ShrlAlgoToolkit/RevitLess/PreviewImage.cs

using System;
using System.Diagnostics;
using System.Drawing;
using System.IO;
using System.IO.Packaging;
using System.Windows.Media.Imaging;

namespace RevitLess
{

    public class PreviewImage : StorageStreamBase
    {

        #region Private Variables

        private byte[] previewData = null;

        #endregion

        #region Constructors

        public PreviewImage(string fileName, StorageInfo storage)
         : base(fileName, storage)
        {
            ReadStructuredStorageFile();
        }

        #endregion

        #region Private Properties

        private byte[] PreviewData
        {
            get
            {
                return previewData;
            }
            set
            {
                previewData = value;
            }
        }

        #endregion

        #region Public Methods

        public Image GetPreviewAsImage()
        {
            if ((PreviewData == null) || (PreviewData.Length <= 0))
            {
                using (Bitmap newBitmap = new Bitmap(128, 128))
                {
                    return newBitmap.Clone() as Bitmap;
                }
            }

            // read past the Revit metadata to the start of the PNG image
            int startingOffset = GetPngStartingOffset();
            if (startingOffset == 0)
            {
                using (Bitmap newBitmap = new Bitmap(128, 128))
                {
                    return newBitmap.Clone() as Bitmap;
                }
            }

            try
            {
                byte[] pngDataBuffer = new byte[PreviewData.GetUpperBound(0) - startingOffset + 1];
                // read the PNG image data into a byte array
                using (MemoryStream ms = new MemoryStream(PreviewData))
                {
                    ms.Position = startingOffset;
                    ms.Read(pngDataBuffer, 0, pngDataBuffer.Length);
                }

                byte[] decoderData = null;

                // if the image data is valid
                if (pngDataBuffer != null)
                {
                    // use a memory stream to decode the PNG image data
                    // and copy the decoded data into a byte array
                    using (MemoryStream ms = new MemoryStream(pngDataBuffer))
                    {
                        PngBitmapDecoder decoder = new PngBitmapDecoder(ms, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);
                        decoderData = BitSourceToArray(decoder.Frames[0]);
                    }
                }

                // if the decoded data is valie
                if ((decoderData != null) && (decoderData.Length > 0))
                {
                    // use another memory stream to create a Bitmap
                    // and then an Image from that Bitmap
                    using (MemoryStream ms = new MemoryStream(decoderData))
                    {
                        using (Bitmap src = new Bitmap(ms))
                        {
                            // 创建一个与 src 无关的深拷贝，并返回该拷贝（不要对其进行 Dispose）
                            Bitmap deepCopy = new Bitmap(src);
                            return (Image)deepCopy;
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex.Message);
            }

            using (Bitmap newBitmap = new Bitmap(128, 128))
            {
                return newBitmap.Clone() as Bitmap;
            }
        }

        #endregion

        #region Private Methods

        private byte[] BitSourceToArray(BitmapSource bitmapSource)
        {
            BitmapEncoder encoder = new JpegBitmapEncoder();
            using (MemoryStream ms = new MemoryStream())
            {
                encoder.Frames.Add(BitmapFrame.Create(bitmapSource));
                encoder.Save(ms);
                return ms.ToArray();
            }
        }

        //internal override void ReadStructuredStorageFile()
        //{
        // if(IsInitialized)
        // {
        //  return;
        // }
        // try
        // {
        //  StreamInfo[] streams = Storage.GetStreams();
        //  foreach(StreamInfo stream in streams)
        //  {
        //   if(stream.Name.ToUpper().Equals("REVITPREVIEW4.0"))
        //   {
        //    PreviewData = ParsePreviewInfo(stream);
        //   }
        //  }
        // }
        // catch(Exception ex)
        // {
        //  LogManager.LogMessage(ex);
        //  IsInitialized = false;
        // }
        // IsInitialized = true;
        //}

        public void ReadStructuredStorageFile()
        {
            if (IsInitialized)
            {
                return;
            }
            try
            {
                StreamInfo[] streams = Storage.GetStreams();
                foreach (StreamInfo stream in streams)
                {
                    if (stream.Name.ToUpper().Equals("REVITPREVIEW4.0"))
                    {
                        PreviewData = ParsePreviewInfo(stream);
                    }
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine(ex.Message);
                IsInitialized = false;
            }
            IsInitialized = true;
        }

        private byte[] ParsePreviewInfo(StreamInfo streamInfo)
        {
            byte[] streamData = null;
            try
            {
                using (Stream streamReader = streamInfo.GetStream(FileMode.Open, FileAccess.Read))
                {
                    streamData = new byte[streamReader.Length];
                    streamReader.Read(streamData, 0, streamData.Length);
                    return streamData;
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                streamData = null;
            }
        }

        private int GetPngStartingOffset()
        {
            bool markerFound = false;
            int startingOffset = 0;
            int previousValue = 0;
            using (MemoryStream ms = new MemoryStream(PreviewData))
            {
                for (int i = 0; i < PreviewData.Length; i++)
                {
                    int currentValue = ms.ReadByte();
                    // possible start of PNG file data
                    if (currentValue == 137)   // 0x89
                    {
                        markerFound = true;
                        startingOffset = i;
                        previousValue = currentValue;
                        continue;
                    }

                    switch (currentValue)
                    {
                        case 80:   // 0x50
                            if (markerFound && (previousValue == 137))
                            {
                                previousValue = currentValue;
                                continue;
                            }
                            markerFound = false;
                            break;

                        case 78:   // 0x4E
                            if (markerFound && (previousValue == 80))
                            {
                                previousValue = currentValue;
                                continue;
                            }
                            markerFound = false;
                            break;

                        case 71:   // 0x47
                            if (markerFound && (previousValue == 78))
                            {
                                previousValue = currentValue;
                                continue;
                            }
                            markerFound = false;
                            break;

                        case 13:   // 0x0D
                            if (markerFound && (previousValue == 71))
                            {
                                previousValue = currentValue;
                                continue;
                            }
                            markerFound = false;
                            break;

                        case 10:   // 0x0A
                            if (markerFound && (previousValue == 26))
                            {
                                return startingOffset;
                            }
                            if (markerFound && (previousValue == 13))
                            {
                                previousValue = currentValue;
                                continue;
                            }
                            markerFound = false;
                            break;

                        case 26:   // 0x1A
                            if (markerFound && (previousValue == 10))
                            {
                                previousValue = currentValue;
                                continue;
                            }
                            markerFound = false;
                            break;
                    }
                }
            }
            return 0;
        }

        #endregion

    }
}