JetsonNano学习（四）OPENCV开启CSI摄像头

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前言

网上非常多的代码打不开的原因是要使用Python2!!!Python2!!!Python2!!!
可能是因为Gstreamer管道只适用于Python2

断电安装CSI摄像头，注意排线线缆的方向和正反。安装完成后上电开机

如果是USB摄像头，安装有手就行

一、检测摄像头是否安装好

JetsonNano终端输入：

ls -l /dev/video*

查看是否查询到: /dev/videoX

二、安装jetcam库

代码如下（示例）：

git clone https://github.com/NVIDIA-AI-IOT/jetcam
cd jetcam
sudo python3 setup.py install

三、示例程序

CSI摄像头_OpenCV（使用python2 编译）

import cv2

# 设置gstreamer管道参数
def gstreamer_pipeline(
    capture_width=1280, #摄像头预捕获的图像宽度
    capture_height=720, #摄像头预捕获的图像高度
    display_width=1280, #窗口显示的图像宽度
    display_height=720, #窗口显示的图像高度
    framerate=60,       #捕获帧率
    flip_method=0,      #是否旋转图像
):
    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,
        )
    )
 
if __name__ == "__main__":
    capture_width = 1280
    capture_height = 720
    display_width = 1280
    display_height = 720
    framerate = 60
    flip_method = 0
 
    # 创建管道
    print(gstreamer_pipeline(capture_width,capture_height,display_width,display_height,framerate,flip_method))
 
    #管道与视频流绑定
    cap = cv2.VideoCapture(gstreamer_pipeline(flip_method=0), cv2.CAP_GSTREAMER)
 
    if cap.isOpened():
        window_handle = cv2.namedWindow("CSI Camera", cv2.WINDOW_AUTOSIZE)
        
        # 逐帧显示
        while cv2.getWindowProperty("CSI Camera", 0) >= 0:
            ret_val, img = cap.read()
            cv2.imshow("CSI Camera", img)
 
            keyCode = cv2.waitKey(30) & 0xFF         
            if keyCode == 27:# ESC键退出
                break
 
        cap.release()
        cv2.destroyAllWindows()
    else:
        print("打开摄像头失败")

CSI摄像头_Jetcam （使用python2 编译）

from jetcam.csi_camera import CSICamera
camera = CSICamera(width=640, height=480)
image = camera.read()
import ipywidgets
from IPython.display import display
from jetcam.utils import bgr8_to_jpeg
image_widget = ipywidgets.Image(format='jpeg')
image_widget.value = bgr8_to_jpeg(image)
display(image_widget)
camera.running = True
def update_image(change):
    image = change['new']
    image_widget.value = bgr8_to_jpeg(image)    
camera.observe(update_image, names='value')
# 断开摄像头连接
camera.unobserve(update_image, names='value')

USB摄像头_OpenCV（使用python3 编译）

import cv2
 
if __name__ == "__main__":
 
    cap = cv2.VideoCapture(3)
 
    if cap.isOpened():
        window_handle = cv2.namedWindow("D435", cv2.WINDOW_AUTOSIZE)
        
        # 逐帧显示
        while cv2.getWindowProperty("D435", 0) >= 0:
            ret_val, img = cap.read()
            cv2.imshow("D435", img)
 
            keyCode = cv2.waitKey(30) & 0xFF         
            if keyCode == 27:# ESC键退出
                break
 
        cap.release()
        cv2.destroyAllWindows()
    else:
        print("打开摄像头失败")

常见问题

调用jetcam库显示RuntimeError: Could not read image from camera

修改usb_camera.py 和 csi_camera.py 20行：

#self.cap = cv2.VideoCapture(self._gst_str(), cv2.CAP_GSTREAMER)
self.cap = cv2.VideoCapture(self.capture_device)

然后重新安装jetcam

摄像头采集数据在jupyter notebook中显示错误

pip3 install ipywidgets
jupyter nbextension enable --py widgetsnbextension
jupyter labextension install @jupyter-widgets/jupyterlab-manager

参照JetsonNano学习（二）

程序编译出现绿屏

终端直接输入命令：

nvgstcapture-1.0

成功调用摄像头

但是程序编译出现绿屏

大概率未使用Python2编译