HDRify

HDRify implements comprehensive support for high dynamic range imaging with support for HDR (Radiance RGBE), EXR (OpenEXR), and JPEG with gain maps (JPEG-R / Ultra HDR) reading and writing in pure JavaScript. No native bindings—works in Node.js and browsers.

→ Online demo — HDR, EXR, Adobe Gain Maps & UltraHDR viewer and converter (the packages/website app from this repo). Try it in your browser.

Features

• Read and write RGB EXR files (PIZ, PXR24, ZIP, ZIPS, and RLE compression)
• Read and write HDR (Radiance RGBE) files
• Read and write both Adobe Gain Map JPEGs and Ultra HDR JPEGS (Android compatible.)
• Tone mappers (ACES, Khronos Neutral, AgX and Reinhart)
• Full TypeScript support
• No DOM or Node.js dependencies (works in browser, web workers, and node.js)
• Written in a functional style to support tree-shaking
• Web app example of HDR, EXR and Ultra HDR conversion and viewing: https://hdrify.benhouston3d.com
• hdrify CLI
• HDRify VS Code Extension — for VS Code and Cursor

Installation

pnpm add hdrify

Main Entry Points

All read functions return HdrifyImage, and all write functions accept it (or derived types). This is the universal intermediate format used across the library.

HdrifyImage

interface HdrifyImage {
  width: number;           // Image width in pixels
  height: number;          // Image height in pixels
  data: Float32Array;     // RGBA pixel data: [R, G, B, A, R, G, B, A, ...]
  metadata?: Record<string, unknown>;  // Format-specific header metadata (e.g. compression, exposure)
}

Usage

Reading an EXR file

import { readExr } from 'hdrify';

const buffer = fs.readFileSync('image.exr');
const imageData = readExr(new Uint8Array(buffer));

console.log(`Image: ${imageData.width}x${imageData.height}`);
// imageData.data is a Float32Array with RGBA values

Reading an HDR file

import { readHdr } from 'hdrify';

const buffer = fs.readFileSync('image.hdr');
const imageData = readHdr(new Uint8Array(buffer));

console.log(`Image: ${imageData.width}x${imageData.height}`);

Reading a JPEG gain map file (JPEG-R / Ultra HDR)

import { readJpegGainMap } from 'hdrify';

const buffer = fs.readFileSync('image.jpg');
const imageData = readJpegGainMap(new Uint8Array(buffer));

console.log(`Image: ${imageData.width}x${imageData.height}`);
// imageData.data is linear HDR Float32Array RGBA; metadata.format is 'ultrahdr' or 'adobe-gainmap'

Converting between formats

import { encodeGainMap, readExr, writeExr, readHdr, writeHdr, writeJpegGainMap } from 'hdrify';

// Convert EXR to HDR
const exrBuffer = fs.readFileSync('input.exr');
const imageData = readExr(new Uint8Array(exrBuffer));
fs.writeFileSync('output.hdr', writeHdr(imageData));

// Convert HDR to EXR
const hdrBuffer2 = fs.readFileSync('input.hdr');
const imageData2 = readHdr(new Uint8Array(hdrBuffer2));
fs.writeFileSync('output.exr', writeExr(imageData2));

// Convert EXR or HDR to JPEG-R (JPEG with gain map—highly compressible HDR)
const imageData3 = readExr(new Uint8Array(fs.readFileSync('input.exr')));
const encoding = encodeGainMap(imageData3, { toneMapping: 'reinhard' });
fs.writeFileSync('output.jpg', writeJpegGainMap(encoding, { quality: 90 }));

Browser usage

import { readExr } from 'hdrify';

const fileInput = document.querySelector('input[type="file"]');
fileInput.addEventListener('change', async (e) => {
  const file = (e.target as HTMLInputElement).files?.[0];
  if (!file) return;
  const arrayBuffer = await file.arrayBuffer();
  const buffer = new Uint8Array(arrayBuffer);

  const imageData = readExr(buffer);
  // Use imageData.data to render to canvas, etc.
});

CLI Tool

The hdrify-cli package is a companion command-line tool for converting and inspecting EXR, HDR, and JPEG gain map (Ultra HDR / Adobe) files. See packages/cli/README.md for full CLI documentation, or install from npm:

pnpm add -g hdrify-cli

Command	Description
hdrify convert <input> <output>	Convert between EXR, HDR, JPEG gain map, PNG, WebP, and JPEG
hdrify info <file>	Display metadata (format, dimensions, compression)
hdrify reference <output>	Create synthetic reference test images

hdrify convert input.exr output.hdr
hdrify convert input.hdr output.exr
hdrify convert input.exr output.jpg    # JPEG-R with gain map (Ultra HDR, default)
hdrify convert input.exr output.jpg --format adobe-gainmap   # Adobe gain map format
hdrify convert input.jpg output.exr    # Read JPEG gain map as input
hdrify info input.exr
hdrify info input.jpg    # JPEG gain map (Ultra HDR / Adobe)
hdrify reference output.exr --compression zip
hdrify convert input.exr output.exr --compression pxr24

Demos

See the online demo link at the top. To run the website locally (packages/website, drag-and-drop and exposure slider):

cd packages/website
pnpm install
pnpm dev

Open http://localhost:3000 and drag-and-drop EXR or HDR files.

Developer (for Contributors)

Check out this git project and run:

# install dependencies
pnpm install

# build packages (hdrify, hdrify-cli)
pnpm build

# run tests
pnpm test

# type-check
pnpm tsgo

# lint
pnpm check

# clean build artifacts
pnpm clean

# publish the npm packages
pnpm make-release:hdrify
pnpm make-release:hdrify-cli

License

MIT

Author

Ben Houston, Sponsored by Land of Assets

Acknowledgements

This project would not have been possible without these two projects which were used a reference:

• Three.js - tone mapping, UltraHDR loader, EXR loader, example images.
• Gainmap.js - Ultra HDR loading, saving, XMP metadata structure and JPEG-R assembly (reference implementation).
• OpenEXR - EXR encoding/decoding for all the various compression formats, example images.