图像<；Bgr，字节>；始终返回Null

我检查图像文件的大小，如果文件很大，我会重新调整大小，以便处理速度更快。但是当我使用调整大小的代码时，我总是得到一个指向image的空引用异常。我尝试调试->返回的调整大小的位图不是空的，而是转换后的图像>image=new image（x）为空。如果我删除了resize函数，代码就可以正常工作。

Image<Bgr, byte> image = null;
foreach (string s in mylist)
{
    Bitmap x = new Bitmap(Bitmap.FromFile(s));
    if (x.Width > 1000 || x.Height > 1000)
    {
        x = ResizekeepAspectRatio(x, 1000, 1000);
        image = new Image<Bgr, byte>(x);
    }
    else
    {
        image = new Image<Bgr, byte>(x);
    }
    work(image, x, s);
}
----------------------------------------------------------------------
Bitmap ResizekeepAspectRatio(Bitmap imgPhoto, int Width, int Height)
{
    int sourceWidth = imgPhoto.Width;
    int sourceHeight = imgPhoto.Height;
    int sourceX = 0;
    int sourceY = 0;
    int destX = 0;
    int destY = 0;
    float nPercent = 0;
    float nPercentW = 0;
    float nPercentH = 0;
    nPercentW = ((float)Width / (float)sourceWidth);
    nPercentH = ((float)Height / (float)sourceHeight);
    if (nPercentH < nPercentW)
    {
        nPercent = nPercentH;
        destX = System.Convert.ToInt16((Width -
                      (sourceWidth * nPercent)) / 2);
    }
    else
    {
        nPercent = nPercentW;
        destY = System.Convert.ToInt16((Height -
                      (sourceHeight * nPercent)) / 2);
    }
    int destWidth = (int)(sourceWidth * nPercent);
    int destHeight = (int)(sourceHeight * nPercent);
    Bitmap bmPhoto = new Bitmap(Width, Height,
                      PixelFormat.Format24bppRgb);
    bmPhoto.SetResolution(imgPhoto.HorizontalResolution,
                     imgPhoto.VerticalResolution);
    Graphics grPhoto = Graphics.FromImage(bmPhoto);
    grPhoto.Clear(Color.Red);
    grPhoto.InterpolationMode =
            InterpolationMode.HighQualityBicubic;
    grPhoto.DrawImage(imgPhoto,
        new Rectangle(destX, destY, destWidth, destHeight),
        new Rectangle(sourceX, sourceY, sourceWidth, sourceHeight),
        GraphicsUnit.Pixel);
    grPhoto.Dispose();
    return bmPhoto;
}