node-opencv
OpenCV bindings for Node.js. OpenCV is the defacto computer vision library - by interfacing with it natively in node, we get powerful real time vision in js.
People are using node-opencv to fly control quadrocoptors, detect faces from webcam images and annotate video streams. If you're using it for something cool, I'd love to hear about it!
Install
You'll need OpenCV 2.3.1 installed.
Then:
npm install opencv
Or to build the repo:
node-gyp rebuild
Examples
Face Detection
cv.readImage("./examples/test.jpg", function(err, im){
im.detectObject("./data/haarcascade_frontalface_alt.xml", {}, function(err, faces){
for (var i=0;i<faces.length; i++){
var x = faces[i]
im.ellipse(x.x + x.width/2, x.y + x.height/2, x.width/2, x.height/2);
}
im.save('./out.jpg');
});
})
API Documentation
Matrix
The matrix is the most useful base datastructure in OpenCV. Things like images are just matrices of pixels.
Creation
new Matrix(width, height)
Or you can use opencv to read in image files. Supported formats are in the OpenCV docs, but jpgs etc are supported.
cv.readImage(filename, function(mat){
...
})
cv.readImage(buffer, function(mat){
...
})
If you need to pipe data into an image, you can use an imagestream:
var s = new cv.ImageStream()
s.on('load', function(matrix){
...
})
fs.createReadStream('./examples/test.jpg').pipe(s);
Accessing Data
var mat = new cv.Matrix.Eye(4,4); // Create identity matrix
mat.get(0,0) // 1
mat.row(0) // [1,0,0,0]
mat.col(4) // [0,0,0,1]
Save
mat.save('./pic.jpg')
or:
var buff = mat.toBuffer()
Image Processing
im.convertGrayscale()
im.canny(5, 300)
im.houghLinesP()
Simple Drawing
im.ellipse(x, y)
im.line([x1,y1], [x2, y2])
Object Detection
There is a shortcut method for Viola-Jones Haar Cascade object detection. This can be used for face detection etc.
mat.detectObject(haar_cascade_xml, opts, function(err, matches){})
Also:
mat.goodFeaturesToTrack
Contours
mat.findCountours
mat.drawContour
mat.drawAllContours
MIT License
The library is distributed under the MIT License - if for some reason that doesn't work for you please get in touch.
Changelog
0.0.10
- Bug Fixes
- @Contra added code that allows thickness and color args for ellipse
- Camshift Support
- @jtlebi added bindings for erode, gaussianBlur, arcLength, approxPolyDP, isConvex, cornerCount
- @gluxon added bindings for inRange
Thanks everyone!
0.0.9
- toBuffer can now take a callback and be run async (re #21)