model.rb in artwork-0.7.0

- old
+ new

@@ -1,13 +1,20 @@
 require 'artwork/thumbnail'
 
 module Artwork
   module Model
-    def artwork_thumb_for(attachment_name, size)
+    def artwork_thumb_for(attachment_name, size, alternative_sizes = nil)
+      size = determine_alternative_size_for(alternative_sizes) || size
+
+      size, base_resolution = size.to_s.split('@')
+      base_resolution ||= Artwork.base_resolution
+
       desired_thumb = Thumbnail.new(size)
       matching_thumb_name = nil
 
+      ratio_for_current_resolution = base_resolution.to_f / Artwork.current_resolution.to_f
+
       if desired_thumb.compatible?
         desired_size = desired_thumb.width / ratio_for_current_resolution
 
         thumbs = attachment_styles_for(attachment_name).map { |thumb_name| Thumbnail.new(thumb_name) }
 
@@ -40,20 +47,26 @@
 
       matching_thumb_name.to_sym
     end
 
     def artwork_url(attachment_name, size, options = {})
-      thumb_name = artwork_thumb_for(attachment_name, size)
+      thumb_name = artwork_thumb_for(attachment_name, size, options)
       send(attachment_name).url(thumb_name, options)
     end
 
     def attachment_styles_for(attachment_name)
       self.class.attachment_definitions[attachment_name.to_sym][:styles].keys
     end
 
     private
 
-    def ratio_for_current_resolution
-      Artwork.default_resolution.to_f / Artwork.current_resolution.to_f
+    def determine_alternative_size_for(alternative_sizes)
+      return unless alternative_sizes
+
+      new_size_definition = alternative_sizes \
+        .sort_by { |max_resolution, size| max_resolution } \
+        .find { |max_resolution, size| Artwork.actual_resolution <= max_resolution }
+
+      new_size_definition.last if new_size_definition
     end
   end
 end