opencv4nodejs

Examples

Face Detection

Face Recognition with the OpenCV face module

Face Landmarks with the OpenCV face module

Face Recognition withface-recognition.js

Hand Gesture Recognition

Object Recognition with Deep Neural Networks

Tensorflow Inception

Single Shot Multibox Detector with COCO

Machine Learning

Object Tracking

Feature Matching

Image Histogram

Boiler plate for combination of opencv4nodejs, express and websockets.

Automating lights by people detection through classifier

How to install

npm install --save opencv4nodejs

npm install --global windows-build-tools

Installing OpenCV Manually

# linux and osx:export OPENCV4NODEJS_DISABLE_AUTOBUILD=1# on windows:set OPENCV4NODEJS_DISABLE_AUTOBUILD=1

Windows

# to install OpenCV 4.1.0choco install OpenCV -y -version 4.1.0

MacOSX

brew updatebrew install opencv@4brew link --force opencv@4

Linux

Installing OpenCV via Auto Build Script

Auto Build Flags

Installing a Specific Version of OpenCV

Installing only a Subset of OpenCV modules

Configuring Environments via package.json

{"name":"my-project","version":"0.0.0","dependencies": {"opencv4nodejs":"^X.X.X"  },"opencv4nodejs": {"disableAutoBuild":1,"opencvIncludeDir":"C:\\tools\\opencv\\build\\include","opencvLibDir":"C:\\tools\\opencv\\build\\x64\\vc14\\lib","opencvBinDir":"C:\\tools\\opencv\\build\\x64\\vc14\\bin"  }}

Usage with Docker

opencv-express - example for opencv4nodejs with express.js and docker

FROM justadudewhohacks/opencv-nodejs

Usage with Electron

opencv-electron - example for opencv4nodejs with electron

"electron-rebuild":"electron-rebuild -w opencv4nodejs"

$ npm run electron-rebuild

constcv=require('opencv4nodejs');

Usage with NW.js

constcv=require('opencv4nodejs');

Quick Start

constcv=require('opencv4nodejs');

Initializing Mat (image matrix), Vec, Point

constrows=100;// heightconstcols=100;// width// empty MatconstemptyMat=newcv.Mat(rows,cols,cv.CV_8UC3);// fill the Mat with default valueconstwhiteMat=newcv.Mat(rows,cols,cv.CV_8UC1,255);constblueMat=newcv.Mat(rows,cols,cv.CV_8UC3,[255,0,0]);// from array (3x3 Matrix, 3 channels)constmatData=[[[255,0,0],[255,0,0],[255,0,0]],[[0,0,0],[0,0,0],[0,0,0]],[[255,0,0],[255,0,0],[255,0,0]]];constmatFromArray=newcv.Mat(matData,cv.CV_8UC3);// from node bufferconstcharData=[255,0, ...];constmatFromArray=newcv.Mat(Buffer.from(charData),rows,cols,cv.CV_8UC3);// Pointconstpt2=newcv.Point(100,100);constpt3=newcv.Point(100,100,0.5);// Vectorconstvec2=newcv.Vec(100,100);constvec3=newcv.Vec(100,100,0.5);constvec4=newcv.Vec(100,100,0.5,0.5);

Mat and Vec operations

constmat0=newcv.Mat(...);constmat1=newcv.Mat(...);// arithmetic operations for Mats and VecsconstmatMultipliedByScalar=mat0.mul(0.5);// scalar multiplicationconstmatDividedByScalar=mat0.div(2);// scalar divisionconstmat0PlusMat1=mat0.add(mat1);// additionconstmat0MinusMat1=mat0.sub(mat1);// subtractionconstmat0MulMat1=mat0.hMul(mat1);// elementwise multiplicationconstmat0DivMat1=mat0.hDiv(mat1);// elementwise division// logical operations Mat onlyconstmat0AndMat1=mat0.and(mat1);constmat0OrMat1=mat0.or(mat1);constmat0bwAndMat1=mat0.bitwiseAnd(mat1);constmat0bwOrMat1=mat0.bitwiseOr(mat1);constmat0bwXorMat1=mat0.bitwiseXor(mat1);constmat0bwNot=mat0.bitwiseNot();

Accessing Mat data

constmatBGR=newcv.Mat(...,cv.CV_8UC3);constmatGray=newcv.Mat(...,cv.CV_8UC1);// get pixel value as vector or number valueconstvec3=matBGR.at(200,100);constgrayVal=matGray.at(200,100);// get raw pixel value as arrayconst[b,g,r]=matBGR.atRaw(200,100);// set single pixel valuesmatBGR.set(50,50,[255,0,0]);matBGR.set(50,50,newVec(255,0,0));matGray.set(50,50,255);// get a 25x25 sub region of the Mat at offset (50, 50)constwidth=25;constheight=25;constregion=matBGR.getRegion(newcv.Rect(50,50,width,height));// get a node buffer with raw Mat dataconstmatAsBuffer=matBGR.getData();// get entire Mat data as JS arrayconstmatAsArray=matBGR.getDataAsArray();

IO

// load image from fileconstmat=cv.imread('./path/img.jpg');cv.imreadAsync('./path/img.jpg',(err,mat)=>{  ...})// save imagecv.imwrite('./path/img.png',mat);cv.imwriteAsync('./path/img.jpg',mat,(err)=>{  ...})// show imagecv.imshow('a window name',mat);cv.waitKey();// load base64 encoded imageconstbase64text='data:image/png;base64,R0lGO..';//Base64 encoded stringconstbase64data=base64text.replace('data:image/jpeg;base64','').replace('data:image/png;base64','');//Strip image type prefixconstbuffer=Buffer.from(base64data,'base64');constimage=cv.imdecode(buffer);//Image is now represented as Mat// convert Mat to base64 encoded jpg imageconstoutBase64=cv.imencode('.jpg',croppedImage).toString('base64');// Perform base64 encodingconsthtmlImg='<img src=data:image/jpeg;base64,'+outBase64+'>';//Create insert into HTML compatible <img> tag// open capture from webcamconstdevicePort=0;constwCap=newcv.VideoCapture(devicePort);// open video captureconstvCap=newcv.VideoCapture('./path/video.mp4');// read frames from captureconstframe=vCap.read();vCap.readAsync((err,frame)=>{  ...});// loop through the captureconstdelay=10;letdone=false;while(!done){letframe=vCap.read();// loop back to start on end of stream reachedif(frame.empty){vCap.reset();frame=vCap.read();}// ...constkey=cv.waitKey(delay);done=key!==255;}

Useful Mat methods

constmatBGR=newcv.Mat(...,cv.CV_8UC3);// convert typesconstmatSignedInt=matBGR.convertTo(cv.CV_32SC3);constmatDoublePrecision=matBGR.convertTo(cv.CV_64FC3);// convert color spaceconstmatGray=matBGR.bgrToGray();constmatHSV=matBGR.cvtColor(cv.COLOR_BGR2HSV);constmatLab=matBGR.cvtColor(cv.COLOR_BGR2Lab);// resizeconstmatHalfSize=matBGR.rescale(0.5);constmat100x100=matBGR.resize(100,100);constmatMaxDimIs100=matBGR.resizeToMax(100);// extract channels and create Mat from channelsconst[matB,matG,matR]=matBGR.splitChannels();constmatRGB=newcv.Mat([matR,matB,matG]);

Drawing a Mat into HTML Canvas

constimg= ...// convert your image to rgba color spaceconstmatRGBA=img.channels===1  ?img.cvtColor(cv.COLOR_GRAY2RGBA)  :img.cvtColor(cv.COLOR_BGR2RGBA);// create new ImageData from raw mat dataconstimgData=newImageData(newUint8ClampedArray(matRGBA.getData()),img.cols,img.rows);// set canvas dimensionsconstcanvas=document.getElementById('myCanvas');canvas.height=img.rows;canvas.width=img.cols;// set image dataconstctx=canvas.getContext('2d');ctx.putImageData(imgData,0,0);

Method Interface

voidGaussianBlur(InputArray src, OutputArray dst, Size ksize,double sigmaX,double sigmaY =0,int borderType = BORDER_DEFAULT);

constsrc=newcv.Mat(...);// invoke with required argumentsconstdst0=src.gaussianBlur(newcv.Size(5,5),1.2);// with optional paramatersconstdst2=src.gaussianBlur(newcv.Size(5,5),1.2,0.8,cv.BORDER_REFLECT);// or pass specific optional parametersconstoptionalArgs={borderType:cv.BORDER_CONSTANT};constdst2=src.gaussianBlur(newcv.Size(5,5),1.2,optionalArgs);

Async API

Async Face Detection

constclassifier=newcv.CascadeClassifier(cv.HAAR_FRONTALFACE_ALT2);// by nesting callbackscv.imreadAsync('./faceimg.jpg',(err,img)=>{if(err){returnconsole.error(err);}constgrayImg=img.bgrToGray();classifier.detectMultiScaleAsync(grayImg,(err,res)=>{if(err){returnconsole.error(err);}const{ objects, numDetections}=res;    ...});});// via Promisecv.imreadAsync('./faceimg.jpg').then(img=>img.bgrToGrayAsync().then(grayImg=>classifier.detectMultiScaleAsync(grayImg)).then((res)=>{const{ objects, numDetections}=res;        ...})).catch(err=>console.error(err));// using async awaittry{constimg=awaitcv.imreadAsync('./faceimg.jpg');constgrayImg=awaitimg.bgrToGrayAsync();const{ objects, numDetections}=awaitclassifier.detectMultiScaleAsync(grayImg);  ...}catch(err){console.error(err);}

With TypeScript

import*ascvfrom'opencv4nodejs'

External Memory Tracking (v4.0.0)

export OPENCV4NODEJS_DISABLE_EXTERNAL_MEM_TRACKING=1 // linuxset OPENCV4NODEJS_DISABLE_EXTERNAL_MEM_TRACKING=1 // windows

process.env.OPENCV4NODEJS_DISABLE_EXTERNAL_MEM_TRACKING=1constcv=require('opencv4nodejs')