生成大小图片问题？

Question

如何将一张小图片变成大图片 
或者将大图片缩小 我本想实现js放大镜特效需要一张大图和一张小图 
由于后台只能上传一张图片所以我想通过程序将图片变大或者缩小 希望大家给点源码谢谢大家了!

Answer 1

我的图片是保存到数据里面的，压缩比率HttpPostedFile UpFile = File1.PostedFile;
Byte[] FileByteArray = new Byte[UpFile.ContentLength]; //图象文件临时储存Byte数组
Stream StreamObject = UpFile.InputStream; //建立数据流对像 
 StreamObject.Read(FileByteArray, 0, UpFile.ContentLength);
 System.Drawing.Image MyImage = System.Drawing.Image.FromStream(StreamObject);
                int width = MyImage.Width;
                int height = MyImage.Height;
                double rate = (width * 1.00) / (height * 1.00);
                if (width > 400 || height > 300)
                {
                    if (rate > 1.33)
                    {
                        if (width > 400)
                        {
                            width = 400;
                        }
                        height = (int)(width / rate);
                    }
                    else
                        if (rate < 1.33)
                        {
                            rate = (height * 1.00) / (width * 1.00);                            if (height > 300)
                            {
                                height = 300;
                            }
                            width = (int)(height / rate);
                        }
                        else
                        {
                            width = 400;
                            height = 300;
                        }                    MemoryStream pic = new MemoryStream();
                    pic = ResizeImageFile(StreamObject, width, height);
                    FileByteArray = pic.ToArray();
                }
                else
                {
                    StreamObject.Read(FileByteArray, 0, UpFile.ContentLength);
                }记得结贴。

Answer 2

#region 生成缩略图的代码
    private static MemoryStream ResizeImageFile(Stream stream, int width, int height)
    {
        Size newSize = new Size(width, height);
        using (System.Drawing.Image oldImage = System.Drawing.Image.FromStream(stream))
        {
            using (Bitmap newImage = new Bitmap(newSize.Width, newSize.Height, PixelFormat.Format24bppRgb))
            {
                using (Graphics canvas = Graphics.FromImage(newImage))
                {
                    canvas.SmoothingMode = SmoothingMode.AntiAlias;
                    canvas.InterpolationMode = InterpolationMode.HighQualityBicubic;
                    canvas.PixelOffsetMode = PixelOffsetMode.HighQuality;
                    canvas.DrawImage(oldImage, new Rectangle(new Point(0, 0), newSize));
                    MemoryStream m = new MemoryStream();
                    newImage.Save(m, ImageFormat.Jpeg);
                    return m;
                }
            }
        }
    }
    #endregion

Answer 3

 只有这个了 参考一下
 VB.NET  上传时将图片更改为缩略图
Dim sfile As String = "file/mytx.gif"  
 Dim fileNames As String
        If Me.Filename.PostedFile.ContentLength > 0 Then
            fileNames = System.IO.Path.GetFileName(Request.Files.Item(0).FileName)
            sfile = "/" & Date.Now.ToString("yyMMddhhmmss") & Request.UserHostAddress.ToString & fileNames
            Try
                GetThumbNail(Filename.PostedFile.FileName, 100, 120, Filename.PostedFile.ContentType.ToString(), False, Filename.PostedFile.InputStream, sfile)
                '   Me.Filename.PostedFile.SaveAs(Server.MapPath("File") & sfile)
                Me.LabSc.Text = "上传文件" & fileNames & "成功"
            Catch ex As Exception
                Me.LabSc.Text = "上传文件" & fileNames & "失败" & ex.ToString
                Return
            End Try
            sfile = "file" & sfile
        End If---------------------------------------------------------------------------------------------------------------------------Private Sub GetThumbNail(ByVal strFileName, ByVal iWidth, ByVal iheight, ByVal strContentType, _
    ByVal blnGetFromFile, ByVal ImgStream, ByVal filename)
        Dim sfile As String = "file/mytx.gif"
        Dim oImg As Image
        If blnGetFromFile Then
            oImg = oImg.FromFile(strFileName)
        Else
            oImg = oImg.FromStream(ImgStream)
        End If
        oImg = oImg.GetThumbnailImage(iWidth, iheight, Nothing, (New IntPtr).Zero)        Dim str As String = filename.ToString
        sfile = Date.Now.ToString("yyMMddhhmmss") & Request.UserHostAddress.ToString & strFileName
        Dim strGuid As String = str.Substring(0, str.LastIndexOf("."))
        strGuid = strGuid
        strGuid = strGuid & str.Substring(str.LastIndexOf("."))
        '保存到本地()
        oImg.Save(Server.MapPath("File") + "\" + strGuid)
    
    End Sub

Answer 4

/// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImagePath">源图路径（物理路径）</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径）</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</param>    
        public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
        {
            System.Drawing.Image originalImage = System.Drawing.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
            System.Drawing.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.HighQualityBicubic;            //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);            long[] quality = new long[1];
            quality[0] = 100;            System.Drawing.Imaging.EncoderParameters encoderParams = new System.Drawing.Imaging.EncoderParameters();
            System.Drawing.Imaging.EncoderParameter encoderParam = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);
            encoderParams.Param[0] = encoderParam;
            ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();//获得包含有关内置图像编码解码器的信息的ImageCodecInfo 对象。
            ImageCodecInfo jpegICI = null;
            for (int i = 0; i < arrayICI.Length; i++)
            {
                if (arrayICI[i].FormatDescription.Equals("JPEG"))
                {
                    jpegICI = arrayICI[i];//设置JPEG编码
                    break;
                }
            }            try
            {
                //以jpg格式保存缩略图
                //bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
                bitmap.Save(thumbnailPath, jpegICI, encoderParams);
            }
            catch (System.Exception e)
            {            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }