Contents

module PictureTag
  module Parsers
    # Returns information regarding image handlers
    class ImageBackend
      def handler_for(format)
        if (vips_formats & all_names(format)).any?
          :vips
        elsif (magick_formats & all_names(format)).any?
          :magick
        else
          raise error_string(format)
        end
      end

      # Returns array of formats that vips can save to
      def vips_formats
        @vips_formats ||= `vips -l`
                          .split('/n')
                          .select { |line| line.include? 'ForeignSave' }
                          .flat_map { |line| line.scan(/\.[a-z]{1,5}/) }
                          .map { |format| format.strip.delete_prefix('.') }
                          .uniq
      end

      # Returns an array of formats that imagemagick can handle.
      def magick_formats
        @magick_formats ||= `convert -version`
                            .scan(/Delegates.*/)
                            .first
                            .delete_prefix('Delegates (built-in):')
                            .split
      end

      # Returns an array of all known names of a format, for the purposes of
      # parsing supported output formats.
      def all_names(format)
        alts = alternates.select { |a| a.include? format }.flatten
        alts.any? ? alts : [format]
      end

      private

      def error_string(format)
        <<~HEREDOC
          No support for generating #{format} files in this environment!
          Libvips known savers: #{vips_formats.join(', ')}
          Imagemagick known savers:  #{magick_formats.join(', ')}
        HEREDOC
      end

      def alternates
        [%w[jpg jpeg], %w[avif heic heif]]
      end
    end
  end
end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
jekyll_picture_tag-2.0.4	lib/jekyll_picture_tag/parsers/image_backend.rb