Commented Unassigned: Issue on opening large image (>2GB Tiff) [1403]

Hi,

We are using magick.net for getting some image informations (get colorspace, bit per sample, etc.) and in some case, we have to transform the same files (dropped in our main app) to tiff. For getting info, we use the code below. On opening large Tiff (>2GB Tiff), we get instantly an OverflowException, Arithmetic operation resulted in an overflow. at ImageMagick.MagickReader.Read(Stream stream)

Any idea we can overcome this. We currently use the V6 of magick.net. Q8 - X64

The whole project is X64 based, not anyCpu.

```
FileStream imageStream = new FileStream(TiffFile, FileMode.Open, FileAccess.Read);
MagickImage currentImage;
ImageMagick.ColorSpace orgColorspace;

try
{
currentImage = new MagickImage(imageStream);
orgColorspace = currentImage.ColorSpace;

if (currentImage.ReadWarning != null)
{
log.Info("RipTiff : Warning on opening file : " + TiffFile + " : " + currentImage.ReadWarning.Message);
}
}
```
Comments: Can you share a link to the input image on something like DropBox or OneDrive? I would like to try to read the image with the latest version of Magick.NET and see if I can reproduce the issue. A lot has changed and I don't provide support on the V6 version of Magick.NET