crestconvert

Private, browser-side image conversion with HEIC support. Files stay on the user's device and are never sent to a conversion server.

Built by Crest Convert, a private online file converter.

Supported formats

• Inputs: HEIC, HEIF, JPG, JPEG, PNG, WebP, GIF and BMP
• Outputs: JPG, PNG and WebP
• Animated GIF input is converted using its first frame

Install

npm install crestconvert

Convert one image

import { convertImage, download } from "crestconvert";

const file = input.files[0];
const result = await convertImage(file, {
  format: "jpg",
  quality: 0.9
});

download(result.blob, result.filename);

Convert a batch to ZIP

import { convertImages, createZip, download } from "crestconvert";

const images = await convertImages(input.files, {
  format: "webp",
  quality: 0.85,
  maxFiles: 50,
  onProgress: (completed, total, filename) => {
    console.log(`${completed}/${total}: ${filename}`);
  }
});

const zip = await createZip(images);
download(zip, "converted-images.zip");

Privacy and runtime

All decoding, encoding and ZIP creation happen locally in the browser. The package makes no network requests and contains no analytics or tracking.

This package is designed for browser applications. It requires Canvas, Blob, File and createImageBitmap support. HEIC and HEIF decoding is provided by the bundled WebAssembly build of libheif-js.

API

• convertImage(blob, options) converts one image.
• convertImages(blobs, options) converts a batch sequentially.
• createZip(images, options) creates a ZIP from converted results.
• download(blob, filename) starts a browser download.
• isSupportedImage(blob, filename?) checks input support.
• supportedInputFormats and supportedOutputFormats expose the format lists.

License

MIT. See THIRD-PARTY-NOTICES.md for dependency licensing.