Image Infrastructure for the Street Art API

image-1.rb

require 'mini_magick'
require 'exifr'

module Useless
  class StreetArt
    class Image
      def initialize(raw_io)
        @raw_io = raw_io
      end

      def base
        @base ||= minimagick_copy
      end

      private

      def minimagick_copy
        # Just instantiate a new instance with the raw image blob
        MiniMagick::Image.read(blob)
      end

      # A binary blob of the original image
      def blob
        @blob ||= begin
          # Make sure the pointer is up front,
          @raw_io.rewind

          # read the bytes,
          blob = @raw_io.read

          # make sure they're un-encoded (encodings can cause multiple bytes to
          # be interpreted as one, which is no good for images),
          blob.force_encoding('BINARY')

          # and return
          blob
        end
      end
    end
  end
end

image-2.rb

module Useless
  class StreetArt
    class Image
      def small
        @small ||= version('100x100')
      end

      def medium
        @medium ||= version('500x500')
      end

      def large
        @large ||= version('1024x1024')
      end

      private

      def version(dimensions)
        # Copy the image
        image = minimagick_copy

        # resize it to the specified dimensions
        image.resize dimensions

        # and return
        image
      end
    end
  end
end

image-3.rb

module Useless
  class StreetArt
    class Image
      def latitude
        @latitude ||= exifr.gps.latitude if exifr and exifr.gps
      end

      def longitude
        @longitude ||= exifr.gps.longitude if exifr and exifr.gps
      end

      def shot_at
        @shot_at ||= exifr.date_time if exifr
      end

      private

      def exifr
        @exifr ||= case base['format']
          when 'JPEG' then EXIFR::JPEG.new(StringIO.new(blob))
          when 'TIFF' then EXIFR::TIFF.new(StringIO.new(blob))
          else nil
          end
      end
    end
  end
end

image-4.rb

module Useless
  class StreetArt
    class Image
      def valid?
        ['JPEG', 'TIFF', 'PNG', 'GIF'].include?(base['format'])
      end
    end
  end
end