README.md
# Image Moments
[](https://github.com/mgcrea/image-moments) [](https://tldrlegal.com/license/mit-license) [](http://travis-ci.org/mgcrea/image-moments) [](https://david-dm.org/mgcrea/image-moments) [](https://david-dm.org/mgcrea/image-moments#info=devDependencies) [](https://codeclimate.com/github/mgcrea/image-moments) [](https://codeclimate.com/github/mgcrea/image-moments)
Compute [Image Moments](https://en.wikipedia.org/wiki/Image_moment) with Javascript!
Moments are well-known for their application in image analysis, since they can be used to derive invariants with respect to specific transformation classes.
## Usage
### Quickstart
1. Fetch raw, central, scale and rotation invariant moments
```js
import imageMoments from 'image-moments';
// Sample greyscale matrix of 4x3, 255 = white, 0 = black
const matrix = [[255, 255, 255, 255], [0, 255, 255, 255], [255, 0, 255, 255]];
const moments = imageMoments(matrix);
```
2. Get image orientation
```js
import {getOrientationFromMoments} from 'image-moments';
const theta = getOrientationFromMoments(moments);
```
### Output
```js
{
// Raw moments
"m00": 126735,
"m01": 1524390,
"m10": 1207170,
"m11": 14488335,
"m02": 24932370,
"m20": 15700860,
"m12": 236865675,
"m21": 188417205,
"m03": 458373210,
"m30": 229570380,
// Centroid
"mx": 12.028169014084508,
"my": 9.525150905432596,
// Translational invariant moments
"mu00": 126735,
"mu11": -31709.78873239441,
"mu20": 4202383.581488935,
"mu02": 6596749.436619717,
"mu21": 168688.29923201213,
"mu12": 143909.71646781557,
"mu30": -39356.39745921243,
"mu03": -211184.61614761315,
// Scale invariant moments
"nu11": -0.0000019742411969914966,
"nu12": 2.5167999382131884e-8,
"nu21": 2.9501461854340094e-8,
"nu02": 0.0004107114876706931,
"nu20": 0.0002616390434560192,
"nu03": -3.693353318438072e-8,
"nu30": -6.8829389095344285e-9,
// Rotation invariant moments
"hu1": 0.0006723505311267123,
"hu2": 4.5207082721958777e-7,
"hu3": 2.2522278857137367e-14,
"hu4": 4.747952002281406e-15,
"hu5": -1.1376366926279648e-30,
"hu6": -4.053410989495849e-20,
"hu7": -1.9354880656758928e-31,
"hu8": -2.0809356074964827e-20
}
```
### Properties
- `{mx, my}` is the centroid on which it would balance when placed on a needle
- `mu*` moments are translational invariant.
- `nu*` moments are translational and scale invariant.
- `hu*` moments are translational, scale and rotation invariant.
### Available scripts
| **Script** | **Description** |
|----------|-------|
| start | Alias of test:watch |
| test | Run mocha unit tests |
| test:watch | Run and watch mocha unit tests |
| lint | Run eslint static tests |
| compile | Compile the library |
| compile:watch | Compile and watch the library |
## Authors
**Olivier Louvignes**
+ http://olouv.com
+ http://github.com/mgcrea
Inspired by [OpenCV](https://github.com/Itseez/opencv/blob/master/modules/imgproc/src/moments.cpp).
## License
```
The MIT License
Copyright (c) 2016 Olivier Louvignes
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
```