DwarfCorp/PSD/PsdFile/Compression/ImageDataFactory.cs

/////////////////////////////////////////////////////////////////////////////////
//
// Photoshop PSD FileType Plugin for Paint.NET
// http://psdplugin.codeplex.com/
//
// This software is provided under the MIT License:
//   Copyright (c) 2006-2007 Frank Blumenberg
//   Copyright (c) 2010-2016 Tao Yue
//
// See LICENSE.txt for complete licensing and attribution information.
//
/////////////////////////////////////////////////////////////////////////////////

using System;
using System.IO.Compression;
using System.Drawing;

namespace PhotoshopFile.Compression
{
  public static class ImageDataFactory
  {
    /// <summary>
    /// Creates an ImageData object to compress or decompress image data.
    /// </summary>
    /// <param name="channel">The Channel associated with the image data.</param>
    /// <param name="data">The image data to be decompressed, or null if
    ///   image data is to be compressed.</param>
    public static ImageData Create(Channel channel, byte[] data)
    {
      var bitDepth = channel.Layer.PsdFile.BitDepth;
      ImageData imageData;
      switch (channel.ImageCompression)
      {
        case ImageCompression.Raw:
          imageData = new RawImage(data, channel.Rect.Size, bitDepth);
          break;

        case ImageCompression.Rle:
          imageData = new RleImage(data, channel.RleRowLengths,
            channel.Rect.Size, bitDepth);
          break;

        case ImageCompression.Zip:
          // Photoshop treats 32-bit Zip as 32-bit ZipPrediction
          imageData = (bitDepth == 32)
            ? CreateZipPredict(data, channel.Rect.Size, bitDepth)
            : new ZipImage(data, channel.Rect.Size, bitDepth);
          break;

        case ImageCompression.ZipPrediction:
          imageData = CreateZipPredict(data, channel.Rect.Size, bitDepth);
          break;

        default:
          throw new PsdInvalidException("Unknown image compression method.");
      }

      // Reverse endianness of multi-byte image data
      imageData = WrapEndianness(imageData);

      return imageData;
    }

    private static ImageData CreateZipPredict(byte[] data, Size size,
      int bitDepth)
    {
      switch (bitDepth)
      {
        case 16:
          return new ZipPredict16Image(data, size);
        case 32:
          return new ZipPredict32Image(data, size);
        default:
          throw new PsdInvalidException(
            "ZIP with prediction is only available for 16 and 32 bit depths."); 
      }
    }

    private static ImageData WrapEndianness(ImageData imageData)
    {
      // Single-byte image does not require endianness reversal
      if (imageData.BitDepth <= 8)
      {
        return imageData;
      }

      // Bytes will be reordered by the compressor, so no wrapper is needed
      if ((imageData is ZipPredict16Image) || (imageData is ZipPredict32Image))
      {
        return imageData;
      }

      return new EndianReverser(imageData);
    }
  }
}