jekyll-picture-tag it is

Gruntfile.js

@@ -35,8 +35,13 @@ module.exports = function(grunt){
         // Jekyll
         jekyll: {
             production : {
-				src: '<%= config.src %>'
+                options: {
+                    lsi: true
+                }
 			},
+            serve: {
+                
+            }
         },
         
         // less
@@ -150,7 +155,7 @@ module.exports = function(grunt){
                     '<%= config.src %>/_layouts/**',
                     '<%= config.src %>/_posts/**'
                 ],
-                tasks: ['jekyll', 'less', 'uglify']
+                tasks: ['jekyll:serve', 'less', 'uglify']
             },
         },
         
@@ -188,7 +193,7 @@ module.exports = function(grunt){
     
     // Dev server
     grunt.registerTask('server', [
-        'jekyll',
+        'jekyll:serve',
         'less',
         'cmq',
         'cssmin',
@@ -205,8 +210,7 @@ module.exports = function(grunt){
     // Production build
     grunt.registerTask('build', [
         'clean',
-        'jekyll',
-        'responsive_images',
+        'jekyll:production',
         'imagemin',
         'less',
         'cmq',

_config.yml

@@ -15,3 +15,21 @@ source:      ./_src
 destination: ./_site
 exclude:     ['design', 'node_modules', '_src/assets/less']
 keep_files:  ['media']
+
+picture:
+  source: "_media"
+  output: "media_gen"
+  markup: "picturefill"
+  presets:
+    default:
+      ppi: [1, 1.5, 2]
+      attr:
+        itemprop: "image"
+      source_medium:
+        media: "(min-width: 35.556em)"
+        width: "640"
+      source_small:
+        media: "(min-width: 26.667em)"
+        width: "480"
+      source_default: 
+        width: "320"

_src/_plugins/picture_tag.rb

@@ -0,0 +1,254 @@
+# Title: Jekyll Picture Tag
+# Authors: Rob Wierzbowski : @robwierzbowski
+#          Justin Reese    : @justinxreese
+#          Welch Canavan   : @xiwcx
+#
+# Description: Easy responsive images for Jekyll.
+#
+# Download: https://github.com/robwierzbowski/jekyll-picture-tag
+# Documentation: https://github.com/robwierzbowski/jekyll-picture-tag/readme.md
+# Issues: https://github.com/robwierzbowski/jekyll-picture-tag/issues
+#
+# Syntax:  {% picture [preset] path/to/img.jpg [source_key: path/to/alt-img.jpg] [attr="value"] %}
+# Example: {% picture poster.jpg alt="The strange case of responsive images" %}
+#          {% picture gallery poster.jpg source_small: poster_closeup.jpg
+#             alt="The strange case of responsive images" class="gal-img" data-selected %}
+#
+# See the documentation for full configuration and usage instructions.
+
+require 'fileutils'
+require 'pathname'
+require 'digest/md5'
+require 'mini_magick'
+
+module Jekyll
+
+  class Picture < Liquid::Tag
+
+    def initialize(tag_name, markup, tokens)
+      @markup = markup
+      super
+    end
+
+    def render(context)
+
+      # Render any liquid variables in tag arguments and unescape template code
+      render_markup = Liquid::Template.parse(@markup).render(context).gsub(/\\\{\\\{|\\\{\\%/, '\{\{' => '{{', '\{\%' => '{%')
+
+      # Gather settings
+      site = context.registers[:site]
+      settings = site.config['picture']
+      markup = /^(?:(?<preset>[^\s.:\/]+)\s+)?(?<image_src>[^\s]+\.[a-zA-Z0-9]{3,4})\s*(?<source_src>(?:(source_[^\s.:\/]+:\s+[^\s]+\.[a-zA-Z0-9]{3,4})\s*)+)?(?<html_attr>[\s\S]+)?$/.match(render_markup)
+      preset = settings['presets'][ markup[:preset] ] || settings['presets']['default']
+
+      raise "Picture Tag can't read this tag. Try {% picture [preset] path/to/img.jpg [source_key: path/to/alt-img.jpg] [attr=\"value\"] %}." unless markup
+
+      # Assign defaults
+      settings['source'] ||= '.'
+      settings['output'] ||= 'generated'
+      settings['markup'] ||= 'picturefill'
+
+      # Prevent Jekyll from erasing our generated files
+      site.config['keep_files'] << settings['output'] unless site.config['keep_files'].include?(settings['output'])
+
+      # Deep copy preset for single instance manipulation
+      instance = Marshal.load(Marshal.dump(preset))
+
+      # Process alternate source images
+      source_src = if markup[:source_src]
+        Hash[ *markup[:source_src].gsub(/:/, '').split ]
+      else
+        {}
+      end
+
+      # Process html attributes
+      html_attr = if markup[:html_attr]
+        Hash[ *markup[:html_attr].scan(/(?<attr>[^\s="]+)(?:="(?<value>[^"]+)")?\s?/).flatten ]
+      else
+        {}
+      end
+
+      if instance['attr']
+        html_attr = instance.delete('attr').merge(html_attr)
+      end
+
+      if settings['markup'] == 'picturefill'
+        html_attr['data-picture'] = nil
+        html_attr['data-alt'] = html_attr.delete('alt')
+      end
+
+      html_attr_string = html_attr.inject('') { |string, attrs|
+        if attrs[1]
+          string << "#{attrs[0]}=\"#{attrs[1]}\" "
+        else
+          string << "#{attrs[0]} "
+        end
+      }
+
+      # Prepare ppi variables
+      ppi = if instance['ppi'] then instance.delete('ppi').sort.reverse else nil end
+      # this might work??? ppi = instance.delete('ppi'){ |ppi|  [nil] }.sort.reverse
+      ppi_sources = {}
+
+      # Switch width and height keys to the symbols that generate_image() expects
+      instance.each { |key, source|
+        raise "Preset #{key} is missing a width or a height" if !source['width'] and !source['height']
+        instance[key][:width] = instance[key].delete('width') if source['width']
+        instance[key][:height] = instance[key].delete('height') if source['height']
+      }
+
+      # Store keys in an array for ordering the instance sources
+      source_keys = instance.keys
+
+      # Raise some exceptions before we start expensive processing
+      raise "Picture Tag can't find the \"#{markup[:preset]}\" preset. Check picture: presets in _config.yml for a list of presets." unless preset
+      raise "Picture Tag can't find this preset source. Check picture: presets: #{markup[:preset]} in _config.yml for a list of sources." unless (source_src.keys - source_keys).empty?
+
+      # Process instance
+      # Add image paths for each source
+      instance.each_key { |key|
+        instance[key][:src] = source_src[key] || markup[:image_src]
+      }
+
+      # Construct ppi sources
+      # Generates -webkit-device-ratio and resolution: dpi media value for cross browser support
+      # Reference: http://www.brettjankord.com/2012/11/28/cross-browser-retinahigh-resolution-media-queries/
+      if ppi
+        instance.each { |key, source|
+          ppi.each { |p|
+            if p != 1
+              ppi_key = "#{key}-x#{p}"
+
+              ppi_sources[ppi_key] = {
+                :width => if source[:width] then (source[:width].to_f * p).round else nil end,
+                :height => if source[:height] then (source[:height].to_f * p).round else nil end,
+                'media' => if source['media']
+                  "#{source['media']} and (-webkit-min-device-pixel-ratio: #{p}), #{source['media']} and (min-resolution: #{(p * 96).round}dpi)"
+                else
+                  "(-webkit-min-device-pixel-ratio: #{p}), (min-resolution: #{(p * 96).to_i}dpi)"
+                end,
+                :src => source[:src]
+              }
+
+              # Add ppi_key to the source keys order
+              source_keys.insert(source_keys.index(key), ppi_key)
+            end
+          }
+        }
+      instance.merge!(ppi_sources)
+      end
+
+      # Generate resized images
+      instance.each { |key, source|
+        instance[key][:generated_src] = generate_image(source, site.source, site.dest, settings['source'], settings['output'])
+      }
+
+      # Construct and return tag
+      if settings['markup'] == 'picturefill'
+
+        source_tags = ''
+        # Picturefill uses reverse source order
+        # Reference: https://github.com/scottjehl/picturefill/issues/79
+        source_keys.reverse.each { |source|
+          media = " data-media=\"#{instance[source]['media']}\"" unless source == 'source_default'
+          source_tags += "<span data-src=\"#{instance[source][:generated_src]}\"#{media}></span>\n"
+        }
+
+        # Note: we can't indent html output because markdown parsers will turn 4 spaces into code blocks
+        picture_tag = "<span #{html_attr_string}>\n"\
+                      "#{source_tags}"\
+                      "<noscript>\n"\
+                      "<img src=\"#{instance['source_default'][:generated_src]}\" alt=\"#{html_attr['data-alt']}\">\n"\
+                      "</noscript>\n"\
+                      "</span>\n"
+
+      elsif settings['markup'] == 'picture'
+
+        source_tags = ''
+        source_keys.each { |source|
+          if source == 'source_default'
+            source_tags += "<img src=\"#{instance[source][:generated_src]}\" alt=\"#{html_attr['alt']}\">\n"
+          else
+            source_tags += "<source src=\"#{instance[source][:generated_src]}\" media=\"#{instance[source]['media']}\">\n"
+          end
+        }
+
+        # Note: we can't indent html output because markdown parsers will turn 4 spaces into code blocks
+        picture_tag = "<picture #{html_attr_string}>\n"\
+                      "#{source_tags}"\
+                      "<p>#{html_attr['alt']}</p>\n"\
+                      "</picture>"
+      end
+
+        # Return the markup!
+        picture_tag
+    end
+
+    def generate_image(instance, site_source, site_dest, image_source, image_dest)
+
+      image = MiniMagick::Image.open(File.join(site_source, image_source, instance[:src]))
+      digest = Digest::MD5.hexdigest(image.to_blob).slice!(0..5)
+
+      image_dir = File.dirname(instance[:src])
+      ext = File.extname(instance[:src])
+      basename = File.basename(instance[:src], ext)
+
+      orig_width = image[:width].to_f
+      orig_height = image[:height].to_f
+      orig_ratio = orig_width/orig_height
+
+      gen_width = if instance[:width]
+        instance[:width].to_f
+      elsif instance[:height]
+        orig_ratio * instance[:height].to_f
+      else
+        orig_width
+      end
+      gen_height = if instance[:height]
+        instance[:height].to_f
+      elsif instance[:width]
+        instance[:width].to_f / orig_ratio
+      else
+        orig_height
+      end
+      gen_ratio = gen_width/gen_height
+
+      # Don't allow upscaling. If the image is smaller than the requested dimensions, recalculate.
+      if orig_width < gen_width || orig_height < gen_height
+        undersize = true
+        gen_width = if orig_ratio < gen_ratio then orig_width else orig_height * gen_ratio end
+        gen_height = if orig_ratio > gen_ratio then orig_height else orig_width/gen_ratio end
+      end
+
+      gen_name = "#{basename}-#{gen_width.round}*#{gen_height.round}-#{digest}#{ext}"
+      gen_dest_dir = File.join(site_dest, image_dest, image_dir)
+      gen_dest_file = File.join(gen_dest_dir, gen_name)
+
+      # Generate resized files
+      unless File.exists?(gen_dest_file)
+
+        warn "Warning:".yellow + " #{instance[:src]} is smaller than the requested output file. It will be resized without upscaling." if undersize
+
+        #  If the destination directory doesn't exist, create it
+        FileUtils.mkdir_p(gen_dest_dir) unless File.exist?(gen_dest_dir)
+
+        # Let people know their images are being generated
+        puts "Generating #{gen_name}"
+
+        # Scale and crop
+        image.combine_options do |i|
+          i.resize "#{gen_width}x#{gen_height}^"
+          i.gravity "center"
+          i.crop "#{gen_width}x#{gen_height}+0+0"
+        end
+
+        image.write gen_dest_file
+      end
+
+      # Return path relative to the site root for html
+      Pathname.new(File.join('/', image_dest, image_dir, gen_name)).cleanpath
+    end
+  end
+end
+
+Liquid::Template.register_tag('picture', Jekyll::Picture)

_src/feed.xml

@@ -32,7 +32,7 @@ layout: nil
     		<id>{{ site.url }}/{{ post.url }}</id>
     		<content type="html">
                 {% if post.image %}
-                    &lt;img src=&quot;{{ site.url }}/media/640/{{ post.image }}&quot; /&gt;
+                    &lt;img src=&quot;{{ site.url }}/media/{{ post.image }}&quot; /&gt;
                 {% endif %}
             
                 {{ post.content | xml_escape }}

_src/index.html

@@ -31,16 +31,7 @@ description: 'Blog of designer & developer Matthias Kretschmann'
             <a class="photoPost" href="{{ post.url }}">
             	<figure class="hmedia">
                     
-                    <span data-picture data-alt="">
-                        <span data-src="/media/320/{{ post.image }}"></span>
-                        <span data-src="/media/640/{{ post.image }}"   data-media="(min-device-pixel-ratio: 1.5)"></span>
-                        <span data-src="/media/640/{{ post.image }}"   data-media="(min-width: 500px)"></span>
-                        <span data-src="/media/1280/{{ post.image }}"  data-media="(min-width: 640px) and (min-device-pixel-ratio: 2.0)"></span>
-
-                        <noscript>
-                            <img src="/media/{{ post.image }}">
-                        </noscript>
-                    </span>
+                    {% picture {{ post.image }} %}
                     
             		<figcaption class="entry-title fn">{{ post.title }}</figcaption>
             		exif
@@ -60,16 +51,7 @@ description: 'Blog of designer & developer Matthias Kretschmann'
                 
                 {% if post.image %}
                     <a href="{{ post.url }}">
-                        <span class="teaser" data-picture data-alt="">
-                            <span data-src="/media/320/{{ post.image }}"></span>
-                            <span data-src="/media/640/{{ post.image }}"   data-media="(min-device-pixel-ratio: 1.5)"></span>
-                            <span data-src="/media/640/{{ post.image }}"   data-media="(min-width: 500px)"></span>
-                            <span data-src="/media/1280/{{ post.image }}"  data-media="(min-width: 640px) and (min-device-pixel-ratio: 2.0)"></span>
-
-                            <noscript>
-                                <img src="/media/{{ post.image }}">
-                            </noscript>
-                        </span>
+                        {% picture {{ post.image }} class="teaser" %}
                     </a>
                 {% endif %}