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File.cs

//
// File.cs:
//
// Author:
//   Ruben Vermeersch (ruben@savanne.be)
//
// Copyright (C) 2009 Ruben Vermeersch
//
// This library is free software; you can redistribute it and/or modify
// it  under the terms of the GNU Lesser General Public License version
// 2.1 as published by the Free Software Foundation.
//
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
// USA
//

using System;
using System.Collections.Generic;
using System.IO;

using TagLib.Image;
using TagLib.IFD;
using TagLib.IFD.Entries;
using TagLib.IFD.Tags;
using TagLib.Xmp;

namespace TagLib.Tiff
{
      /// <summary>
      ///    This class extends <see cref="TagLib.Tiff.BaseTiffFile" /> to provide tagging
      ///    and properties support for Tiff files.
      /// </summary>
      [SupportedMimeType("taglib/tiff", "tiff")]
      [SupportedMimeType("taglib/tif", "tif")]
      [SupportedMimeType("image/tiff")]
00043       public class File : BaseTiffFile
      {
#region Private Fields

            /// <summary>
            ///    Contains the media properties.
            /// </summary>
00050             private Properties properties;

#endregion

#region Constructors

            /// <summary>
            ///    Constructs and initializes a new instance of <see
            ///    cref="File" /> for a specified path in the local file
            ///    system and specified read style.
            /// </summary>
            /// <param name="path">
            ///    A <see cref="string" /> object containing the path of the
            ///    file to use in the new instance.
            /// </param>
            /// <param name="propertiesStyle">
            ///    A <see cref="ReadStyle" /> value specifying at what level
            ///    of accuracy to read the media properties, or <see
            ///    cref="ReadStyle.None" /> to ignore the properties.
            /// </param>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="path" /> is <see langword="null" />.
            /// </exception>
00073             public File (string path, ReadStyle propertiesStyle)
                  : this (new File.LocalFileAbstraction (path),
                        propertiesStyle)
            {
            }

            /// <summary>
            ///    Constructs and initializes a new instance of <see
            ///    cref="File" /> for a specified path in the local file
            ///    system.
            /// </summary>
            /// <param name="path">
            ///    A <see cref="string" /> object containing the path of the
            ///    file to use in the new instance.
            /// </param>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="path" /> is <see langword="null" />.
            /// </exception>
00091             public File (string path) : base (path)
            {
            }

            /// <summary>
            ///    Constructs and initializes a new instance of <see
            ///    cref="File" /> for a specified file abstraction and
            ///    specified read style.
            /// </summary>
            /// <param name="abstraction">
            ///    A <see cref="IFileAbstraction" /> object to use when
            ///    reading from and writing to the file.
            /// </param>
            /// <param name="propertiesStyle">
            ///    A <see cref="ReadStyle" /> value specifying at what level
            ///    of accuracy to read the media properties, or <see
            ///    cref="ReadStyle.None" /> to ignore the properties.
            /// </param>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="abstraction" /> is <see langword="null"
            ///    />.
            /// </exception>
00113             public File (File.IFileAbstraction abstraction,
                         ReadStyle propertiesStyle) : base (abstraction)
            {
                  ImageTag = new CombinedImageTag (TagTypes.TiffIFD | TagTypes.XMP);

                  Mode = AccessMode.Read;
                  try {
                        Read (propertiesStyle);
                        TagTypesOnDisk = TagTypes;
                  } finally {
                        Mode = AccessMode.Closed;
                  }
            }

            /// <summary>
            ///    Constructs and initializes a new instance of <see
            ///    cref="File" /> for a specified file abstraction.
            /// </summary>
            /// <param name="abstraction">
            ///    A <see cref="IFileAbstraction" /> object to use when
            ///    reading from and writing to the file.
            /// </param>
            /// <exception cref="ArgumentNullException">
            ///    <paramref name="abstraction" /> is <see langword="null"
            ///    />.
            /// </exception>
00139             protected File (IFileAbstraction abstraction) : base (abstraction)
            {
            }

#endregion

#region Public Properties

            /// <summary>
            ///    Gets the media properties of the file represented by the
            ///    current instance.
            /// </summary>
            /// <value>
            ///    A <see cref="TagLib.Properties" /> object containing the
            ///    media properties of the file represented by the current
            ///    instance.
            /// </value>
00156             public override TagLib.Properties Properties {
                  get { return properties; }
            }

#endregion

#region Public Methods

            /// <summary>
            ///    Saves the changes made in the current instance to the
            ///    file it represents.
            /// </summary>
00168             public override void Save ()
            {
                  Mode = AccessMode.Write;
                  try {
                        WriteFile ();

                        TagTypesOnDisk = TagTypes;
                  } finally {
                        Mode = AccessMode.Closed;
                  }
            }

#endregion

#region Private Methods

            /// <summary>
            ///    Render the whole file and write it back.
            /// </summary>
00187             private void WriteFile ()
            {
                  // Check, if IFD0 is contained
                  IFDTag exif = ImageTag.Exif;
                  if (exif == null)
                        throw new Exception ("Tiff file without tags");

                  UpdateTags (exif);

                  // first IFD starts at 8
                  uint first_ifd_offset = 8;
                  ByteVector data = RenderHeader (first_ifd_offset);

                  var renderer = new IFDRenderer (IsBigEndian, exif.Structure, first_ifd_offset);

                  data.Add (renderer.Render ());

                  Insert (data, 0, Length);
            }

            /// <summary>
            ///    Update the XMP stored in the Tiff IFD
            /// </summary>
            /// <param name="exif">
            ///    A <see cref="IFDTag"/> The Tiff IFD to update the entries
            /// </param>
00213             private void UpdateTags (IFDTag exif)
            {
                  // update the XMP entry
                  exif.Structure.RemoveTag (0, (ushort) IFDEntryTag.XMP);

                  XmpTag xmp = ImageTag.Xmp;
                  if (xmp != null)
                        exif.Structure.AddEntry (0, new ByteVectorIFDEntry ((ushort) IFDEntryTag.XMP, xmp.Render ()));
            }

            /// <summary>
            ///    Reads the file with a specified read style.
            /// </summary>
            /// <param name="propertiesStyle">
            ///    A <see cref="ReadStyle" /> value specifying at what level
            ///    of accuracy to read the media properties, or <see
            ///    cref="ReadStyle.None" /> to ignore the properties.
            /// </param>
00231             protected void Read (ReadStyle propertiesStyle)
            {
                  Mode = AccessMode.Read;
                  try {
                        uint first_ifd_offset = ReadHeader ();
                        ReadIFD (first_ifd_offset);

                        // Find XMP data
                        var xmp_entry = ImageTag.Exif.Structure.GetEntry (0, (ushort) IFDEntryTag.XMP) as ByteVectorIFDEntry;
                        if (xmp_entry != null) {
                              ImageTag.AddTag (new XmpTag (xmp_entry.Data.ToString (), this));
                        }

                        if (propertiesStyle == ReadStyle.None)
                              return;

                        properties = ExtractProperties ();
                  } finally {
                        Mode = AccessMode.Closed;
                  }
            }

            /// <summary>
            ///    Attempts to extract the media properties of the main
            ///    photo.
            /// </summary>
            /// <returns>
            ///    A <see cref="Properties" /> object with a best effort guess
            ///    at the right values. When no guess at all can be made,
            ///    <see langword="null" /> is returned.
            /// </returns>
00262             protected virtual Properties ExtractProperties ()
            {
                  int width = 0, height = 0;

                  IFDTag tag = GetTag (TagTypes.TiffIFD) as IFDTag;
                  IFDStructure structure = tag.Structure;

                  width = (int) (structure.GetLongValue (0, (ushort) IFDEntryTag.ImageWidth) ?? 0);
                  height = (int) (structure.GetLongValue (0, (ushort) IFDEntryTag.ImageLength) ?? 0);

                  if (width > 0 && height > 0) {
                        return new Properties (TimeSpan.Zero, CreateCodec (width, height));
                  }

                  return null;
            }

            /// <summary>
            ///    Create a codec that describes the photo properties.
            /// </summary>
            /// <returns>
            ///    A <see cref="Codec" /> object.
            /// </returns>
00285             protected virtual Codec CreateCodec (int width, int height)
            {
                  return new Codec (width, height);
            }

#endregion
      }
}

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