Found a bug in windows cmake when trying to recompile opencv – apparently it cannot reset the file date stamp correctly, so fails to uncompress the source zip, and the whole generation process crashes..

I fixed it in the opencv source by replacing this line in the OpenCVDownload.cmake file (under the cmake source folder) by using the 7zip software instead of default unzipper..

 

execute_process(COMMAND "${CMAKE_COMMAND}" -E tar xzf "${CACHE_CANDIDATE}"

with

 

execute_process(COMMAND 7z x "${CACHE_CANDIDATE}"

and making sure the path is set to the 7zip executable 7z.exe

This is a quick step-by-step guide for installing opencv

1) Backup your existing opencv build files

2) Install Code::Blocks http://www.codeblocks.org/downloads/26 select current version codeblocks-17.12-setup.exe

3) Install TDM-GCC – making sure the 64-bit version is selected http://tdm-gcc.tdragon.net/download

Note: compiler binary file path will be automatically added to your pc’s path environment.

4) Download the source of OpenCV 4.x.x from https://opencv.org/releases.html as a zip file

Create folders:

C:\opencv\source\
C:\opencv\build\

Unzip the downloaded zip file in the source folder c:\opencv\source\ just created, so you get a folder like C:\opencv\source\opencv-4.x.x

5) Install CMake (uninstall any previous version as major changes made) https://cmake.org/download/

6) Setup to build the binaries:

Open cmake, set source path to C:\opencv\source\opencv-4.x.x and binary path to C:\opencv\build.

Click Configure

Choose CodeBlock—MinGW Makefiles as compiler.

After configuring, options will appear in red, some of these need disabling..

Disable: WITH_MSMF, set ENABLE_PRECOMPILED_HEADERS=OFF, WITH_IPP=OFF WITH_TBB=OFF (these options are for visual studio)

WITH_OPENCL_D3D11_NV=OFF

Note: you can use cmake’s search tool to search for these option eg. enter IPP to disable WITH_IPP etc

Next select/click the Generate button.

A codeblocks project file (opencv.cbp) will be made in C:\opencv\build

7) Now build the binaries:

Open the opencv.cbp file in code::blocks

Go to “settings”, choose “compiler” and click “Toolchain executable”. In the “compiler’s installation directory” field choose C:\TDM-GCC-64\bin (binary folder of the TDM compiler installed earlier)

Set the following:

c compile: gcc.exe
c++ compiler: g++.exe (but see note below on handling C++ 11 ISO errors)
Linker for dynamic libs: g++.exe
linker for static libs: ar.exe

Then use Select build > select target > install

Then press the build button to start the building of the binaries – this can take hours to process.

Add C:\opencv\build\install\x64\mingw\bin to the system environment path

8) Now setup up code::blocks to compile an opencv program.

Go to settings -> compiler. Select “search directories” and in the “compiler” tab chose the followings:

C:\opencv\build\install\include
C:\opencv\build\install\include\opencv2

Select “Linker” tab and add “C:\opencv\build\install\x64\mingw\lib”

Go to “Linker Settings” and add all the libraries from “C:\opencv\build\install\x64\mingw\lib” folder so it looks like this..

9) Final configuration – on opencv 4.0.1 you might get a C++ 11 ISO error on compiling, so I recommend just adding this to the C++ compiler option under “Toolchain executable”. In the “compiler’s installation directory”:

c++ compiler: g++.exe -std=c++11

Edit your cpp code (remember to setup as console applications). Then build, then run.. and all been well your script will run on opencv (note many constant values have changed between opencv releases, so highly likely you will need to change your code)

Hope this is useful.

 

If you use youtube-dl or other similar youtube video downloading software for legally downloading videos you might get an error –  Unable to download Youtube videos – SSL: CERTIFICATE_VERIFY_FAILED

The following method fixed it for myself..

run certmgr.msc

 

 

 

 

menu -> action -> find certificates.

 

 

 

 

 

choose “look in fields: issued to”

On the “contains” field type enter “google”.

click “find now”

mark all the expired certs (sort by expiry date)

right click and choose “delete”

 

 

 

 

 

Now try using your video downloading software again – may now work fine.