kivy画个半圆

from kivy.uix.boxlayout import BoxLayout
from kivy.app import App

class BoxLayoutWidget(BoxLayout):
    def __init__(self,**kwargs):
        super().__init__(**kwargs)

class BoxLayoutApp(App):
    def build(self):
        return BoxLayoutWidget()

if __name__ == '__main__':
    BoxLayoutApp().run()

=======================kv====================

<BoxLayoutWidget>:
    canvas:
        Color:
            rgba:[1,1,1,1]
        # 椭圆
        Ellipse:
            size:self.width*0.5,self.height*0.15
            pos:self.x+100,self.y+1
            source:'back.jpg'
            # 开始角度12点方向开始   end>start逆时针画
            angle_start:0
            # 结束角度
            angle_end:45
        
    ScatterLayout:
        Button:
            text:'1'
            size_hint:[.1,.1]