上传缩略图如何实现不变形？等比例缩放

[postcha]

目前上传图片和生成缩略图的代码：

//这是标题图片上传方法
                if (image != null)
                {
                    string year = DateTime.Now.Year.ToString();
                    string month = DateTime.Now.Month.ToString("00");
                    string day = DateTime.Now.Day.ToString("00");

                    string fileFolder = string.Concat("Upload/", year, "/", month, "/", day);
                    string path = HostingEnvironment.MapPath("~/" + fileFolder);

                    if (!Directory.Exists(path))
                    {
                        //在Upload目录下创建了一个文件夹   
                        Directory.CreateDirectory(path);
                    }
                    string imagename = image.FileName;
                    string fileType = Path.GetExtension(image.FileName).ToLower();
                    if (fileType == ".jpeg" || fileType == ".jpg" || fileType == ".png" || fileType == ".gif")
                    {
                        Random ran = new Random();
                        string ename = DateTime.Now.ToString("yyyyMMddhhmmssfff") + ran.Next(9999);
                        //上传后生成的图片名
                        string name = ename + fileType;

                        image.SaveAs(Path.Combine(path, name));
                        string imageurl = string.Concat(HostingEnvironment.ApplicationVirtualPath, fileFolder, "/", name);

                        //生成标题图片
                        //缩略图名
                        string thumbName = ename + "_500x200" + fileType;

                        //缩略图绝对路径
                        string thumbPath = string.Concat(HostingEnvironment.ApplicationPhysicalPath, fileFolder, "/", thumbName);

                        // 设置缩略图保存路径
                        FileStream stream = new FileStream(Path.GetFullPath(thumbPath), FileMode.OpenOrCreate);

                        // 缩放上传的文件
                        Image OrigImage = Image.FromStream(image.InputStream);



                        // 创建缩略图对象
                        Bitmap TempBitmap = new Bitmap(550, 200);
                        // 创建缩略图画质
                        Graphics NewImage = Graphics.FromImage(TempBitmap);
                        NewImage.CompositingQuality = CompositingQuality.HighQuality;
                        NewImage.SmoothingMode = SmoothingMode.HighQuality;
                        NewImage.InterpolationMode = InterpolationMode.HighQualityBicubic;
                        // 创建Rectangle对象进行绘制
                        Rectangle imageRectangle = new Rectangle(0, 0, 550, 200);
                        NewImage.DrawImage(OrigImage, imageRectangle);
                        // 保存缩略图
                        TempBitmap.Save(stream, OrigImage.RawFormat);
                        // 释放资源
                        NewImage.Dispose();
                        TempBitmap.Dispose();
                        OrigImage.Dispose();
                        stream.Close();
                        stream.Dispose();

                        newArticle.ImageUrl = imageurl;
                    }
                }

但是这样，直接指定了宽、高，难免会造成图片变形。所以想改造在成宽度固定550，然后高度自适应。相当于windows中的图片查看器，改变窗体大小，图片也会相应的改变，图片不变形。
这个应该就是等比例缩话吧，上面的代码如何改造 ？

[postcha]

1楼的代码不错，马上试一下。

[tptptp00]

想完全不变形是不可能的

[nitaiyoucala]

要想不变形，只能截取了。

[porschev]

/// <summary>
/// 获取一个图片按等比例缩小后的大小。
/// </summary>
/// <param name="maxWidth">需要缩小到的宽度</param>
/// <param name="maxHeight">需要缩小到的高度</param>
/// <param name="imageOriginalWidth">图片的原始宽度</param>
/// <param name="imageOriginalHeight">图片的原始高度</param>
/// <returns>返回图片按等比例缩小后的实际大小</returns>
public static Size GetNewSize(int maxWidth, int maxHeight, int imageOriginalWidth, int imageOriginalHeight)
{
    double w = 0.0;
    double h = 0.0;
    double sw = Convert.ToDouble(imageOriginalWidth);
    double sh = Convert.ToDouble(imageOriginalHeight);
    double mw = Convert.ToDouble(maxWidth);
    double mh = Convert.ToDouble(maxHeight);
    if (sw < mw && sh < mh)
    {
        w = sw;
        h = sh;
    }
    else if ((sw / sh) > (mw / mh))
    {
        w = maxWidth;
        h = (w * sh) / sw;
    }
    else
    {
        h = maxHeight;
        w = (h * sw) / sh;
    }
    return new Size(Convert.ToInt32(w), Convert.ToInt32(h));
}
/// <summary>
/// 对给定的一个图片（Image对象）生成一个指定大小的缩略图。
/// </summary>
/// <param name="originalImage">原始图片</param>
/// <param name="thumMaxWidth">缩略图的宽度</param>
/// <param name="thumMaxHeight">缩略图的高度</param>
/// <returns>返回缩略图的Image对象</returns>
public static System.Drawing.Image GetThumbNailImage(System.Drawing.Image originalImage, int thumMaxWidth, int thumMaxHeight)
{
    Size thumRealSize = Size.Empty;
    System.Drawing.Image newImage = originalImage;
    Graphics graphics = null;
    try
    {
        thumRealSize = GetNewSize(thumMaxWidth, thumMaxHeight, originalImage.Width, originalImage.Height);
        newImage = new Bitmap(thumRealSize.Width, thumRealSize.Height);
        graphics = Graphics.FromImage(newImage);
        graphics.CompositingQuality = CompositingQuality.HighQuality;
        graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
        graphics.SmoothingMode = SmoothingMode.HighQuality;
        graphics.Clear(Color.Transparent);
        graphics.DrawImage(originalImage, new Rectangle(0, 0, thumRealSize.Width, thumRealSize.Height), new Rectangle(0, 0, originalImage.Width, originalImage.Height), GraphicsUnit.Pixel);
    }
    catch { }
    finally
    {
        if (graphics != null)
        {
            graphics.Dispose();
            graphics = null;
        }
    }
    return newImage;
}

[adonis_net]

[Quote=引用 6 楼 porschev 的回复:]
C# code

/// <summary>
/// 获取一个图片按等比例缩小后的大小。
/// </summary>
/// <param name="maxWidth">需要缩小到的宽度</param>
/// <param name="maxHeight">需要缩小到的高度</param>
/// <param name="imageOriginalWidth">图片的原始宽度</para……
[/Quote]
同意.

[EnForGrass]

Asp.net真正生成高质量不变形缩略图片
http://www.cnblogs.com/leeolevis/archive/2009/02/03/1383132.html

[huayy]

等比缩放，在展示的时候，有那种DIV+CSS可以按比例展示的。
类似 http://www.ktlm.cn/student.html

[postcha]

楼上的也太贵了。。

[ycproc]

 /// <summary>  
        /// 根据源图片生成缩略图  
        /// </summary>  
        /// <param name="imgPath_old">源图(大图)物理路径</param>  
        /// <param name="imgPath_new">缩略图物理路径(生成的缩略图将保存到该物理位置)</param>  
        /// <param name="width">缩略图宽度</param>  
        /// <param name="height">缩略图高度</param>  
        /// <param name="mode">缩略图缩放模式(取值"HW":指定高宽缩放,可能变形；取值"W":按指定宽度,高度按比例缩放；取值"H":按指定高度,宽度按比例缩放；取值"Cut":按指定高度和宽度裁剪,不变形)；取值"DB":等比缩放,以值较大的作为标准进行等比缩放</param>  
        /// <param name="type">即将生成缩略图的文件的扩展名(仅限：JPG、GIF、PNG、BMP)</param>  
        public static void MakeThumbnail(string imgPath_old, string imgPath_new, int width, int height, string mode, string imageType, int xx, int yy)
        {
            System.Drawing.Image img = System.Drawing.Image.FromFile(imgPath_old);
            int towidth = width; int toheight = height;
            int x = 0; int y = 0; int ow = img.Width;
            int oh = img.Height; switch (mode)
            {
                case "HW":  //指定高宽压缩
                    if ((double)img.Width / (double)img.Height > (double)width / (double)height)//判断图形是什么形状
                    {
                        towidth = width;
                        toheight = img.Height * width / img.Width;
                    }
                    else if ((double)img.Width / (double)img.Height == (double)width / (double)height)
                    {
                        towidth = width;
                        toheight = height;
                    }
                    else
                    {
                        toheight = height;
                        towidth = img.Width * height / img.Height;
                    }
                    break;
                case "W":  //指定宽，高按比例   
                    toheight = img.Height * width / img.Width;
                    break;
                case "H":  //指定高，宽按比例  
                    towidth = img.Width * height / img.Height;
                    break;
                case "Cut":   //指定高宽裁减（不变形）   
                    if ((double)img.Width / (double)img.Height > (double)towidth / (double)toheight)
                    {
                        oh = img.Height;
                        ow = img.Height * towidth / toheight;
                        y = yy; x = (img.Width - ow) / 2;
                    }
                    else
                    {
                        ow = img.Width;
                        oh = img.Width * height / towidth;
                        x = xx; y = (img.Height - oh) / 2;
                    } break;
                case "DB":    // 按值较大的进行等比缩放（不变形）   
                    if ((double)img.Width / (double)towidth < (double)img.Height / (double)toheight)
                    {
                        toheight = height;
                        towidth = img.Width * height / img.Height;
                    }
                    else
                    {
                        towidth = width;
                        toheight = img.Height * width / img.Width;
                    } 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(img, 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 
                switch (imageType.ToLower())
                {
                    case "gif":
                        img.Save(imgPath_new, ImageFormat.Jpeg);//生成缩略图
                        break;
                    case "jpg":
                        bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Jpeg);
                        break;
                    case "bmp":
                        bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Bmp);
                        break;
                    case "png":
                        bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Png);
                        break;
                    default:
                        bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Jpeg);
                        break;
                }
                ////保存缩略图  
                // bitmap.Save(imgPath_new);
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                img.Dispose();
                bitmap.Dispose(); g.Dispose();
            }
        }

[postcha]

我怎么觉得大家的方法都复杂了呢？

// 创建缩略图对象
Bitmap TempBitmap = new Bitmap(550, 550 * OrigImage.Height / OrigImage.Width);

// 创建Rectangle对象进行绘制
Rectangle imageRectangle = new Rectangle(0, 0, 550, 550 * OrigImage.Height / OrigImage.Width);

我就修改了上面这样的二句，图片就不变形了。

[anzhiqiang_touzi]

http://download.csdn.net/detail/anzhiqiang_touzi/1069856

很好用的
两年前写的