54 lines
1.2 KiB
Python
54 lines
1.2 KiB
Python
#!/usr/bin/env python
|
|
from struct import unpack
|
|
|
|
|
|
## Matrix operations
|
|
##
|
|
MATRIX_IDENTITY = (1, 0, 0, 1, 0, 0)
|
|
|
|
def mult_matrix((a1,b1,c1,d1,e1,f1), (a0,b0,c0,d0,e0,f0)):
|
|
'''Multiplies two matrices.'''
|
|
return (a0*a1+c0*b1, b0*a1+d0*b1,
|
|
a0*c1+c0*d1, b0*c1+d0*d1,
|
|
a0*e1+c0*f1+e0, b0*e1+d0*f1+f0)
|
|
|
|
def translate_matrix((a,b,c,d,e,f), (x,y)):
|
|
return (a,b,c,d,e+x,f+y)
|
|
|
|
def apply_matrix((a,b,c,d,e,f), (x,y)):
|
|
'''Applies a matrix to coordinates.'''
|
|
return (a*x+c*y+e, b*x+d*y+f)
|
|
|
|
def apply_matrix_norm((a,b,c,d,e,f), (p,q)):
|
|
'''equiv to apply_matrix(M, (p,q)) - apply_matrix(M, (0,0))'''
|
|
return (a*p+c*q, b*p+d*q)
|
|
|
|
|
|
## Utilities
|
|
##
|
|
def choplist(n, seq):
|
|
'''Groups every n elements of the list.'''
|
|
r = []
|
|
for x in seq:
|
|
r.append(x)
|
|
if len(r) == n:
|
|
yield tuple(r)
|
|
r = []
|
|
return
|
|
|
|
def nunpack(s, default=0):
|
|
'''Unpacks up to 4 bytes big endian.'''
|
|
l = len(s)
|
|
if not l:
|
|
return default
|
|
elif l == 1:
|
|
return ord(s)
|
|
elif l == 2:
|
|
return unpack('>H', s)[0]
|
|
elif l == 3:
|
|
return unpack('>L', '\x00'+s)[0]
|
|
elif l == 4:
|
|
return unpack('>L', s)[0]
|
|
else:
|
|
return TypeError('invalid length: %d' % l)
|