Error configuring OpenCV project with CMake on Windows - opencv

Question

I used the prebuilt OpenCV 3.0.0 version. It works when I create a Visual Studio project directly, and when I add include and library directories.
Now I am making a CMakeList.txt file (so that I can run the same code on different systems). It will be used to create the Visual Studio project on Windows, and Makefile on Unixes, etc.
cmake_minimum_required(VERSION 2.8)
project( Facade )
find_package( OpenCV REQUIRED )
add_executable( Facade grammar.cpp )
target_link_libraries( Facade ${OpenCV_LIBS} )
When I generate the Visual Studio file on Windows, I got the following error:
CMake Warning at C:/opencv/build/OpenCVConfig.cmake:166 (message):
Found OpenCV Windows Pack but it has no binaries compatible with your
configuration.
You should manually point CMake variable OpenCV_DIR to your build of OpenCV
library.
Call Stack (most recent call first):
CMakeLists.txt:3 (find_package)
CMake Error at CMakeLists.txt:3 (find_package):
Found package configuration file:
C:/opencv/build/OpenCVConfig.cmake
but it set OpenCV_FOUND to FALSE so package "OpenCV" is considered to be
NOT FOUND.
Currently, OpenCV_DIR is C:\opencv\build, where it holds the CMake files. If I point OpenCV_DIR to C:\opencv\build\x64\vc12, it says, can't find CMake files.
How do I fix this?

Answer 1

What generator string did you use for the CMake configuration step? For VC12 x64, you need to use -G "Visual Studio 12 Win64" (if you were using CMake 3, you would use -G "Visual Studio 12 2013 Win64"). Note that you need to include Win64 at the end to get the x64 platform.
It is rather convenient that the OpenCV CMake config script is checking to make sure you are using the x64 binaries. You configured CMake to build 32-bit binaries, which would cause a runtime error if you were able to get an executable built.

Answer 2

Just in case anybody else has this problem, I got it from using old CMake config scripts. With VS2017 installed, I was getting this error- turns out that some auto-generated CMAKE configs have something like this:
elseif(MSVC_VERSION EQUAL 1910)
set(OpenCV_RUNTIME vc15)
I checked MSVC_VERSION and it was 1916, which is still VC15, but the files erroneously missed that. I changed to:
elseif((MSVC_VERSION EQUAL 1910) OR (MSVC_VERSION GREATER 1910))
set(OpenCV_RUNTIME vc15)
and it worked like a charm.