public byte[] Decompress()
{
if (_compressed[0] != HALC.RedundancyMagicSignature[0] || _compressed[1] != HALC.RedundancyMagicSignature[1])
{
throw new InvalidImageException("Missing signature");
}
_decompressionPointer += HALC.RedundancyMagicSignature.Length;
while (HasMoreBytes())
{
switch (GetCommand())
{
case HALC.Command.Literal:
UseLiteral();
break;
case HALC.Command.RLE:
UseRLE();
break;
case HALC.Command.ShortPointer:
UseShortPointer();
break;
case HALC.Command.LongPointer:
UseLongPointer();
break;
}
}
return(_builder.GetBytes());
}
public byte[] Compress()
{
_builder.Append(HALC.RedundancyMagicSignature);
var literalBuffer = new ByteArrayBuilder();
while (HasMoreBytes())
{
var repeatCount = GetRepeatCount();
// try RLE first
if (repeatCount > HALC.RLECommandLength)
{
if (literalBuffer.Length > 0)
{
UseLiteral(literalBuffer.GetBytes());
literalBuffer = new ByteArrayBuilder();
}
UseRLE(repeatCount);
}
else
{
var previousOccurance = GetPreviousOccurance();
if (previousOccurance.BestMatchLength > HALC.ShortPointerCommandLength &&
previousOccurance.BestMatchOffset <= HALC.MaxShortPointerOffset &&
previousOccurance.BestMatchLength <= HALC.MaxShortPointerLength)
{
if (literalBuffer.Length > 0)
{
UseLiteral(literalBuffer.GetBytes());
literalBuffer = new ByteArrayBuilder();
}
UseShortPointer(previousOccurance);
}
else if (previousOccurance.BestMatchLength > HALC.LongPointerCommandLength)
{
if (literalBuffer.Length > 0)
{
UseLiteral(literalBuffer.GetBytes());
literalBuffer = new ByteArrayBuilder();
}
UseLongPointer(previousOccurance);
}
else
{
literalBuffer.Append(_uncompressed[_compressionPointer]);
_compressionPointer++;
}
}
}
if (literalBuffer.Length > 0)
{
UseLiteral(literalBuffer.GetBytes());
}
return(_builder.GetBytes());
}
public byte[] Compress()
{
_builder.Append(HALC.ProbabilityMagicSignature);
// build huffman tree
var histogram = GetHistogram();
var nodes = histogram.Select(kvp => new Frequency(kvp.Key, kvp.Value)).OrderBy(f => f.Count).ToList();
var indexedNodes = nodes.ToDictionary(f => f.B, f => f);
while (nodes.Count() > 1)
{
var left = nodes[0];
var right = nodes[1];
var newNode = new Frequency(left, right);
nodes.Remove(left);
nodes.Remove(right);
nodes.Add(newNode);
nodes = nodes.OrderBy(f => f.Count).ToList();
}
// output tree
var bitBuilder = new BitArrayBuilder();
nodes[0].OutputAndBuildPaths(bitBuilder, new List <bool>());
_builder.Append(bitBuilder.GetBytes());
// output huffman codes for each byte
bitBuilder = new BitArrayBuilder();
foreach (var b in _data)
{
var node = indexedNodes[b];
foreach (var p in node.Path)
{
bitBuilder.Append(p);
}
}
_builder.Append(bitBuilder.GetBytes());
return(_builder.GetBytes());
}