[sorenjan]

Are there any tools that transform HTML and other files? For example, lets say I have an <img> tag with a src attribute that points to a local image. Can I automatically replace that with a <picture> tag with various formats (jpg, webp, avif) and sizes?

[M2Ys4U]

I think Parcel[0] is what you want for that use-case.[1]

[0] https://parceljs.org/

[1] https://parceljs.org/recipes/image/

[lioeters]

Rehype is an HTML processor with an ecosystem of plugins: https://github.com/rehypejs/rehype/

[eyelidlessness]

In ESBuild you’ll need a plugin for this. The plugin API is really simple but you’ll likely be gluing other tools together to achieve it.

[tannhaeuser]

SGML can transform HTML and all other forms of markup, though it's neither limited to that use, nor does it readily bundle image converters/compressors even though that sure has always been a plausible use case for SGML-based pipelines.

[darekkay]

Check out PostHTML: https://github.com/posthtml/posthtml