哪位大神可以帮忙看一下

Question

fu是个上传控件，因为在后台里做了一个上传预览，所以fu是存在session中的，是想把上传的图片变成固定的大小
之前做过这样一个测试 记忆中可以实现
但现在上传之后的图片成了黑黑的一片
代码是这样的
System.Drawing.Image image = System.Drawing.Image.FromStream(fu.PostedFile.InputStream);
                    int width = image.Width;
                    int heigh = image.Height;
                    int max = heigh;
                    if (width != 358 || heigh != 358)
                    {
                        try
                        {
                            System.Drawing.Image newImg;
                            string n = DateTime.Now.Ticks.ToString();
                            fileName = "MuProductImages/" + n + geshi;
                            serverpath1 = serverpath1 + n + geshi; ;                            //如果存在这个图片就删除   
                            if (File.Exists(serverpath1))
                            {
                                File.Delete(serverpath1);
                            }
                            if (width != heigh)
                            {
                                //保存为宽，高为358 的新图片   
                                newImg = new Bitmap(image, 358, 358);
                            }
                            else
                            {
                                newImg = new Bitmap(358, 358);
                            }
                            //保存   
                            newImg.Save(serverpath1,ImageFormat.Jpeg);
                            return true;
                        }
                        catch (Exception ex)
                        {
                            Response.Write("<script >alert('图片缩小失败！');</script>");
                            throw ex;
                        }
                    }
                    else
                    {
                        string n = DateTime.Now.Ticks.ToString();
                        fileName = "MuProductImages/" + n + geshi;
                        serverpath1 = serverpath1 + n + geshi;
                        fu.SaveAs(serverpath1);
                        return true;
                    }
在线等待

Answer 1

给你一个生成缩略图的方法，你可以直接调用，也可以修改你自己的。
/// <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
            System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;            //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(System.Drawing.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 System.Drawing.Rectangle(0, 0, towidth, toheight),
                new System.Drawing.Rectangle(x, y, ow, oh),
                System.Drawing.GraphicsUnit.Pixel);            try
            {
                //以jpg格式保存缩略图
                bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }

Answer 2

Refer:
http://www.cnblogs.com/insus/articles/2060601.html

Answer 3

大神，我找到原因了，之前是从文件流里读取的，因为从session里读取的fileupload的stream没有值，所以创建图片都是空的或黑的，但是从物理文件读取并创建缩略图，图片的体积没变小，而且变大了2倍，这个太纠结了，有什么方法能让图片体积变小吗

Answer 4

你需要处理图片的质量的，不是简单的保存。
你要么用我给你的方法调用。要么你自己配置下图片质量
System.Drawing.Drawing2D.InterpolationMode属性
System.Drawing.Drawing2D.SmoothingMode属性