/// <summary>
		/// Contructor from a <see cref="DicomCompressedPixelData"/> instance.
		/// </summary>
		/// <param name="compressedPixelData"></param>
		public DicomUncompressedPixelData(DicomCompressedPixelData compressedPixelData)
			: base(compressedPixelData)
		{
			if (BitsAllocated > 8)
			{
				_pd = new DicomAttributeOW(DicomTags.PixelData);
			}
			else
			{
				var pdTag = DicomTagDictionary.GetDicomTag(DicomTags.PixelData);
				var obTag = new DicomTag(DicomTags.PixelData, pdTag.Name, pdTag.VariableName, DicomVr.OBvr, pdTag.MultiVR, pdTag.VMLow, pdTag.VMHigh, pdTag.Retired);
				_pd = new DicomAttributeOB(obTag);
			}
			InitializeFrameData(this, _pd);
		}
        public void ChangeTransferSyntax(TransferSyntax newTransferSyntax, IDicomCodec inputCodec, DicomCodecParameters inputParameters)
        {
            IDicomCodec codec = inputCodec;
            DicomCodecParameters parameters = inputParameters;
            if (newTransferSyntax.Encapsulated && TransferSyntax.Encapsulated)
                throw new DicomCodecException("Source and destination transfer syntaxes encapsulated");

            if (newTransferSyntax.Encapsulated)
            {
                if (codec == null)
                {
                    codec = DicomCodecRegistry.GetCodec(newTransferSyntax);
                    if (codec == null)
                    {
                        Platform.Log(LogLevel.Error, "Unable to get registered codec for {0}", newTransferSyntax);
                        throw new DicomCodecException("No registered codec for: " + newTransferSyntax.Name);
                    }
                }
                if (parameters == null)
                    parameters = DicomCodecRegistry.GetCodecParameters(newTransferSyntax, DataSet);

            	DicomAttribute pixelData;
                if (DataSet.TryGetAttribute(DicomTags.PixelData, out pixelData))
                {
                    if (pixelData.IsNull)
                        throw new DicomCodecException("Sop pixel data has no valid value and cannot be compressed.");

                	new OverlayPlaneModuleIod(DataSet).ExtractEmbeddedOverlays();

					var pd = new DicomUncompressedPixelData(DataSet);
					using (var pixelStream = ((DicomAttributeBinary) pixelData).AsStream())
					{
						//Before compression, make the pixel data more "typical", so it's harder to mess up the codecs.
						//NOTE: Could combine mask and align into one method so we're not iterating twice, but I prefer having the methods separate.
						if (DicomUncompressedPixelData.RightAlign(pixelStream, pd.BitsAllocated, pd.BitsStored, pd.HighBit))
						{
							var newHighBit = (ushort) (pd.HighBit - pd.LowBit);
							Platform.Log(LogLevel.Debug, "Right aligned pixel data (High Bit: {0}->{1}).", pd.HighBit, newHighBit);

							pd.HighBit = newHighBit; //correct high bit after right-aligning.
							DataSet[DicomTags.HighBit].SetUInt16(0, newHighBit);
						}
						if (DicomUncompressedPixelData.ZeroUnusedBits(pixelStream, pd.BitsAllocated, pd.BitsStored, pd.HighBit))
						{
							Platform.Log(LogLevel.Debug, "Zeroed some unused bits before compression.");
						}
					}

                	// Set transfer syntax before compression, the codecs need it.
					var fragments = new DicomCompressedPixelData(pd) { TransferSyntax = newTransferSyntax };
                	codec.Encode(pd, fragments, parameters);
                    fragments.UpdateMessage(this);

                    //TODO: should we validate the number of frames in the compressed data?
                    if (!DataSet.TryGetAttribute(DicomTags.PixelData, out pixelData) || pixelData.IsNull)
                        throw new DicomCodecException("Sop has no pixel data after compression.");
                }
                else
                {
                    //A bit cheap, but check for basic image attributes - if any exist
                    // and are non-empty, there should probably be pixel data too.

                    DicomAttribute attribute;
                    if (DataSet.TryGetAttribute(DicomTags.Rows, out attribute) && !attribute.IsNull)
                        throw new DicomCodecException("Suspect Sop appears to be an image (Rows is non-empty), but has no pixel data.");

                    if (DataSet.TryGetAttribute(DicomTags.Columns, out attribute) && !attribute.IsNull)
                        throw new DicomCodecException("Suspect Sop appears to be an image (Columns is non-empty), but has no pixel data.");

                    TransferSyntax = newTransferSyntax;
                }
            }
            else
            {
                if (codec == null)
                {
                    codec = DicomCodecRegistry.GetCodec(TransferSyntax);
                    if (codec == null)
                    {
                        Platform.Log(LogLevel.Error, "Unable to get registered codec for {0}", TransferSyntax);

                        throw new DicomCodecException("No registered codec for: " + TransferSyntax.Name);
                    }

                    if (parameters == null)
                        parameters = DicomCodecRegistry.GetCodecParameters(TransferSyntax, DataSet);
                }

				DicomAttribute pixelData;
				if (DataSet.TryGetAttribute(DicomTags.PixelData, out pixelData))
				{
					if (pixelData.IsNull)
						throw new DicomCodecException("Sop pixel data has no valid value and cannot be decompressed.");

					var fragments = new DicomCompressedPixelData(DataSet);
                    var pd = new DicomUncompressedPixelData(fragments);

                    codec.Decode(fragments, pd, parameters);

                    pd.TransferSyntax = TransferSyntax.ExplicitVrLittleEndian;
                    TransferSyntax = TransferSyntax.ExplicitVrLittleEndian;

                    pd.UpdateMessage(this);

					//TODO: should we validate the number of frames in the decompressed data?
					if (!DataSet.TryGetAttribute(DicomTags.PixelData, out pixelData) || pixelData.IsNull)
						throw new DicomCodecException("Sop has no pixel data after decompression.");
				}
                else
                {
					//NOTE: doing this for consistency, really.
					DicomAttribute attribute;
					if (DataSet.TryGetAttribute(DicomTags.Rows, out attribute) && !attribute.IsNull)
						throw new DicomCodecException("Suspect Sop appears to be an image (Rows is non-empty), but has no pixel data.");

					if (DataSet.TryGetAttribute(DicomTags.Columns, out attribute) && !attribute.IsNull)
						throw new DicomCodecException("Suspect Sop appears to be an image (Columns is non-empty), but has no pixel data.");
					
					TransferSyntax = TransferSyntax.ExplicitVrLittleEndian;
                }
            }
        }