相似变换 SimilarityTransform 以及skimage源码

http://scikit-image.org/docs/dev/api/skimage.transform.html#skimage.transform.SimilarityTransform

https://github.com/scikit-image/scikit-image/blob/master/skimage/transform/_geometric.py#L1040

https://blog.csdn.net/u014096352/article/details/53526747

2D similarity transformation.

Has the following form:

X = a0 * x - b0 * y + a1 =
  = s * x * cos(rotation) - s * y * sin(rotation) + a1

Y = b0 * x + a0 * y + b1 =
  = s * x * sin(rotation) + s * y * cos(rotation) + b1

where s is a scale factor and the homogeneous transformation matrix is:

[[a0  b0  a1]
 [b0  a0  b1]
 [0   0    1]]

The similarity transformation extends the Euclidean transformation with a single scaling factor in addition to the rotation and translation parameters.