get hex color of pixel; implementation of answer here http://stackoverflow.com/a/8894580/1076207; solution to MiniMagick::CommandBuilder error in Rails 3.2.x

minimagick-pixel-at-get-hex-color.rb

# get hex color of pixel
# implementation of answer here http://stackoverflow.com/a/8894580/1076207
# solution to MiniMagick::CommandBuilder error in Rails 3.2.x 

# config/application.rb
module AwesomeAppName
  class Application < Rails::Application
    config.after_initialize do
      require Rails.root.join('lib', 'gem_ext.rb')
    end
  end
end

# lib/gem_ext.rb
require "gem_ext/mini_magick"

# lib/gem_ext/mini_magick.rb
require "gem_ext/mini_magick/image"

# lib/gem_ext/mini_magick/image.rb
module MiniMagick
  class Image
    def pixel_at(x, y)
      case run_command("convert", "#{escaped_path}[1x1+#{x}+#{y}]", "-depth 8", "txt:").split("\n")[1]
      when /^0,0:.*(#[\da-fA-F]{6}).*$/ then $1
      else nil
      end
    end
  end
end

# example
#$ rails console
#Loading development environment (Rails 3.2.13)
image = MiniMagick::Image.open(File.expand_path('~/Desktop/truck.png'))
#=> #<MiniMagick::Image:0x007f9bb8cc3638 @path="/var/folders/1q/fn23z3f11xd7glq3_17vhmt00000gp/T/mini_magick20140403-1936-phy9c9.png", @tempfile=#<File:/var/folders/1q/fn23z3f11xd7glq3_17vhmt00000gp/T/mini_magick20140403-1936-phy9c9.png (closed)>>
image.pixel_at(1,1)
#=> "#01A30D"