GAMES101 OpenCV环境安装

Opencv 库编译

作业2中用到了OpenCV

Step 1.下载源码

1. 下载OpenCV 源码 OpenCV 4.5.4
2. 下载OpenCV_contrib OpenCV_contrib 4.5.4
   注意：这两个源码的版本号要一致

Step 2. 使用CMake编译

1. 将源码解压后，不要放在有中文路径的目录
2. 使用管理员权限打开CMake, 一开始未使用，发现点击Configure时会报错，使用管理员权限打开CMake后，点击Configure未报错。
3. 源码目录：opencv-4.5.4
4. build目录：OpenCV_build(以下简称build目录)
   

注意：选择版本，我这里是x64 版本。
为什么要选x64版本原因

“因为代码中有使用std::optional这个特性，这个特性是c  17中才有的，这个坑反应了好久才找到原因。
改完之后发现使用默认的x86设置，std::optional依然会报错，所以选了x64之后，环境就彻底配好了。所以第一步对应的库也要安装64位的。”

Step3. 解决CMake 过程中的报错

上述在Config过程中，会报很多错误，主要是一些下载的原因：

错误1： 错误的Python版本:

CMake’s ‘find_host_package(PythonInterp 2.7)’ found wrong Python version

Found PythonInterp: C:/Program Files/Python310/python.exe (found suitable version "3.10.11", minimum required is "2.7") 
CMake Warning at cmake/OpenCVDetectPython.cmake:81 (message):
  CMake's 'find_host_package(PythonInterp 2.7)' found wrong Python version:

  PYTHON_EXECUTABLE=C:/Program Files/Python310/python.exe

  PYTHON_VERSION_STRING=3.10.11

  Consider providing the 'PYTHON2_EXECUTABLE' variable via CMake command line
  or environment variables

Call Stack (most recent call first):
  cmake/OpenCVDetectPython.cmake:271 (find_python)
  CMakeLists.txt:622 (include)
  

错误1 解决办法

修改opencv-4.5.4\cmake\OpenCVDetectPython.cmake最后部分内容

if(PYTHON_DEFAULT_EXECUTABLE)
    set(PYTHON_DEFAULT_AVAILABLE "TRUE")
elseif(PYTHON3_EXECUTABLE AND PYTHON3INTERP_FOUND)
    # Use Python 3 as default Python interpreter
    set(PYTHON_DEFAULT_AVAILABLE "TRUE")
    set(PYTHON_DEFAULT_EXECUTABLE "${PYTHON3_EXECUTABLE}")
elseif(PYTHON2_EXECUTABLE AND PYTHON2INTERP_FOUND)
    # Use Python 2 as fallback Python interpreter (if there is no Python 3)
    set(PYTHON_DEFAULT_AVAILABLE "TRUE")
    set(PYTHON_DEFAULT_EXECUTABLE "${PYTHON2_EXECUTABLE}")
endif()

参考链接1.How to use Cmake to build opencv with python 3 instead of python 2
参考链接2.Install OpenCV GPU with CUDA for Windows10

错误2：下载ippicv_2020_win_ia32_20191018_general.zip失败

Download: ippicv_2020_win_intel64_20191018_general.zip
Download failed

IPPICV: Download: ippicv_2020_win_intel64_20191018_general.zip
Try 1 failed
CMake Warning at cmake/OpenCVDownload.cmake:202 (message):
  IPPICV: Download failed: 35;"SSL connect error"

  For details please refer to the download log file:

  C:/Resource/OpenCV/OpenCV_build/CMakeDownloadLog.txt

Call Stack (most recent call first):
  3rdparty/ippicv/ippicv.cmake:37 (ocv_download)
  cmake/OpenCVFindIPP.cmake:259 (download_ippicv)
  cmake/OpenCVFindLibsPerf.cmake:12 (include)
  CMakeLists.txt:727 (include)

错误2 解决办法

1. 下载ippicv_2020_win_intel64_20191018_general.zip压缩文件
   打开build目录下的CMakeDownloadLog.txt文件，里面会提示下载的链接，

https://raw.githubusercontent.com/opencv/opencv_3rdparty/xxxxxx/ippicv/ippicv_2020_win_intel64_20191018_general.zip

2. 拷贝压缩文件
   直接在浏览器内下载下来，然后将文件保存到opencv-4.5.4/3dparty/ippicv文件夹中
   
3. 修改ippicv.cmake 文件

  set(THE_ROOT "${OpenCV_BINARY_DIR}/3rdparty/ippicv")
  # ocv_download(FILENAME ${OPENCV_ICV_NAME}
               # HASH ${OPENCV_ICV_HASH}
               # URL
                 # "${OPENCV_IPPICV_URL}"
                 # "$ENV{OPENCV_IPPICV_URL}"
                 # "https://raw.githubusercontent.com/opencv/opencv_3rdparty/${IPPICV_COMMIT}/ippicv/"
               # DESTINATION_DIR "${THE_ROOT}"
               # ID IPPICV
               # STATUS res
               # UNPACK RELATIVE_URL)

错误3：ffmpeg相关文件下载失败

opencv_videoio_ffmpeg.dll
opencv_videoio_ffmpeg_64.dll
ffmpeg_version.cmake

FFMPEG: Download: opencv_videoio_ffmpeg.dll
Try 1 failed
CMake Warning at cmake/OpenCVDownload.cmake:202 (message):
  FFMPEG: Download failed: 35;"SSL connect error"

  For details please refer to the download log file:

  C:/Resource/OpenCV/OpenCV_build/CMakeDownloadLog.txt

Call Stack (most recent call first):
  3rdparty/ffmpeg/ffmpeg.cmake:20 (ocv_download)
  modules/videoio/cmake/detect_ffmpeg.cmake:14 (download_win_ffmpeg)
  modules/videoio/cmake/init.cmake:7 (include)
  modules/videoio/cmake/init.cmake:11 (add_backend)
  cmake/OpenCVModule.cmake:298 (include)
  cmake/OpenCVModule.cmake:361 (_add_modules_1)
  cmake/OpenCVModule.cmake:385 (ocv_glob_modules)
  CMakeLists.txt:917 (ocv_register_modules)


FFMPEG: Download: opencv_videoio_ffmpeg_64.dll
Try 1 failed
CMake Warning at cmake/OpenCVDownload.cmake:202 (message):
  FFMPEG: Download failed: 35;"SSL connect error"

  For details please refer to the download log file:

  C:/Resource/OpenCV/OpenCV_build/CMakeDownloadLog.txt

Call Stack (most recent call first):
  3rdparty/ffmpeg/ffmpeg.cmake:20 (ocv_download)
  modules/videoio/cmake/detect_ffmpeg.cmake:14 (download_win_ffmpeg)
  modules/videoio/cmake/init.cmake:7 (include)
  modules/videoio/cmake/init.cmake:11 (add_backend)
  cmake/OpenCVModule.cmake:298 (include)
  cmake/OpenCVModule.cmake:361 (_add_modules_1)
  cmake/OpenCVModule.cmake:385 (ocv_glob_modules)
  CMakeLists.txt:917 (ocv_register_modules)


FFMPEG: Download: ffmpeg_version.cmake
Try 1 failed
CMake Warning at cmake/OpenCVDownload.cmake:202 (message):
  FFMPEG: Download failed: 35;"SSL connect error"

  For details please refer to the download log file:

  C:/Resource/OpenCV/OpenCV_build/CMakeDownloadLog.txt

Call Stack (most recent call first):
  3rdparty/ffmpeg/ffmpeg.cmake:20 (ocv_download)
  modules/videoio/cmake/detect_ffmpeg.cmake:14 (download_win_ffmpeg)
  modules/videoio/cmake/init.cmake:7 (include)
  modules/videoio/cmake/init.cmake:11 (add_backend)
  cmake/OpenCVModule.cmake:298 (include)
  cmake/OpenCVModule.cmake:361 (_add_modules_1)
  cmake/OpenCVModule.cmake:385 (ocv_glob_modules)
  CMakeLists.txt:917 (ocv_register_modules)

错误3 解决办法

1. 下载缺失的两个文件
   参考CMakeDownloadLog.txt 里面的链接下载dll文件， ffmpeg_version.cmake的链接另存为文件，最后得到三个文件，如下所示：
   
2. 复制文件到opencv-4.5.4/3dparty/ffmepg目录
   
3. 修改ffmpeg.cmake文件

 set(status TRUE)
  # foreach(id ${ids})
    # ocv_download(FILENAME ${name_${id}}
               # HASH ${FFMPEG_FILE_HASH_${id}}
               # URL
                 # "$ENV{OPENCV_FFMPEG_URL}"
                 # "${OPENCV_FFMPEG_URL}"
                 # "https://raw.githubusercontent.com/opencv/opencv_3rdparty/${FFMPEG_BINARIES_COMMIT}/ffmpeg/"
               # DESTINATION_DIR ${FFMPEG_DOWNLOAD_DIR}
               # ID FFMPEG
               # RELATIVE_URL
               # STATUS res)
    # if(NOT res)
      # set(status FALSE)
    # endif()
  # endforeach()

但仍然不够，到这里再次执行Configure时，会继续报错：

  CMake Error at modules/videoio/cmake/detect_ffmpeg.cmake:16 (include):
  include could not find requested file:

    C:/Resource/OpenCV/OpenCV_build/3rdparty/ffmpeg/ffmpeg_version.cmake
Call Stack (most recent call first):
  modules/videoio/cmake/init.cmake:7 (include)
  modules/videoio/cmake/init.cmake:11 (add_backend)
  cmake/OpenCVModule.cmake:298 (include)
  cmake/OpenCVModule.cmake:361 (_add_modules_1)
  cmake/OpenCVModule.cmake:385 (ocv_glob_modules)
  CMakeLists.txt:917 (ocv_register_modules)

参考链接Error at modules/videoio/cmake/detect_ffmpeg.cmake
网友的解决方案

I have encountered the same problem,mainly because cmake can't find ffmpeg_version.cmake file：
the src code file has a 3rdparty, 
and your build dir has a 3rdparty, 
cmake only search your build dir for ffmpeg_version.cmake, 
so just copy the src 3rdparty's ffmpeg to the build dir's 3rdparty. bingo! problem fixed.

因此，按照上述描述，将opencv-4.5.4/3rdparty/ffmpeg整个文件夹拷贝到build目录下的3rdparty目录下，如下所示：

Step 4. 配置opencv_contrib

继续报错

在配置opencv_contrib后，点击configure,会继续报错，还是因为没有下载成功的原因，
主要是wechat_qrcode 和 xfeatures2d 相关的文件。根据CMakeDownloadLog.txt里面的提示链接，手动下载缺失的文件，最后存放到build目录下的downloads目录下对应的文件夹：最后文件夹里面的文件如下所示。

• wechat_qrcode
  

• xfeatures2d
  
  至此，再次点击Congifure后，没有出现错误。

Step 5. 选择BUILD_opencv_world选项

这样，最后的库文件是一个dll文件。
OpenCV cmake配置项BUILD_opencv_world的说明

按照默认的CMakeLists.txt配置，BUILD_opencv_world默认是OFF状态，没有勾选。
编译生成的项目，会在build\lib\Debug目录下生成大量的lib和dll文件。
例如：有时网上设置项目环境时有人在链接器附加依赖项时需添加下列lib，当照着配置后会报错找不到…lib,在你的/x64/lib文件夹下压根没这些东西是因为你在编译的时候勾选了BUILD_opencv_world。
CMake中有一个选项名为BUILD_opencv_world，默认是不勾选的，它可以把所有的组件综合到一个名为opencv_world310d.lib或opencv_world310.lib的文件中，使以后配置工程时输入此单一文件即可。

如果编译成功，会生成下面两个lib

Step 6. 点击Generate

如果成功，显示Generate done.

  Install to:                    C:/Resource/OpenCV/OpenCV_build/install
-----------------------------------------------------------------

Configuring done
Generating done

生成OpenCV.sln工程

Step 7. 编译OpenCV.sln工程

菜单栏->生成->选择生成的项目配置。
注意：这里如果没有安装Python的Debug版本，在编译的时候，会报错。

编译时遇到的报错

LINK : fatal error LNK1104: 无法打开文件“python310_d.lib”

报错的原因参考无法打开pythonxxx_d.lib

所以应该是安装Python的时候，没有选择Debug版本。后来我重新卸载了已安装的Python，重新安装时选择Python Debug版本。
重新编译后成功

编译成功后生成的库和dll,以及include

• install
  里面是我们需要的lib、dll以及头文件
  
  

添加环境变量

系统属性->环境变量->Path->添加opencv 库路径

测试是否安装成功

新建一个空的工程：

• 设置工程属性
  

• Demo

#include	<iostream>
#include	<opencv2/opencv.hpp>

using namespace cv;
using namespace std;

int main() {
	Mat img = imread("C:\\Resource\\OpenCV\\OpenCV_Project\\OpenCVTest\\x64\\Debug\\scenetext01.jpg");
	imshow("img", img);
	waitKey();
}

• 输出
  

• 弹出的INFO信息
  
  关于这些信息

• 如何避免这些错误
  参考这个网友提供的，我猜是因为Configure的时候没有勾选相关的内容勾选相关选项
  
  但是我这里没有试验，因为编译库的话又要好久~~

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