BitMiracle.LibJpeg.Classic.jpeg_decompress_struct.jpeg_start_decompress C# (CSharp) Method

        public bool jpeg_start_decompress()
        {
            if (m_global_state == JpegState.DSTATE_READY)
            {
                /* First call: initialize master control, select active modules */
                m_master = new jpeg_decomp_master(this);
                if (m_buffered_image)
                {
                    /* No more work here; expecting jpeg_start_output next */
                    m_global_state = JpegState.DSTATE_BUFIMAGE;
                    return true;
                }
                m_global_state = JpegState.DSTATE_PRELOAD;
            }

            if (m_global_state == JpegState.DSTATE_PRELOAD)
            {
                /* If file has multiple scans, absorb them all into the coef buffer */
                if (m_inputctl.HasMultipleScans())
                {
                    for ( ; ; )
                    {
                        ReadResult retcode;
                        /* Call progress monitor hook if present */
                        if (m_progress != null)
                            m_progress.Updated();

                        /* Absorb some more input */
                        retcode = m_inputctl.consume_input();
                        if (retcode == ReadResult.JPEG_SUSPENDED)
                            return false;

                        if (retcode == ReadResult.JPEG_REACHED_EOI)
                            break;

                        /* Advance progress counter if appropriate */
                        if (m_progress != null && (retcode == ReadResult.JPEG_ROW_COMPLETED || retcode == ReadResult.JPEG_REACHED_SOS))
                        {
                            m_progress.Pass_counter++;
                            if (m_progress.Pass_counter >= m_progress.Pass_limit)
                            {
                                /* underestimated number of scans; ratchet up one scan */
                                m_progress.Pass_limit += m_total_iMCU_rows;
                            }
                        }
                    }
                }

                m_output_scan_number = m_input_scan_number;
            }
            else if (m_global_state != JpegState.DSTATE_PRESCAN)
                ERREXIT(J_MESSAGE_CODE.JERR_BAD_STATE, (int)m_global_state);

            /* Perform any dummy output passes, and set up for the final pass */
            return output_pass_setup();
        }

        private static void decompress(Stream input, DecompressOptions options, Stream output)
        {
            Debug.Assert(input != null);
            Debug.Assert(options != null);
            Debug.Assert(output != null);

            /* Initialize the JPEG decompression object with default error handling. */
            jpeg_decompress_struct cinfo = new jpeg_decompress_struct(new cd_jpeg_error_mgr());

            /* Insert custom marker processor for COM and APP12.
             * APP12 is used by some digital camera makers for textual info,
             * so we provide the ability to display it as text.
             * If you like, additional APPn marker types can be selected for display,
             * but don't try to override APP0 or APP14 this way (see libjpeg.doc).
             */
            cinfo.jpeg_set_marker_processor((int)JPEG_MARKER.COM, new jpeg_decompress_struct.jpeg_marker_parser_method(printTextMarker));
            cinfo.jpeg_set_marker_processor((int)JPEG_MARKER.APP0 + 12, printTextMarker);

            /* Specify data source for decompression */
            cinfo.jpeg_stdio_src(input);

            /* Read file header, set default decompression parameters */
            cinfo.jpeg_read_header(true);

            applyOptions(cinfo, options);

            /* Initialize the output module now to let it override any crucial
             * option settings (for instance, GIF wants to force color quantization).
             */
            djpeg_dest_struct dest_mgr = null;

            switch (options.OutputFormat)
            {
                case IMAGE_FORMATS.FMT_BMP:
                    dest_mgr = new bmp_dest_struct(cinfo, false);
                    break;
                case IMAGE_FORMATS.FMT_OS2:
                    dest_mgr = new bmp_dest_struct(cinfo, true);
                    break;
                default:
                    cinfo.ERREXIT((int)ADDON_MESSAGE_CODE.JERR_UNSUPPORTED_FORMAT);
                    break;
            }

            dest_mgr.output_file = output;

            /* Start decompressor */
            cinfo.jpeg_start_decompress();

            /* Write output file header */
            dest_mgr.start_output();

            /* Process data */
            while (cinfo.Output_scanline < cinfo.Output_height)
            {
                int num_scanlines = cinfo.jpeg_read_scanlines(dest_mgr.buffer, dest_mgr.buffer_height);
                dest_mgr.put_pixel_rows(num_scanlines);
            }

            /* Finish decompression and release memory.
             * I must do it in this order because output module has allocated memory
             * of lifespan JPOOL_IMAGE; it needs to finish before releasing memory.
             */
            dest_mgr.finish_output();
            cinfo.jpeg_finish_decompress();

            /* All done. */
            if (cinfo.Err.Num_warnings != 0)
                Console.WriteLine("Corrupt-data warning count is not zero");
        }