def _mkanchors(ws, hs, x_ctr, y_ctr):
    """Given a vector of widths (ws) and heights (hs) around a center
    (x_ctr, y_ctr), output a set of anchors (windows).
    """
    ws = ws[:, np.newaxis]
    hs = hs[:, np.newaxis]
    anchors = np.hstack(
        (
            x_ctr - 0.5 * (ws - 1),
            y_ctr - 0.5 * (hs - 1),
            x_ctr + 0.5 * (ws - 1),
            y_ctr + 0.5 * (hs - 1)
        )
    )
    return anchors
Given a vector of widths (ws) and heights (hs) around a center
    (x_ctr, y_ctr), output a set of anchors (windows).
    
detectron/modeling/generate_anchors.py