def scale_transform(sx, sy):
"""
Return a pure scale transformation as an Affine instance; sx and
sy are LazyValue instances (Values or binary opertations on
values)
"""
return Affine(sx, zero(), zero(), sy, zero(), zero())
def scale_translation_transform(tx, ty, sx, sy):
"""
Return a pure scale and translation transformation; tx, ty, sx and
sy are LazyValue instances (Values or binary opertations on
values)
"""
affine = Affine(sx, zero(), zero(), sy, tx, ty)
func = identity_funcxy()
return Transformation(affine, func)
def multiply_affines(v1, v2):
"""
v1 and v2 are Affine instances
"""
a1, b1, c1, d1, tx1, ty1 = v1.as_vec6()
a2, b2, c2, d2, tx2, ty2 = v2.as_vec6()
a = a1 * a2 + c1 * b2
b = b1 * a2 + d1 * b2
c = a1 * c2 + c1 * d2
d = b1 * c2 + d1 * d2
tx = a1 * tx2 + c1 * ty2 + tx1
ty = b1 * tx2 + d1 * ty2 + ty1
return Affine(a, b, c, d, tx, ty)
def translation_transform(tx, ty):
"""
return a pure tranlational transformation tx and ty are LazyValue
instances (Values or binary opertations on values)
"""
return Affine(zero(), zero(), zero(), zero(), tx, ty)
def identity_affine():
"""
Get an affine transformation that maps x,y -> x,y
"""
return Affine(one(), zero(), zero(), one(), zero(), zero())
