[搞点好玩的] JETSONNANO 受苦记 -- 004(摄像头启动)

学校终于解封了，看了个知乎上的人日合订本，咱们好好记录这个时代吧。
yahboom采用的是jetbot里面的一个camera.py脚本定义的各个接口，也是基于opencv的，但是里面原来是为了在jupyter notebook显示用的，这里是参照别人写了一个显示摄像头捕捉画面的代码，具体如下：

import cv2

def gstreamer_pipeline(
    capture_width=640,
    capture_height=640,
    display_width=224,
    display_height=224,
    framerate=24,
    flip_method=0,
):
    return (
        "nvarguscamerasrc ! "
        "video/x-raw(memory:NVMM), "
        "width=(int)%d, height=(int)%d, "
        "format=(string)NV12, framerate=(fraction)%d/1 ! "
        "nvvidconv flip-method=%d ! "
        "video/x-raw, width=(int)%d, height=(int)%d, format=(string)BGRx ! "
        "videoconvert ! "
        "video/x-raw, format=(string)BGR ! appsink"
        % (
            capture_width,
            capture_height,
            framerate,
            flip_method,
            display_width,
            display_height,
        )
    )
 
def show_camera():
    cap = cv2.VideoCapture(gstreamer_pipeline(flip_method=0), cv2.CAP_GSTREAMER)
 
    while cap.isOpened():
        flag, img = cap.read()
        cv2.imshow("CSI Camera", img)
        kk = cv2.waitKey(1)
 
        # do other things
 
        if kk == ord('q'): 
            break
 
    cap.release()
    cv2.destroyAllWindows()
    

'''
from jetbot import Camera
camera = Camera.instance(width=224, height=224)
import ipywidgets.widgets as widgets
image = widgets.Image(format='jpeg', width=224, height=224)
display(image)
from jetbot import bgr8_to_jpeg
import traitlets
camera_link = traitlets.dlink((camera, 'value'), (image, 'value'), transform=bgr8_to_jpeg)
'''

if __name__ == "__main__":
    show_camera()

显示的图片结果：

原始的camera.py代码内容：

import traitlets
from traitlets.config.configurable import SingletonConfigurable
import atexit
import cv2
import threading
import numpy as np


class Camera(SingletonConfigurable):
    
    value = traitlets.Any()
    
    # config
    width = traitlets.Integer(default_value=224).tag(config=True)
    height = traitlets.Integer(default_value=224).tag(config=True)
    fps = traitlets.Integer(default_value=21).tag(config=True)
    capture_width = traitlets.Integer(default_value=3280).tag(config=True)
    capture_height = traitlets.Integer(default_value=2464).tag(config=True)

    def __init__(self, *args, **kwargs):
        self.value = np.empty((self.height, self.width, 3), dtype=np.uint8)
        super(Camera, self).__init__(*args, **kwargs)

        try:
            self.cap = cv2.VideoCapture(self._gst_str(), cv2.CAP_GSTREAMER)

            re, image = self.cap.read()

            if not re:
                raise RuntimeError('Could not read image from camera.')

            self.value = image
            self.start()
        except:
            self.stop()
            raise RuntimeError(
                'Could not initialize camera.  Please see error trace.')

        atexit.register(self.stop)

    def _capture_frames(self):
        while True:
            re, image = self.cap.read()
            if re:
                self.value = image
            else:
                break
                
    def _gst_str(self):
        return 'nvarguscamerasrc ! video/x-raw(memory:NVMM), width=%d, height=%d, format=(string)NV12, framerate=(fraction)%d/1 ! nvvidconv ! video/x-raw, width=(int)%d, height=(int)%d, format=(string)BGRx ! videoconvert ! appsink' % (
                self.capture_width, self.capture_height, self.fps, self.width, self.height)
    
    def start(self):
        if not self.cap.isOpened():
            self.cap.open(self._gst_str(), cv2.CAP_GSTREAMER)
        if not hasattr(self, 'thread') or not self.thread.isAlive():
            self.thread = threading.Thread(target=self._capture_frames)
            self.thread.start()

    def stop(self):
        if hasattr(self, 'cap'):
            self.cap.release()
        if hasattr(self, 'thread'):
            self.thread.join()
            
    def restart(self):
        self.stop()
        self.start()