asp.net压缩图片怎么保持纵横比？

Question

这个代码是网上copy的，选择了cut这个，但是压缩出来的图片会变形，因为一些原图有一些宽一点，有一些就正方形，
宽的那些会变形，而正方形的不会。。还有更好的代码么/// <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 1

public enum ZoomMode
    {
        Fixed,
        GeometricProportion,
        Cut
    }
public static void SaveThumbnail(Stream sr, string savePath, int width, int height, ZoomMode zoomMode)
        {            using (Image originalImg = Image.FromStream(sr))
            {
                Size size = originalImg.Size;
                switch (zoomMode)
                {
                    case ZoomMode.GeometricProportion:
                        float scale = Math.Min((float)width / size.Width, (float)height / size.Height);
                        size = new Size((int)(scale * size.Width), (int)(scale * size.Height));
                        break;
                    case ZoomMode.Fixed:
                        size = new Size(width, height);
                        break;
                    case ZoomMode.Cut:
                        float newScale = (float)width / height;
                        if (size.Width < size.Height * newScale)
                        {
                            size = new Size(size.Width, Convert.ToInt32(size.Width / newScale));
                        }
                        else
                        {
                            size = new Size(Convert.ToInt32(size.Height * newScale), size.Height);
                        }
                        break;
                }
                Bitmap bmp;
                if (zoomMode == ZoomMode.Cut)
                    bmp = new Bitmap(width, height);
                else
                    bmp = new Bitmap(size.Width, size.Height);                using (bmp)
                using (Graphics g = Graphics.FromImage(bmp))
                {
                    g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                    g.Clear(Color.Transparent);                    if (zoomMode != ZoomMode.Cut)
                        g.DrawImage(originalImg, 0, 0, size.Width, size.Height);
                    else
                        g.DrawImage(originalImg, new Rectangle(0, 0, width, height), new Rectangle(0, 0, size.Width, size.Height), GraphicsUnit.Pixel);                    bmp.Save(savePath, ImageFormat.Jpeg);
                }
            }        }