Do you have the IIS virtual directory set up for the thumbnails? The setup should look like that, a virtual directory under /EPiServerCommunity/Modules/ImageGallery/Thumbnails or something like that which points to the actual thumbnails storage folder in the community file folder.

I do. Some of the thumbnails actually work, while others do not (and are missing from the file system).

My theory was therefore that some of these thumbsnails were created during the testing phase on other machines. So I'd like to force the system to re-create these if possible, since they exist in db but not on disk? The originals are all there from what I can see.

// Kristian

I don't think it's easy. I had this problem in a site a few years ago, running community 3.0/3.1. In the production environment actually. For some reason some images disappeared now and then (ill-timed app-pool recycles?). The worst thing about it is that you can't administer the users because the portrait thumbnail is visible in the user administration which causes it to crash if the file is missing...

What I did back then was to write a scheduled job which simply checked all thumbnails if they existed on disk. If they didn't, they were replaced by a dummy image and then the Image object was removed (if you try to do that without first placing the dummy file - yes, there will be an exception...). I suppose you could do the same, but grab the original and re-upload it as a new Image object which would also create new thumbnails.

I don't have any code left and it feels like there might be a simpler way too.

Thank you Magnus for your assistance. I much appreciate it.

What I ended up doing was that I used Reflection to look inside the CreateThumbnail method of ImageGalleryFactory (EPiServer.Community.ImageGallery.Data). The first half creates db-entries, which I already had, so I skipped to the second part.

Thumbnail thumbnail = null;

                System.Drawing.Size size = GetImageSize(imageSize);

                thumbnail = image.GetThumbnail(size.Width, size.Height, ThumbnailFormat.ReduceAndCrop);

                // Thumbnail path
                string path = System.Web.Hosting.HostingEnvironment.MapPath(ImageGalleryModule.GetVirtualThumbnailPath(image.ImageGallery.ID));
            
                // Thumbnail filename
                string fileName = Path.Combine(path, string.Concat(new object[] { image.ID, "_", Convert.ToString(thumbnail.ID), ImageGalleryModule.ImageExtension }));

                // If the thumbnail exists, just return it
                if (File.Exists(fileName))
                {
                    return new UrlBuilder(thumbnail.Url).Uri;
                }
                else
                {
                    // Otherwise, use the CreateThumbnail logic to "re-create" it
                    System.Drawing.Image original =                        
                        System.Drawing.Image.FromFile(Path.Combine(ImageGalleryModule.GetAbsoluteImageGalleryPath(image.ImageGallery.ID), image.ID + ImageGalleryModule.ImageExtension));

                    if ((original != null) && (path != null))
                    {
                        Bitmap bitmap = null;
                        if ((image.Width == size.Width) && (image.Height == size.Height))
                        {
                            bitmap = new Bitmap(original);
                        }
                        else
                        {
                            bitmap = GetReducedAndCroppedImage(original, size.Width, size.Height, Color.Transparent);
                        }

                        original.Dispose();

                        if (ImageGalleryModule.ImageFormat == System.Drawing.Imaging.ImageFormat.Jpeg)
                        {
                            SaveJpegWithCompressionSetting(bitmap, fileName, ImageGalleryModule.ImageQuality);
                        }
                        else
                        {
                            bitmap.Save(fileName, ImageGalleryModule.ImageFormat);
                        }
                        bitmap.Dispose();
                    }
                    else
                    {
                        thumbnail = null;
                    }
                }

                if (thumbnail != null)
                {
                    return new UrlBuilder(thumbnail.Url).Uri;
                }

  All this inside the GetThumbnailUri method that was being used by my startpage box to fetch member images. (Some private methods from inside ImageGalleryFactory were also copied out, but I've excluded these for brevity.)

This works like a charm and I am a happy man :)  

Nice, thanks for sharing the code!