Subsample a numpy array (or an image) using bilinear interpolation

subsample_image.py

def subsample_image(coords, img):
    """
    Given a list of floating point coordinates (Nx2) in the image,
    return the pixel value at each location using bilinear interpolation.
    """
    if len(img.shape) == 2:
        img = np.expand_dims(img, 2)
    xs, ys = coords[:, 0], coords[:, 1]
    pxs = np.floor(xs).astype(int)
    pys = np.floor(ys).astype(int)
    dxs = xs-pxs
    dys = ys-pys
    wxs, wys = 1.0-dxs, 1.0-dys
    
    weights =  np.multiply(img[pys, pxs, :].T      , wxs*wys).T
    weights += np.multiply(img[pys, pxs+1, :].T    , dxs*wys).T
    weights += np.multiply(img[pys+1, pxs, :].T    , wxs*dys).T
    weights += np.multiply(img[pys+1, pxs+1, :].T  , dxs*dys).T
    return weights