Bloom.ImageProcessing.LowResImageCache.GetPathToResizedImage C# (CSharp) Method

        public string GetPathToResizedImage(string originalPath)
        {
            //don't mess with Bloom UI images
            if (new[] {"/img/","placeHolder", "Button"}.Any(s => originalPath.Contains(s)))
                return originalPath;

            string resizedPath;
            if(_paths.TryGetValue(originalPath, out resizedPath))
            {
                if (File.Exists(resizedPath) && new FileInfo(originalPath).LastWriteTimeUtc <= new FileInfo(resizedPath).LastWriteTimeUtc)
                {
                        return resizedPath;
                }
                else
                {
                    _paths.Remove(originalPath);
                }
            }
            using (var originalImage = PalasoImage.FromFile(originalPath))
            {
                if (!originalPath.Contains("Button") && !ImageUtils.AppearsToBeJpeg(originalImage))
                {
                    ((Bitmap)originalImage.Image).MakeTransparent(Color.White); //instead of white, show the background color
                }

                if (originalImage.Image.Width > TargetDimension || originalImage.Image.Height > TargetDimension)
                {
                    var maxDimension = Math.Max(originalImage.Image.Width, originalImage.Image.Height);
                    double shrinkFactor = (TargetDimension/(double) maxDimension);

                    var destWidth = (int) (shrinkFactor*originalImage.Image.Width);
                    var destHeight = (int) (shrinkFactor*originalImage.Image.Height);
                    using (var b = new Bitmap(destWidth, destHeight))
                    {
                        using (Graphics g = Graphics.FromImage((Image) b))
                        {
                            //in version 1.0, we used .NearestNeighbor. But if there is a border line down the right size (as is common for thumbnails that,
                            //are, for example, re-inserted into Teacher's Guides), then the line gets cut off. So I switched it to HighQualityBicubic
                            g.InterpolationMode = InterpolationMode.HighQualityBicubic; //.NearestNeighbor;//or smooth it: HighQualityBicubic
                            g.DrawImage(originalImage.Image, 0, 0, destWidth, destHeight);
                        }

                        var temp = Path.Combine(_cacheFolder, Path.GetRandomFileName() + Path.GetExtension(originalPath));

                        //Hatton July 2012:
                        //Once or twice I saw a GDI+ error on the Save below, when the app 1st launched.
                        //I verified that if there is an IO error, that's what it you get (a GDI+ error).
                        //I looked once, and the %temp%/Bloom directory wasn't there, so that's what I think caused the error.
                        //It's not clear why the temp/bloom directory isn't there... possibly it was there a moment ago
                        //but then some startup thread cleared and deleted it? (we are now running on a thread responding to the http request)

                        Exception error = null;
                        for (int i = 0; i < 5; i++) //try up to five times, a second apart
                        {
                            try
                            {
                                error = null;

                                if (!Directory.Exists(Path.GetDirectoryName(temp)))
                                {
                                    Directory.CreateDirectory(Path.GetDirectoryName(temp));
                                }
                                b.Save(temp, originalImage.Image.RawFormat);
                                break;
                            }
                            catch (Exception e)
                            {
                                Logger.WriteEvent("Error in LowResImage while trying to write image.");
                                Logger.WriteEvent(e.Message);
                                error = e;
                                Thread.Sleep(1000); //wait a second before trying again
                            }
                        }
                        if (error != null)
                        {
                            //NB: this will be on a non-UI thread, so it probably won't work well!
                            ErrorReport.NotifyUserOfProblem(error,
                                "Bloom is having problem saving a low-res version to your temp directory, at " + temp +
                                "\r\n\r\nYou might want to quit and restart Bloom. In the meantime, Bloom will try to use the full-res images.");
                            return originalPath;
                        }

                        try
                        {
                            _paths.Add(originalPath, temp); //remember it so we can reuse if they show it again, and later delete
                        }
                        catch (Exception)
                        {
                            // it happens sometimes that though it wasn't in the _paths when we entered, it is now
                            // I haven't tracked it down... possibly we get a new request for the image while we're busy compressing it?
                        }

                        return temp;
                    }
                }
                else
                {
                    return originalPath;
                }
            }
        }

        protected override bool ProcessRequest(IRequestInfo info)
        {
            if (base.ProcessRequest(info))
            {
                return(true);
            }

            if (!_useCache)
            {
                return(false);
            }

            var r = GetLocalPathWithoutQuery(info);

            if (r.EndsWith(".png") || r.EndsWith(".jpg"))
            {
                info.ContentType = r.EndsWith(".png") ? "image/png" : "image/jpeg";
                r = r.Replace("thumbnail", "");
                //if (r.Contains("thumb"))
                {
                    if (File.Exists(r))
                    {
                        info.ReplyWithImage(_cache.GetPathToResizedImage(r));
                        return(true);
                    }
                }
            }
            return(false);
        }