diff --git a/lib/dragonfly/content.rb b/lib/dragonfly/content.rb
index 271ae557f..dbf9f6233 100644
--- a/lib/dragonfly/content.rb
+++ b/lib/dragonfly/content.rb
@@ -1,8 +1,8 @@
-require 'base64'
-require 'forwardable'
-require 'dragonfly/has_filename'
-require 'dragonfly/temp_object'
-require 'dragonfly/utils'
+require "base64"
+require "forwardable"
+require "dragonfly/has_filename"
+require "dragonfly/temp_object"
+require "dragonfly/utils"
 
 module Dragonfly
 
@@ -16,11 +16,10 @@ module Dragonfly
   # It is acted upon in generator, processor, analyser and datastore methods and provides a standard interface for updating content,
   # no matter how that content first got there (whether in the form of a String/Pathname/File/etc.)
   class Content
-
     include HasFilename
     extend Forwardable
 
-    def initialize(app, obj="", meta=nil)
+    def initialize(app, obj = "", meta = nil)
       @app = app
       @meta = {}
       @previous_temp_objects = []
@@ -79,7 +78,7 @@ def name=(name)
     # @example "image/jpeg"
     # @return [String]
     def mime_type
-      meta['mime_type'] || app.mime_type_for(ext)
+      meta["mime_type"] || app.mime_type_for(ext)
     end
 
     # Set the content using a pre-registered generator
@@ -93,7 +92,7 @@ def generate!(name, *args)
 
     # Update the content using a pre-registered processor
     # @example
-    #   content.process!(:convert, "-resize 300x300")
+    #   content.process!(:thumb, "300x300")
     # @return [Content] self
     def process!(name, *args)
       app.get_processor(name).call(self, *args)
@@ -111,10 +110,10 @@ def analyse(name)
     # @param obj [String, Pathname, Tempfile, File, Content, TempObject] can be any of these types
     # @param meta [Hash] - should be json-like, i.e. contain no types other than String, Number, Boolean
     # @return [Content] self
-    def update(obj, meta=nil)
+    def update(obj, meta = nil)
       meta ||= {}
-      self.temp_object = TempObject.new(obj, meta['name'])
-      self.meta['name'] ||= temp_object.name if temp_object.name
+      self.temp_object = TempObject.new(obj, meta["name"])
+      self.meta["name"] ||= temp_object.name if temp_object.name
       clear_analyser_cache
       add_meta(obj.meta) if obj.respond_to?(:meta)
       add_meta(meta)
@@ -135,7 +134,7 @@ def add_meta(meta)
     #     "file --mime-type #{path}"
     #   end
     #   # ===> "beach.jpg: image/jpeg"
-    def shell_eval(opts={})
+    def shell_eval(opts = {})
       should_escape = opts[:escape] != false
       command = yield(should_escape ? shell.escape(path) : path)
       run command, :escape => should_escape
@@ -148,7 +147,7 @@ def shell_eval(opts={})
     #     "/usr/local/bin/generate_text gumfry -o #{path}"
     #   end
     # @return [Content] self
-    def shell_generate(opts={})
+    def shell_generate(opts = {})
       ext = opts[:ext] || self.ext
       should_escape = opts[:escape] != false
       tempfile = Utils.new_tempfile(ext)
@@ -165,7 +164,7 @@ def shell_generate(opts={})
     #     "convert -resize 20x10 #{old_path} #{new_path}"
     #   end
     # @return [Content] self
-    def shell_update(opts={})
+    def shell_update(opts = {})
       ext = opts[:ext] || self.ext
       should_escape = opts[:escape] != false
       tempfile = Utils.new_tempfile(ext)
@@ -176,7 +175,7 @@ def shell_update(opts={})
       update(tempfile)
     end
 
-    def store(opts={})
+    def store(opts = {})
       datastore.write(self, opts)
     end
 
@@ -188,7 +187,7 @@ def b64_data
     end
 
     def close
-      previous_temp_objects.each{|temp_object| temp_object.close }
+      previous_temp_objects.each { |temp_object| temp_object.close }
       temp_object.close
     end
 
@@ -199,6 +198,7 @@ def inspect
     private
 
     attr_reader :previous_temp_objects
+
     def temp_object=(temp_object)
       previous_temp_objects.push(@temp_object) if @temp_object
       @temp_object = temp_object
@@ -215,6 +215,5 @@ def clear_analyser_cache
     def run(command, opts)
       shell.run(command, opts)
     end
-
   end
 end
diff --git a/lib/dragonfly/image_magick/commands.rb b/lib/dragonfly/image_magick/commands.rb
new file mode 100644
index 000000000..32a85339e
--- /dev/null
+++ b/lib/dragonfly/image_magick/commands.rb
@@ -0,0 +1,35 @@
+module Dragonfly
+  module ImageMagick
+    module Commands
+      module_function
+
+      def convert(content, args = "", opts = {})
+        convert_command = content.env[:convert_command] || "convert"
+        format = opts["format"]
+
+        input_args = opts["input_args"] if opts["input_args"]
+        delegate_string = "#{opts["delegate"]}:" if opts["delegate"]
+        frame_string = "[#{opts["frame"]}]" if opts["frame"]
+
+        content.shell_update :ext => format do |old_path, new_path|
+          "#{convert_command} #{input_args} #{delegate_string}#{old_path}#{frame_string} #{args} #{new_path}"
+        end
+
+        if format
+          content.meta["format"] = format.to_s
+          content.ext = format
+          content.meta["mime_type"] = nil # don't need it as we have ext now
+        end
+      end
+
+      def generate(content, args, format)
+        format = format.to_s
+        convert_command = content.env[:convert_command] || "convert"
+        content.shell_generate :ext => format do |path|
+          "#{convert_command} #{args} #{path}"
+        end
+        content.add_meta("format" => format)
+      end
+    end
+  end
+end
diff --git a/lib/dragonfly/image_magick/generators/convert.rb b/lib/dragonfly/image_magick/generators/convert.rb
deleted file mode 100644
index b49d487d6..000000000
--- a/lib/dragonfly/image_magick/generators/convert.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-module Dragonfly
-  module ImageMagick
-    module Generators
-      class Convert
-
-        def call(content, args, format)
-          format = format.to_s
-          convert_command = content.env[:convert_command] || 'convert'
-          content.shell_generate :ext => format do |path|
-            "#{convert_command} #{args} #{path}"
-          end
-          content.add_meta('format' => format)
-        end
-
-      end
-    end
-  end
-end
-
diff --git a/lib/dragonfly/image_magick/generators/plain.rb b/lib/dragonfly/image_magick/generators/plain.rb
index 9d15de2fe..f0ed84559 100644
--- a/lib/dragonfly/image_magick/generators/plain.rb
+++ b/lib/dragonfly/image_magick/generators/plain.rb
@@ -1,25 +1,31 @@
+require "dragonfly/image_magick/commands"
+require "dragonfly/param_validators"
+
 module Dragonfly
   module ImageMagick
     module Generators
       class Plain
+        include ParamValidators
 
-        def call(content, width, height, opts={})
+        def call(content, width, height, opts = {})
+          validate_all!([width, height], &is_number)
+          validate_all_keys!(opts, %w(colour color format), &is_word)
           format = extract_format(opts)
-          colour = opts['colour'] || opts['color'] || 'white'
-          content.generate!(:convert, "-size #{width}x#{height} xc:#{colour}", format)
-          content.add_meta('format' => format, 'name' => "plain.#{format}")
+
+          colour = opts["colour"] || opts["color"] || "white"
+          Commands.generate(content, "-size #{width}x#{height} xc:#{colour}", format)
+          content.add_meta("format" => format, "name" => "plain.#{format}")
         end
 
-        def update_url(url_attributes, width, height, opts={})
+        def update_url(url_attributes, width, height, opts = {})
           url_attributes.name = "plain.#{extract_format(opts)}"
         end
 
         private
 
         def extract_format(opts)
-          opts['format'] || 'png'
+          opts["format"] || "png"
         end
-
       end
     end
   end
diff --git a/lib/dragonfly/image_magick/generators/plasma.rb b/lib/dragonfly/image_magick/generators/plasma.rb
index 4d590cb4b..93bcf21e8 100644
--- a/lib/dragonfly/image_magick/generators/plasma.rb
+++ b/lib/dragonfly/image_magick/generators/plasma.rb
@@ -1,24 +1,28 @@
+require "dragonfly/image_magick/commands"
+
 module Dragonfly
   module ImageMagick
     module Generators
       class Plasma
+        include ParamValidators
 
-        def call(content, width, height, opts={})
+        def call(content, width, height, opts = {})
+          validate_all!([width, height], &is_number)
+          validate!(opts["format"], &is_word)
           format = extract_format(opts)
-          content.generate!(:convert, "-size #{width}x#{height} plasma:fractal", format)
-          content.add_meta('format' => format, 'name' => "plasma.#{format}")
+          Commands.generate(content, "-size #{width}x#{height} plasma:fractal", format)
+          content.add_meta("format" => format, "name" => "plasma.#{format}")
         end
 
-        def update_url(url_attributes, width, height, opts={})
+        def update_url(url_attributes, width, height, opts = {})
           url_attributes.name = "plasma.#{extract_format(opts)}"
         end
 
         private
 
         def extract_format(opts)
-          opts['format'] || 'png'
+          opts["format"] || "png"
         end
-
       end
     end
   end
diff --git a/lib/dragonfly/image_magick/generators/text.rb b/lib/dragonfly/image_magick/generators/text.rb
index 5c4a8659a..8f1e5a3b9 100644
--- a/lib/dragonfly/image_magick/generators/text.rb
+++ b/lib/dragonfly/image_magick/generators/text.rb
@@ -1,100 +1,111 @@
-require 'dragonfly/hash_with_css_style_keys'
+require "dragonfly/hash_with_css_style_keys"
+require "dragonfly/image_magick/commands"
+require "dragonfly/param_validators"
 
 module Dragonfly
   module ImageMagick
     module Generators
       class Text
+        include ParamValidators
 
         FONT_STYLES = {
-          'normal'  => 'normal',
-          'italic'  => 'italic',
-          'oblique' => 'oblique'
+          "normal" => "normal",
+          "italic" => "italic",
+          "oblique" => "oblique",
         }
 
         FONT_STRETCHES = {
-          'normal'          => 'normal',
-          'semi-condensed'  => 'semi-condensed',
-          'condensed'       => 'condensed',
-          'extra-condensed' => 'extra-condensed',
-          'ultra-condensed' => 'ultra-condensed',
-          'semi-expanded'   => 'semi-expanded',
-          'expanded'        => 'expanded',
-          'extra-expanded'  => 'extra-expanded',
-          'ultra-expanded'  => 'ultra-expanded'
+          "normal" => "normal",
+          "semi-condensed" => "semi-condensed",
+          "condensed" => "condensed",
+          "extra-condensed" => "extra-condensed",
+          "ultra-condensed" => "ultra-condensed",
+          "semi-expanded" => "semi-expanded",
+          "expanded" => "expanded",
+          "extra-expanded" => "extra-expanded",
+          "ultra-expanded" => "ultra-expanded",
         }
 
         FONT_WEIGHTS = {
-          'normal'  => 'normal',
-          'bold'    => 'bold',
-          'bolder'  => 'bolder',
-          'lighter' => 'lighter',
-          '100'     => 100,
-          '200'     => 200,
-          '300'     => 300,
-          '400'     => 400,
-          '500'     => 500,
-          '600'     => 600,
-          '700'     => 700,
-          '800'     => 800,
-          '900'     => 900
+          "normal" => "normal",
+          "bold" => "bold",
+          "bolder" => "bolder",
+          "lighter" => "lighter",
+          "100" => 100,
+          "200" => 200,
+          "300" => 300,
+          "400" => 400,
+          "500" => 500,
+          "600" => 600,
+          "700" => 700,
+          "800" => 800,
+          "900" => 900,
         }
 
-        def update_url(url_attributes, string, opts={})
+        IS_COLOUR = ->(param) {
+          /\A(#\w+|rgba?\([\d\.,]+\)|\w+)\z/ === param
+        }
+
+        def update_url(url_attributes, string, opts = {})
           url_attributes.name = "text.#{extract_format(opts)}"
         end
 
-        def call(content, string, opts={})
+        def call(content, string, opts = {})
+          validate_all_keys!(opts, %w(font font_family), &is_words)
+          validate_all_keys!(opts, %w(color background_color stroke_color), &IS_COLOUR)
+          validate!(opts["format"], &is_word)
+
           opts = HashWithCssStyleKeys[opts]
           args = []
           format = extract_format(opts)
-          background = opts['background_color'] || 'none'
-          font_size = (opts['font_size'] || 12).to_i
+          background = opts["background_color"] || "none"
+          font_size = (opts["font_size"] || 12).to_i
+          font_family = opts["font_family"] || opts["font"]
           escaped_string = "\"#{string.gsub(/"/, '\"')}\""
 
           # Settings
           args.push("-gravity NorthWest")
           args.push("-antialias")
           args.push("-pointsize #{font_size}")
-          args.push("-font \"#{opts['font']}\"") if opts['font']
-          args.push("-family '#{opts['font_family']}'") if opts['font_family']
-          args.push("-fill #{opts['color']}") if opts['color']
-          args.push("-stroke #{opts['stroke_color']}") if opts['stroke_color']
-          args.push("-style #{FONT_STYLES[opts['font_style']]}") if opts['font_style']
-          args.push("-stretch #{FONT_STRETCHES[opts['font_stretch']]}") if opts['font_stretch']
-          args.push("-weight #{FONT_WEIGHTS[opts['font_weight']]}") if opts['font_weight']
+          args.push("-family '#{font_family}'") if font_family
+          args.push("-fill #{opts["color"]}") if opts["color"]
+          args.push("-stroke #{opts["stroke_color"]}") if opts["stroke_color"]
+          args.push("-style #{FONT_STYLES[opts["font_style"]]}") if opts["font_style"]
+          args.push("-stretch #{FONT_STRETCHES[opts["font_stretch"]]}") if opts["font_stretch"]
+          args.push("-weight #{FONT_WEIGHTS[opts["font_weight"]]}") if opts["font_weight"]
           args.push("-background #{background}")
           args.push("label:#{escaped_string}")
 
           # Padding
-          pt, pr, pb, pl = parse_padding_string(opts['padding']) if opts['padding']
-          padding_top    = (opts['padding_top']    || pt || 0)
-          padding_right  = (opts['padding_right']  || pr || 0)
-          padding_bottom = (opts['padding_bottom'] || pb || 0)
-          padding_left   = (opts['padding_left']   || pl || 0)
+          pt, pr, pb, pl = parse_padding_string(opts["padding"]) if opts["padding"]
+          padding_top = (opts["padding_top"] || pt).to_i
+          padding_right = (opts["padding_right"] || pr).to_i
+          padding_bottom = (opts["padding_bottom"] || pb).to_i
+          padding_left = (opts["padding_left"] || pl).to_i
 
-          content.generate!(:convert, args.join(' '), format)
+          Commands.generate(content, args.join(" "), format)
 
           if (padding_top || padding_right || padding_bottom || padding_left)
             dimensions = content.analyse(:image_properties)
-            text_width  = dimensions['width']
-            text_height = dimensions['height']
-            width  = padding_left + text_width  + padding_right
-            height = padding_top  + text_height + padding_bottom
+            text_width = dimensions["width"]
+            text_height = dimensions["height"]
+            width = padding_left + text_width + padding_right
+            height = padding_top + text_height + padding_bottom
 
             args = args.slice(0, args.length - 2)
             args.push("-size #{width}x#{height}")
             args.push("xc:#{background}")
             args.push("-annotate 0x0+#{padding_left}+#{padding_top} #{escaped_string}")
-            content.generate!(:convert, args.join(' '), format)
+            Commands.generate(content, args.join(" "), format)
           end
 
-          content.add_meta('format' => format, 'name' => "text.#{format}")
+          content.add_meta("format" => format, "name" => "text.#{format}")
         end
 
         private
 
         def extract_format(opts)
-          opts['format'] || 'png'
+          opts["format"] || "png"
         end
 
         # Use css-style padding declaration, i.e.
@@ -103,25 +114,23 @@ def extract_format(opts)
         # 10 5 10   (top, left/right, bottom)
         # 10 5 10 5 (top, right, bottom, left)
         def parse_padding_string(str)
-          padding_parts = str.gsub('px','').split(/\s+/).map{|px| px.to_i}
+          padding_parts = str.gsub("px", "").split(/\s+/).map { |px| px.to_i }
           case padding_parts.size
           when 1
             p = padding_parts.first
-            [p,p,p,p]
+            [p, p, p, p]
           when 2
-            p,q = padding_parts
-            [p,q,p,q]
+            p, q = padding_parts
+            [p, q, p, q]
           when 3
-            p,q,r = padding_parts
-            [p,q,r,q]
+            p, q, r = padding_parts
+            [p, q, r, q]
           when 4
             padding_parts
           else raise ArgumentError, "Couldn't parse padding string '#{str}' - should be a css-style string"
           end
         end
       end
-
     end
   end
 end
-
diff --git a/lib/dragonfly/image_magick/plugin.rb b/lib/dragonfly/image_magick/plugin.rb
index 41aa091fe..2a9f2a439 100644
--- a/lib/dragonfly/image_magick/plugin.rb
+++ b/lib/dragonfly/image_magick/plugin.rb
@@ -1,11 +1,11 @@
-require 'dragonfly/image_magick/analysers/image_properties'
-require 'dragonfly/image_magick/generators/convert'
-require 'dragonfly/image_magick/generators/plain'
-require 'dragonfly/image_magick/generators/plasma'
-require 'dragonfly/image_magick/generators/text'
-require 'dragonfly/image_magick/processors/convert'
-require 'dragonfly/image_magick/processors/encode'
-require 'dragonfly/image_magick/processors/thumb'
+require "dragonfly/image_magick/analysers/image_properties"
+require "dragonfly/image_magick/generators/plain"
+require "dragonfly/image_magick/generators/plasma"
+require "dragonfly/image_magick/generators/text"
+require "dragonfly/image_magick/processors/encode"
+require "dragonfly/image_magick/processors/thumb"
+require "dragonfly/image_magick/commands"
+require "dragonfly/param_validators"
 
 module Dragonfly
   module ImageMagick
@@ -13,37 +13,36 @@ module ImageMagick
     # The ImageMagick Plugin registers an app with generators, analysers and processors.
     # Look at the source code for #call to see exactly how it configures the app.
     class Plugin
-
-      def call(app, opts={})
+      def call(app, opts = {})
         # ENV
-        app.env[:convert_command] = opts[:convert_command] || 'convert'
-        app.env[:identify_command] = opts[:identify_command] || 'identify'
+        app.env[:convert_command] = opts[:convert_command] || "convert"
+        app.env[:identify_command] = opts[:identify_command] || "identify"
 
         # Analysers
         app.add_analyser :image_properties, ImageMagick::Analysers::ImageProperties.new
         app.add_analyser :width do |content|
-          content.analyse(:image_properties)['width']
+          content.analyse(:image_properties)["width"]
         end
         app.add_analyser :height do |content|
-          content.analyse(:image_properties)['height']
+          content.analyse(:image_properties)["height"]
         end
         app.add_analyser :format do |content|
-          content.analyse(:image_properties)['format']
+          content.analyse(:image_properties)["format"]
         end
         app.add_analyser :aspect_ratio do |content|
           attrs = content.analyse(:image_properties)
-          attrs['width'].to_f / attrs['height']
+          attrs["width"].to_f / attrs["height"]
         end
         app.add_analyser :portrait do |content|
           attrs = content.analyse(:image_properties)
-          attrs['width'] <= attrs['height']
+          attrs["width"] <= attrs["height"]
         end
         app.add_analyser :landscape do |content|
           !content.analyse(:portrait)
         end
         app.add_analyser :image do |content|
           begin
-            content.analyse(:image_properties)['format'] != 'pdf'
+            content.analyse(:image_properties)["format"] != "pdf"
           rescue Shell::CommandFailed
             false
           end
@@ -55,29 +54,25 @@ def call(app, opts={})
         app.define(:image?) { image }
 
         # Generators
-        app.add_generator :convert, ImageMagick::Generators::Convert.new
         app.add_generator :plain, ImageMagick::Generators::Plain.new
         app.add_generator :plasma, ImageMagick::Generators::Plasma.new
         app.add_generator :text, ImageMagick::Generators::Text.new
 
         # Processors
-        app.add_processor :convert, Processors::Convert.new
         app.add_processor :encode, Processors::Encode.new
         app.add_processor :thumb, Processors::Thumb.new
         app.add_processor :rotate do |content, amount|
-          content.process!(:convert, "-rotate #{amount}")
+          ParamValidators.validate!(amount, &ParamValidators.is_number)
+          Commands.convert(content, "-rotate #{amount}")
         end
 
         # Extra methods
-        app.define :identify do |cli_args=nil|
+        app.define :identify do |cli_args = nil|
           shell_eval do |path|
             "#{app.env[:identify_command]} #{cli_args} #{path}"
           end
         end
-
       end
-
     end
   end
 end
-
diff --git a/lib/dragonfly/image_magick/processors/convert.rb b/lib/dragonfly/image_magick/processors/convert.rb
deleted file mode 100644
index edbf6a488..000000000
--- a/lib/dragonfly/image_magick/processors/convert.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-module Dragonfly
-  module ImageMagick
-    module Processors
-      class Convert
-
-        def call(content, args='', opts={})
-          convert_command = content.env[:convert_command] || 'convert'
-          format = opts['format']
-
-          input_args = opts['input_args'] if opts['input_args']
-          delegate_string = "#{opts['delegate']}:" if opts['delegate']
-          frame_string = "[#{opts['frame']}]" if opts['frame']
-
-          content.shell_update :ext => format do |old_path, new_path|
-            "#{convert_command} #{input_args} #{delegate_string}#{old_path}#{frame_string} #{args} #{new_path}"
-          end
-
-          if format
-            content.meta['format'] = format.to_s
-            content.ext = format
-            content.meta['mime_type'] = nil # don't need it as we have ext now
-          end
-        end
-
-        def update_url(attrs, args='', opts={})
-          format = opts['format']
-          attrs.ext = format if format
-        end
-
-      end
-    end
-  end
-end
diff --git a/lib/dragonfly/image_magick/processors/encode.rb b/lib/dragonfly/image_magick/processors/encode.rb
index 37c027db3..d113ea7c9 100644
--- a/lib/dragonfly/image_magick/processors/encode.rb
+++ b/lib/dragonfly/image_magick/processors/encode.rb
@@ -1,18 +1,29 @@
+require "dragonfly/image_magick/commands"
+
 module Dragonfly
   module ImageMagick
     module Processors
       class Encode
+        include ParamValidators
+
+        WHITELISTED_ARGS = %w(quality)
+
+        IS_IN_WHITELISTED_ARGS = ->(args_string) {
+          args_string.scan(/-\w+/).all? { |arg|
+            WHITELISTED_ARGS.include?(arg.sub("-", ""))
+          }
+        }
 
-        def update_url(attrs, format, args="")
+        def update_url(attrs, format, args = "")
           attrs.ext = format.to_s
         end
 
-        def call(content, format, args="")
-          content.process!(:convert, args, 'format' => format)
+        def call(content, format, args = "")
+          validate!(format, &is_word)
+          validate!(args, &IS_IN_WHITELISTED_ARGS)
+          Commands.convert(content, args, "format" => format)
         end
-
       end
     end
   end
 end
-
diff --git a/lib/dragonfly/image_magick/processors/thumb.rb b/lib/dragonfly/image_magick/processors/thumb.rb
index 5f28831bd..539ba799e 100644
--- a/lib/dragonfly/image_magick/processors/thumb.rb
+++ b/lib/dragonfly/image_magick/processors/thumb.rb
@@ -1,32 +1,40 @@
+require "dragonfly/image_magick/commands"
+
 module Dragonfly
   module ImageMagick
     module Processors
       class Thumb
+        include ParamValidators
 
         GRAVITIES = {
-          'nw' => 'NorthWest',
-          'n'  => 'North',
-          'ne' => 'NorthEast',
-          'w'  => 'West',
-          'c'  => 'Center',
-          'e'  => 'East',
-          'sw' => 'SouthWest',
-          's'  => 'South',
-          'se' => 'SouthEast'
+          "nw" => "NorthWest",
+          "n" => "North",
+          "ne" => "NorthEast",
+          "w" => "West",
+          "c" => "Center",
+          "e" => "East",
+          "sw" => "SouthWest",
+          "s" => "South",
+          "se" => "SouthEast",
         }
 
         # Geometry string patterns
-        RESIZE_GEOMETRY         = /\A\d*x\d*[><%^!]?\z|\A\d+@\z/ # e.g. '300x200!'
+        RESIZE_GEOMETRY = /\A\d*x\d*[><%^!]?\z|\A\d+@\z/ # e.g. '300x200!'
         CROPPED_RESIZE_GEOMETRY = /\A(\d+)x(\d+)#(\w{1,2})?\z/ # e.g. '20x50#ne'
-        CROP_GEOMETRY           = /\A(\d+)x(\d+)([+-]\d+)?([+-]\d+)?(\w{1,2})?\z/ # e.g. '30x30+10+10'
+        CROP_GEOMETRY = /\A(\d+)x(\d+)([+-]\d+)?([+-]\d+)?(\w{1,2})?\z/ # e.g. '30x30+10+10'
 
-        def update_url(url_attributes, geometry, opts={})
-          format = opts['format']
+        def update_url(url_attributes, geometry, opts = {})
+          format = opts["format"]
           url_attributes.ext = format if format
         end
 
-        def call(content, geometry, opts={})
-          content.process!(:convert, args_for_geometry(geometry), opts)
+        def call(content, geometry, opts = {})
+          validate!(opts["format"], &is_word)
+          validate!(opts["frame"], &is_number)
+          Commands.convert(content, args_for_geometry(geometry), {
+            "format" => opts["format"],
+            "frame" => opts["frame"],
+          })
         end
 
         def args_for_geometry(geometry)
@@ -37,11 +45,11 @@ def args_for_geometry(geometry)
             resize_and_crop_args($1, $2, $3)
           when CROP_GEOMETRY
             crop_args(
-              'width' => $1,
-              'height' => $2,
-              'x' => $3,
-              'y' => $4,
-              'gravity' => $5
+              "width" => $1,
+              "height" => $2,
+              "x" => $3,
+              "y" => $4,
+              "gravity" => $5,
             )
           else raise ArgumentError, "Didn't recognise the geometry string #{geometry}"
           end
@@ -54,26 +62,24 @@ def resize_args(geometry)
         end
 
         def crop_args(opts)
-          raise ArgumentError, "you can't give a crop offset and gravity at the same time" if opts['x'] && opts['gravity']
+          raise ArgumentError, "you can't give a crop offset and gravity at the same time" if opts["x"] && opts["gravity"]
 
-          width   = opts['width']
-          height  = opts['height']
-          gravity = GRAVITIES[opts['gravity']]
-          x       = "#{opts['x'] || 0}"
-          x = '+' + x unless x[/\A[+-]/]
-          y       = "#{opts['y'] || 0}"
-          y = '+' + y unless y[/\A[+-]/]
+          width = opts["width"]
+          height = opts["height"]
+          gravity = GRAVITIES[opts["gravity"]]
+          x = "#{opts["x"] || 0}"
+          x = "+" + x unless x[/\A[+-]/]
+          y = "#{opts["y"] || 0}"
+          y = "+" + y unless y[/\A[+-]/]
 
           "#{"-gravity #{gravity} " if gravity}-crop #{width}x#{height}#{x}#{y} +repage"
         end
 
         def resize_and_crop_args(width, height, gravity)
-          gravity = GRAVITIES[gravity || 'c']
+          gravity = GRAVITIES[gravity || "c"]
           "-resize #{width}x#{height}^^ -gravity #{gravity} -crop #{width}x#{height}+0+0 +repage"
         end
-
       end
     end
   end
 end
-
diff --git a/lib/dragonfly/param_validators.rb b/lib/dragonfly/param_validators.rb
new file mode 100644
index 000000000..ac17a23bf
--- /dev/null
+++ b/lib/dragonfly/param_validators.rb
@@ -0,0 +1,37 @@
+module Dragonfly
+  module ParamValidators
+    class InvalidParameter < RuntimeError; end
+
+    module_function
+
+    IS_NUMBER = ->(param) {
+      param.is_a?(Numeric) || /\A[\d\.]+\z/ === param
+    }
+
+    IS_WORD = ->(param) {
+      /\A\w+\z/ === param
+    }
+
+    IS_WORDS = ->(param) {
+      /\A[\w ]+\z/ === param
+    }
+
+    def is_number; IS_NUMBER; end
+    def is_word; IS_WORD; end
+    def is_words; IS_WORDS; end
+
+    def validate!(parameter, &validator)
+      return if parameter.nil?
+      raise InvalidParameter unless validator.(parameter)
+    end
+
+    def validate_all!(parameters, &validator)
+      parameters.each { |p| validate!(p, &validator) }
+    end
+
+    def validate_all_keys!(obj, keys, &validator)
+      parameters = keys.map { |key| obj[key] }
+      validate_all!(parameters, &validator)
+    end
+  end
+end
diff --git a/spec/dragonfly/image_magick/commands_spec.rb b/spec/dragonfly/image_magick/commands_spec.rb
new file mode 100644
index 000000000..cc0bacb54
--- /dev/null
+++ b/spec/dragonfly/image_magick/commands_spec.rb
@@ -0,0 +1,98 @@
+require "spec_helper"
+require "dragonfly/image_magick/commands"
+
+describe Dragonfly::ImageMagick::Commands do
+  include Dragonfly::ImageMagick::Commands
+
+  let(:app) { test_app }
+
+  def sample_content(name)
+    Dragonfly::Content.new(app, SAMPLES_DIR.join(name))
+  end
+
+  describe "convert" do
+    let(:image) { sample_content("beach.png") } # 280x355
+
+    it "should allow for general convert commands" do
+      convert(image, "-scale 56x71")
+      image.should have_width(56)
+      image.should have_height(71)
+    end
+
+    it "should allow for general convert commands with added format" do
+      convert(image, "-scale 56x71", "format" => "gif")
+      image.should have_width(56)
+      image.should have_height(71)
+      image.should have_format("gif")
+      image.meta["format"].should == "gif"
+    end
+
+    it "should work for commands with parenthesis" do
+      convert(image, "\\( +clone -sparse-color Barycentric '0,0 black 0,%[fx:h-1] white' -function polynomial 2,-2,0.5 \\) -compose Blur -set option:compose:args 15 -composite")
+      image.should have_width(280)
+    end
+
+    it "should work for files with spaces/apostrophes in the name" do
+      image = Dragonfly::Content.new(app, SAMPLES_DIR.join("mevs' white pixel.png"))
+      convert(image, "-resize 2x2!")
+      image.should have_width(2)
+    end
+
+    it "allows converting specific frames" do
+      gif = sample_content("gif.gif")
+      convert(gif, "-resize 50x50")
+      all_frames_size = gif.size
+
+      gif = sample_content("gif.gif")
+      convert(gif, "-resize 50x50", "frame" => 0)
+      one_frame_size = gif.size
+
+      one_frame_size.should < all_frames_size
+    end
+
+    it "accepts input arguments for convert commands" do
+      image2 = image.clone
+      convert(image, "")
+      convert(image2, "", "input_args" => "-extract 50x50+10+10")
+
+      image.should_not equal_image(image2)
+      image2.should have_width(50)
+    end
+
+    it "allows converting using specific delegates" do
+      expect {
+        convert(image, "", "format" => "jpg", "delegate" => "png")
+      }.to call_command(app.shell, %r{convert png:/[^']+?/beach\.png /[^']+?\.jpg})
+    end
+
+    it "maintains the mime_type meta if it exists already" do
+      convert(image, "-resize 10x")
+      image.meta["mime_type"].should be_nil
+
+      image.add_meta("mime_type" => "image/png")
+      convert(image, "-resize 5x")
+      image.meta["mime_type"].should == "image/png"
+      image.mime_type.should == "image/png" # sanity check
+    end
+
+    it "doesn't maintain the mime_type meta on format change" do
+      image.add_meta("mime_type" => "image/png")
+      convert(image, "", "format" => "gif")
+      image.meta["mime_type"].should be_nil
+      image.mime_type.should == "image/gif" # sanity check
+    end
+  end
+
+  describe "generate" do
+    let (:image) { Dragonfly::Content.new(app) }
+
+    before(:each) do
+      generate(image, "-size 1x1 xc:white", "png")
+    end
+
+    it { image.should have_width(1) }
+    it { image.should have_height(1) }
+    it { image.should have_format("png") }
+    it { image.meta.should == { "format" => "png" } }
+  end
+end
diff --git a/spec/dragonfly/image_magick/generators/convert_spec.rb b/spec/dragonfly/image_magick/generators/convert_spec.rb
deleted file mode 100644
index 3d8c235d7..000000000
--- a/spec/dragonfly/image_magick/generators/convert_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require 'spec_helper'
-
-describe Dragonfly::ImageMagick::Generators::Convert do
-  let (:generator) { Dragonfly::ImageMagick::Generators::Convert.new }
-  let (:app) { test_app }
-  let (:image) { Dragonfly::Content.new(app) }
-
-  describe "calling convert" do
-    before(:each) do
-      generator.call(image, "-size 1x1 xc:white", 'png')
-    end
-    it {image.should have_width(1)}
-    it {image.should have_height(1)}
-    it {image.should have_format('png')}
-    it {image.meta.should == {'format' => 'png'}}
-  end
-
-end
-
diff --git a/spec/dragonfly/image_magick/generators/plain_spec.rb b/spec/dragonfly/image_magick/generators/plain_spec.rb
index 86ae8d3ab..7eafe8636 100644
--- a/spec/dragonfly/image_magick/generators/plain_spec.rb
+++ b/spec/dragonfly/image_magick/generators/plain_spec.rb
@@ -1,4 +1,5 @@
-require 'spec_helper'
+require "spec_helper"
+require "dragonfly/param_validators"
 
 describe Dragonfly::ImageMagick::Generators::Plain do
   let (:generator) { Dragonfly::ImageMagick::Generators::Plain.new }
@@ -9,32 +10,32 @@
     before(:each) do
       generator.call(image, 3, 2)
     end
-    it {image.should have_width(3)}
-    it {image.should have_height(2)}
-    it {image.should have_format('png')}
-    it {image.meta.should == {'format' => 'png', 'name' => 'plain.png'}}
+    it { image.should have_width(3) }
+    it { image.should have_height(2) }
+    it { image.should have_format("png") }
+    it { image.meta.should == { "format" => "png", "name" => "plain.png" } }
   end
 
   describe "specifying the format" do
     before(:each) do
-      generator.call(image, 1, 1, 'format'=> 'gif')
+      generator.call(image, 1, 1, "format" => "gif")
     end
-    it {image.should have_format('gif')}
-    it {image.meta.should == {'format' => 'gif', 'name' => 'plain.gif'}}
+    it { image.should have_format("gif") }
+    it { image.meta.should == { "format" => "gif", "name" => "plain.gif" } }
   end
 
   describe "specifying the colour" do
     it "works with English spelling" do
-      generator.call(image, 1, 1, 'colour' => 'red')
+      generator.call(image, 1, 1, "colour" => "red")
     end
 
     it "works with American spelling" do
-      generator.call(image, 1, 1, 'color' => 'red')
+      generator.call(image, 1, 1, "color" => "red")
     end
 
     it "blows up with a bad colour" do
       expect {
-        generator.call(image, 1, 1, 'colour' => 'lardoin')
+        generator.call(image, 1, 1, "colour" => "lardoin")
       }.to raise_error(Dragonfly::Shell::CommandFailed)
     end
   end
@@ -42,9 +43,34 @@
   describe "urls" do
     it "updates the url" do
       url_attributes = Dragonfly::UrlAttributes.new
-      generator.update_url(url_attributes, 1, 1, 'format' => 'gif')
-      url_attributes.name.should == 'plain.gif'
+      generator.update_url(url_attributes, 1, 1, "format" => "gif")
+      url_attributes.name.should == "plain.gif"
     end
   end
 
+  describe "param validations" do
+    {
+      "color" => "white -write bad.png",
+      "colour" => "white -write bad.png",
+      "format" => "png -write bad.png",
+    }.each do |opt, value|
+      it "validates bad opts like #{opt} = '#{value}'" do
+        expect {
+          generator.call(image, 1, 1, opt => value)
+        }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+      end
+    end
+
+    it "validates width" do
+      expect {
+        generator.call(image, "1 -write bad.png", 1)
+      }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+    end
+
+    it "validates height" do
+      expect {
+        generator.call(image, 1, "1 -write bad.png")
+      }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+    end
+  end
 end
diff --git a/spec/dragonfly/image_magick/generators/plasma_spec.rb b/spec/dragonfly/image_magick/generators/plasma_spec.rb
index 0ecc1c629..2f91b9a72 100644
--- a/spec/dragonfly/image_magick/generators/plasma_spec.rb
+++ b/spec/dragonfly/image_magick/generators/plasma_spec.rb
@@ -1,4 +1,4 @@
-require 'spec_helper'
+require "spec_helper"
 
 describe Dragonfly::ImageMagick::Generators::Plasma do
   let (:generator) { Dragonfly::ImageMagick::Generators::Plasma.new }
@@ -10,23 +10,42 @@
       generator.call(image, 5, 3)
       image.should have_width(5)
       image.should have_height(3)
-      image.should have_format('png')
-      image.meta.should == {'format' => 'png', 'name' => 'plasma.png'}
+      image.should have_format("png")
+      image.meta.should == { "format" => "png", "name" => "plasma.png" }
     end
 
     it "allows changing the format" do
-      generator.call(image, 1, 1, 'format' => 'jpg')
-      image.should have_format('jpeg')
-      image.meta.should == {'format' => 'jpg', 'name' => 'plasma.jpg'}
+      generator.call(image, 1, 1, "format" => "jpg")
+      image.should have_format("jpeg")
+      image.meta.should == { "format" => "jpg", "name" => "plasma.jpg" }
     end
   end
 
   describe "urls" do
     it "updates the url" do
       url_attributes = Dragonfly::UrlAttributes.new
-      generator.update_url(url_attributes, 1, 1, 'format' => 'jpg')
-      url_attributes.name.should == 'plasma.jpg'
+      generator.update_url(url_attributes, 1, 1, "format" => "jpg")
+      url_attributes.name.should == "plasma.jpg"
     end
   end
-end
 
+  describe "param validations" do
+    it "validates format" do
+      expect {
+        generator.call(image, 1, 1, "format" => "png -write bad.png")
+      }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+    end
+
+    it "validates width" do
+      expect {
+        generator.call(image, "1 -write bad.png", 1)
+      }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+    end
+
+    it "validates height" do
+      expect {
+        generator.call(image, 1, "1 -write bad.png")
+      }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+    end
+  end
+end
diff --git a/spec/dragonfly/image_magick/generators/text_spec.rb b/spec/dragonfly/image_magick/generators/text_spec.rb
index 16eabd5b0..8ef5f8959 100644
--- a/spec/dragonfly/image_magick/generators/text_spec.rb
+++ b/spec/dragonfly/image_magick/generators/text_spec.rb
@@ -1,4 +1,4 @@
-require 'spec_helper'
+require "spec_helper"
 
 describe Dragonfly::ImageMagick::Generators::Text do
   let (:generator) { Dragonfly::ImageMagick::Generators::Text.new }
@@ -7,62 +7,62 @@
 
   describe "creating a text image" do
     before(:each) do
-      generator.call(image, "mmm", 'font_size' => 12)
+      generator.call(image, "mmm", "font_size" => 12)
     end
-    it {image.should have_width(20..40)} # approximate
-    it {image.should have_height(10..20)}
-    it {image.should have_format('png')}
-    it {image.meta.should == {'format' => 'png', 'name' => 'text.png'}}
+    it { image.should have_width(20..40) } # approximate
+    it { image.should have_height(10..20) }
+    it { image.should have_format("png") }
+    it { image.meta.should == { "format" => "png", "name" => "text.png" } }
   end
 
   describe "specifying the format" do
     before(:each) do
-      generator.call(image, "mmm", 'format' => 'gif')
+      generator.call(image, "mmm", "format" => "gif")
     end
-    it {image.should have_format('gif')}
-    it {image.meta.should == {'format' => 'gif', 'name' => 'text.gif'}}
+    it { image.should have_format("gif") }
+    it { image.meta.should == { "format" => "gif", "name" => "text.gif" } }
   end
 
   describe "padding" do
     before(:each) do
       image_without_padding = image.clone
-      generator.call(image_without_padding, "mmm", 'font_size' => 12)
+      generator.call(image_without_padding, "mmm", "font_size" => 12)
       @width = image_properties(image_without_padding)[:width].to_i
       @height = image_properties(image_without_padding)[:height].to_i
     end
     it "1 number shortcut" do
-      generator.call(image, "mmm", 'padding' => '10')
+      generator.call(image, "mmm", "padding" => "10")
       image.should have_width(@width + 20)
       image.should have_height(@height + 20)
     end
     it "2 numbers shortcut" do
-      generator.call(image, "mmm", 'padding' => '10 5')
+      generator.call(image, "mmm", "padding" => "10 5")
       image.should have_width(@width + 10)
       image.should have_height(@height + 20)
     end
     it "3 numbers shortcut" do
-      generator.call(image, "mmm", 'padding' => '10 5 8')
+      generator.call(image, "mmm", "padding" => "10 5 8")
       image.should have_width(@width + 10)
       image.should have_height(@height + 18)
     end
     it "4 numbers shortcut" do
-      generator.call(image, "mmm", 'padding' => '1 2 3 4')
+      generator.call(image, "mmm", "padding" => "1 2 3 4")
       image.should have_width(@width + 6)
       image.should have_height(@height + 4)
     end
     it "should override the general padding declaration with the specific one (e.g. 'padding-left')" do
-      generator.call(image, "mmm", 'padding' => '10', 'padding-left' => 9)
+      generator.call(image, "mmm", "padding" => "10", "padding-left" => 9)
       image.should have_width(@width + 19)
       image.should have_height(@height + 20)
     end
     it "should ignore 'px' suffixes" do
-      generator.call(image, "mmm", 'padding' => '1px 2px 3px 4px')
+      generator.call(image, "mmm", "padding" => "1px 2px 3px 4px")
       image.should have_width(@width + 6)
       image.should have_height(@height + 4)
     end
     it "bad padding string" do
-      lambda{
-        generator.call(image, "mmm", 'padding' => '1 2 3 4 5')
+      lambda {
+        generator.call(image, "mmm", "padding" => "1 2 3 4 5")
       }.should raise_error(ArgumentError)
     end
   end
@@ -70,8 +70,39 @@
   describe "urls" do
     it "updates the url" do
       url_attributes = Dragonfly::UrlAttributes.new
-      generator.update_url(url_attributes, "mmm", 'format' => 'gif')
-      url_attributes.name.should == 'text.gif'
+      generator.update_url(url_attributes, "mmm", "format" => "gif")
+      url_attributes.name.should == "text.gif"
+    end
+  end
+
+  describe "param validations" do
+    {
+      "font" => "Times New Roman -write bad.png",
+      "font_family" => "Times New Roman -write bad.png",
+      "color" => "rgb(255, 34, 55) -write bad.png",
+      "background_color" => "rgb(255, 52, 55) -write bad.png",
+      "stroke_color" => "rgb(255, 52, 55) -write bad.png",
+      "format" => "png -write bad.png",
+    }.each do |opt, value|
+      it "validates bad opts like #{opt} = '#{value}'" do
+        expect {
+          generator.call(image, "some text", opt => value)
+        }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+      end
+    end
+
+    ["rgb(33,33,33)", "rgba(33,33,33,0.5)", "rgb(33.5,33.5,33.5)", "#fff", "#efefef", "blue"].each do |colour|
+      it "allows #{colour.inspect} as a colour specification" do
+        generator.call(image, "mmm", "color" => colour)
+      end
+    end
+
+    ["rgb(33, 33, 33)", "something else", "blue:", "f#ff"].each do |colour|
+      it "disallows #{colour.inspect} as a colour specification" do
+        expect {
+          generator.call(image, "mmm", "color" => colour)
+        }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+      end
     end
   end
 end
diff --git a/spec/dragonfly/image_magick/plugin_spec.rb b/spec/dragonfly/image_magick/plugin_spec.rb
index 3ceb31956..6f12c27db 100644
--- a/spec/dragonfly/image_magick/plugin_spec.rb
+++ b/spec/dragonfly/image_magick/plugin_spec.rb
@@ -1,25 +1,24 @@
-require 'spec_helper'
+require "spec_helper"
 
 describe "a configured imagemagick app" do
-
-  let(:app){ test_app.configure_with(:imagemagick) }
-  let(:image){ app.fetch_file(SAMPLES_DIR.join('beach.png')) }
+  let(:app) { test_app.configure_with(:imagemagick) }
+  let(:image) { app.fetch_file(SAMPLES_DIR.join("beach.png")) }
 
   describe "env variables" do
-    let(:app){ test_app }
+    let(:app) { test_app }
 
     it "allows setting the convert command" do
       app.configure do
-        plugin :imagemagick, :convert_command => '/bin/convert'
+        plugin :imagemagick, :convert_command => "/bin/convert"
       end
-      app.env[:convert_command].should == '/bin/convert'
+      app.env[:convert_command].should == "/bin/convert"
     end
 
     it "allows setting the identify command" do
       app.configure do
-        plugin :imagemagick, :identify_command => '/bin/identify'
+        plugin :imagemagick, :identify_command => "/bin/identify"
       end
-      app.env[:identify_command].should == '/bin/identify'
+      app.env[:identify_command].should == "/bin/identify"
     end
   end
 
@@ -33,7 +32,7 @@
     end
 
     it "should return the aspect ratio" do
-      image.aspect_ratio.should == (280.0/355.0)
+      image.aspect_ratio.should == (280.0 / 355.0)
     end
 
     it "should say if it's portrait" do
@@ -60,39 +59,39 @@
     end
 
     it "should return false for pdfs" do
-      image.encode('pdf').image?.should be_falsey
-    end unless ENV['SKIP_FLAKY_TESTS']
+      image.encode("pdf").image?.should be_falsey
+    end unless ENV["SKIP_FLAKY_TESTS"]
   end
 
   describe "processors that change the url" do
     before do
-      app.configure{ url_format '/:name' }
+      app.configure { url_format "/:name" }
     end
 
-    describe "convert" do
+    describe "thumb" do
       it "sanity check with format" do
-        thumb = image.convert('-resize 1x1!', 'format' => 'jpg')
+        thumb = image.thumb("1x1!", "format" => "jpg")
         thumb.url.should =~ /^\/beach\.jpg\?.*job=\w+/
         thumb.width.should == 1
-        thumb.format.should == 'jpeg'
-        thumb.meta['format'].should == 'jpg'
+        thumb.format.should == "jpeg"
+        thumb.meta["format"].should == "jpg"
       end
 
       it "sanity check without format" do
-        thumb = image.convert('-resize 1x1!')
+        thumb = image.thumb("1x1!")
         thumb.url.should =~ /^\/beach\.png\?.*job=\w+/
         thumb.width.should == 1
-        thumb.format.should == 'png'
-        thumb.meta['format'].should be_nil
+        thumb.format.should == "png"
+        thumb.meta["format"].should be_nil
       end
     end
 
     describe "encode" do
       it "sanity check" do
-        thumb = image.encode('jpg')
+        thumb = image.encode("jpg")
         thumb.url.should =~ /^\/beach\.jpg\?.*job=\w+/
-        thumb.format.should == 'jpeg'
-        thumb.meta['format'].should == 'jpg'
+        thumb.format.should == "jpeg"
+        thumb.meta["format"].should == "jpg"
       end
     end
   end
@@ -100,13 +99,13 @@
   describe "other processors" do
     describe "encode" do
       it "should encode the image to the correct format" do
-        image.encode!('gif')
-        image.format.should == 'gif'
+        image.encode!("gif")
+        image.format.should == "gif"
       end
 
       it "should allow for extra args" do
-        image.encode!('jpg', '-quality 1')
-        image.format.should == 'jpeg'
+        image.encode!("jpg", "-quality 1")
+        image.format.should == "jpeg"
         image.size.should < 2000
       end
     end
@@ -117,8 +116,13 @@
         image.width.should == 355
         image.height.should == 280
       end
-    end
 
+      it "disallows bad parameters" do
+        expect {
+          image.rotate!("90 -write bad.png").apply
+        }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+      end
+    end
   end
 
   describe "identify" do
@@ -127,5 +131,4 @@
       image.identify("-format %h").chomp.should == "355"
     end
   end
-
 end
diff --git a/spec/dragonfly/image_magick/processors/convert_spec.rb b/spec/dragonfly/image_magick/processors/convert_spec.rb
deleted file mode 100644
index 48f29c8f8..000000000
--- a/spec/dragonfly/image_magick/processors/convert_spec.rb
+++ /dev/null
@@ -1,88 +0,0 @@
-require 'spec_helper'
-
-describe Dragonfly::ImageMagick::Processors::Convert do
-
-  def sample_content(name)
-    Dragonfly::Content.new(app, SAMPLES_DIR.join(name))
-  end
-
-  let(:app){ test_app }
-  let(:image){ sample_content('beach.png') } # 280x355
-  let(:processor){ Dragonfly::ImageMagick::Processors::Convert.new }
-
-  it "should allow for general convert commands" do
-    processor.call(image, '-scale 56x71')
-    image.should have_width(56)
-    image.should have_height(71)
-  end
-
-  it "should allow for general convert commands with added format" do
-    processor.call(image, '-scale 56x71', 'format' => 'gif')
-    image.should have_width(56)
-    image.should have_height(71)
-    image.should have_format('gif')
-    image.meta['format'].should == 'gif'
-  end
-
-  it "should work for commands with parenthesis" do
-    processor.call(image, "\\( +clone -sparse-color Barycentric '0,0 black 0,%[fx:h-1] white' -function polynomial 2,-2,0.5 \\) -compose Blur -set option:compose:args 15 -composite")
-    image.should have_width(280)
-  end
-
-  it "should work for files with spaces/apostrophes in the name" do
-    image = Dragonfly::Content.new(app, SAMPLES_DIR.join("mevs' white pixel.png"))
-    processor.call(image, "-resize 2x2!")
-    image.should have_width(2)
-  end
-
-  it "updates the url with format if given" do
-    url_attributes = Dragonfly::UrlAttributes.new
-    processor.update_url(url_attributes, '-scale 56x71', 'format' => 'gif')
-    url_attributes.ext.should == 'gif'
-  end
-
-  it "allows converting specific frames" do
-    gif = sample_content('gif.gif')
-    processor.call(gif, '-resize 50x50')
-    all_frames_size = gif.size
-
-    gif = sample_content('gif.gif')
-    processor.call(gif, '-resize 50x50', 'frame' => 0)
-    one_frame_size = gif.size
-
-    one_frame_size.should < all_frames_size
-  end
-
-  it "accepts input arguments for convert commands" do
-    image2 = image.clone
-    processor.call(image, '')
-    processor.call(image2, '', 'input_args' => '-extract 50x50+10+10')
-
-    image.should_not equal_image(image2)
-    image2.should have_width(50)
-  end
-
-  it "allows converting using specific delegates" do
-    expect {
-      processor.call(image, '', 'format' => 'jpg', 'delegate' => 'png')
-    }.to call_command(app.shell, %r{convert png:/[^']+?/beach\.png /[^']+?\.jpg})
-  end
-
-  it "maintains the mime_type meta if it exists already" do
-    processor.call(image, '-resize 10x')
-    image.meta['mime_type'].should be_nil
-
-    image.add_meta('mime_type' => 'image/png')
-    processor.call(image, '-resize 5x')
-    image.meta['mime_type'].should == 'image/png'
-    image.mime_type.should == 'image/png' # sanity check
-  end
-
-  it "doesn't maintain the mime_type meta on format change" do
-    image.add_meta('mime_type' => 'image/png')
-    processor.call(image, '', 'format' => 'gif')
-    image.meta['mime_type'].should be_nil
-    image.mime_type.should == 'image/gif' # sanity check
-  end
-
-end
diff --git a/spec/dragonfly/image_magick/processors/encode_spec.rb b/spec/dragonfly/image_magick/processors/encode_spec.rb
new file mode 100644
index 000000000..c5269db6e
--- /dev/null
+++ b/spec/dragonfly/image_magick/processors/encode_spec.rb
@@ -0,0 +1,30 @@
+require "spec_helper"
+
+describe Dragonfly::ImageMagick::Processors::Encode do
+  let (:app) { test_imagemagick_app }
+  let (:image) { Dragonfly::Content.new(app, SAMPLES_DIR.join("beach.png")) } # 280x355
+  let (:processor) { Dragonfly::ImageMagick::Processors::Encode.new }
+
+  it "encodes to a different format" do
+    processor.call(image, "jpeg")
+    image.should have_format("jpeg")
+  end
+
+  describe "param validations" do
+    it "validates the format param" do
+      expect {
+        processor.call(image, "jpeg -write bad.png")
+      }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+    end
+
+    it "allows good args" do
+      processor.call(image, "jpeg", "-quality 10")
+    end
+
+    it "disallows bad args" do
+      expect {
+        processor.call(image, "jpeg", "-write bad.png")
+      }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+    end
+  end
+end
diff --git a/spec/dragonfly/image_magick/processors/thumb_spec.rb b/spec/dragonfly/image_magick/processors/thumb_spec.rb
index 5fbdf6c70..e02131682 100644
--- a/spec/dragonfly/image_magick/processors/thumb_spec.rb
+++ b/spec/dragonfly/image_magick/processors/thumb_spec.rb
@@ -1,88 +1,80 @@
-require 'spec_helper'
-require 'ostruct'
+require "spec_helper"
+require "ostruct"
 
 describe Dragonfly::ImageMagick::Processors::Thumb do
-
   let (:app) { test_imagemagick_app }
-  let (:image) { Dragonfly::Content.new(app, SAMPLES_DIR.join('beach.png')) } # 280x355
+  let (:image) { Dragonfly::Content.new(app, SAMPLES_DIR.join("beach.png")) } # 280x355
   let (:processor) { Dragonfly::ImageMagick::Processors::Thumb.new }
 
   it "raises an error if an unrecognized string is given" do
-    expect{
-      processor.call(image, '30x40#ne!')
+    expect {
+      processor.call(image, "30x40#ne!")
     }.to raise_error(ArgumentError)
   end
 
   describe "resizing" do
-
     it "works with xNN" do
-      processor.call(image, 'x30')
+      processor.call(image, "x30")
       image.should have_width(24)
       image.should have_height(30)
     end
 
     it "works with NNx" do
-      processor.call(image, '30x')
+      processor.call(image, "30x")
       image.should have_width(30)
       image.should have_height(38)
     end
 
     it "works with NNxNN" do
-      processor.call(image, '30x30')
+      processor.call(image, "30x30")
       image.should have_width(24)
       image.should have_height(30)
     end
 
     it "works with NNxNN!" do
-      processor.call(image, '30x30!')
+      processor.call(image, "30x30!")
       image.should have_width(30)
       image.should have_height(30)
     end
 
     it "works with NNxNN%" do
-      processor.call(image, '25x50%')
+      processor.call(image, "25x50%")
       image.should have_width(70)
       image.should have_height(178)
     end
 
     describe "NNxNN>" do
-
       it "doesn't resize if the image is smaller than specified" do
-        processor.call(image, '1000x1000>')
+        processor.call(image, "1000x1000>")
         image.should have_width(280)
         image.should have_height(355)
       end
 
       it "resizes if the image is larger than specified" do
-        processor.call(image, '30x30>')
+        processor.call(image, "30x30>")
         image.should have_width(24)
         image.should have_height(30)
       end
-
     end
 
     describe "NNxNN<" do
-
       it "doesn't resize if the image is larger than specified" do
-        processor.call(image, '10x10<')
+        processor.call(image, "10x10<")
         image.should have_width(280)
         image.should have_height(355)
       end
 
       it "resizes if the image is smaller than specified" do
-        processor.call(image, '400x400<')
+        processor.call(image, "400x400<")
         image.should have_width(315)
         image.should have_height(400)
       end
-
     end
-
   end
 
   describe "cropping" do # Difficult to test here other than dimensions
-
     it "crops" do
-      processor.call(image, '10x20+30+30')
+      processor.call(image, "10x20+30+30")
       image.should have_width(10)
       image.should have_height(20)
     end
@@ -90,11 +82,11 @@
     it "crops with gravity" do
       image2 = image.clone
 
-      processor.call(image, '10x8nw')
+      processor.call(image, "10x8nw")
       image.should have_width(10)
       image.should have_height(8)
 
-      processor.call(image2, '10x8se')
+      processor.call(image2, "10x8se")
       image2.should have_width(10)
       image2.should have_height(8)
 
@@ -103,77 +95,86 @@
 
     it "raises if given both gravity and offset" do
       expect {
-        processor.call(image, '100x100+10+10se')
+        processor.call(image, "100x100+10+10se")
       }.to raise_error(ArgumentError)
     end
 
     it "works when the crop area is outside the image" do
-      processor.call(image, '100x100+250+300')
+      processor.call(image, "100x100+250+300")
       image.should have_width(30)
       image.should have_height(55)
     end
 
     it "crops twice in a row correctly" do
-      processor.call(image, '100x100+10+10')
-      processor.call(image, '50x50+0+0')
+      processor.call(image, "100x100+10+10")
+      processor.call(image, "50x50+0+0")
       image.should have_width(50)
       image.should have_height(50)
     end
-
   end
 
   describe "resize_and_crop" do
-
     it "crops to the correct dimensions" do
-      processor.call(image, '100x100#')
+      processor.call(image, "100x100#")
       image.should have_width(100)
       image.should have_height(100)
     end
 
     it "resizes before cropping" do
       image2 = image.clone
-      processor.call(image, '100x100#')
-      processor.call(image2, '100x100c')
+      processor.call(image, "100x100#")
+      processor.call(image2, "100x100c")
       image2.should_not equal_image(image)
     end
 
     it "works with gravity" do
       image2 = image.clone
-      processor.call(image, '10x10#nw')
-      processor.call(image, '10x10#se')
+      processor.call(image, "10x10#nw")
+      processor.call(image, "10x10#se")
       image2.should_not equal_image(image)
     end
-
   end
 
   describe "format" do
     let (:url_attributes) { OpenStruct.new }
 
     it "changes the format if passed in" do
-      processor.call(image, '2x2', 'format' => 'jpeg')
-      image.should have_format('jpeg')
+      processor.call(image, "2x2", "format" => "jpeg")
+      image.should have_format("jpeg")
     end
 
     it "doesn't change the format if not passed in" do
-      processor.call(image, '2x2')
-      image.should have_format('png')
+      processor.call(image, "2x2")
+      image.should have_format("png")
     end
 
     it "updates the url ext if passed in" do
-      processor.update_url(url_attributes, '2x2', 'format' => 'png')
-      url_attributes.ext.should == 'png'
+      processor.update_url(url_attributes, "2x2", "format" => "png")
+      url_attributes.ext.should == "png"
     end
 
     it "doesn't update the url ext if not passed in" do
-      processor.update_url(url_attributes, '2x2')
+      processor.update_url(url_attributes, "2x2")
       url_attributes.ext.should be_nil
     end
   end
 
   describe "args_for_geometry" do
     it "returns the convert arguments used for a given geometry" do
-      expect(processor.args_for_geometry('30x40')).to eq('-resize 30x40')
+      expect(processor.args_for_geometry("30x40")).to eq("-resize 30x40")
     end
   end
 
+  describe "param validations" do
+    {
+      "format" => "png -write bad.png",
+      "frame" => "0] -write bad.png [",
+    }.each do |opt, value|
+      it "validates bad opts like #{opt} = '#{value}'" do
+        expect {
+          processor.call(image, "30x30", opt => value)
+        }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+      end
+    end
+  end
 end
diff --git a/spec/dragonfly/param_validators_spec.rb b/spec/dragonfly/param_validators_spec.rb
new file mode 100644
index 000000000..3907f6d57
--- /dev/null
+++ b/spec/dragonfly/param_validators_spec.rb
@@ -0,0 +1,89 @@
+require "spec_helper"
+require "dragonfly/param_validators"
+
+describe Dragonfly::ParamValidators do
+  include Dragonfly::ParamValidators
+
+  describe "validate!" do
+    it "does nothing if the parameter meets the condition" do
+      validate!("thing") { |t| t === "thing" }
+    end
+
+    it "raises if the parameter doesn't meet the condition" do
+      expect {
+        validate!("thing") { |t| t === "ting" }
+      }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+    end
+
+    it "does nothing if the parameter is nil" do
+      validate!(nil) { |t| t === "thing" }
+    end
+  end
+
+  describe "validate_all!" do
+    it "allows passing an array of parameters to validate" do
+      validate_all!(["a", "b"]) { |p| /\w/ === p }
+      expect {
+        validate_all!(["a", " "]) { |p| /\w/ === p }
+      }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+    end
+  end
+
+  describe "validate_all_keys!" do
+    it "allows passing an array of parameters to validate" do
+      obj = { "a" => "A", "b" => "B" }
+      validate_all_keys!(obj, ["a", "b"]) { |p| /\w/ === p }
+      expect {
+        validate_all_keys!(obj, ["a", "b"]) { |p| /[a-z]/ === p }
+      }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+    end
+  end
+
+  describe "is_number" do
+    [3, 3.14, "3", "3.2"].each do |val|
+      it "validates #{val.inspect}" do
+        validate!(val, &is_number)
+      end
+    end
+
+    ["", "3 2", "hello4", {}, []].each do |val|
+      it "validates #{val.inspect}" do
+        expect {
+          validate!(val, &is_number)
+        }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+      end
+    end
+  end
+
+  describe "is_word" do
+    ["hello", "helLo", "HELLO"].each do |val|
+      it "validates #{val.inspect}" do
+        validate!(val, &is_word)
+      end
+    end
+
+    ["", "hel%$lo", "hel lo", "hel-lo", {}, []].each do |val|
+      it "validates #{val.inspect}" do
+        expect {
+          validate!(val, &is_word)
+        }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+      end
+    end
+  end
+
+  describe "is_words" do
+    ["hello there", "Hi", "  What is Up "].each do |val|
+      it "validates #{val.inspect}" do
+        validate!(val, &is_words)
+      end
+    end
+
+    ["", "hel%$lo", "What's up", "hel-lo", {}, []].each do |val|
+      it "validates #{val.inspect}" do
+        expect {
+          validate!(val, &is_words)
+        }.to raise_error(Dragonfly::ParamValidators::InvalidParameter)
+      end
+    end
+  end
+end
diff --git a/spec/functional/shell_commands_spec.rb b/spec/functional/shell_commands_spec.rb
index 65f41781a..06c4f12be 100644
--- a/spec/functional/shell_commands_spec.rb
+++ b/spec/functional/shell_commands_spec.rb
@@ -1,33 +1,30 @@
-require 'spec_helper'
+require "spec_helper"
 
 describe "using the shell" do
-
   let (:app) { test_app }
 
   describe "shell injection" do
     it "should not allow it!" do
       app.configure_with(:imagemagick)
       begin
-        app.generate(:plain, 10, 10, 'white').convert("-resize 5x5 ; touch tmp/stuff").apply
+        app.generate(:plain, 10, 10, "white; touch tmp/stuff").apply
       rescue Dragonfly::Shell::CommandFailed
       end
-      File.exist?('tmp/stuff').should be_falsey
+      File.exist?("tmp/stuff").should be_falsey
     end
   end
 
   describe "env variables with imagemagick" do
     it "allows configuring the convert path" do
-      app.configure_with(:imagemagick, :convert_command => '/bin/convert')
+      app.configure_with(:imagemagick, :convert_command => "/bin/convert")
       app.shell.should_receive(:run).with(%r[/bin/convert], hash_including)
-      app.create("").thumb('30x30').apply
+      app.create("").thumb("30x30").apply
     end
 
     it "allows configuring the identify path" do
-      app.configure_with(:imagemagick, :identify_command => '/bin/identify')
+      app.configure_with(:imagemagick, :identify_command => "/bin/identify")
       app.shell.should_receive(:run).with(%r[/bin/identify], hash_including).and_return("JPG 1 1")
       app.create("").width
     end
   end
-
 end
-
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index fdaeba319..c3cd3986f 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -2,19 +2,19 @@
 require "bundler"
 Bundler.setup(:default, :test)
 
-$LOAD_PATH.unshift(File.join(File.dirname(__FILE__), '..', 'lib'))
+$LOAD_PATH.unshift(File.join(File.dirname(__FILE__), "..", "lib"))
 $LOAD_PATH.unshift(File.dirname(__FILE__))
-require 'rspec'
-require 'dragonfly'
-require 'fileutils'
-require 'tempfile'
-require 'webmock/rspec'
-require 'pry'
+require "rspec"
+require "dragonfly"
+require "fileutils"
+require "tempfile"
+require "webmock/rspec"
+require "pry"
 
 # Requires supporting files with custom matchers and macros, etc,
-Dir["#{File.dirname(__FILE__)}/support/**/*.rb"].each {|f| require f}
+Dir["#{File.dirname(__FILE__)}/support/**/*.rb"].each { |f| require f }
 
-SAMPLES_DIR = Pathname.new(File.expand_path('../../samples', __FILE__))
+SAMPLES_DIR = Pathname.new(File.expand_path("../../samples", __FILE__))
 
 RSpec.configure do |c|
   c.include ModelHelpers
@@ -25,8 +25,8 @@ def todo
   raise "TODO"
 end
 
-require 'logger'
-LOG_FILE = 'tmp/test.log'
+require "logger"
+LOG_FILE = "tmp/test.log"
 FileUtils.rm_rf(LOG_FILE)
 Dragonfly.logger = Logger.new(LOG_FILE)
 
@@ -36,7 +36,7 @@ def todo
   end
 end
 
-def test_app(name=nil)
+def test_app(name = nil)
   app = Dragonfly::App.instance(name)
   app.datastore = Dragonfly::MemoryDataStore.new
   app.secret = "test secret"
@@ -45,8 +45,6 @@ def test_app(name=nil)
 
 def test_imagemagick_app
   test_app.configure do
-    generator :convert, Dragonfly::ImageMagick::Generators::Convert.new
-    processor :convert, Dragonfly::ImageMagick::Processors::Convert.new
     analyser :image_properties, Dragonfly::ImageMagick::Analysers::ImageProperties.new
   end
 end