opencv 的 Python/Kivy 相机小部件错误

我一直在尝试制作一个打开设备相机的应用程序，但出现此错误：

    [CRITICAL          ] [Camera      ] Unable to find any valuable Camera provider at all!
videocapture - ImportError: No module named VideoCapture
  File "C:\Users\Gaston\Downloads\Kivy-1.9.0-py2.7-win32-x86\kivy27\kivy\core\__init__.py", line 57, in core_select_lib
    fromlist=[modulename], level=0)
  File "C:\Users\Gaston\Downloads\Kivy-1.9.0-py2.7-win32-x86\kivy27\kivy\core\camera\camera_videocapture.py", line 15, in <module>
    from VideoCapture import Device

opencv - ImportError: No module named cv
  File "C:\Users\Gaston\Downloads\Kivy-1.9.0-py2.7-win32-x86\kivy27\kivy\core\__init__.py", line 57, in core_select_lib
    fromlist=[modulename], level=0)
  File "C:\Users\Gaston\Downloads\Kivy-1.9.0-py2.7-win32-x86\kivy27\kivy\core\camera\camera_opencv.py", line 20, in <module>
    import cv

尝试安装 opencv 但仍然无法正常工作。我的代码与kivy中的代码示例相同docs:

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.boxlayout import BoxLayout
import time
Builder.load_string('''
<CameraClick>:
    orientation: 'vertical'
    Camera:
        id: camera
        resolution: (640, 480)
        play: False
    ToggleButton:
        text: 'Play'
        on_press: camera.play = not camera.play
        size_hint_y: None
        height: '48dp'
    Button:
        text: 'Capture'
        size_hint_y: None
        height: '48dp'
        on_press: root.capture()
''')


class CameraClick(BoxLayout):
    def capture(self):
        '''
        Function to capture the images and give them the names
        according to their captured time and date.
        '''
        camera = self.ids['camera']
        timestr = time.strftime("%Y%m%d_%H%M%S")
        camera.export_to_png("IMG_{}.png".format(timestr))
        print("Captured")


class TestCamera(App):

    def build(self):
        return CameraClick()


TestCamera().run()