学步园

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： 

Java代码  

1. /// <summary>   
2.    /// asp.net上传图片并生成缩略图   
3.    /// </summary>   
4.    /// <param name="upImage">HtmlInputFile控件</param>   
5.    /// <param name="sSavePath">保存的路径,些为相对服务器路径的下的文件夹</param>   
6.    /// <param name="sThumbExtension">缩略图的thumb</param>   
7.    /// <param name="intThumbWidth">生成缩略图的宽度</param>   
8.    /// <param name="intThumbHeight">生成缩略图的高度</param>   
9.    /// <returns>缩略图名称</returns>   
10.    public string UpLoadImage(HtmlInputFile upImage, string sSavePath, string sThumbExtension, int intThumbWidth, int intThumbHeight)   
11.    {   
12.        string sThumbFile = "";   
13.        string sFilename = "";           
14.   
15.        if (upImage.PostedFile != null)   
16.        {   
17.            HttpPostedFile myFile = upImage.PostedFile;   
18.            int nFileLen = myFile.ContentLength;   
19.            if (nFileLen == 0)   
20.                return "没有选择上传图片";               
21.   
22.            //获取upImage选择文件的扩展名   
23.            string extendName = System.IO.Path.GetExtension(myFile.FileName).ToLower();   
24.            //判断是否为图片格式   
25.            if (extendName != ".jpg" && extendName != ".jpge" && extendName != ".gif" && extendName != ".bmp" && extendName != ".png")   
26.                return "图片格式不正确";   
27.               
28.   
29.            byte[] myData = new Byte[nFileLen];   
30.            myFile.InputStream.Read(myData, 0, nFileLen);   
31.   
32.            sFilename = System.IO.Path.GetFileName(myFile.FileName);   
33.            int file_append = 0;   
34.            //检查当前文件夹下是否有同名图片,有则在文件名+1   
35.            while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))   
36.            {   
37.                file_append++;   
38.                sFilename = System.IO.Path.GetFileNameWithoutExtension(myFile.FileName)   
39.                    + file_append.ToString() + extendName;   
40.            }   
41.            System.IO.FileStream newFile   
42.                = new System.IO.FileStream(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename),   
43.                System.IO.FileMode.Create, System.IO.FileAccess.Write);   
44.            newFile.Write(myData, 0, myData.Length);   
45.            newFile.Close();   
46.   
47.            //以上为上传原图   
48.   
49.            try   
50.            {   
51.                //原图加载   
52.                using (System.Drawing.Image sourceImage = System.Drawing.Image.FromFile(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename)))   
53.                {   
54.                    //原图宽度和高度   
55.                    int width = sourceImage.Width;   
56.                    int height = sourceImage.Height;   
57.                    int smallWidth;   
58.                    int smallHeight;   
59.   
60.                    //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)   
61.                    if (((decimal)width) / height <= ((decimal)intThumbWidth) / intThumbHeight)   
62.                    {   
63.                        smallWidth = intThumbWidth;   
64.                        smallHeight = intThumbWidth * height / width;   
65.                    }   
66.                    else   
67.                    {   
68.                        smallWidth = intThumbHeight * width / height;   
69.                        smallHeight = intThumbHeight;   
70.                    }   
71.   
72.                    //判断缩略图在当前文件夹下是否同名称文件存在   
73.                    file_append = 0;   
74.                    sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) + extendName;   
75.   
76.                    while (System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sThumbFile)))   
77.                    {   
78.                        file_append++;   
79.                        sThumbFile = sThumbExtension + System.IO.Path.GetFileNameWithoutExtension(myFile.FileName) +   
80.                            file_append.ToString() + extendName;   
81.                    }   
82.                    //缩略图保存的绝对路径   
83.                    string smallImagePath = System.Web.HttpContext.Current.Server.MapPath(sSavePath) + sThumbFile;   
84.   
85.                    //新建一个图板,以最小等比例压缩大小绘制原图   
86.                    using (System.Drawing.Image bitmap = new System.Drawing.Bitmap(smallWidth, smallHeight))   
87.                    {   
88.                        //绘制中间图   
89.                        using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap))   
90.                        {   
91.                            //高清,平滑   
92.                            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;   
93.                            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;   
94.                            g.Clear(Color.Black);   
95.                            g.DrawImage(   
96.                            sourceImage,   
97.                            new System.Drawing.Rectangle(0, 0, smallWidth, smallHeight),   
98.                            new System.Drawing.Rectangle(0, 0, width, height),   
99.                            System.Drawing.GraphicsUnit.Pixel   
100.                            );   
101.                        }   
102.                        //新建一个图板,以缩略图大小绘制中间图   
103.                        using (System.Drawing.Image bitmap1 = new System.Drawing.Bitmap(intThumbWidth, intThumbHeight))   
104.                        {   
105.                            //绘制缩略图   
106.                            using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap1))   
107.                            {   
108.                                //高清,平滑   
109.                                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;   
110.                                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;   
111.                                g.Clear(Color.Black);   
112.                                int lwidth = (smallWidth - intThumbWidth) / 2;   
113.                                int bheight = (smallHeight - intThumbHeight) / 2;   
114.                                g.DrawImage(bitmap, new Rectangle(0, 0, intThumbWidth, intThumbHeight), lwidth, bheight, intThumbWidth, intThumbHeight, GraphicsUnit.Pixel);   
115.                                g.Dispose();   
116.                                bitmap1.Save(smallImagePath, System.Drawing.Imaging.ImageFormat.Jpeg);   
117.                            }   
118.                        }   
119.                    }   
120.                }   
121.            }   
122.            catch   
123.            {   
124.                //出错则删除   
125.                System.IO.File.Delete(System.Web.HttpContext.Current.Server.MapPath(sSavePath + sFilename));   
126.                return "图片格式不正确";   
127.            }   
128.            //返回缩略图名称   
129.            return sThumbFile;   
130.        }   
131.