A processor for Paperclip performing standard thumbnailing tasks and adds a logo stamp at specified position to the image

image.rb

class Image < ActiveRecord::Base

  has_attached_file :image, :styles => {  :small => ['60x60#', :jpg],
                                          :thumb =>  ['150x150#', :jpg],
                                          :normal => {
                                            :processors => [:logostamp],
                                            :geometry => '660x660',
                                            :format => :jpg,
                                            :logostamp_geometry => "+5+5"
                                          }
                                        },
                            :default_style => :normal

end

logostamp.rb

module Paperclip
  # Handles thumbnailing images that are uploaded.
  class Logostamp < Processor

    attr_accessor :current_geometry, :target_geometry, :format, :whiny, :convert_options, :source_file_options

    # Creates a Thumbnail object set to work on the +file+ given. It
    # will attempt to transform the image into one defined by +target_geometry+
    # which is a "WxH"-style string. +format+ will be inferred from the +file+
    # unless specified. Thumbnail creation will raise no errors unless
    # +whiny+ is true (which it is, by default. If +convert_options+ is
    # set, the options will be appended to the convert command upon image conversion
    def initialize file, options = {}, attachment = nil
      super
       
      geometry             = options[:geometry]
      @file                = file
      @crop                = geometry[-1,1] == '#'
      @target_geometry     = Geometry.parse geometry
      @current_geometry    = Geometry.from_file @file
      @source_file_options = options[:source_file_options]
      @convert_options     = options[:convert_options]
      @whiny               = options[:whiny].nil? ? true : options[:whiny]
      @format              = options[:format]

      @source_file_options = @source_file_options.split(/\s+/) if @source_file_options.respond_to?(:split)
      @convert_options     = @convert_options.split(/\s+/)     if @convert_options.respond_to?(:split)

      @current_format      = File.extname(@file.path)
      @basename            = File.basename(@file.path, @current_format)
      
      # Logostamp specific options
      @logostamp_path      = options[:logostamp_path] || Rails.root.join('public/images/logostamp.png')
      @logostamp_position  = options[:logostamp_position].nil? ? "SouthEast" : options[:position]
      @logostamp_geometry  = options[:logostamp_geometry]

    end

    # Returns true if the +target_geometry+ is meant to crop.
    def crop?
      @crop
    end

    # Returns true if the image is meant to make use of additional convert options.
    def convert_options?
      !@convert_options.nil? && !@convert_options.empty?
    end

    # Performs the conversion of the +file+ into a thumbnail. Returns the Tempfile
    # that contains the new image.
    def make
      src = @file
      dst = Tempfile.new([@basename, @format ? ".#{@format}" : ''])
      dst.binmode

      begin
        parameters = []
        parameters << source_file_options
        parameters << ":source"
        parameters << transformation_command
        parameters << convert_options
        parameters << ":dest"
        
        logostamp = []
        logostamp << "-gravity #{@logostamp_position}"
        logostamp << "-geometry #{@logostamp_geometry}" if @logostamp_geometry.present?
        logostamp << "#{@logostamp_path} #{File.expand_path(dst.path)} #{File.expand_path(dst.path)}"

        parameters = parameters.flatten.compact.join(" ").strip.squeeze(" ")
        logostamp = logostamp.flatten.compact.join(" ").strip.squeeze(" ")

        success = Paperclip.run("convert", parameters, :source => "#{File.expand_path(src.path)}[0]", :dest => File.expand_path(dst.path)) and
                  Paperclip.run("composite", logostamp)
      rescue PaperclipCommandLineError => e
        raise PaperclipError, "There was an error processing the thumbnail for #{@basename}" if @whiny
      end

      dst
    end

    # Returns the command ImageMagick's +convert+ needs to transform the image
    # into the thumbnail.
    def transformation_command
      scale, crop = @current_geometry.transformation_to(@target_geometry, crop?)
      trans = []
      trans << "-resize" << %["#{scale}"] unless scale.nil? || scale.empty?
      trans << "-crop" << %["#{crop}"] << "+repage" if crop?      
      trans
    end
  end
end

A processor for Paperclip performing standard thumbnailing tasks and adds a logo stamp at specified position to the image.

Possible options are:

• logostamp_path: Path to the logo file. Defaults to RAILS_ROOT/public/images/logostamp.png
• logostamp_position: Where to place the stamp? Possible options are NorthWest, North, NorthEast, West, Center, East, SouthWest, South, SouthEast
• logostamp_geometry: Advanced geometry configuration for placing the stamp. E.g. :logostamp_geometry => "+5+5" alongside :logostamp_position => "SouthEast" option places the stamp in the lower left corner of the image but adds a padding of 5 pixels on the right and the bottom to the stamp. For a complete description see Imagemagick documentation.