Resemble.js

Analyse and compare images with Javascript and HTML5. More info & Resemble.js Demo. Now compatible with Node.js.

Get it

npm install resemblejs

bower install resemblejs

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);
	/*
	{
	  misMatchPercentage : 100, // %
	  isSameDimensions: true, // or false
	  dimensionDifference: { width: 0, height: -1 }, // defined if dimensions are not the same
	  getImageDataUrl: function(){}
	}
	*/
});

Scale second image to dimensions of the first one:

//diff.useOriginalSize();
diff.scaleToSameSize();

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

// diff.ignoreNothing();
// diff.ignoreColors();
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
});
// resembleControl.repaint();

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.

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

Node.js

Ensure you also have the canvas peer dependency installed alongside resemblejs. See here for instructions on how to install canvas on your platform.

The API under Node is the same as the browser API with an additional Promise based convenience method called compareImages that also allows you to read/write from Node Buffers.

Node Example

const compareImage = require('resemblejs/compareImage');

// The parameters can be Node Buffers
// data is the same as usual with an additional getBuffer() function
const data = await compareImages(
	fs.readFileSync('./demoassets/People.jpg'),
	fs.readFileSync('./demoassets/People2.jpg')
);

fs.writeFileSync('./output.png', data.getBuffer());

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Created by James Cryer and the Huddle development team.