android中带有opencv的kivy相机应用程序显示黑屏

问题描述

我正在尝试在 Kivy 中构建基于 OpenCv 的相机 Android 应用:

I'm trying to build an camera Android app based on OpenCv in Kivy:

ma​​in.py

import kivy
from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.camera import Camera
import cv2
from kivy.uix.image import Image
from kivy.clock import Clock
from kivy.graphics.texture import Texture
import numpy as np

class KivyCamera(Image):
    def __init__(self, capture, fps, **kwargs):
        super(KivyCamera, self).__init__(**kwargs)
        self.capture = capture
        Clock.schedule_interval(self.update, 1.0 / fps)

    def update(self, dt):
        ret, frame = self.capture.read()

        if ret:
            # convert it to texture
            buf1 = cv2.flip(frame, 0)
            buf = buf1.tostring()
            image_texture = Texture.create(size=(frame.shape[1], frame.shape[0]), colorfmt='bgr')
            image_texture.blit_buffer(buf, colorfmt='bgr', bufferfmt='ubyte')
            # display image from the texture
            self.texture = image_texture

class MainApp(App):
    def build(self):
        self.capture = cv2.VideoCapture(0)
        self.camera = KivyCamera(capture=self.capture, fps=30)
        return self.camera

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

buildozer.spec

[app]
title = Test_app
package.name = myapp
package.domain = org.test
source.dir = .
source.include_exts = py,png,jpg,kv,atlas,xml
version = 0.1
requirements = python3,kivy,numpy,opencv
orientation = portrait

# Android specific
fullscreen = 0
android.permissions = INTERNET, ACCESS_FINE_LOCATION, WRITE_EXTERNAL_STORAGE, CAMERA
android.arch = armeabi-v7a
[buildozer]
log_level = 2
warn_on_root = 1

代码在 Windows 中成功运行.然后我用 buildozer for android 构建了代码，当我打开 Android 应用程序时，它显示一个黑屏，屏幕左角有一个小方块.我认为 cv2.VideoCapture() 工作不正常.所以我将 cv2.VideoCapture(0) 更改为 cv2.VideoCapture(-1) 和 cv2.VideoCapture(1).但两者都不起作用.

Code works successfully in windows. Then i have build the the code with buildozer for android, when I open the Android App it shows a black screen with a small square in the left corner of the screen. I think the cv2.VideoCapture() is not working properly.So I change cv2.VideoCapture(0) to cv2.VideoCapture(-1) and to cv2.VideoCapture(1). But both doesn't work.

谁能帮我解决这个问题?

Can anyone help me out with this ?

推荐答案

我有 2 个解决方案可以让它在 Android 上运行.

I have 2 solutions to get it to work on Android.

解决方案 1:

我的灵感来自 GitHub 上的 kivy-for-android-opencv-demo:链接！因为 Kivy 不再支持 Python2，所以这里是我针对 Python3 的解决方案.

I was inspired by kivy-for-android-opencv-demo, found on GitHub: link! Because Kivy no longer supports Python2, here is my solution for Python3.

main.py

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.graphics.texture import Texture
from kivy.uix.camera import Camera
from kivy.lang import Builder
import numpy as np
import cv2

Builder.load_file("myapplayout.kv")

class AndroidCamera(Camera):
    camera_resolution = (640, 480)
    counter = 0

    def _camera_loaded(self, *largs):
        self.texture = Texture.create(size=np.flip(self.camera_resolution), colorfmt='rgb')
        self.texture_size = list(self.texture.size)

    def on_tex(self, *l):
        if self._camera._buffer is None:
            return None
        frame = self.frame_from_buf()
        self.frame_to_screen(frame)
        super(AndroidCamera, self).on_tex(*l)

    def frame_from_buf(self):
        w, h = self.resolution
        frame = np.frombuffer(self._camera._buffer.tostring(), 'uint8').reshape((h + h // 2, w))
        frame_bgr = cv2.cvtColor(frame, 93)
        return np.rot90(frame_bgr, 3)

    def frame_to_screen(self, frame):
        frame_rgb = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
        cv2.putText(frame_rgb, str(self.counter), (20, 50), cv2.FONT_HERSHEY_SIMPLEX, 1, (0, 255, 0), 2, cv2.LINE_AA)
        self.counter += 1
        flipped = np.flip(frame_rgb, 0)
        buf = flipped.tostring()
        self.texture.blit_buffer(buf, colorfmt='rgb', bufferfmt='ubyte')

class MyLayout(BoxLayout):
    pass

class MyApp(App):
    def build(self):
        return MyLayout()

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

myappayout.kv

myapplayout.kv

<MyLayout>
    orientation: 'vertical'
    size: root.width, root.height

    AndroidCamera:
        index: 0
        resolution: self.camera_resolution
        allow_stretch: True
        play: True

在 buildozer.spec 中:

in buildozer.spec:

requirements = python3,kivy==2.0.0,opencv==4.5.2,numpy
android.permissions = CAMERA

解决方案 2:

Solution 2:

我从显示的相机图像的小部件中获取帧，每秒 4 次.如果您不需要每一个框架，并且不需要在框架顶部绘制文本或框等内容，那么这是一个简单的解决方案.

I get the frame from the widget of the displayed camera image, 4 times a second. If you don't need every single frame, and it's not necessary to draw things like text or boxes on top of the frames, then it's an easy solution.

main.py

from kivy.app import App
from kivy.uix.camera import Camera
from kivy.uix.boxlayout import BoxLayout
from kivy.lang import Builder
from kivy.clock import Clock
import numpy as np
import cv2

Builder.load_file('myapplayout.kv')

class AndroidCamera(Camera):
    camera_resolution = (640, 480)
    cam_ratio = camera_resolution[0] / camera_resolution[1]

class MyLayout(BoxLayout):
    pass


class MyApp(App):
    counter = 0

    def build(self):
        return MyLayout()

    def on_start(self):
        Clock.schedule_once(self.get_frame, 5)

    def get_frame(self, dt):
        cam = self.root.ids.a_cam
        image_object = cam.export_as_image(scale=round((400 / int(cam.height)), 2))
        w, h = image_object._texture.size
        frame = np.frombuffer(image_object._texture.pixels, 'uint8').reshape(h, w, 4)
        gray = cv2.cvtColor(frame, cv2.COLOR_RGBA2GRAY)
        self.root.ids.frame_counter.text = f'frame: {self.counter}'
        self.counter += 1
        Clock.schedule_once(self.get_frame, 0.25)

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

myappayout.kv

myapplayout.kv

<MyLayout>:
    orientation: 'vertical'
    size: root.width, root.height

    GridLayout:
        rows: 2

        RelativeLayout:
            size_hint: 1, 0.8

            AndroidCamera:
                index: 0
                id: a_cam
                resolution: self.camera_resolution
                allow_stretch: True
                play: True
                canvas.before:
                    PushMatrix
                    Rotate:
                        angle: -90
                        origin: self.center
                    Scale:
                        x: self.cam_ratio
                        y: self.cam_ratio
                        origin: self.center
                canvas.after:
                    PopMatrix

        Label:
            size_hint: 1, 0.2
            id: frame_counter
            font_size: self.height * 0.4
            text: ''

buildozer.spec 与解决方案 1 中的相同.

The buildozer.spec is the same as in solution 1.

最后，安装后别忘了给相机添加权限.(我的代码中没有包含权限请求.)

Finally, don't forget to add permission to camera after installation. (No permission request is included in my code.)

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