pura-processing

Pure-Ruby, zero-dependency base layer for pipeline-style image processing.

Provides the Chainable DSL, Builder, Pipeline, and abstract Processor classes — the image-backend-agnostic foundation that originated in the excellent image_processing gem by Janko Marohnić, repackaged without any runtime dependency on ruby-vips or mini_magick.

Why this exists

image_processing ties its chainable DSL to two backend gems (ruby-vips and mini_magick) as runtime dependencies. Any downstream gem that just wants the abstraction (but ships its own backend) is forced to drag in C extensions transitively.

pura-processing extracts the backend-agnostic layer so that gems like pura-image can offer a drop-in ImageProcessing-compatible API with zero C compiler requirements.

Installation

# Gemfile
gem "pura-processing"

gem install pura-processing

No system libraries. No compiler. Works on CRuby, JRuby, TruffleRuby, and ruby.wasm.

Usage

pura-processing does not perform image I/O on its own — it provides the abstract pipeline. You subclass Pura::Processing::Processor and implement load_image / save_image / any operation macros:

require "pura/processing"

class MyProcessor < Pura::Processing::Processor
  accumulator :image, MyImageClass

  def self.load_image(source, **_options)
    MyImageClass.open(source)
  end

  def self.save_image(image, destination, **_options)
    image.write(destination)
  end

  def resize_to_limit(width, height, **_options)
    image.resize(width, height)
  end
end

module MyApp
  extend Pura::Processing::Chainable

  class Processor < MyProcessor
  end
end

MyApp.source("photo.jpg")
     .resize_to_limit(400, 400)
     .call(destination: "out.jpg")

The chainable API matches image_processing: source, convert, loader, saver, apply, operation, call, and any unknown method is interpreted as a processor operation (method_missing forwarding).

Attribution

The pipeline layer is adapted from image_processing 1.14.0 under the MIT License. See NOTICE for the upstream copyright and license text. Each source file in lib/pura/processing/ carries a header pointing to the upstream file it was adapted from.

License

MIT. See LICENSE.