image-hash

Alt-Image-Hash

Alternative JavaScript image hashing library.

npm i @alttiri/image-hash

The library to generate a perceptual hash for ImageData input.

Supported perceptual hashes:

• dHash (difference hash)
• aHash (average hash)
• mHash (median hash)
• bHash (block hash)

Basic examples

import {dHash} from "@alttiri/image-hash";

const imagePath = "alyson_hannigan_500x500.jpg";
const imageData = await getImageData(imagePath);
const hash = dHash(imageData);
console.log(hash.hex); // "8f94b43434245452"

const hash1 = dHash(await getImageData("kittens-3264x2448.jpg"));
const hash2 = dHash(await getImageData("kittens-960x720.jpg"));

console.log(hash1.hex); // "e020acce864cae8a"
console.log(hash2.hex); // "e020acce864cae8a"
console.log(hash1.diff(hash2)); // 0

How to get ImageData?

The reasonable question is how to get ImageData.

On Node.js I recommend to use sharp library. On browsers get ImageData with OffscreenCanvas.

It’s only ~20 lines of code (node, browser).

But for convenience I created a library @alttiri/get-image-data:

npm i @alttiri/get-image-data

Also, for Node.js application do not forget to install sharp dependency:

npm i sharp

Then just import it:

• For a Node.js app:

    import {getImageDataWithSharp as getImageData} from "@alttiri/get-image-data";
  

• Fow a web app:

    import {getImageDataWithCanvas as getImageData} from "@alttiri/get-image-data";
  

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Full Node.js example

npm i @alttiri/image-hash @alttiri/get-image-data sharp

import {getImageDataWithSharp as getImageData} from "@alttiri/get-image-data";
import {dHash} from "@alttiri/image-hash";

const imagePath = "alyson_hannigan_500x500.jpg";
const imageData = await getImageData(imagePath);
const hash = dHash(imageData);
console.log(hash.hex); // "8f94b43434245452"

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