Rails Paperclip how to use filter options of ImageMagick? - ruby-on-rails

Question

I recently implemented Paperclip with Rails and want to try out some of the filter options from ImageMagick such as blur. I've not been able to find any examples of how to do this. Does it get passed through :style as another option?
:styles => { :medium => "300x300#", :thumb => "100x100#" }
#plang's answer was correct but I wanted to give the exact solution to the blur, just in case someone was looking and found this question:
:convert_options => { :all => "-blur 0x8" }
// -blur {radius}x{sigma}
Which changed this:
To this:

Answer 1

I did not test this, but you should be able to use the "convert_options" parameter, like this:
:convert_options => { :all => ‘-colorspace Gray’ }
Have a look at https://github.com/thoughtbot/paperclip/blob/master/lib/paperclip/thumbnail.rb
I personnaly use my own processor.
In Model:
has_attached_file :logo,
:url => PaperclipAssetsController.config_url,
:path => PaperclipAssetsController.config_path,
:styles => {
:grayscale => { :processors => [:grayscale] }
}
In lib:
module Paperclip
# Handles grayscale conversion of images that are uploaded.
class Grayscale < Processor
def initialize file, options = {}, attachment = nil
super
#format = File.extname(#file.path)
#basename = File.basename(#file.path, #format)
end
def make
src = #file
dst = Tempfile.new([#basename, #format])
dst.binmode
begin
parameters = []
parameters << ":source"
parameters << "-colorspace Gray"
parameters << ":dest"
parameters = parameters.flatten.compact.join(" ").strip.squeeze(" ")
success = Paperclip.run("convert", parameters, :source => "#{File.expand_path(src.path)}[0]", :dest => File.expand_path(dst.path))
rescue PaperclipCommandLineError => e
raise PaperclipError, "There was an error during the grayscale conversion for #{#basename}" if #whiny
end
dst
end
end
end
This might not be 100% necessary for a simple grayscale conversion, but it works!

Answer 2

Rails 5, Paperclip 5 update
Instead of having to add a library now, you can just call out to ImageMagick's convert command on the system to use its grayscale option. You can do the same for blur or any of the other ImageMagick options, but I needed to do this for conversion to grayscale.
In your model (client that has a logo):
class Client < ApplicationRecord
has_attached_file :logo,
styles: { thumb: "243x243#", grayscale: "243x243#" }
# ensure it's an image
validates_attachment_content_type :logo, content_type: /\Aimage\/.*\z/
# optional, just for name and url to be required
validates :name, presence: true
validates :url, presence: true
after_save :convert_grayscale
def convert_grayscale
system "convert #{self.logo.path(:thumb)} -grayscale Rec709Luminance #{self.logo.path(:grayscale)}"
end
def logo_attached?
self.logo.file?
end
end
Then just use in the view like this (per Paperclips github docs).
In your view:
<%= image_tag(client.logo.url(:grayscale), class: 'thumbnail', alt: client.name, title: client.name) %>
or with a link if you prefer:
<%= link_to(image_tag(client.logo.url(:grayscale), class: 'thumbnail', alt: client.name, title: client.name), client.url ) %>