How can I create thumbnail with carrierwave and a imagemagick script?

Question

I'm using carrierwave to creating thumbnails, but I don't know how can -i use with this script.

mogrify -resize 246x246 -background none -gravity center -extent 246x246 -format png -quality 75 -path thumbs penguins.jpg

This script creating thumbnails and works good, but I would like to use this or similar in carrierwave versions.

Answer 1

The documentation on doing advanced configuration of image manipulation with carrierwave is here:

https://github.com/carrierwaveuploader/carrierwave/wiki/How-to%3A-Efficiently-converting-image-formats#full-example

If you look at the def mogrify section, you see that in the img.format("png") do |c| block is where the image manipulation options are passed.

That variable c is actually an instance of MiniMagick, which is a thin wrapper around mogrify.

https://github.com/minimagick/minimagick/

The full API for MiniMagick is not quite there, but if you dig into the source, you can find they have a list of all the possible methods they use here:

https://github.com/minimagick/minimagick/blob/master/lib/mini_magick.rb#L39

And those are all defined down below:

https://github.com/minimagick/minimagick/blob/master/lib/mini_magick.rb#L456

I would suggest adding the options you want to your own uploader:

 def mogrify(options = {})
    manipulate! do |img|
      img.format("png") do |c|
        # Add other options here:

        c.gravity     options[:gravity]
        c.background  options[:background]
        c.extend      options[:extend]
        c.quality     options[:quality]

        # Original options follow:

        c.fuzz        "3%"
        c.trim
        c.rotate      "#{options[:rotate]}" if options.has_key?(:rotate)
        c.resize      "#{options[:resolution]}>" if options.has_key?(:resolution)
        c.resize      "#{options[:resolution]}<" if options.has_key?(:resolution)
        c.push        '+profile'
        c.+           "!xmp,*"
        c.profile     "#{Rails.root}/lib/color_profiles/sRGB_v4_ICC_preference_displayclass.icc"
        c.colorspace  "sRGB"
      end
      img
    end
  end

Answer 2

in your app/uploaders/image_uploader.rb

do something like this

class ImageUploader < CarrierWave::Uploader::Base
  include CarrierWave::RMagick

  storage :file

  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

  version :thumb do
    process :resize_to_limit => [246, 246]
  end
end

Take a look at this rails cast 253-carrierwave-file-uploads