smart packing helper classes

lib/compass/sass_extensions/sprites/image_row.rb

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+require 'forwardable'
+
+module Compass
+  module SassExtensions
+    module Sprites
+      class ImageRow
+        extend Forwardable
+
+        attr_reader :images, :max_width
+        def_delegators :@images, :last, :delete, :empty?, :length
+        
+        def initialize(max_width)
+          @images = []
+          @max_width = max_width
+        end
+        
+        def add(image)
+          return false if !will_fit?(image)
+          @images << image
+          true
+        end
+
+        alias :<< :add
+        
+        def height
+          images.map(&:height).max
+        end
+        
+        def width
+          images.map(&:width).max
+        end
+
+        def total_width
+          images.inject(0) {|sum, img| sum + img.width }
+        end
+        
+        def efficiency
+          1 - (total_width.to_f / max_width.to_f)
+        end
+
+        def will_fit?(image)
+          (total_width + image.width) <= max_width
+        end
+      end
+    end
+  end
+end

lib/compass/sass_extensions/sprites/row_fitter.rb

@@ -0,0 +1,86 @@
+require 'forwardable'
+
+module Compass
+  module SassExtensions
+    module Sprites
+      class RowFitter
+        extend Forwardable
+
+        attr_reader :images, :rows
+        def_delegators :rows, :[]
+
+        def initialize(images)
+          @images = images.sort {|a,b| a.height <=> b.height }
+          @rows = []
+        end
+
+        def fit!(style = :scan)
+          send("#{style}_fit")
+          @rows
+        end
+
+        def width
+          @width ||= @images.collect(&:width).max
+        end
+        
+        def height
+          @height ||= @rows.inject(0) {|sum, row| sum += row.height}
+        end
+
+        def efficiency
+          @rows.inject(0) { |sum, row| sum += row.efficiency } ** @rows.length
+        end
+
+        private
+        def new_row(image = nil)
+          row = Compass::SassExtensions::Sprites::ImageRow.new(width)
+          row.add(image) if image
+          row
+        end
+
+        def fast_fit
+          row = new_row
+          @images.each do |image|
+            if !row.add(image)
+              @rows << row
+              row = new_row(image)
+            end
+          end
+
+          @rows << row
+        end
+
+        def scan_fit
+          fast_fit
+
+          moved_images = []
+
+          begin
+            removed = false
+
+            catch :done do
+              @rows.each do |row|
+                (@rows - [ row ]).each do |other_row|
+                  other_row.images.each do |image|
+                    if !moved_images.include?(image)
+                      if row.will_fit?(image)
+                        other_row.delete(image)
+                        row << image
+
+                        @rows.delete(other_row) if other_row.empty?
+                        removed = true
+
+                        moved_images << image
+                        throw :done
+                      end
+                    end
+                  end
+                end
+              end
+            end
+          end while removed
+        end
+      end
+    end
+  end
+end