Speed up image cropping and resizing

[krikru]

[qubvel]

Hi @krikru Thanks for proposed changes, but I am not sure that OpenCV dependencies is a good choice, you could wrap it in try except block, if cv2 is exists use it, else skimage.

[krikru]

I have updated my pull request. How does this code look?

[krikru]

@qubvel I have three pending pull requests, including this one. Will they be merged?

[Clara85]

Opencv returns BGR image, while scikit-image returns RGB image, I wonder if you tested the result?

[krikru]

@Clara85 Tested in what regard? When resizing, OpenCV only returns a BGR image if it is fed a BGR image as input; if you feed it an RGB image it will also return an RGB image (it has no way of telling whether the image is a BGR or an RGB image, and therefore won't rearrange the channel order).