EV Petr
2016-11-01 14:12:19 UTC
Hi all,
A few days ago I worked on the Moebius transformation of an image for a
course in Complex Analysis:
http://nbviewer.jupyter.org/github/empet/Math/blob/master/Moebius-transform-image.ipynb
Iâm mathematician and had no previous knowledge in image processing.
Reading a few references across the web I succeeded to understand
how the scipy.ndimage.interpolation.geometric_transform works.
Discussing with a colleague who had the book Learning SciPy for Numerical
and Scientific Computing - Second Edition
https://www.safaribooksonline.com/library/view/learning-scipy-for/9781783987702/
he told me that my implementation differ from that in this book (see here a
snippet showing the authors code:
Loading Image...
)
I realized that the authors of the book did not know that
geometric_transform implements the backward method, and instead of the
inverse Moebius transform they passed the transform itself to
geometric_transform function. I left a message on one of the authors github
page, pointing out this issue, but it appears that he doesnât agree with me
(in fact he doesnât understand the key point of the filled issue:
https://github.com/rojassergio/Learning-Scipy/issues/1#issuecomment-257555364
).
That is why I ask people on this forum, who are more skilled than we are,
to express their opinion. On friday I will illustrate for a group of
student how the Moebius transform works and want to know whether my
implementation is correct.
Thanks,
EP
â
A few days ago I worked on the Moebius transformation of an image for a
course in Complex Analysis:
http://nbviewer.jupyter.org/github/empet/Math/blob/master/Moebius-transform-image.ipynb
Iâm mathematician and had no previous knowledge in image processing.
Reading a few references across the web I succeeded to understand
how the scipy.ndimage.interpolation.geometric_transform works.
Discussing with a colleague who had the book Learning SciPy for Numerical
and Scientific Computing - Second Edition
https://www.safaribooksonline.com/library/view/learning-scipy-for/9781783987702/
he told me that my implementation differ from that in this book (see here a
snippet showing the authors code:
Loading Image...
)I realized that the authors of the book did not know that
geometric_transform implements the backward method, and instead of the
inverse Moebius transform they passed the transform itself to
geometric_transform function. I left a message on one of the authors github
page, pointing out this issue, but it appears that he doesnât agree with me
(in fact he doesnât understand the key point of the filled issue:
https://github.com/rojassergio/Learning-Scipy/issues/1#issuecomment-257555364
).
That is why I ask people on this forum, who are more skilled than we are,
to express their opinion. On friday I will illustrate for a group of
student how the Moebius transform works and want to know whether my
implementation is correct.
Thanks,
EP
â