CMake 在编译使用 OpenCV 的项目时遇到问题

Question

我使用的是 Linux Mint 19.1 Tessa。

我按照here 中的说明安装 OpenCV。现在我将它安装在目录“/home/dell/opencv”中。

我尝试通过运行命令“cmake”来运行位于“/home/dell/opencv/samples/cpp/example_cmake/”的示例项目。在终端上，我收到以下错误：

CMake Error at CMakeLists.txt:14 (find_package):
  By not providing "FindOpenCV.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "OpenCV", but
  CMake did not find one.

  Could not find a package configuration file provided by "OpenCV" with any
  of the following names:

    OpenCVConfig.cmake
    opencv-config.cmake

  Add the installation prefix of "OpenCV" to CMAKE_PREFIX_PATH or set
  "OpenCV_DIR" to a directory containing one of the above files.  If "OpenCV"
  provides a separate development package or SDK, be sure it has been
  installed.


-- Configuring incomplete, errors occurred!
See also "/home/dell/opencv/samples/cpp/example_cmake/CMakeFiles/CMakeOutput.log".

“CMakeLists.txt”文件包含以下内容：

# cmake needs this line
cmake_minimum_required(VERSION 3.1)

# Enable C++11
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED TRUE)

# Define project name
project(opencv_example_project)

# Find OpenCV, you may need to set OpenCV_DIR variable
# to the absolute path to the directory containing OpenCVConfig.cmake file
# via the command line or GUI
find_package(OpenCV REQUIRED)

# If the package has been found, several variables will
# be set, you can find the full list with descriptions
# in the OpenCVConfig.cmake file.
# Print some message showing some of them
message(STATUS "OpenCV library status:")
message(STATUS "    config: ${OpenCV_DIR}")
message(STATUS "    version: ${OpenCV_VERSION}")
message(STATUS "    libraries: ${OpenCV_LIBS}")
message(STATUS "    include path: ${OpenCV_INCLUDE_DIRS}")

# Declare the executable target built from your sources
add_executable(opencv_example example.cpp)

# Link your application with OpenCV libraries
target_link_libraries(opencv_example LINK_PRIVATE ${OpenCV_LIBS})

我在互联网上搜索了很多，这似乎是一个常见问题。但是，按照我找到的说明，我仍然没有设法解决它。

我在浏览 OpenCV 文件夹时注意到的一件事是我拥有的版本（我认为它是最新的）确实不包含任何“OpenCVConfig.cmake”文件，如您所见 @987654322 @。但是，我在 github 上找到的最旧版本的 OpenCV 有这个文件，你可以看到 here。

那么，也许某些配置设置为这个最旧的版本并导致冲突？如何更改它并使其适用于最新版本？我认为这一定很容易解决，但我是新手。

提前致谢。

Answer 1

CMake 会告诉你该怎么做：

将“OpenCV”的安装前缀添加到CMAKE_PREFIX_PATH或设置 “OpenCV_DIR”到包含上述文件之一的目录。

另一种选择 - 请再次阅读您粘贴的文件 CMakeLists.txt 中的 cmets。

他们说：

您可能需要设置 OpenCV_DIR 变量 到包含 OpenCVConfig.cmake 的目录的绝对路径

另一个问题 - 源代码构建，通过将点传递给 cmake 来执行。最好为构建文件创建单独的目录。

以这种方式构建可以让您轻松地将构建目录添加到.gitignore，并且不会使用已编译的二进制文件污染您的源代码存储库。此外，如果出现问题，您可以删除该构建目录并从头开始。这比一个一个地处理文件要容易得多。

所以，你需要像下面这样调用 CMake

mkdir build
cd build 
OpenCV_DIR=/home/dell/opencv cmake ..

或

mkdir build
cd build
cmake .. -DCMAKE_PREFIX_PATH=/home/dell/opencv

或者以下也可以解决问题

mkdir build
cd build
cmake .. -DOpenCV_DIR=/home/dell/opencv

Answer 2

如下更新您的 OpenCV 搜索目录路径，

find_package(OpenCV 3.4 REQUIRED PATHS "/usr/local/opencv/" NO_DEFAULT_PATH)