      110                }  

      111            }  

      112            catch 

      113            {  

      114                //出错则删除  

      115                System.IO.File.Delete(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename));  

      116                return "图片格式不正确";  

      117            }  

      118            //返回缩略图名称  

      119            return sThumbFile;  

      120        }  

      121        return "没有选择图片";  

      122    }