C# ResizeSettings.GetValueOrDefault方法代码示例

        private void ApplyResizeSettings(ResizeSettings settings, GhostscriptSettings ghostscriptSettings)
        {
            // Parse resize settings

            // - graphicsAlphaBits
            int graphicsAlphaBits = settings.GetValueOrDefault("graphicsbits", 0);
            if(!_validAlphaBitValues.Contains(graphicsAlphaBits))
            {
                // Use default value
                graphicsAlphaBits = _validAlphaBitValues.Last();
            }
            ghostscriptSettings.Add(GhostscriptArgument.GraphicsAlphaBits, graphicsAlphaBits);

            // - textAlphaBits
            int textAlphaBits = settings.GetValueOrDefault("textbits", 0);
            if(!_validAlphaBitValues.Contains(textAlphaBits))
            {
                // Use default value
                textAlphaBits = _validAlphaBitValues.Last();
            }
            ghostscriptSettings.Add(GhostscriptArgument.TextAlphaBits, textAlphaBits);

            ghostscriptSettings[GhostscriptArgument.GridFitTT] = (settings.Get<bool>("gridfit") == true ? 2 : 0).ToString(NumberFormatInfo.InvariantInfo);
            ghostscriptSettings[GhostscriptArgument.AlignToPixels] = (settings.Get<bool>("subpixels") == true ? 1 : 0).ToString(NumberFormatInfo.InvariantInfo);
            if (settings.Get<bool>("printed",true) == false) ghostscriptSettings.Remove(GhostscriptArgument.Printed);
        }

        public override Bitmap DecodeStream(Stream s, ResizeSettings settings, string optionalPath)
        {
            if(string.IsNullOrEmpty(optionalPath))
            {
                if (s.CanSeek) {
                    //Check the header instead if no filename is present.
                    byte[] header = new byte[4];
                    s.Read(header, 0, 4);
                    bool isPdf = (header[0] == '%' && header[1] == 'P' && header[2] == 'D' && header[3] == 'F');
                    s.Seek(-4, SeekOrigin.Current); //Restore position.

                    if (!isPdf) return null;
                } else {
                    return null; //It's not seekable, we can't check the header.
                }
            } else if(!_supportedExtensions.Contains(Path.GetExtension(optionalPath), StringComparer.OrdinalIgnoreCase))
            {
                // Not a supported format
                return null;
            }

            // Do not allow decoding if Ghostscript there are issues with performing this decode
            IIssue[] issues = GetIssues().ToArray();
            if(issues.Length > 0)
            {
                string message = string.Join(Environment.NewLine, issues.Select(x => x.Summary).ToArray());
                throw new InvalidOperationException(message);
            }

            // Must write input stream to a temporary file for Ghostscript to process.
            FileInfo tempInputPathInfo = new FileInfo(Path.GetTempFileName());
            try
            {
                using(FileStream tempInputStream = tempInputPathInfo.Create())
                {
                    StreamExtensions.CopyToStream(s, tempInputStream);
                }

                // Get information about the PDF such as page count and media boxes
                // Although this creates a second trip to Ghostscript engine, it's not possible to generate a rendered image in exact
                // dimensions requested. Skipping this step will cause a rendered image, of some size, to be resized further.
                PdfInfo pdfInfo = GetPdfInfo(tempInputPathInfo.FullName);

                // Extract the requested page number from resize settings, or default to first page
                int pageNumber = settings.GetValueOrDefault("page", 1);

                // Try to get the page number from PDF info. If not available, abort. This is caused by
                // requesting a page that does not exist.
                PageInfo pageInfo = pdfInfo.Pages.SingleOrDefault(x => x.Number == pageNumber);
                if(pageInfo == null)
                {
                    return null;
                }

                // We only support media box (as opposed to clip, bleed, art, etc.) If this is not available, abort.
                if(pageInfo.MediaBox == null)
                {
                    return null;
                }

                // Get the output size of the generated bitmap by applying the resize settings and media box.
                Size outputSize = (pageInfo.Rotate == -90 || pageInfo.Rotate == 90) ?
                    GetOutputSize(settings, pageInfo.MediaBox.Height,pageInfo.MediaBox.Width)
                    : GetOutputSize(settings, pageInfo.MediaBox.Width, pageInfo.MediaBox.Height) ;

                // Create default Ghostscript settings and apply the resize settings.
                GhostscriptSettings ghostscriptSettings = new GhostscriptSettings
                                                          {
                                                              GhostscriptArgument.NoPause,
                                                              GhostscriptArgument.Quiet,
                                                              GhostscriptArgument.Safer,
                                                              GhostscriptArgument.Batch,
                                                              {GhostscriptArgument.OutputDevice, "pngalpha"},
                                                              {GhostscriptArgument.MaxBitmap, 24000000},
                                                              {GhostscriptArgument.RenderingThreads, 4},
                                                              {GhostscriptArgument.GridFitTT, 0},
                                                              {GhostscriptArgument.AlignToPixels, 0}, //Subpixel rendering depends on output device... perhaps testing would help determine if 1 would be better?
                                                              {GhostscriptArgument.FirstPage, pageNumber},
                                                              {GhostscriptArgument.LastPage, pageNumber},
                                                              GhostscriptArgument.Printed,
                                                              GhostscriptArgument.PdfFitPage,
                                                              GhostscriptArgument.FixedMedia,
                                                              {GhostscriptArgument.Height, outputSize.Height},
                                                              {GhostscriptArgument.Width, outputSize.Width}
                                                          };
                ApplyResizeSettings(settings, ghostscriptSettings);

                // Have Ghostscript process the input to a PNG file with transparency.
                // The PNG will be reloaded and further processed by the resizer pipeline.
                FileInfo tempOutputPathInfo = new FileInfo(Path.GetTempFileName());
                try
                {
                    // Add output file and input file. The input file must be the very last argument.
                    ghostscriptSettings.Add(GhostscriptArgument.OutputFile, tempOutputPathInfo.FullName);
                    ghostscriptSettings.Add(tempInputPathInfo.FullName);
                    _engine.Execute(ghostscriptSettings);

                    // NOTE: Do not dispose of memory stream because it is used as the backing source for the loaded bitmap.
                    MemoryStream memoryStream = new MemoryStream((int)tempOutputPathInfo.Length);
                    using(FileStream fileStream = tempOutputPathInfo.Open(FileMode.Open))
//.........这里部分代码省略.........