Add the ability to directly invoke rounding method

round_corners.rb

@@ -1,29 +1,25 @@
 module Paperclip
   class RoundCorners < Paperclip::Thumbnail
 
-    def parse_opts(key)
-      opt = @options["border_radius_#{key}".to_sym] || @options["border_radius_#{key.delete('_')}".to_sym] || @options[:border_radius]
-      opt.nil? ? nil : opt.to_i
-    end
-
-    def transformation
-      trans = " \\( +clone  -threshold -1 "
-      trans << "-draw 'fill black polygon 0,0 0,#{@topleft} #{@topleft},0 fill white circle #{@topleft},#{@topleft} #{@topleft},0' " unless @topleft.nil?
-      trans << "-draw 'fill black polygon #{@left},0 #{@left},#{@topright} #{@left-@topright},0 fill white circle #{@left-@topright},#{@topright} #{@left},#{@topright}' " unless @topright.nil?
-      trans << "-draw 'fill black polygon 0,#{@bottom} #{@bottomleft},#{@bottom} 0,#{@bottom-@bottomleft} fill white circle #{@bottomleft},#{@bottom-@bottomleft} #{@bottomleft},#{@bottom}' " unless @bottomleft.nil?
-      trans << "-draw 'fill black polygon #{@left},#{@bottom} #{@left},#{@bottom-@bottomright} #{@left-@bottomright},#{@bottom} fill white circle #{@left-@bottomright},#{@bottom-@bottomright} #{@left},#{@bottom-@bottomright}' " unless @bottomright.nil?
-      trans << "\\) +matte -compose CopyOpacity -composite "
-    end
-
-    def round_corners(dst)
-      options = [
-        "#{ File.expand_path(@thumbnail.path) }[0]",
+    def self.round(source, destination, topleft, topright, bottomleft, bottomright)
+      # Need to `-1` becuase when drawing, the coordinates start from 0
+      left = Paperclip::Geometry.from_file(source).width.to_i - 1
+      bottom = Paperclip::Geometry.from_file(source).height.to_i - 1
+
+      transformation = " \\( +clone  -threshold -1 "
+      transformation << "-draw 'fill black polygon 0,0 0,#{topleft} #{topleft},0 fill white circle #{topleft},#{topleft} #{topleft},0' " unless topleft.nil?
+      transformation << "-draw 'fill black polygon #{left},0 #{left},#{topright} #{left-topright},0 fill white circle #{left-topright},#{topright} #{left},#{topright}' " unless topright.nil?
+      transformation << "-draw 'fill black polygon 0,#{bottom} #{bottomleft},#{bottom} 0,#{bottom-bottomleft} fill white circle #{bottomleft},#{bottom-bottomleft} #{bottomleft},#{bottom}' " unless bottomleft.nil?
+      transformation << "-draw 'fill black polygon #{left},#{bottom} #{left},#{bottom-bottomright} #{left-bottomright},#{bottom} fill white circle #{left-bottomright},#{bottom-bottomright} #{left},#{bottom-bottomright}' " unless bottomright.nil?
+      transformation << "\\) +matte -compose CopyOpacity -composite "
+
+      Paperclip.run('convert', [
+        "#{File.expand_path(source.path)}[0]",
         transformation,
-        "#{ File.expand_path(dst.path) }"
-      ].flatten.compact.join(" ")
+        "#{File.expand_path(destination.path)}"
+      ].flatten.compact.join(" "))
 
-      Paperclip.run('convert', options)
-      dst
+      destination
     end
 
     def initialize(file, options = {}, attachment = nil)
@@ -39,18 +35,19 @@ def initialize(file, options = {}, attachment = nil)
       @process = @topleft || @topright || @bottomleft || @bottomright
     end
 
+    def parse_opts(key)
+      opt = @options["border_radius_#{key}".to_sym] || @options["border_radius_#{key.delete('_')}".to_sym] || @options[:border_radius]
+      opt.nil? ? nil : opt.to_i
+    end
+
     def make
       @thumbnail = super
 
       if @process
-        # Need to `-1` becuase when drawing, the coordinates start from 0
-        @left = Paperclip::Geometry.from_file(@thumbnail).width.to_i - 1
-        @bottom = Paperclip::Geometry.from_file(@thumbnail).height.to_i - 1
-
-        dst = Tempfile.new([@basename, @format].compact.join("."))
-        dst.binmode
+        destination = Tempfile.new([@basename, @format].compact.join("."))
+        destination.binmode
 
-        return round_corners(dst)
+        return Paperclip::RoundCorners.round(@thumbnail, destination, @topleft, @topright, @bottomleft, @bottomright)
       else
         return @thumbnail
       end