title: Difference between SimilarityTransform (scikit-image) and warpAffine (openCV)?
body: <p>I am currently studying <a href="https://github.com/deepinsight/insightface" rel="nofollow noreferrer">insightface</a> and in particular <a href="https://github.com/deepinsight/insightface/blob/3fb3f12c3c516482c6810b06e95dbcc7c0d4c177/src/common/face_preprocess.py#L46-L111" rel="nofollow noreferrer">this preprocess function</a>.</p>
  
  <p>It uses both scikit-image <code>SimilarityTransform</code> function (<a href="https://scikit-image.org/docs/dev/api/skimage.transform.html#skimage.transform.SimilarityTransform" rel="nofollow noreferrer">documentation</a>) and openCV <code>warpAffine</code> function (<a href="https://docs.opencv.org/2.4/modules/imgproc/doc/geometric_transformations.html#warpaffine" rel="nofollow noreferrer">documentation</a>)</p>
  
  <p>Is there a fundamental difference between the two or are they simply two different ways of calling the same mathematical transformation ?</p>