gen-srcset

Generate <picture /> srcset with AVIF support.

Requirements

Node.js 22 or newer; Node.js 24 LTS is recommended. Older Node.js versions are no longer supported.

Development

Use Yarn Classic 1.22.22 (npm install --global yarn@1.22.22), then run:

yarn install --frozen-lockfile
yarn validate

yarn validate lints the source, runs the existing unit tests, builds the CLI, and checks real JPEG, PNG and AVIF output. CI validates Node.js 22 and 24 on pushes and pull requests.

Publishing only runs after a non-prerelease GitHub release is published and validation passes. The release tag must be v followed by the package version (for example, v0.4.1). Keep the CLI version in src/index.js in sync when bumping the package version. Publishing requires the existing NPM_TOKEN repository secret. Pushing to main does not publish a package.

Cli arguments

• -i --input: input file
• -o --output: output path (optional, defaults to current path)
• -b --breakpoints: image widths that gen-srcset should generate
• -n --noAvif: skip AVIF output
• -h --help: displays this section

Example usage

yarn gen-srcset --input=images/cat-image.jpg --breakpoints="480, 720, 1080"

This will generate these files:

• cat-image_480.jpg
• cat-image_720.jpg
• cat-image_1080.jpg
• cat-image_480.avif
• cat-image_720.avif
• cat-image_1080.avif

and you can use these files like this:

<picture>
  <source srcset="cat-image-480.avif 480w" type="image/avif" />
  <source srcset="cat-image-720.avif 720w" type="image/avif" />
  <source srcset="cat-image-1080.avif 1080w" type="image/avif" />

  <source srcset="cat-image-480.jpg 480w" type="image/jpg" />
  <source srcset="cat-image-720.jpg 720w" type="image/jpg" />
  <source srcset="cat-image-1080.jpg 1080w" type="image/jpg" />

  <img src="cat-image-480.jpg" alt="cat" />
</picture>

LICENSE

MIT License

Copyright (c) 2021 ilyas akın

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.