from math import log
from collections import Counter
import sys
s1 = "CODAGEINFORMATIONETCALCUL"
s2 = "TOBEORNOTTOBEORTOBEORNOT"
# print(len(s1) * 8)
# print(len(s2) * 8)
# sys.exit()
def entropy(p):
return -sum(pi * log(pi, 2) for pi in p)
"""print(entropy([0.5, 0.5]))
print(entropy([0.4, 0.6]))
print(entropy([0.01, 0.99]))
print(entropy([0.99, 0.01]))"""
# sys.exit()
def string_entropy(s):
n = len(s)
c = Counter(s)
p = []
for nb_occ in c.values():
p.append(nb_occ / n)
return entropy(p)
# print(Counter("coucou"))
# print(string_entropy(s1), 'bits pour', s1)
# print(string_entropy(s2), 'bits pour', s2)
# sys.exit()
img1 = ["11111111",
"11111111",
"00000000",
"00000000",
"11111111",
"11111111",
"00000000",
"00000000"]
# sys.exit()
img2 = [("1" * 4 + "0" * 4) * 8]
# Comment couper une liste
l = list(range(20))
print(l)
print(l[5:15:2])
#print(l[a:b:-1])
print(l[:-1])
print(l[::-1]) # Inverser
# sys.exit()
img3 = ["10" * 4, "01" * 4, "0" * 16, "1" * 16, "0" * 16]
print(bin(1)[2:].zfill(3))
# sys.exit()
def binary(n):
return bin(n - 1)[2:].zfill(3) # Rempli avec des 0 à gauche
def rle(img):
seq = ''.join(img)
n = len(seq)
current = ''
nb_occ = 0
encoding = ""
for i in range(n):
if seq[i] != current or nb_occ == 8:
if current:
# print(current, nb_occ)
encoding += current + binary(nb_occ)
current = seq[i]
nb_occ = 1
else:
nb_occ += 1
encoding += current + binary(nb_occ)
return encoding
print(rle(img1), len(rle(img1)))
print(rle(img2), len(rle(img2)))
print(rle(img3), len(rle(img3)))
# sys.exit()
new_img3 = ["2" * 4 + "1" * 4 + "0" * 8 + "3" * 8 + "0" * 8]
# print(rle(new_img3), len(rle(new_img3)))
N = 1000000
freq = [0.45, 0.13, 0.12, 0.16, 0.09, 0.05]
length = [1, 3, 3, 3, 4, 4]
# print(sum(freq[i] * length[i] * N for i in range(6)) / (3 * N))
print('huffman', sum(freq[i] * length[i] for i in range(6)))
print('shannon', entropy(freq))
def lzw(s):
dico = {}
# Initialize
for value in range(255):
dico[chr(value)] = value
new_value = 256
acc = ""
encoding = []
for letter in s:
acc += letter
if acc not in dico:
dico[acc] = new_value
this_code = dico[acc[:-1]]
new_value += 1
encoding.append(this_code)
acc = acc[-1]
this_code = dico[acc]
for letter, v in dico.items():
if v > 255:
print(letter, v)
encoding.append(this_code)
return encoding
encoding = lzw("TOBEORNOTTOBEORTOBEORNOT")
print(encoding)
print(''.join(list(map(chr, encoding))))
# sys.exit()
def decode_lzw(encoding):
dico = {}
# Initialize
for value in range(255):
dico[value] = chr(value)
new_value = 256
plain = ""
last_output = ""
for code in encoding:
if code in dico:
output = dico[code]
plain += output
if last_output:
dico[new_value] = last_output + output[0]
new_value += 1
last_output = output
return plain
print(decode_lzw([84, 79, 66, 69, 79, 82, 78, 79, 84, 256, 258, 260, 265, 259, 261, 263]))
