import networkx as nx

def crea_graf_rects(lr):
    g = nx.Graph()
    g.add_nodes_from(lr)
    for i in range(len(lr)):
        for j in range(i):
            x = lr[i] & lr[j]
            if x.color == 'negre':
                g.add_edge(lr[i], lr[j], àrea=x.amplada() * x.alçada())
    return g