Menpo supports the full family of affine 2D and 3D transformations. These operations are simply defined as the operations that preserve straight lines. The affine transformation family is a subclass of the homogenous family that does not allow operations like perspective projection. In this notebook, we will focus on commonly used affine transformations such as translations, scales and rotations.
It's important to note that these transformations will work on both PointCloud and it's subclasses and Images (through the use of the warp_ methods). To start with, let's make a few objects to play around with.
In [1]:
%matplotlib inline
import numpy as np
import matplotlib.pyplot as plt
from menpo.shape import PointCloud
from menpo.image import Image
# A unit square centered at (0.5, 0.5)
points = np.array([[0, 0], [0, 1], [1, 0], [1, 1]])
plt.plot(points[:, 0], points[:, 1], 'bo')
# A PointCloud containing a copy of the unit square
pcloud = PointCloud(points)
pcloud.view(new_figure=True)
# A small black image
image = Image.init_blank([100, 100], fill=1)
image.view(new_figure=True);
In [2]:
%matplotlib inline
from menpo.transform import Translation
small_2d_translation = Translation([-5, 5])
translated_pcloud = small_2d_translation.apply(pcloud)
# Notice it is now centered around (-4.5, 5.5)
translated_pcloud.view();
In [3]:
%matplotlib inline
from menpo.image import BooleanImage
small_2d_translation = Translation([-50, 50])
translated_image = image.warp_to_mask(BooleanImage.init_blank([100, 100]), small_2d_translation)
# Notice it is now centered around (-4.5, 5.5)
translated_image.view();