Installing OpenCV on Windows for Rust

Feburary 22 2023

I’m dying to install Infinite-Storage-Glitch on windows, but unfortunately the program requires an opencv dependency to compile.

Because Infinite-Storage-Glitch uses the opencv-rust library as a dependency, we can go to the windows package section of opencv-rust to see the windows installation instructions.

opencv-rust lists two options to install opencv:

Option 1 is to install it through the chocolatey package manager on Windows. However, chocolatey package maintainers often neglect to update their chocolatey packages, and so chocolatey packages fall behind in versioning. As of writing this article, version 4.7.0 of opencv has been out for 3 months, but the package is still not updated.
Option 2, is to install opencv-rust through vcpkg. However, this installation is is next to impossible, because vcpkg will recompile the entire windows operating system, leading to long-until-after-you-die-of-old-age compile times.

And so, Option 3, which I have created, is to directly navigate to https://opencv.org/releases/ and download the latest “windows” opencv installer.

How to Install the Official OpenCV Compiled Binary to Compile Rust Programs

Run the .exe installer. Choose an easy-to-reach download path, like C:\Users\user\Downloads.

Now we must set three environment variables.

1. Set the Required OpenCV Environment Variables to Compile Rust Programs

The steps listed here were inspired by https://github.com/twistedfall/opencv-rust/issues/118#issuecomment-619608278 and https://github.com/twistedfall/opencv-rust/issues/113#issue-596076777.

We need to create 3 environment variables: OPENCV_INCLUDE_PATHS, OPENCV_LINK_LIBS, and OPENCV_LINK_PATHS.

To create an environment variable, open the Windows Search Bar. Type edit environment variables for your account, then click enter. In the menu, under User variables for [your username], click on New....

The values for each of the 3 environment variable as of ver 4.7.0 are as follows:

OPENCV_LINK_LIBS=opencv_world470
OPENCV_LINK_PATHS=C:\Users\user\Downloads\opencv\build\x64\vc16\lib

The location of this path may have changed since 4.7.0. It should include the opencv_worldxxx.lib files, as well as various .cmake files.

OPENCV_INCLUDE_PATHS=C:\Users\user\Downloads\opencv\build\include

The location of this path may have changed since 4.7.0. It should include the opencv2 folder, and inside the opencv2 folder, there should be various .hpp and .h files.

Finally, we will install the opencv binary to our runtime path.

2. Add OpenCV to `PATH`

As of version 4.7.0, the path to the opencv executables are located at C:\Users\user\Downloads\opencv\build\x64\vc16\bin.

The location of this path may have changed since 4.7.0. It should include opencv_worldxxx.dll and opencv_worldxxx.pdb files, as well as various .exe and .dll files.

Open the Windows Search Bar. Type edit environment variables for your account, then click enter. In the menu, under User variables for [your username], click on Path. Here, click new, and press v while holding ctrl to paste in the path we have previously copied.

3. Install `clang` for Windows

Unfortunatey, opencv-rust still requires us to download and extract the clang compiler and add it to path. The easiest way to download clang is via the winget package manager: winget install llvm.

Alternatively, goto the LLVM downloads page. Next, find the latest llvm version. Click on the latest page link. Finally, click on the link with the label LLVM-x.x.x-win64.exe to download the file. Run the .exe and follow the instructions to extract its contents.

After the install, we must add clang’s bin directory to path. Copy the path C:\Program Files\LLVM\bin and add it to PATH.

4. Now try to compile any opencv project

Open a new terminal window, or if you are using a graphical editor restart the editor and the editor’s shell. Navigate to a Rust project that uses opencv as a dependency. Then type cargo run and hit enter for profit.

opencv for Rust has been the most convoluted program I’ve ever installed in all my life. Arch Linux install is easier as it’s actually documented. There’s no way it should be this difficult.