[scikit-image] How to see full image after transformation not the cropped one

[Stefan van der Walt]

Hi Serge



On Sun, Apr 2, 2017, at 15:30, Serge Shakhov via scikit-image wrote:

> But I didn't find an answer.

> I'm doing 2D piecewise affine transformation with
> skimage.transform.PiecewiseAffineTransform
> Result image is heavily cropped.

> I tried to play with output_shape, mode and clip parameters but
> without any effect, image is still cropped.
> Could anyone point me what am I doing wrong?



I thought we had this implemented, but I guess not yet.  You can
see how here:


https://github.com/scikit-image/skimage-tutorials/blob/master/lectures/adv3_panorama-stitching.ipynb


Specifically:


*from* *skimage.transform* *import* SimilarityTransform

*# Shape of middle image, our registration target* r, c = image.shape

*# Note that transformations take coordinates in (x, y) format,* *# not
(row, column), in order to be consistent with most literature* corners =
np.array([[, ],  [, r],  [c, ],  [c, r]])

*# Warp the image corners to their new positions* warped_corners =
my_tf(corners)

*# The overall output shape will be max - min* corner_min =
np.min(corners, axis=0) corner_max = np.max(corners, axis=0)
output_shape = (corner_max - corner_min)

*# Ensure integer shape with np.ceil and dtype conversion* output_shape
= np.ceil(output_shape[::-1]).astype(int)


That calculates the shape you want.  You now need to modify the
transform to output an image inside of this shape:

*from* *skimage.transform* *import* warp *
# This in-plane offset is the only necessary transformation for the
# middle image*
offset = SimilarityTransform(translation=-corner_min)

shifted_transform = (my_tf + offset).inverse pano0_warped = warp(image,
shifted_transform, order=3,  output_shape=output_shape, cval=-1)


Let us know how that goes!



Stéfan


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