imresize.py 文件源码

def contributions(in_length, out_length, scale, kernel, k_width):
    if scale < 1:
        h = lambda x: scale * kernel(scale * x)
        kernel_width = 1.0 * k_width / scale
    else:
        h = kernel
        kernel_width = k_width
    x = np.arange(1, out_length+1).astype(np.float64)
    u = x / scale + 0.5 * (1 - 1 / scale)
    left = np.floor(u - kernel_width / 2)
    P = int(ceil(kernel_width)) + 2
    ind = np.expand_dims(left, axis=1) + np.arange(P) - 1 # -1 because indexing from 0
    indices = ind.astype(np.int32)
    weights = h(np.expand_dims(u, axis=1) - indices - 1) # -1 because indexing from 0
    weights = np.divide(weights, np.expand_dims(np.sum(weights, axis=1), axis=1))
    aux = np.concatenate((np.arange(in_length), np.arange(in_length - 1, -1, step=-1))).astype(np.int32)
    indices = aux[np.mod(indices, aux.size)]
    ind2store = np.nonzero(np.any(weights, axis=0))
    weights = weights[:, ind2store]
    indices = indices[:, ind2store]
    return weights, indices