我如何使用 Kivy (Python) 相机

Question

I try to use uix.camera widget and show some wideo from my web-camera. I looked into the documentation and try to use this simply code. But it's just show me a white creen withoud any video (I enabled playing). What I'm doing wrong? Maybe some useful docs\\tutorial exist (because from official documentation I understanding a little from many). Thanks for any help.

import kivy
kivy.require('1.9.1')

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.camera import Camera

class MainApp(App):
    def build(self):
        return Camera(play=True)

if __name__== "__main__":
    MainApp().run()

Answer 1

You need to specify resolution. In my case, I also needed to specify index=1, that is the second camera plugged in my computer.

Example:

import kivy
kivy.require('1.9.1')

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.camera import Camera

class MainApp(App):
    def build(self):
        return Camera(play=True, index=1, resolution=(640,480))

if __name__== "__main__":
    MainApp().run()

Answer 2

除了play=True之外resolution=[x, y]您似乎还需要设置resolution=[x, y]属性，因为默认设置不起作用。

Answer 3

The following are the Kivy examples to use camera.

from kivy.app import App
from kivy.lang import Builder


kv = ''' 
BoxLayout:
    orientation: 'vertical'

    Camera:
        id: camera
        resolution: 399, 299

    BoxLayout:
        orientation: 'horizontal'
        size_hint_y: None
        height: '48dp'
        Button:
            text: 'Start'
            on_release: camera.play = True

        Button:
            text: 'Stop'
            on_release: camera.play = False
'''


class CameraApp(App):
    def build(self):
        return Builder.load_string(kv)


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

Example 2 :-

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_" + timestr)
        print("Captured")


class TestCamera(App):

    def build(self):
        return CameraClick()


TestCamera().run()

Answer 4

I just faced the same problem and found out that Kivy is very slow when creating widget for usb webcam device. If you have set the index and other parameters properly, maybe just waiting a little longer for Kivy to create the video widget then you could see the webcam view shows in the window, but I am still trying to find out the reason why Kivy takes so long time (about a minute) to create usb webcam widget, hope someone could give some advices about this problem.

Answer 5

I tried using the code as suggested by @Thiago. It didnt work, I suspect its not detecting my USB camera that I have plugged into my Raspberry Pi4.

Following is the code I am using and I also ran a query in the terminal to obtain the camera type that is plugged in (only one plugged in).

The Code:

import kivy

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.camera import Camera

class MainApp(App):
    def build(self):
        return Camera(play=True, index=0, resolution=(640,480))

if __name__== "__main__":
    MainApp().run()

Terminal Output:

pi@raspberrypi:~ $ v4l2-ctl --list-formats
ioctl: VIDIOC_ENUM_FMT
Type: Video Capture
[0]: 'MJPG' (Motion-JPEG, compressed)
[1]: 'YUYV' (YUYV 4:2:2)