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using System;
using System.Collections;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Text;

// Reading CorelDRAW Palettes Part 1, .pal files
// https://www.cyotek.com/blog/reading-coreldraw-palettes-part-1-pal-files
// Copyright © 2018 Cyotek Ltd. All Rights Reserved.

// This work is licensed under the Creative Commons Attribution 4.0 International License.
// To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

// Found this example useful? 
// https://www.paypal.me/cyotek

namespace Cyotek.Demonstrations.CorelDrawPaletteLoader
{
  internal sealed class CorelDrawPalette : IEnumerable<Color>
  {
    #region Constants

    private readonly List<Color> _palette;

    private readonly char[] _whitespace =
    {
      ' '
    };

    #endregion

    #region Constructors

    public CorelDrawPalette()
    {
      _palette = new List<Color>();
    }

    public CorelDrawPalette(IEnumerable<Color> colors)
    {
      if (colors == null)
      {
        throw new ArgumentNullException(nameof(colors));
      }

      _palette = new List<Color>(colors);
    }

    #endregion

    #region Static Methods

    public static CorelDrawPalette LoadFrom(string fileName)
    {
      CorelDrawPalette palette;

      palette = new CorelDrawPalette();
      palette.Load(fileName);

      return palette;
    }

    public static CorelDrawPalette LoadFrom(Stream stream)
    {
      CorelDrawPalette palette;

      palette = new CorelDrawPalette();
      palette.Load(stream);

      return palette;
    }

    #endregion

    #region Properties

    public int Count
    {
      get { return _palette.Count; }
    }

    public Color this[int index]
    {
      get { return _palette[index]; }
    }

    #endregion

    #region Methods

    public void Load(string fileName)
    {
      using (Stream stream = File.OpenRead(fileName))
      {
        this.Load(stream);
      }
    }

    public void Load(Stream stream)
    {
      _palette.Clear();

      using (TextReader reader = new StreamReader(stream, Encoding.ASCII))
      {
        string line;

        while ((line = reader.ReadLine()) != null && (line.Length == 0 || line[0] != (char)26))
        {
          if (!string.IsNullOrEmpty(line))
          {
            int lastQuote;
            int numberPosition;
            byte cyan;
            byte magenta;
            byte yellow;
            byte black;
            //string name;

            lastQuote = line.LastIndexOf('"');

            if (lastQuote == -1)
            {
              throw new InvalidDataException("Unable to parse line.");
            }

            //name = line.Substring(1, lastQuote - 1);

            numberPosition = lastQuote + 1;
            cyan = this.NextNumber(line, ref numberPosition);
            magenta = this.NextNumber(line, ref numberPosition);
            yellow = this.NextNumber(line, ref numberPosition);
            black = this.NextNumber(line, ref numberPosition);

            //string[] parts;

            //parts = line.Substring(lastQuote + 1).Split(_whitespace, StringSplitOptions.RemoveEmptyEntries);
            //cyan = byte.Parse(parts[0]);
            //magenta = byte.Parse(parts[1]);
            //yellow = byte.Parse(parts[2]);
            //black = byte.Parse(parts[3]);

            _palette.Add(this.ConvertCmykToRgb(cyan, magenta, yellow, black));
          }
        }
      }
    }

    public Color[] ToArray()
    {
      return _palette.ToArray();
    }

    private Color ConvertCmykToRgb(int c, int m, int y, int k)
    {
      int r;
      int g;
      int b;
      float multiplier;

      multiplier = 1 - k / 100F;

      r = Convert.ToInt32(255 * (1 - c / 100F) * multiplier);
      g = Convert.ToInt32(255 * (1 - m / 100F) * multiplier);
      b = Convert.ToInt32(255 * (1 - y / 100F) * multiplier);

      return Color.FromArgb(r, g, b);
    }

    private byte NextNumber(string line, ref int start)
    {
      int length;
      int valueLength;
      int maxLength;
      byte result;

      // skip any leading spaces
      while (char.IsWhiteSpace(line[start]))
      {
        start++;
      }

      length = line.Length;
      maxLength = Math.Min(3, length - start);
      valueLength = 0;

      for (int i = 0; i < maxLength; i++)
      {
        if (char.IsDigit(line[start + i]))
        {
          valueLength++;
        }
        else
        {
          break;
        }
      }

      result = byte.Parse(line.Substring(start, valueLength));

      start += valueLength;

      return result;
    }

    #endregion

    #region IEnumerable<Color> Interface

    public IEnumerator<Color> GetEnumerator()
    {
      return ((IEnumerable<Color>)_palette).GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
      return this.GetEnumerator();
    }

    #endregion
  }
}