Show a thumbnail image in gallery but download the original

I have a gallery of images that are loaded dynamically from the database. The original images weigh approximately 3Mb each, so I am making a Thumbnail of each one so I can optimize my web page. Thanks to the thumbnail, the images now weigh approximately between 300kb and 500kb.

The images when I get them from the database, I save them in a list and this is passed through the thumbnail function, and then sent to the view.

My problem is the following: I want each image to be downloadable either all together or one by one. I have been able to complete this task successfully, but the images that are downloaded are the thumbnails, when the ones I want to download are the originals.

How could I load the thumbnail images in the gallery and download the original ones?

I have tried to save the copies in a folder both in TMP/Temp, create a new directory such as wwwroot/TemporalImages, or save them in memory. The problem with the folders is that I don't have write permissions. And with saving the images in memory I did not find something that worked, since most of them I saw use Bitmap or Encoder but I get a warning that they are only functional for Windows, and my project is hosted on a Linux server.

I need your help, I've had this problem for a few days and I can't find a way around it.

// I recover the images with the Query, then pass the list to "Chang Image Size"
private List<OrderViewModel> ViewOrder(string identi)
        {
            List<OrderViewModel> OrderList;
            string query;

            try
            {
                OrderList = new List<OrderViewModel>();
                query = "query";

                OrderList = SelectMySqlConnection(query);

                ChangeImageSize(orderList);

                return OrderList;
            }
            catch (Exception ex)
            {
                throw new Exception(ex.ToString());
            }
    }
 
 // I create the temporary folder (tempFolder), do a foreach loop for the List and save each image
 private void ChangeImageSize(List<OrderViewModel> orderViewModels)
        {
            const int thumbnailWidth = 500;
            string tempFolder;

            try
            {
                tempFolder = TemporaryFolder();

                foreach (var item in orderViewModels)
                {
                    var imageResult = Image.Load("wwwroot/" + item.getImages());

                    this.SaveImage(imageResult, tempFolder, thumbnailWidth);
                }
            }
            catch (Exception ex)
            {
                ViewBag.error = ex.Message.ToString();
                throw new Exception(ex.Message);
            }
        }
//Resize the image and then save it
private void SaveImage(Image image, string name, int resizeWidth)
        {
            var width = image.Width;
            var height = image.Height;

            if (width > resizeWidth)
            {
                height = (int)((double)resizeWidth / width * height);
                width = resizeWidth;
            }

            image
                .Mutate(i => i.Resize(new Size(width, height)));

            image.Metadata.ExifProfile = null;

            image.SaveAsJpeg(name, new JpegEncoder
            {
                Quality = 100
            });
        }
//Create or recover temporalFolder
        private string TemporalFolder()
        {
            DirectoryInfo result = Directory.CreateDirectory(@"wwwroot/imgAndroid/TemporalImages/");

            return result.FullName;
        }

In addition to all that, when I try it locally or in production, I have this error:

System.Exception: Access to the path 'C:\Users\Users\source\repos\DevelopmentWebLogistica\WebLogistica\wwwroot\TemporalImages' is denied. at WebLogistica.Controllers.HomeController.ChangeImageSize(List`1 orderViewModels) in C:\Users\Users\source\repos\DevelopmentWebLogistica\WebLogistica\Controllers\HomeController.cs:line 289 at WebLogistica.Controllers.HomeController.VerOrder(String identi) in C:\Users\Users\source\repos\DevelopmentWebLogistics\WebLogistics\Controllers\HomeController.cs:line 157

Line 157 is ChangeImageSize(orderList);