CODEWITHSUNDEEP
python
user2297781
user2297781

Reputation:

Is there a nice way to slice Python numpy ndarrays without checking sign of the bounds?

This is part of some code I've been working on to quickly align images. It works well, but the syntax is ugly. Is there a better way to write this?

def shift_int(image, base, y, x):
    """
    Quickly shift an image with respect to a base and return a parameter that
    is minimized when the images are well aligned, and not biased towards
    large shifts

    image -- The input image that is shifted
    base -- The second image to match
    y -- An offset along axis 0
    x -- An offset along axis 1
    """
    new_image = image.copy()
    new_base = base.copy()

    if y > 0:
        new_image = new_image[:-y]
        new_base = new_base[y:]

    if y < 0:
        new_image = new_image[-y:]
        new_base = new_base[:y]

    if x > 0:
        new_image = new_image[:,:-x]
        new_base = new_base[:,x:]

    if x < 0:
        new_image = new_image[:,-x:]
        new_base = new_base[:,:x]

    return np.mean((new_im-new_base)**2)

Upvotes: 1

Views: 44

Answers (1)

eph
eph

Reputation: 2028

h, w = np.shape(new_image)
new_image = new_image[max(0, -y):min(h, h-y),max(0, -x):min(w, w-x)]

h, w = np.shape(new_base)
new_base = new_base[max(0, y):min(h, h+y),max(0, x):min(w, w+x)]

Upvotes: 1

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