automatic image size calculations

lib/middleman/base.rb

@@ -104,6 +104,7 @@ class Middleman::Base
   disable :relative_assets
   disable :maruku
   disable :smush_pngs
+  disable :automatic_image_sizes
   
   # Default build features
   configure :build do

lib/middleman/fastimage.rb

@@ -0,0 +1,282 @@
+# FastImage finds the size or type of an image given its uri.
+# It is careful to only fetch and parse as much of the image as is needed to determine the result.
+# It does this by using a feature of Net::HTTP that yields strings from the resource being fetched
+# as soon as the packets arrive.
+#
+# No external libraries such as ImageMagick are used here, this is a very lightweight solution to 
+# finding image information.
+#
+# FastImage knows about GIF, JPEG, BMP and PNG files.
+#
+# FastImage can also read files from the local filesystem by supplying the path instead of a uri.
+# In this case FastImage uses the open-uri library to read the file in chunks of 256 bytes until
+# it has enough. This is possibly a useful bandwidth-saving feature if the file is on a network
+# attached disk rather than truly local.
+#
+# === Examples
+#   require 'fastimage'
+#
+#   FastImage.size("http://stephensykes.com/images/ss.com_x.gif")
+#   => [266, 56]
+#   FastImage.type("http://stephensykes.com/images/pngimage")
+#   => :png
+#   FastImage.type("/some/local/file.gif")
+#   => :gif
+#
+# === References
+# * http://snippets.dzone.com/posts/show/805
+# * http://www.anttikupila.com/flash/getting-jpg-dimensions-with-as3-without-loading-the-entire-file/
+# * http://pennysmalls.com/2008/08/19/find-jpeg-dimensions-fast-in-ruby/
+# * http://imagesize.rubyforge.org/
+#
+require 'net/https'
+require 'open-uri'
+
+module Middleman
+  class FastImage
+    attr_reader :size, :type
+
+    class FastImageException < StandardError # :nodoc:
+    end
+    class MoreCharsNeeded < FastImageException # :nodoc:
+    end
+    class UnknownImageType < FastImageException # :nodoc:
+    end
+    class ImageFetchFailure < FastImageException # :nodoc:
+    end
+    class SizeNotFound < FastImageException # :nodoc:
+    end
+
+    DefaultTimeout = 2
+  
+    LocalFileChunkSize = 256
+
+    # Returns an array containing the width and height of the image.
+    # It will return nil if the image could not be fetched, or if the image type was not recognised.
+    #
+    # By default there is a timeout of 2 seconds for opening and reading from a remote server.
+    # This can be changed by passing a :timeout => number_of_seconds in the options.
+    #
+    # If you wish FastImage to raise if it cannot size the image for any reason, then pass
+    # :raise_on_failure => true in the options.
+    #
+    # FastImage knows about GIF, JPEG, BMP and PNG files.
+    #
+    # === Example
+    #
+    #   require 'fastimage'
+    #
+    #   FastImage.size("http://stephensykes.com/images/ss.com_x.gif")
+    #   => [266, 56]
+    #   FastImage.size("http://stephensykes.com/images/pngimage")
+    #   => [16, 16]
+    #   FastImage.size("http://farm4.static.flickr.com/3023/3047236863_9dce98b836.jpg")
+    #   => [500, 375]
+    #   FastImage.size("http://www-ece.rice.edu/~wakin/images/lena512.bmp")
+    #   => [512, 512]
+    #   FastImage.size("test/fixtures/test.jpg")
+    #   => [882, 470]
+    #   FastImage.size("http://pennysmalls.com/does_not_exist")
+    #   => nil
+    #   FastImage.size("http://pennysmalls.com/does_not_exist", :raise_on_failure=>true)
+    #   => raises FastImage::ImageFetchFailure
+    #   FastImage.size("http://stephensykes.com/favicon.ico", :raise_on_failure=>true)
+    #   => raises FastImage::UnknownImageType
+    #   FastImage.size("http://stephensykes.com/favicon.ico", :raise_on_failure=>true, :timeout=>0.01)
+    #   => raises FastImage::ImageFetchFailure
+    #   FastImage.size("http://stephensykes.com/images/faulty.jpg", :raise_on_failure=>true)
+    #   => raises FastImage::SizeNotFound
+    #
+    # === Supported options
+    # [:timeout]
+    #   Overrides the default timeout of 2 seconds.  Applies both to reading from and opening the http connection.
+    # [:raise_on_failure]
+    #   If set to true causes an exception to be raised if the image size cannot be found for any reason.
+    #
+    def self.size(uri, options={})
+      new(uri, options).size
+    end
+
+    # Returns an symbol indicating the image type fetched from a uri.
+    # It will return nil if the image could not be fetched, or if the image type was not recognised.
+    #
+    # By default there is a timeout of 2 seconds for opening and reading from a remote server.
+    # This can be changed by passing a :timeout => number_of_seconds in the options.
+    #
+    # If you wish FastImage to raise if it cannot find the type of the image for any reason, then pass
+    # :raise_on_failure => true in the options.
+    #
+    # === Example
+    #
+    #   require 'fastimage'
+    #
+    #   FastImage.type("http://stephensykes.com/images/ss.com_x.gif")
+    #   => :gif
+    #   FastImage.type("http://stephensykes.com/images/pngimage")
+    #   => :png
+    #   FastImage.type("http://farm4.static.flickr.com/3023/3047236863_9dce98b836.jpg")
+    #   => :jpeg
+    #   FastImage.type("http://www-ece.rice.edu/~wakin/images/lena512.bmp")
+    #   => :bmp
+    #   FastImage.type("test/fixtures/test.jpg")
+    #   => :jpeg
+    #   FastImage.type("http://pennysmalls.com/does_not_exist")
+    #   => nil
+    #
+    # === Supported options
+    # [:timeout]
+    #   Overrides the default timeout of 2 seconds.  Applies both to reading from and opening the http connection.
+    # [:raise_on_failure]
+    #   If set to true causes an exception to be raised if the image type cannot be found for any reason.
+    #
+    def self.type(uri, options={})
+      new(uri, options.merge(:type_only=>true)).type
+    end
+
+    def initialize(uri, options={})
+      @property = options[:type_only] ? :type : :size
+      @timeout = options[:timeout] || DefaultTimeout
+      @uri = uri
+      @parsed_uri = URI.parse(uri.gsub(/\s/, "%20"))
+      if @parsed_uri.scheme == "http" || @parsed_uri.scheme == "https"
+        fetch_using_http
+      else
+        fetch_using_open_uri
+      end
+      raise SizeNotFound if options[:raise_on_failure] && @property == :size && !@size
+    rescue Timeout::Error, SocketError, Errno::ECONNREFUSED, Errno::EHOSTUNREACH, Errno::ECONNRESET, ImageFetchFailure
+      raise ImageFetchFailure if options[:raise_on_failure]
+    rescue Errno::ENOENT
+      raise ImageFetchFailure if options[:raise_on_failure]    
+    rescue UnknownImageType
+      raise UnknownImageType if options[:raise_on_failure]
+    end
+
+    private
+
+    def fetch_using_http
+      setup_http
+      @http.request_get(@parsed_uri.request_uri) do |res|
+        raise ImageFetchFailure unless res.is_a?(Net::HTTPSuccess)
+        res.read_body do |str|
+          break if parse_packet(str)
+        end
+      end
+    end
+
+    def setup_http
+      @http = Net::HTTP.new(@parsed_uri.host, @parsed_uri.port)
+      @http.use_ssl = (@parsed_uri.scheme == "https")
+      @http.verify_mode = OpenSSL::SSL::VERIFY_NONE
+      @http.open_timeout = @timeout
+      @http.read_timeout = @timeout
+    end
+
+    def fetch_using_open_uri
+      open(@uri) do |s|
+        while str = s.read(LocalFileChunkSize)
+          break if parse_packet(str)
+        end
+      end
+    end
+
+    # returns true once result is achieved
+    #
+    def parse_packet(str)
+      @str = (@unused_str || "") + str
+      @strpos = 0
+      begin
+        result = send("parse_#{@property}")
+        if result 
+          instance_variable_set("@#{@property}", result)
+          true
+        end
+      rescue MoreCharsNeeded
+        false
+      end
+    end
+
+    def parse_size
+      @type = parse_type unless @type
+      send("parse_size_for_#{@type}")
+    end
+
+    def get_chars(n)
+      if @strpos + n - 1 >= @str.size
+        @unused_str = @str[@strpos..-1]
+        raise MoreCharsNeeded
+      else
+        result = @str[@strpos..(@strpos + n - 1)]
+        @strpos += n
+        result
+      end
+    end
+
+    def get_byte
+      get_chars(1).unpack("C")[0]
+    end
+
+    def read_int(str)
+      size_bytes = str.unpack("CC")
+      (size_bytes[0] << 8) + size_bytes[1]
+    end
+
+    def parse_type
+      case get_chars(2)
+      when "BM"
+        :bmp
+      when "GI"
+        :gif
+      when 0xff.chr + 0xd8.chr
+        :jpeg
+      when 0x89.chr + "P"
+        :png
+      else
+        raise UnknownImageType
+      end
+    end
+
+    def parse_size_for_gif
+      get_chars(9)[4..8].unpack('SS')
+    end
+
+    def parse_size_for_png
+      get_chars(23)[14..22].unpack('NN')
+    end
+
+    def parse_size_for_jpeg
+      loop do
+        @state = case @state
+        when nil
+          get_chars(2)
+          :started
+        when :started
+          get_byte == 0xFF ? :sof : :started          
+        when :sof
+          c = get_byte
+          if (0xe0..0xef).include?(c)
+            :skipframe
+          elsif [0xC0..0xC3, 0xC5..0xC7, 0xC9..0xCB, 0xCD..0xCF].detect {|r| r.include? c}
+            :readsize
+          else
+            :skipframe
+          end
+        when :skipframe
+          @skip_chars = read_int(get_chars(2)) - 2
+          :do_skip
+        when :do_skip
+          get_chars(@skip_chars)
+          :started
+        when :readsize
+          s = get_chars(7)
+          return [read_int(s[5..6]), read_int(s[3..4])]
+        end
+      end
+    end
+
+    def parse_size_for_bmp
+      d = get_chars(27)[12..26]
+      d[0] == 40 ? d[4..-1].unpack('LL') : d[4..8].unpack('SS')
+    end
+  end
+end

lib/middleman/features/automatic_image_sizes.rb

@@ -0,0 +1,27 @@
+require "middleman/fastimage"
+
+class Middleman::Base
+  alias_method :pre_automatic_image_tag, :image_tag
+  helpers do
+    def image_tag(path, params={})
+      params[:alt] ||= ""
+      prefix = options.http_images_path rescue options.images_dir
+      
+      if (!params[:width] || !params[:height]) && !path.include?("://")
+        begin
+          real_path = File.join(options.public, asset_url(path, prefix))
+          if File.exists? real_path
+            dimensions = Middleman::FastImage.size(real_path, :raise_on_failure => true)
+            params[:width]  ||= dimensions[0]
+            params[:height] ||= dimensions[1]
+          end
+        rescue
+        end
+      end
+      
+      params = params.merge(:src => asset_url(path, prefix))
+      params = params.map { |k,v| %Q{#{k}="#{v}"}}.join(' ')
+      "<img #{params} />"
+    end
+  end
+end