def dataDecompressing(compressingDictionary_, compressedData_):
decompressedData_ = []
priorPointer = compressedData_.pop(0)
decompressedData_.append(compressingDictionary_[priorPointer])
for nextPointer in compressedData_:
lastKey = compressingDictionary_.keys()[-1]
if nextPointer not in compressingDictionary_.keys():
newEntry = list(
listTools.flatten([
compressingDictionary_[priorPointer],
list(
listTools.flatten(
compressingDictionary_[priorPointer]))[0]
]))
decompressedData_ += newEntry
else:
newEntry = list(
listTools.flatten([
compressingDictionary_[priorPointer],
list(listTools.flatten(
compressingDictionary_[nextPointer]))[0]
]))
decompressedData_ += list(
listTools.flatten(compressingDictionary_[nextPointer]))
compressingDictionary_[lastKey + 1] = newEntry
priorPointer = nextPointer
return decompressedData_
def dataCompressing(compressingDictionary_, rawData_):
compressingDictionary_ = dict(compressingDictionary_)
dataLength = len(rawData_)
compressedData_ = []
i = 0
currentValue = rawData_[i]
while i < dataLength - 1:
lastKey = compressingDictionary_.keys()[-1]
nextValue = rawData_[i + 1]
currentEntry = list(listTools.flatten([currentValue, nextValue]))
if currentEntry in compressingDictionary_.values():
currentValue = currentEntry
else:
dictionaryKey = compressingDictionary_.keys()[
compressingDictionary_.values().index(currentValue)]
compressedData_.append(dictionaryKey)
compressingDictionary_[lastKey + 1] = currentEntry
currentValue = nextValue
i += 1
dictionaryKey = compressingDictionary_.keys()[
compressingDictionary_.values().index(currentValue)]
compressedData_.append(dictionaryKey)
return compressedData_
def entropy(indexesList):
indexesList = list(flatten(indexesList))
indexHistogram = frequencyDictionary(indexesList)
nIndexes = sum(indexHistogram.values())
H = 0
for indexFrequency in indexHistogram.values():
Pr = float(indexFrequency) / nIndexes
H += Pr * math.log(Pr, 2)
if H > 0:
H *= -1
return H
def LZWHuffman(indexesList, compressionDictionary):
indexesList = list(flatten(indexesList))
compressedData = integerLZW.dataCompressing(compressionDictionary,
indexesList)
compressedData, huffmanDict = HuffmanCoding.dataCompressing(compressedData)
dictionaryLength = len(compressionDictionary.keys())
nBits = int(math.floor(math.log(dictionaryLength - 1) / math.log(2)) + 1)
bitsRawData = len(indexesList) * nBits
bitsCompressedData = len(compressedData)
compressionRatio = (float(bitsRawData) / bitsCompressedData)
return compressionRatio