blurhash rails-7 with libvips

readme.md

  # application.rb
  config.active_storage.variant_processor = :vips
  config.active_storage.analyzers = [ BlurhashAnalyzer ]

refered: https://ledermann.dev/blog/2020/08/01/progressive-image-loading-with-blurhash/

analyzer.rb

class BlurhashAnalyzer < ActiveStorage::Analyzer::ImageAnalyzer::Vips
  def metadata
    read_image do |image|
      if rotated_image?(image)
        { width: image.height, height: image.width }
      else
        { width: image.width, height: image.height }
      end.merge blurhash(image)
    end
  end

  private

  def blurhash(vips_image)
    # image was rotated when ImageProcessing load it, so we need read the original version from disk
    processed_image = ImageProcessing::Vips.source(vips_image.filename).resize_and_pad(200, 200).call
    thumbnail = ::Vips::Image.new_from_file processed_image.path

    {
      blurhash: Blurhash.encode(
        thumbnail.width,
        thumbnail.height,
        ::Vips::Region.new(thumbnail).fetch(0, 0, thumbnail.width, thumbnail.height).unpack('C*')
      )
    }
  rescue StandardError => e
    raise e if Rails.env.development?
    Rails.logger.error "#{'#' * 10 } Error while encoding Blurhash: #{e}"
    {}
  end
end