petyr 0.0.2

2D Affine and Projective Transformations

petyr

Affine and Projective transformations for Python 3. Fast and chainable operations.

Install

pip3 install petyr

from petyr import Affine

Applying Transformation

p = np.array([[0,0],[1,0],[1,1],[0,1]]).T
rotate_and_move = Affine().rotate(90).translate(2,1)
print(rotate_and_move)

3x3 Affine Transformation
[[ 0. -1.  2.]
 [ 1.  0.  1.]
 [ 0.  0.  1.]]

q = rotate_45 * p
print(q)

[[2. 2. 1. 1.]
 [1. 2. 2. 1.]]

Finding Transformation

Affine().from_points(p,q)

3x3 Affine Transformation
[[-0. -1.  2.]
 [ 1.  0.  1.]
 [ 0.  0.  1.]]

Basic Operations

Translation

at = Affine()
at.translate(tx=1, ty=3)

3x3 Affine Transformation
[[1. 0. 2.]
 [0. 1. 3.]
 [0. 0. 1.]]

Scaling

at = Affine()
at.scale(1.05, 2)

3x3 Affine Transformation
[[1.05 0.   0.  ]
 [0.   2.   0.  ]
 [0.   0.   1.  ]]

Rotation

at = Affine()
at.rotate(45)

3x3 Affine Transformation
[[ 0.707 -0.707  0.   ]
 [ 0.707  0.707  0.   ]
 [ 0.     0.     1.   ]]

Shearing

at = Affine()
at.shear(10, 45)

3x3 Affine Transformation
[[1.    0.176 0.   ]
 [1.    1.    0.   ]
 [0.    0.    1.   ]]

Inversion

at = Affine()
at.rotate(90).scale(2)
at_inv = at.invert()
at * at_inv

3x3 Affine Transformation
[[1. 0. 0.]
 [0. 1. 0.]
 [0. 0. 1.]]

Operation Chaining

Mutiple operations can be chained together.

at = Affine()
at.scale(2,2).rotate(90)
at.shear(10, 0).translate(-3, 4)

3x3 Affine Transformation
[[ 0.353 -2.    -3.   ]
 [ 2.     0.     4.   ]
 [ 0.     0.     1.   ]]

Multiple transforms can be multiplied together.

a = Affine()
a.translate(2,3)
b = Affine()
b.scale(4,5)
a * b

3x3 Affine Transformation
[[4. 0. 2.]
 [0. 5. 3.]
 [0. 0. 1.]]