npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

@steelydylan/resemblejs

v4.1.1

Published

Image analysis and comparison with HTML5

Downloads

12

Readme

Low-maintenance mode: Two to four times a year the library author will spend some time to keep the library useful. Feel free to raise issues and contribute improvements, but please be aware that it may be sometime before a response is given.


Get it

npm install resemblejs

Node.js

Resemble.js uses node-canvas for Node.js support. This is a pre-built dependency that may fail in certain environments. If you are using Resemble.js for in-browser analysis only, you can skip the node-canvas dependency with npm install --no-optional. If you need Node.js support and the Canvas dependency fails, try using a previous version of Resemble.js, or npm install --build-from-source.

Example

Retrieve basic analysis on an image:

var api = resemble(fileData).onComplete(function (data) {
    console.log(data);
    /*
	{
	  red: 255,
	  green: 255,
	  blue: 255,
	  brightness: 255
	}
	*/
});

Use resemble to compare two images:

var diff = resemble(file)
    .compareTo(file2)
    .ignoreColors()
    .onComplete(function (data) {
        console.log(data);
    });

Scale second image to dimensions of the first one:

diff.scaleToSameSize();

You can also change the comparison method after the first analysis:

diff.ignoreAntialiasing();

And change the output display style:

resemble.outputSettings({
    errorColor: {
        red: 255,
        green: 0,
        blue: 255
    },
    errorType: "movement",
    transparency: 0.3,
    largeImageThreshold: 1200,
    useCrossOrigin: false,
    outputDiff: true
});
// .repaint();

Note: resemble.outputSettings mutates global state, effecting all subsequent call to Resemble.

It is possible to narrow down the area of comparison, by specifying a bounding box measured in pixels from the top left:

const box = {
    left: 100,
    top: 200,
    right: 200,
    bottom: 600
};
resemble.outputSettings({ boundingBox: box });
resemble.outputSettings({ boundingBoxes: [box1, box2] });

You can also exclude part of the image from comparison, by specifying the excluded area in pixels from the top left:

const box = {
    left: 100,
    top: 200,
    right: 200,
    bottom: 600
};
resemble.outputSettings({ ignoredBox: box });
resemble.outputSettings({ ignoredBoxes: [box1, box2] });

Another way to exclude parts of the image from comparison, is using the ignoreAreasColoredWith option. Any pixels that match the specified color on a reference image will be excluded from comparison:

const color = {
    r: 255,
    g: 0,
    b: 0,
    a: 255
};
resemble.outputSettings({ ignoreAreasColoredWith: color });

By default, the comparison algorithm skips pixels when the image width or height is larger than 1200 pixels. This is there to mitigate performance issues.

You can modify this behaviour by setting the largeImageThreshold option to a different value. Set it to 0 to switch it off completely.

Resemble.js also supports Data URIs as strings:

resemble.outputSettings({ useCrossOrigin: false });
var diff = resemble("data:image/jpeg;base64,/9j/4AAQSkZJRgAB...").compareTo("data:image/jpeg;base64,/9j/,/9j/4AAQSkZJRg...");

useCrossOrigin is true by default, you might need to set it to false if you're using Data URIs.

If you'd like resemble to return early:

resemble(img1)
    .compareTo(img2)
    .setReturnEarlyThreshold(8)
    .onComplete((data) => {
        /* do something */
    });

Single callback api

The resemble.compare API provides a convenience function that is used as follows:

const compare = require("resemblejs").compare;

function getDiff() {
    const options = {
        returnEarlyThreshold: 5
    };

    compare(image1, image2, options, function (err, data) {
        if (err) {
            console.log("An error!");
        } else {
            console.log(data);
        }
    });
}

Node.js

Usage

The API under Node is the same as on the resemble.compare but promise based:

const compareImages = require("resemblejs/compareImages");
const fs = require("mz/fs");

async function getDiff() {
    const options = {
        output: {
            errorColor: {
                red: 255,
                green: 0,
                blue: 255
            },
            errorType: "movement",
            transparency: 0.3,
            largeImageThreshold: 1200,
            useCrossOrigin: false,
            outputDiff: true
        },
        scaleToSameSize: true,
        ignore: "antialiasing"
    };

    const data = await compareImages(await fs.readFile("./your-image-path/People.jpg"), await fs.readFile("./your-image-path/People2.jpg"), options);

    await fs.writeFile("./output.png", data.getBuffer());
}

getDiff();

Tests

To run the tests on Node (using Jest), type:

npm run test

There are also some in-browser tests. To run these install and run a http-server such as http-server from the root of the project. Then in the browser, navigate to localhost:8080/chai-tests/test.html, open up the developer console to see the results.

Dockerfile

For convenience I've added a simple Dockerfile to run the NodeJS tests in an Ubuntu container

docker build -t rsmbl/resemble .
docker run rsmbl/resemble

Reference to academic papers

As people have asked in the past, Resemble.js hasn't knowingly implemented any published ideas. RGBA colour comparison is simple and straightforward when working with the Canvas API. The antialiasing algorithm was developed at Huddle over several days of trial-and-error using various false-positive results from PhantomCSS tests.


Created by James Cryer and the Huddle development team.