Pura-image: pure-Ruby Active Storage variant_processor with no system dependencies #57228

Hi Rails community,

Wanted to share a project aimed at the "system library install dance" pain in Active Storage setup.

What it is

pura-image — a pure-Ruby image processing library that drops into Active Storage as a variant_processor. The full integration is one config line:

# Gemfile
gem "pura-image"

# config/application.rb
config.active_storage.variant_processor = :pura

Models and views stay exactly the same:

class User < ApplicationRecord
  has_one_attached :avatar do |attachable|
    attachable.variant :thumb, resize_to_limit: [200, 200]
  end
end

What changes for Rails users

• No brew install vips for new dev setup
• No apt-get install libvips-dev imagemagick line in your Dockerfile
• No system-library setup on CI
• Works on Heroku / Fly.io / Render without buildpack drama
• Works on Windows without MSYS2 dance
• As of v0.3.0, even the image_processing runtime gem dependency is gone — replaced by an in-house pura-processing. So the dependency story is now literal: zero gems, zero system libs.

Browser playground

komagata.github.io/pura-image

The page boots ruby.wasm and runs ImageProcessing::Pura chains in the browser. To be precise, only the image-processing layer runs in wasm — Active Storage itself (blob storage, variant orchestration) doesn't run in the browser. But it's a nice way to see that a Rails variant definition can survive in a wasm sandbox.

Tradeoffs

• JPEG / WebP encoding is slower than libvips. Fine for typical avatar / thumbnail workloads, not for high-volume image pipelines.
• The library is young — please benchmark against your real workload before swapping it in production.
• 7 formats supported (JPEG, PNG, BMP, GIF, TIFF, ICO, WebP), image_processing gem-compatible API, MIT.

Why this might fit Rails 8 direction

The Solid Queue / Solid Cache / Solid Cable line is removing external infrastructure dependencies in favor of "it just works with what you already have." pura-image applies the same idea to image processing: the default Active Storage experience can be one bundle install instead of a per-OS setup guide.

GitHub: https://github.com/komagata/pura-image
Writeup with benchmarks: https://dev.to/komagata/active-storage-without-libvips-or-imagemagick-a-pure-ruby-alternative-4o99

Would love feedback from anyone who tries it on a real Rails app, especially failure modes I haven't hit yet.