★嵌入式ARM开发全套案例代码：https://pan.baidu.com/s/1ksCQN__jD8ZrJhw8sWzhwQ?pwd=vvfz

3.3. OpenCV 编译和安装

不少客户遇到OpenCV的问题多集中在如何获取mipi摄像头的数据。因为OpenCV使用的V4l2协议和Rockchip编写的mipi摄像头驱动协议不同，所以不能直接使用OpenCV的摄像头API。本节讲述如何编译Opencv并添加GStreamer API支持。

3.3.1. 要求

• OS： Ubuntu18.04 / Debian 10

• OpenCV version： 3.4.15

• Board: RK3399

3.3.2. 编译和安装

1. 搭建python3.7虚拟环境

   # 依次安装gcc和cmake等编译环境
   # 安装python3.7-tk 和 python3.7-dev
   # 安装virtualenv虚拟环境
   sudo apt install gcc cmake git build-essential \
   python3-tk python3.7-dev \
   virtualenv
   

2. 创建python3.7虚拟环境

   virtualenv -p /usr/bin/python3.7m /home/firefly/venv
   # 使用虚拟环境，如果想退出可以在终端输入 deactivate
   source /home/firefly/venv/bin/activate
   

3. 安装Opencv所需的环境包

   # 安装编译环境、gtk包和相关编解码库
   sudo apt install cmake build-essential libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev libtbb2 libtbb-dev libjpeg-dev libpng-dev libtiff-dev libdc1394-22-dev libjasper-dev# 注意！如果安装了rknn_toolkit(or lite)则不需要再安装Python-numpy，否则会导致rknn_toolkit(or lite)无法使用
   sudo apt install python-numpy
   

4. 下载Opencv

   # 创建文件夹
   mkdir opencv
   cd opencv# 下载 opencv-3.4.15.zip
   wget https://github.com/opencv/opencv/archive/refs/tags/3.4.15.zip
   unzip opencv-3.4.15.zip
   

5. 配置

   mkdir build
   cd build# 让 OpenCV 和 Python3 之间建立联系
   cmake -D CMAKE_BUILD_TYPE=RELEASE \
   -D 	PYTHON_DEFAULT_EXECUTABLE=$(python -c "import sys; print(sys.executable)")\
   -D PYTHON3_EXECUTABLE=$(python -c "import sys; print(sys.executable)")  \
   -D PYTHON3_NUMPY_INCLUDE_DIRS=$(python -c "import numpy; print (numpy.get_include())")  \
   -D PYTHON3_PACKAGES_PATH=$(python -c "from distutils.sysconfig import get_python_lib; print(get_python_lib())")  \
   ../opencv-3.4.15
   

6. 如需支持Gstreamer API，则进行以下配置操作否则跳过

   sudo apt install libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev
   cmake -D WITH_GSTREAMER=ON ../opencv-3.4.15
   

7. 编译安装

   # 如果板子内存不超过2G，建议不超过-j4
   make -j6
   # 安装的过程需要sudo权限
   sudo make install
   

3.3.3. 测试

1. 测试

   source /home/firefly/venv/bin/activate
   git clone https://gitlab.com/firefly-linux/test_code/rkisp-v4l2.git
   cd mipi_video_demo/OpenCV_Python
   python3 opencv_gst_test.py
   

2. opencv_gst_test.py 代码

   import numpy as np
   import cv2 as cv
   import os
   import timecap = cv.VideoCapture('v4l2src device=/dev/video1 ! video/x-raw, format=NV12, width=640, height=480, framerate=30/1 ! videoconvert ! appsink', cv.CAP_GSTREAMER)if not cap.isOpened():print("Cannot capture from camera. Exiting.")os._exit()
   last_time = time.time()while(True):ret, frame = cap.read()this_time = time.time()print (str((this_time-last_time)*1000)+'ms')last_time = this_time;cv.imshow('frame', frame)if cv.waitKey(1) & 0xFF == ord('q'):breakcap.release()
   cv.destroyAllWindows()