diff --git a/Makefile b/Makefile
index f7c3612..f52e12b 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 .PHONY : test test-coverage
 
 test :
-	testrb -b tests/*
+	testrb -b tests/*.rb
 
 test-coverage :
 	rcov -x '\/jruby\/lib\/' -x '\/tests\/data\/' tests/*.rb
\ No newline at end of file
diff --git a/classes/Filter.rb b/classes/Filter.rb
index 36c6e78..fad68e5 100644
--- a/classes/Filter.rb
+++ b/classes/Filter.rb
@@ -45,41 +45,6 @@ class Filter
     recalc_pixels
   end
 
-  #
-  # Build a temporary PNG from an SVG file
-  #
-  def inkscape(input, target)
-    params = []
-
-    width = @config['width']
-    height = @config['height']
-    inkscape_target = target
-
-    if @config['rotate']
-      case @config['rotate']
-        when 90, -90
-          t = width; width = height; height = t
-          inkscape_target = target + "-pre.png"
-      end
-    end
-
-    if width && (width.to_i != 0); params << "-w #{width} "; end
-    if height && (height.to_i != 0); params << "-h #{height} "; end
-
-    system("inkscape -e \"#{inkscape_target}\" -y 1.0 #{params.join(" ")} \"#{input}\"")
-
-    if @config['rotate']
-      command = [
-        "\"#{inkscape_target}\"",
-        "-rotate #{@config['rotate']}",
-        "\"#{target}\""
-      ]
-
-      convert(command)
-      File.unlink(inkscape_target)
-    end
-  end
-
   def convert(command, verbose = false)
     if verbose
       puts "convert " + (verbose ? "-verbose " : "" ) + [ command ].flatten.join(" ")
diff --git a/modules/ImageProcessing.rb b/modules/ImageProcessing.rb
new file mode 100644
index 0000000..354b3cb
--- /dev/null
+++ b/modules/ImageProcessing.rb
@@ -0,0 +1,57 @@
+module ImageProcessing
+  def setup_inkscape(target)
+    params = []
+
+    width = @config['width']
+    height = @config['height']
+    inkscape_target = target
+
+    if @config['rotate']
+      case @config['rotate']
+        when 90, -90
+          t = width; width = height; height = t
+          inkscape_target = target + "-pre.png"
+      end
+    end
+
+    if width && (width.to_i != 0)
+      params << "-w #{width}"
+    end
+    if height && (height.to_i != 0)
+      params << "-h #{height}"
+    end
+
+    [ params, inkscape_target ]
+  end
+
+  #
+  # Build a PNG from an SVG file
+  #
+  def inkscape(input, target)
+    params, inkscape_target = setup_inkscape(target)
+
+    call_system("inkscape -e \"#{inkscape_target}\" -y 1.0 #{params.join(" ")} \"#{input}\"")
+
+    if @config['rotate']
+      command = [
+        "\"#{inkscape_target}\"",
+        "-rotate #{@config['rotate']}",
+        "\"#{target}\""
+      ]
+
+      convert(command)
+      File.unlink(inkscape_target)
+    end
+  end
+
+  def convert(command, verbose = false)
+    if verbose
+      puts "convert " + (verbose ? "-verbose " : "" ) + [ command ].flatten.join(" ")
+    end
+    call_system("convert " + (verbose ? "-verbose " : "" ) + [ command ].flatten.join(" "))
+  end
+
+  def call_system(command)
+    Kernel.system(command)
+  end
+end
diff --git a/tests/test_image_processing.rb b/tests/test_image_processing.rb
new file mode 100644
index 0000000..63579aa
--- /dev/null
+++ b/tests/test_image_processing.rb
@@ -0,0 +1,32 @@
+require "test/unit"
+require File.dirname(__FILE__) + '/../modules/ImageProcessing.rb'
+
+class TestImageProcessing < Test::Unit::TestCase
+  def setup
+    @instance = Class.new do
+      include ImageProcessing
+
+      attr_accessor :config
+    end.new
+  end
+
+  def test_setup_inkscape
+    [
+      [ {}, [], 'target' ],
+      [ { 'width' => 'test' }, [], 'target' ],
+      [ { 'width' => 200 }, ['-w 200'], 'target' ],
+      [ { 'height' => 'test' }, [], 'target' ],
+      [ { 'height' => 200 }, ['-h 200'], 'target' ],
+      [ { 'rotate' => 0 }, [], 'target' ],
+      [ { 'rotate' => 90 }, [], 'target-pre.png' ],
+      [ { 'rotate' => 90, 'width' => 50, 'height' => 75 }, ['-w 75', '-h 50'], 'target-pre.png' ],
+    ].each do |config, expected_params, expected_target|
+      @instance.config = config
+
+      params, inkscape_target = @instance.setup_inkscape('target')
+
+      assert_equal expected_params, params
+      assert_equal inkscape_target, expected_target
+    end
+  end
+end