LosslessCompress returning 'The stream should be writeable. Arg_ParamName_Name'

[oztrkkaan]

public IDataResult<List<string>> CompressAndSaveImage(List<IFormFile> formFiles, string path)
        {
            List<string> FileNames = new();


            foreach (var formFile in formFiles)
            {
                using (var fileStream = formFile.OpenReadStream())
                {
                    using (MagickImage image = new(fileStream))
                    {
                        string fileName = Guid.NewGuid().ToString();
                        fileStream.Position = 0;
                        ImageOptimizer optimizer = new();
                        optimizer.LosslessCompress(fileStream);
                        image.Format = MagickFormat.WebP;
                        fileName +=$".{image.Format}";
                        image.Write($"wwwroot/Uploads/{path}/{fileName}");
                        FileNames.Add(fileName);
                    }
                }
            }
            return new SuccessDataResult<List<string>>(FileNames);
        }

I can save image when don't use optimizer.LosslessCompress(fileStream); but when use it throwing exception;
'The stream should be writeable. Arg_ParamName_Name'
How can I solve it ?

[dlemstra]

You will need a stream that supports both reading and writing.