// tree traversal
public void StoreCodes(HuffmanTreeNode root, string s)
{
// base case; if the left and right are null then its a leaf node and store the code s generated by traversing the tree.
if (root.Left == null && root.Right == null && Char.IsLetter(root.Char))
{
// codetable char
if (!CodeTable.ContainsKey(root.Char))
{
CodeTable.Add(root.Char, s);
}
CodeTable[root.Char] = s;
Console.WriteLine("\t\t" + root.Char + ":" + s);
return;
}
// if we go to left then add "0" to the code., if we go to the right add "1" to the code.
// recursive calls for left and right sub-tree of the generated tree.
StoreCodes(root.Left, s + "0");
StoreCodes(root.Right, s + "1");
}
public List <int> Decompress(string imageData, int startCodeLength, int colorTableSize)
{
var clearCode = colorTableSize;
var endOfInformation = colorTableSize + 1;
ImageData = imageData;
InitializeCodeTable(colorTableSize);
var result = new List <int>();
var codeLength = startCodeLength;
//first code from 0 to codeLength is always control code - CC, ignore it
var pos = codeLength;
var code = Convert.ToInt32(Reverse(ImageData.Substring(pos, codeLength)), 2);
result.AddRange(CodeTable[code]);
pos += codeLength;
var nextCode = 0;
var codeLengthIncreaseThreshold = 1 << codeLength;
while (endOfInformation != nextCode)
{
if (nextCode == clearCode)
{
InitializeCodeTable(colorTableSize);
//skip CC control code
pos += codeLength;
codeLength = startCodeLength;
codeLengthIncreaseThreshold = 1 << codeLength;
code = Convert.ToInt32(Reverse(ImageData.Substring(pos, codeLength)), 2);
result.AddRange(CodeTable[code]);
pos += codeLength;
}
var prevCode = code;
if (CodeTable.Count == codeLengthIncreaseThreshold)
{
codeLength++;
codeLengthIncreaseThreshold = 1 << codeLength;
}
// if (codeLength == 13)
// {
// codeLength = 12;
//
// }
code = Convert.ToInt32(Reverse(ImageData.Substring(pos, codeLength)), 2);
pos += codeLength;
nextCode = Convert.ToInt32(Reverse(ImageData.Substring(pos, codeLength)), 2);
if (CodeTable.ContainsKey(code))
{
result.AddRange(CodeTable[code]);
var k = CodeTable[code][0];
CodeTable[CodeTable.Count] = CodeTable[prevCode].Concat(new List <int> {
k
}).ToList();
}
else
{
var prevCodeValue = CodeTable[prevCode];
var k = prevCodeValue[0];
result.AddRange(prevCodeValue.Concat(new List <int> {
k
}).ToList());
CodeTable[CodeTable.Count] = prevCodeValue.Concat(new List <int> {
k
}).ToList();
}
}
return(result);
}
