asp.net上传图片生成缩略图
时间：2010-09-06 来源：海滨小城
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：
| 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 | } |
HtmlInputFile控件我想大家都应该知道的，就是input type=file....这个会在后面的一起学asp.net章节中讲解
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