LZW数据压缩 [英] LZW Data Compression

问题描述

我正在寻找可以在C#中压缩和解压缩Word文档的LZW压缩算法.我已经在Google上搜索了它，但没有给我我需要的答案.谁能帮助我获得相应的代码，并让我了解如何在我的项目中真正实现LZW.

I'm looking for LZW compression algorithm in c# that can compress and decompress word documents. I've search it on google but it didn't give me the answer that i need. Can anyone help me to have the code for it and for me to understand how to really implement LZW in my project.

推荐答案

这是我在我的项目中使用的LZW的实现:

Here is the implementation of LZW which i used in my project :

namespace LZW
{
    public class Program
    {
        public static void Main(string[] args)
        {
            List<int> compressed = Compress("string to be compressed");
            Console.WriteLine(string.Join(", ", compressed));
            string decompressed = Decompress(compressed);
            Console.WriteLine(decompressed);
        }

        public static List<int> Compress(string uncompressed)
        {
            // build the dictionary
            Dictionary<string, int> dictionary = new Dictionary<string, int>();
            for (int i = 0; i < 256; i++)
                dictionary.Add(((char)i).ToString(), i);

            string w = string.Empty;
            List<int> compressed = new List<int>();

            foreach (char c in uncompressed)
            {
                string wc = w + c;
                if (dictionary.ContainsKey(wc))
                {
                    w = wc;
                }
                else
                {
                    // write w to output
                    compressed.Add(dictionary[w]);
                    // wc is a new sequence; add it to the dictionary
                    dictionary.Add(wc, dictionary.Count);
                    w = c.ToString();
                }
            }

            // write remaining output if necessary
            if (!string.IsNullOrEmpty(w))
                compressed.Add(dictionary[w]);

            return compressed;
        }

        public static string Decompress(List<int> compressed)
        {
            // build the dictionary
            Dictionary<int, string> dictionary = new Dictionary<int, string>();
            for (int i = 0; i < 256; i++)
                dictionary.Add(i, ((char)i).ToString());

            string w = dictionary[compressed[0]];
            compressed.RemoveAt(0);
            StringBuilder decompressed = new StringBuilder(w);

            foreach (int k in compressed)
            {
                string entry = null;
                if (dictionary.ContainsKey(k))
                    entry = dictionary[k];
                else if (k == dictionary.Count)
                    entry = w + w[0];

                decompressed.Append(entry);

                // new sequence; add it to the dictionary
                dictionary.Add(dictionary.Count, w + entry[0]);

                w = entry;
            }

            return decompressed.ToString();
        }
    }
}

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