fit_center_rect.py

import math 

def fit_center_rect(total_length, item_length):

    ret_list = []

    float_fit = float(total_length)/item_length
    int_fit = int(math.ceil(float_fit))

    # add one to the count if we have an even number
    if int_fit % 2 == 0:
        int_fit += 1

    # calculate the protrusion beyong the edges
    protrusion = 0
    if int_fit > 1:
        protrusion = ((int_fit * item_length) - total_length)*.5

    for i in range(int_fit):
        p1 = max(0, (i * item_length - protrusion))
        p2 = min(total_length, (p1 + item_length))

        if i == 0:
            p2 -= protrusion

        ret_list.append((p1, p2))

    return ret_list


w = 400
h = 300

rw = 100
rh = 210


px_list = fit_center_rect(w, rw)
print(px_list)

py_list = fit_center_rect(h, rh)
print(py_list)