#region PDFsharp - A .NET library for processing PDF
//
// Authors:
//   Stefan Lange (mailto:Stefan.Lange@pdfsharp.com)
//
// Copyright (c) 2005-2008 empira Software GmbH, Cologne (Germany)
//
// http://www.pdfsharp.com
// http://sourceforge.net/projects/pdfsharp
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
// DEALINGS IN THE SOFTWARE.
#endregion

using System;
using System.Diagnostics;
using System.Collections;
using System.Text;
using System.IO;
#if GDI
using System.Drawing;
using System.Drawing.Imaging;
#endif
#if WPF
using System.Windows.Media;
#endif
using PdfSharp.Drawing;
using PdfSharp.Fonts.TrueType;
using PdfSharp.Internal;

namespace PdfSharp.Pdf.Advanced
{
  /// <summary>
  /// Represents a PDF soft mask.
  /// </summary>
  public class PdfSoftMask : PdfDictionary
  {
    /// <summary>
    /// Initializes a new instance of the <see cref="PdfXObject"/> class.
    /// </summary>
    /// <param name="document">The document that owns the object.</param>
    public PdfSoftMask(PdfDocument document)
      : base(document)
    {
      Elements.SetName(Keys.Type, "/Mask");
    }

    /// <summary>
    /// Predefined keys of this dictionary.
    /// </summary>
    public class Keys : KeysBase
    {
      /// <summary>
      /// (Optional) The type of PDF object that this dictionary describes;
      /// if present, must be Mask for a soft-mask dictionary.
      /// </summary>
      [KeyInfo(KeyType.Name | KeyType.Optional, FixedValue = "Mask")]
      public const string Type = "/Type";

      /// <summary>
      /// (Required) A subtype specifying the method to be used in deriving the mask values
      /// from the transparency group specified by the G entry:
      /// Alpha: Use the group’s computed alpha, disregarding its color.
      /// Luminosity: Convert the group’s computed color to a single-component luminosity value.
      /// </summary>
      [KeyInfo(KeyType.Name | KeyType.Required)]
      public const string S = "/S";

      /// <summary>
      /// (Required) A transparency group XObject to be used as the source of alpha
      /// or color values for deriving the mask. If the subtype S is Luminosity, the
      /// group attributes dictionary must contain a CS entry defining the color space
      /// in which the compositing computation is to be performed.
      /// </summary>
      [KeyInfo(KeyType.Stream | KeyType.Required)]
      public const string G = "/G";

      /// <summary>
      /// (Optional) An array of component values specifying the color to be used
      /// as the backdrop against which to composite the transparency group XObject G.
      /// This entry is consulted only if the subtype S is Luminosity. The array consists of
      /// n numbers, where n is the number of components in the color space specified
      /// by the CS entry in the group attributes dictionary.
      /// Default value: the color space’s initial value, representing black.
      /// </summary>
      [KeyInfo(KeyType.Array | KeyType.Optional)]
      public const string BC = "/BC";

      /// <summary>
      /// (Optional) A function object specifying the transfer function to be used in
      /// deriving the mask values. The function accepts one input, the computed
      /// group alpha or luminosity (depending on the value of the subtype S), and
      /// returns one output, the resulting mask value. Both the input and output
      /// must be in the range 0.0 to 1.0; if the computed output falls outside this
      /// range, it is forced to the nearest valid value. The name Identity may be
      /// specified in place of a function object to designate the identity function.
      /// Default value: Identity.
      /// </summary>
      [KeyInfo(KeyType.FunctionOrName | KeyType.Optional)]
      public const string TR = "/TR";
    }
  }
}