Carrierwave with Mini Magick images optimization.

carrierwave.rb

module CarrierWave
  module MiniMagick
    
    def quality(percentage)
      manipulate! do |img|
        img.quality(percentage.to_s)
        img = yield(img) if block_given?
        img
      end
    end

    def slimming combine_options = {}
      manipulate! do |img|
        img.combine_options do |cmd|
          if @file.content_type == 'image/jpeg'
            cmd.strip
            cmd.sampling_factor "2x2"
            cmd.depth "8"
            cmd.filter "Lanczos"
            cmd.unsharp "0.25x0.08+8.3+0.045"
            cmd.dither "None"
            cmd.posterize "136"
            cmd.quality "80"
            cmd.define "jpeg:fancy-upsampling=off"
            cmd.interlace "JPEG"
            cmd.colorspace "sRGB"
          elsif @file.content_type == 'image/png'
            cmd.quantize "transparent"
            cmd.colors "255"
            cmd.depth "8"
            cmd.dither "FloydSteinberg"
            cmd.define "png:compression-level=9"
            cmd.define "png:exclude-chunk=all"
            cmd.colorspace "sRGB"
          end
          append_combine_options cmd, combine_options
        end
        img = yield(img) if block_given?
        img
      end
    end
  end
end