Generic image coordinate transformation using a matrix

[Johannes Schönberger]

You would have to reorder the dimensions of your coordinate matrix to `(2, 2832, 4256)`.

Johannes Schönberger

On Sep 11, 2014, at 4:56 AM, Maik Riechert <maik.riechert at arcor.de> wrote:

> I just tested it and it doesn't work yet.
> My image is an uint8 array of shape (2832, 4256, 3), and the coordinate array is float32 (2832, 4256, 2) but when using skimage.transform.warp(im, undistCoords) I get:
> 
> 
> Traceback (most recent call last):
>   File ...
>     imUndistorted = skimage.transform.warp(im, undistCoords)
>   File "/home/mriecher/.local/lib/python2.7/site-packages/skimage/transform/_geometric.py", line 1153, in warp
>     mode=mode, order=order, cval=cval)
>   File "/usr/lib/python2.7/dist-packages/scipy/ndimage/interpolation.py", line 289, in map_coordinates
>     raise RuntimeError('invalid shape for coordinate array')
> RuntimeError: invalid shape for coordinate array
> 
> Looking at map_coordinates:
> 
>     if coordinates.shape[0] != input.ndim:
>         raise RuntimeError('invalid shape for coordinate array')
> 
> I tried some other array shapes but couldn't make it work. What's the correct way here?
> 
> Maik
> 
> 
> Am Mittwoch, 10. September 2014 19:44:11 UTC+2 schrieb Johannes Schönberger:
> Mark, can you check, that this works for you? 
> 
> https://github.com/scikit-image/scikit-image/pull/1142 
> 
> Johannes Sch önberger 
> 
> On Sep 10, 2014, at 1:23 PM, Johannes Sch önberger <js... at demuc.de> wrote: 
> 
> > Hi Mark, 
> > 
> > You can do this with `ndimage.map_coordinates`, see https://github.com/scikit-image/scikit-image/blob/master/skimage/transform/_geometric.py#L1134 for an usage example. 
> > 
> > But we should add this feature, so that `warp` also directly takes the coordinates. I opened a new issue for this: https://github.com/scikit-image/scikit-image/issues/1141 
> > 
> > Johannes Sch önberger 
> > 
> > On Sep 10, 2014, at 11:06 AM, Maik Riechert <maik.r... at arcor.de> wrote: 
> > 
> >> Hi, 
> >> 
> >> When I want to undistort photographs I use the lensfunpy library (https://pypi.python.org/pypi/lensfunpy) which provides me with a coordinates array of shape (h,w,2), that is for each input pixel it provides the undistorted pixel location. When using OpenCV I can do undistortedImage = cv2.remap(image, undistCoords, None, cv2.INTER_LANCZOS4). I saw that there is the skimage.transform.warp function but I'm not sure how or if I can use that in my case. I would be glad for some directions. 
> >> 
> >> Thanks 
> >> Maik 
> >> 
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