Also abstract out the string geometry parser from Thumbnail, to reduce coupling.

lib/paperclip/thumbnail.rb

@@ -18,19 +18,20 @@ module Paperclip
     # Options include:
     #
     #   +geometry+ - the desired width and height of the thumbnail
-    #   +file_geometry_parser+ - an object with a method named +from_file+ that takes an image file and produces its geometry. Defaults to Paperclip::Geometry
+    #   +file_geometry_parser+ - an object with a method named +from_file+ that takes an image file and produces its geometry and a +transformation_to+. Defaults to Paperclip::Geometry
+    #   +string_geometry_parser+ - an object with a method named +parse+ that takes a string and produces an object with +width+, +height+, and +to_s+ accessors. Defaults to Paperclip::Geometry
     #   +source_file_options+ - flags passed to the +convert+ command that influence how the source file is read
     #   +convert_options+ - flags passed to the +convert+ command that influence how the image is processed
-    #   +whiny+ - whether to raise an error when processing fails. Defaults to true.
+    #   +whiny+ - whether to raise an error when processing fails. Defaults to true
     #   +format+ - the desired filename extension
-    #   +animated+ - whether to merge all the layers in the image. Defaults to true.
+    #   +animated+ - whether to merge all the layers in the image. Defaults to true
     def initialize(file, options = {}, attachment = nil)
       super
 
-      geometry             = options[:geometry]
+      geometry             = options[:geometry] # this is not an option
       @file                = file
       @crop                = geometry[-1,1] == '#'
-      @target_geometry     = Geometry.parse(geometry)
+      @target_geometry     = (options[:string_geometry_parser] || Geometry).parse(geometry)
       @current_geometry    = (options[:file_geometry_parser] || Geometry).from_file(@file)
       @source_file_options = options[:source_file_options]
       @convert_options     = options[:convert_options]

test/thumbnail_test.rb

@@ -225,7 +225,7 @@ class ThumbnailTest < Test::Unit::TestCase
       end
     end
 
-    context "passing a custom geometry parser" do
+    context "passing a custom file geometry parser" do
       should "produce the appropriate transformation_command" do
         GeoParser = Class.new do
           def self.from_file(file)
@@ -236,7 +236,7 @@ class ThumbnailTest < Test::Unit::TestCase
           end
         end
 
-        thumb = Paperclip::Thumbnail.new(@file, :geometry => "50x50", :file_geometry_parser => GeoParser)
+        thumb = Paperclip::Thumbnail.new(@file, :geometry => '50x50', :file_geometry_parser => GeoParser)
 
         transformation_command = thumb.transformation_command
 
@@ -250,6 +250,27 @@ class ThumbnailTest < Test::Unit::TestCase
           %{expected #{transformation_command.inspect} to include '"SCALE"'}
       end
     end
+
+    context "passing a custom geometry string parser" do
+      should "produce the appropriate transformation_command" do
+        GeoParser = Class.new do
+          def self.parse(s)
+            new
+          end
+
+          def to_s
+            "151x167"
+          end
+        end
+
+        thumb = Paperclip::Thumbnail.new(@file, :geometry => '50x50', :string_geometry_parser => GeoParser)
+
+        transformation_command = thumb.transformation_command
+
+        assert transformation_command.include?('"151x167"'),
+          %{expected #{transformation_command.inspect} to include '151x167'}
+      end
+    end
   end
 
   context "A multipage PDF" do