Building 32bit libraries opencv

Question

I recently downloaded and built opencv in my 64-bit Windows machine using cmake. All the binaries are included in the install folder and it contains only the folders as shown below:

I don't know how to config cmake to produce binaries for x86. I'm asking this, because I'm using Qt Creator 32bit with MinGW and I'm getting problems while linking and compiling the code. What's the proper way to do the build? I'm using mingw compiler suite.

Note: The downloaded package contains the pre-built binaries for x86 but there are none for MinGW, but only for Visual Studio.

Solution

Steps for mingw from with cmake-gui from this guide. We could also do this easily on command prompt with cmake and -m32 option. But using cmake-gui will give you more idea about the options available for opencv configuration and bring you in better position if you want to customize opencv build tomorrow ( like enabling java wrapper or OpenCL etc ).

1. Start cmake-gui.

2. Set source path to downloaded opencv directory and build path to your choice as in image

   

3. Click Configure button and specify generator as mingw makefiles as in image

   

4. Choose compilers ( here we choose 32 bit ) as in image and click Finish button.

5. An options page will be listed.

   5.1. Edit CMAKE_INSTALL_PREFIX to change the install location if you want to.

   5.2. Select ENABLE_CXX11 if it isn't already selected.

   5.3. Change other options only if you are familiar with them. Then click Configure again and then click 'Generate` to generate make files.

6. Modify opencv\sources\modules\videoio\src\cap_dshow.cpp and add this define at the top of the file:

   #define STRSAFE_NO_DEPRECATE
   

7. In command prompt( at build path ) type mingw32-make ( add mingw32-make folder to PATH if required )

8. On completion, type mingw32-make install