Failed to build opencv4nodejs with precompiled 4.1.1

[RomanVeretenov]

Error Message

Error: Cannot find module '.../node_modules/@u4/opencv4nodejs/build/Release/opencv4nodejs'

Steps to reproduce:

• I have installed the prebuilt opencv for jetson 4.1.1 (available through specific NVIDIA debian repositories, but it seems that the problem isn't connected espetially with NVIDIA prebuilt binaries).
• I have set the following variables

export OPENCV4NODEJS_DISABLE_AUTOBUILD=1
export OPENCV4NODEJS_AUTOBUILD_OPENCV_VERSION=4.1.1

• I run npm i @u4/opencv4nodejs
• I get no error messages, everything seems to be working ok
• I run the following command to test a binding
  node -e "const cv = require('@u4/opencv4nodejs'); const cap = new cv.VideoCapture('./video.mp4'); const im = cap.read(); console.log(im)"
• I get the following error stack

<...>/node_modules/@u4/opencv4nodejs/lib/cvloader.js:62
            throw err;
            ^

Error: Cannot find module '<...>/node_modules/@u4/opencv4nodejs/build/Release/opencv4nodejs'
Require stack:
- <...>/node_modules/@u4/opencv4nodejs/lib/cvloader.js
- <...>/node_modules/@u4/opencv4nodejs/lib/opencv4nodejs.js
- <...>/[eval]
    at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
    at Function.Module._load (node:internal/modules/cjs/loader:778:27)
    at Module.require (node:internal/modules/cjs/loader:999:19)
    at require (node:internal/modules/cjs/helpers:102:18)
    at getOpenCV (<...>/node_modules/@u4/opencv4nodejs/lib/cvloader.js:54:23)
    at loadOpenCV (<...>/node_modules/@u4/opencv4nodejs/lib/opencv4nodejs.js:6:48)
    at Object.<anonymous> (<...>/node_modules/@u4/opencv4nodejs/lib/opencv4nodejs.js:21:12)
    at Module._compile (node:internal/modules/cjs/loader:1099:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10)
    at Module.load (node:internal/modules/cjs/loader:975:32) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [
    '<...>/node_modules/@u4/opencv4nodejs/lib/cvloader.js',
    '<...>/node_modules/@u4/opencv4nodejs/lib/opencv4nodejs.js',
    '<...>/[eval]'
  ]
}

How to fix

The module is not built. Using @u4/opencv-build and node-gyp I have found out, that the compilation failes here opencv4nodejs/cc/highgui/highguiConstants.cc:30
the constant WND_PROP_TOPMOST was intoduced only in OpenCV 4.1.2 while in opencv4nodejs code it stands for 3.4.8

Please replace this

#if CV_VERSION_GREATER_EQUAL(3, 4, 8)
	FF_SET_CV_CONSTANT(target, WND_PROP_TOPMOST);
#endif

with

#if CV_VERSION_GREATER_EQUAL(4, 1, 2)
	FF_SET_CV_CONSTANT(target, WND_PROP_TOPMOST);
#endif

Manual Build - Environment Information

OpenCV version 4.1.1
With OpenCV-contrib? (extra modules): no

OS: Ubuntu

[RomanVeretenov]

Created a PR
#78

[UrielCh]

Merged, thx for the PR