Limiting image dimensions based on aspect ratio within Paperclip and ImageMagick - ruby-on-rails

Question

My rails app uses Paperclip and ImageMagick to process uploaded photos.
I currently have it set up like this
as_attached_file :photo, :styles => { :original => "1500x1500>", :thumb => "400x400>#", :large => "1080x1080>" }, :convert_options => { :thumb => '-quality 60', :large => '-quality 60'}, :default_url => "/missing.png"
If someone uploads an image with dimension 1000x100 (10:1 aspect ratio) for example I would like to limit the aspect ratio (on the :large and :original) so that it will crop the image if the aspect ratio is too extreme.
ie: if ratio is beyond 4:1 or 1:4 then crop

Answer 1

The best way to do this is to implement a custom processor. That way you can implement your logic and decide when to change the image the way you want.
See an example implementation of a custom processor. In my case I needed to apply a watermark on the images.
lib/paperclip_processors/watermark.rb
module Paperclip
class Watermark < Thumbnail
attr_accessor :format, :watermark_path, :watermark_gravity, :watermark_dissolve
def initialize file, options = {}, attachment = nil
super
#file = file
#format = options[:format]
#watermark_path = options[:watermark_path]
#watermark_gravity = options[:watermark_gravity].nil? ? "center" : options[:watermark_gravity]
#watermark_dissolve = options[:watermark_dissolve].nil? ? 40 : options[:watermark_dissolve]
#current_format = File.extname(#file.path)
#basename = File.basename(#file.path, #current_format)
end
def make
return #file unless watermark_path
dst = Tempfile.new([#basename, #format].compact.join("."))
dst.binmode
command = "composite"
params = "-gravity #{#watermark_gravity} -dissolve #{#watermark_dissolve} #{watermark_path} #{fromfile} #{tofile(dst)}"
begin
success = Paperclip.run(command, params)
rescue PaperclipCommandLineError
raise PaperclipError, "There was an error processing the watermark for #{#basename}"
end
dst
end
def fromfile
"\"#{ File.expand_path(#file.path) }[0]\""
end
def tofile(destination)
"\"#{ File.expand_path(destination.path) }[0]\""
end
end
end
models/image.rb
has_attached_file :file,
processors: [:thumbnail, :watermark],
styles: {
layout: "100%",
preview: {geometry: "900x900>", watermark_path: "#{Rails.root}/app/assets/images/watermarks/watermark_200.png"},
thumbnail: "300x300>",
miniature: "150x150>"
},
convert_options: {
layout: "-units PixelsPerInch -density 100",
preview: "-units PixelsPerInch -density 72",
thumbnail: "-units PixelsPerInch -density 72",
miniature: "-units PixelsPerInch -density 72"
}
You can refer to the documentation for custom processors:
https://github.com/thoughtbot/paperclip#custom-attachment-processors