Friendly-img-hash-js NPM

friendly-img-hash-js

A js implementation of https://docs.rs/img_hash/ which itself is based on the work of http://www.hackerfactor.com/.

NOTE: If you want a no dependency, bare bones, and synchronous version of this library then check out https://www.npmjs.com/package/img-hash-js-core.

Installation via NPM

npm install friendly-img-hash-js

Get started quickly

Browser example:

import { hash } from 'friendly-img-hash-js';

// Image formats support depends on your browser
// https://en.wikipedia.org/wiki/Comparison_of_web_browsers#Image_format_support

// Construct a hash!
const result = await hash('https://my-sweet-image-url.png');

Nodejs Example:

import { hash } from 'friendly-img-hash-js';

// Image formats supported are jpeg, png, webp, bitmap, tiff, and avif

// Construct a hash!
const result = await hash('./some/file/on/disk.png');

Detailed examples and options

You can see all options, including defaults, inside the file index.js. Options can be mixed and matched as much as you like!

Different output types.

import { hash, Convert } from 'friendly-img-hash-js';

// You can specify the output format as one of the following
// BigInt -> an integer number like 7930450656421763612n
// Base64 -> a base64 string like KNCo2Uw3LtY=
// HexString -> a hex string like 6e0e9edaccc85a1c
// BitArray -> an array of bits like [0, 0, 1, 1, 0, 1, ...]

// Example of how to specify that option
console.log(
  await hash(image {
    output: Convert.options.BigInt
  })
);

Different hash algorithms.

import { hash, Hash } from 'friendly-img-hash-js';

// All of these come from 
// https://github.com/abonander/img_hash/blob/dbfb37f9251fea8f7efeabbb2267ddb1fcd21ca6/src/alg/mod.rs#L20

// You can specify the output format as one of the following
// Mean -> Simple algorithm, not very resiliant
// Gradient -> Very effective and efficient algorithm, recommended!
// VerticalGradient -> Same as gradient, but better for tall images
// DoubleGradient -> Computationally expensive, but may improve results

// Example of how to specify that option
console.log(
  await hash(image, {
    algorithm: Hash.options.Gradient
  })
);

Enable Discrete Cosine Transform (DCT)

import { hash, Dct } from 'friendly-img-hash-js';

const imageBytes = // get your image bytes following the examples above.

// You can specify the output format as one of the following
// None -> do not enable DCT
// Type2 -> enable DCT, more computation and slightly more robust results

// Example of how to specify that option
console.log(
  await hash(image, {
    dct: {
      algorithm: Dct.options.Type2
    }
  })
);

If you want to write your own algorithm, you can for any option. Here is an example of writing a custom hash function (MEDIAN) and a custom output function (BinaryString).

import { hash } from 'friendly-img-hash-js';

console.log(
  await hash(image, {
    // Dimension is required because of custom algorithm
    dimension: (width, height) => ({ width, height }), 
    algorithm: (bytes) => {
      const half = Math.floor(bytes.length / 2);
      const median = [...bytes].sort().at(half);
      return bytes.map((b) => b >= median).map((b) => (b ? 1 : 0));
    },
    output: (hashBits) => hashBits.join(''),
  })
); // Outputs "001010011001..."

Comparing Hashes

If you want to then compare two hashes, use something like Hamming distance or Levenshtein distance

import { hash, Convert } from 'friendly-img-hash-js';
import leven from 'leven';

const config = { output: Convert.options.BigInt };

const result1 = await hash(image1, config);
const result2 = await hash(image2, config);

if (leven(result1.toString(), result2.toString()) <= 12) {
  console.log ('Images are very similar!');
}