adwellj/opencv4nodejs install.md

## opencv4nodejs install.md

      
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              opencv4nodejs install.md
            
          
    Installation

Start with node-gyp

You can install with npm:
$ npm install -g node-gyp
You will also need to install:
On Windows

Option 1 (what I've used)

From an elevated PowerShell or CMD.exe (run as Administrator), install all the required tools and configurations using Microsoft's windows-build-tools using npm install --global --production windows-build-tools.
If you already have Visual Studio installed, then Visual Studio Build Tools may fail. In that case launch cmd and enter npm config set msvs_version 2017.
Option 2

Install tools and configuration manually:

Install Visual C++ Build Environment: Visual Studio Build Tools
(using "Visual C++ build tools" workload) or Visual Studio 2017 Community
(using the "Desktop development with C++" workload)
Install Python 2.7 (v3.x.x is not supported), and run npm config set python python2.7 (or see below for further instructions on specifying the proper Python version and path.)
Launch cmd, npm config set msvs_version 2017

If the above steps didn't work for you, please visit Microsoft's Node.js Guidelines for Windows for additional tips.
If you have multiple Python versions installed, you can identify which Python
version node-gyp uses by setting the '--python' variable:
$ node-gyp --python /path/to/python2.7
If node-gyp is called by way of npm, and you have multiple versions of
Python installed, then you can set npm's 'python' config key to the appropriate
value:
$ npm config set python /path/to/executable/python2.7
If windows-build-tools was installed, the Python 2.7 path should be C:\Users\<user>\.windows-build-tools\python27\.
Use the command below to check npm's 'python' config key value:
$ npm config get python

Install CMake

Download and install x64 version from: CMake Downloads
Add to PATH during install
Will need to execute remaining commands in new terminal for cmake to be recognized. Use cmake --version to confirm that it's installed and available.

Install opencv4nodejs:

Auto build

Verify that git is installed by using git --version; install if necessary.
If you do not want to set up OpenCV on your own you can simply let this package auto install OpenCV 3.4 + OpenCV contrib 3.4 (might take some time):
$ npm i -g opencv4nodejs
I've gotten errors about Visual Studio on a clean install (using just the windows-build-tools; not Visual Studio), and resolved that with a restart. I had also installed Visual Studio Build Tools, but the restart might have been all that was needed.
In order to prevent build errors during an npm install, your package.json should not include opencv4nodejs, and instead should include/require the global package either by requiring it by absolute path or setting the NODE_PATH environment variable to /usr/lib/node_modules in your Dockerfile and requiring the package as you normally would.
I chose to add a NODE_PATH environment variable. The install path will be displayed in the output of the previous command, but for me it was in C:\Users\<user>\AppData\Roaming\npm\node_modules.