primitives.py 文件源码

def get_arrow_im(pt, fColor=Color(0.0, 0.0, 0.0), arrowWidth=3.0):
    x, y = pt.x(), pt.y()
    sz   = int(np.ceil(max(abs(x), abs(y))))
    data = np.zeros((sz, sz, 4), dtype=np.uint8)
    surface = cairo.ImageSurface.create_for_data(data, 
                            cairo.FORMAT_ARGB32, sz, sz)
    cr      = cairo.Context(surface)
    #Create a transparent source
    cr.set_source_rgba(1.0, 1.0, 1.0, 0.0)
    cr.paint()
    #Start making the arrow
    cr.set_source_rgba(fColor.b, fColor.g, fColor.r, fColor.a)
    if x>=0 and y>=0:
        xSt, ySt = 0, 0
    elif x>0 and y < 0:
        xSt, ySt = 0, sz
    elif x <0 and y<0:
        xSt, ySt = sz, sz
    else:
        xSt, ySt = sz, 0
    stPoint = gm.Point(xSt, ySt) 
    cr.move_to(xSt, ySt)
    pt = pt + stPoint
    dirVec = pt - stPoint
    mag    = dirVec.mag()
    cr.line_to(pt.x(), pt.y())
    cr.set_line_width(arrowWidth)
    side1 = dirVec.rotate_point(-150)
    side1.scale(0.2)
    ang1  = pt + side1  
    cr.line_to(ang1.x(), ang1.y())
    side2 = dirVec.rotate_point(150)
    side2.scale(0.2)
    ang2  = pt + side2
    cr.move_to(pt.x(), pt.y())
    cr.line_to(ang2.x(), ang2.y())
    cr.stroke()
    return cr, data, stPoint