def golomb_trans(s, base, e):
bs = '{0:0%db}' % e
result = '1'
mins = []
deltas = np.array(s.split(',')[2:], dtype='int')
mins.append(int(s.split(',')[0]))
mins.append(int(s.split(',')[1]))
m = 2**e
for i in range(2):
q = mins[i]/m
r = mins[i] - m*q
if q >= m:
result += '1'*int(q/m) +'0' + bs.format(q%m) + bs.format(r)
else:
result += '0' + bs.format(q) + bs.format(r)
for v in deltas:
if v >= m:
q = int(v) / m
r = int(v) % m
result += '1'*int(q) +'0' + bs.format(r)
else:
result += '0' + bs.format(v)
bits = len(result)
result = helpers.base_encode(int(result, 2), base)
return {'encoding': result, 'bit_len': bits}
def golomb_trans(s, base, e):
bs = '{0:0%db}' % e
result = '1'
mins = []
deltas = np.array(s.split(',')[2:], dtype='int')
mins.append(int(s.split(',')[0]))
mins.append(int(s.split(',')[1]))
m = 2**e
for i in range(2):
q = mins[i]/m
r = mins[i] - m*q
if q >= m:
result += '1'*int(q/m) +'0' + bs.format(q%m) + bs.format(r)
else:
result += '0' + bs.format(q) + bs.format(r)
for v in deltas:
if v >= m:
q = int(v) / m
r = int(v) % m
result += '1'*int(q) +'0' + bs.format(r)
else:
result += '0' + bs.format(v)
bits = len(result)
result = helpers.base_encode(int(result, 2), base)
return {'encoding': result, 'bit_len': bits}
def encode(delta_str, n_vertices, base, m=False):
"""Encodes delta string as a big integer.
Args:
delta_str: A string with delta coordinates in reference to min_x and min_y, min_x and min_y also included
n_vertices: Number of vertices in the polygon
base
Returns:
A dict mapping keys to corresponding compression results.
big_str: big string encoding of delta_str in a particular base (current base 62)
big_bit_len: length of binary representation of big_str
shannon_bit_bound: Shannon bound of number of bits needed to encode the polygon
"""
delta_arr = delta_str.split(',')
n_to_skip = 2 #since the min and max are appended to the beginning of the polygon argument
coords = map(int, delta_arr[n_to_skip:])
d_x = [coords[2*i] for i in range(n_vertices)]
d_y = [coords[2*i + 1] for i in range(n_vertices)]
x_delta = max(d_x)# - min(d_x)
y_delta = max(d_y)# - min(d_y)
Dx_min = int(delta_arr[0])
Dy_min = int(delta_arr[1])
big_num = 0
M = max(x_delta, y_delta) + 2
for i in xrange(n_vertices):
if i == 0:
big_num = big_num * M * M + (d_x[i] + 1) * M + d_y[i] + 1
else:
big_num = big_num * M * M + (d_x[i]) * M + d_y[i]
big_num = big_num*const.x_factor + Dx_min
big_num = big_num*const.y_factor + Dy_min
M_encode = helpers.base_encode(M - 2, base)
big_str = M_encode + helpers.base_encode(big_num, base) # prefix and postfix not appended
if decode(big_str, coords, base, m):
return {'big_str': big_str, 'big_num': big_num, 'M': M, 'bit_len': big_num.bit_length() + M.bit_length(), 'len': len(big_str) - len(M_encode) + 2}
else:
return False
def encode(delta_str, n_vertices, base, m=False):
"""Encodes delta string as a big integer.
Args:
delta_str: A string with delta coordinates in reference to min_x and min_y, min_x and min_y also included
n_vertices: Number of vertices in the polygon
base
Returns:
A dict mapping keys to corresponding compression results.
big_str: big string encoding of delta_str in a particular base (current base 62)
big_bit_len: length of binary representation of big_str
shannon_bit_bound: Shannon bound of number of bits needed to encode the polygon
"""
delta_arr = delta_str.split(',')
n_to_skip = 2 #since the min and max are appended to the beginning of the polygon argument
coords = map(int, delta_arr[n_to_skip:])
d_x = [coords[2*i] for i in range(n_vertices)]
d_y = [coords[2*i + 1] for i in range(n_vertices)]
x_delta = max(d_x)# - min(d_x)
y_delta = max(d_y)# - min(d_y)
Dx_min = int(delta_arr[0])
Dy_min = int(delta_arr[1])
big_num = 0
M = max(x_delta, y_delta) + 2
for i in xrange(n_vertices):
if i == 0:
big_num = big_num * M * M + (d_x[i] + 1) * M + d_y[i] + 1
else:
big_num = big_num * M * M + (d_x[i]) * M + d_y[i]
big_num = big_num*const.x_factor + Dx_min
big_num = big_num*const.y_factor + Dy_min
M_encode = helpers.base_encode(M - 2, base)
big_str = M_encode + helpers.base_encode(big_num, base) # prefix and postfix not appended
if decode(big_str, coords, base, m):
return {'big_str': big_str, 'big_num': big_num, 'M': M, 'bit_len': big_num.bit_length() + M.bit_length(), 'len': len(big_str) - len(M_encode) + 2}
else:
return False
