Generate Thumbnail From pdf in rails paperclip - ruby-on-rails

Question

How can I generate the first page of a pdf as a thumbnail in paperclip?
I tried a lot but it's not working
has_attached_file :book_url, :styles => {
:thumb => "100x100#",
:small => "150x150>",
:medium => "200x200" }
This is giving the name of the pdf as a link but it's not giving the first page of the pdf
<%= link_to 'My PDF', #book.book_url.url %>

Answer 1

Tadas' answer is right, but for those who need more context, you can do something like this: The model below only creates thumbnails for certain kinds of files (e.g. it doesn't make thumbnails of audio files), but does make thumbnails for pdfs, image files, and video files:
class Record < ActiveRecord::Base
print self # for logging on heroku
belongs_to :user
# Ensure user has provided the required fields
validates :title, presence: true
validates :file_upload, presence: true
validates :description, presence: true
# Use the has_attached_file method to add a file_upload property to the Record
# class.
has_attached_file :file_upload,
# In order to determine the styles of the image we want to save
# e.g. a small style copy of the image, plus a large style copy
# of the image, call the check_file_type method
styles: lambda { |a| a.instance.check_file_type },
processors: lambda {
|a| a.is_video? ? [ :ffmpeg ] : [ :thumbnail ]
}
# Validate that we accept the type of file the user is uploading
# by explicitly listing the mimetypes we are willing to accept
validates_attachment_content_type :file_upload,
:content_type => [
"video/mp4",
"video/quicktime",
"image/jpg",
"image/jpeg",
"image/png",
"image/gif",
"application/pdf",
"audio/mpeg",
"audio/x-mpeg",
"audio/mp3",
"audio/x-mp3",
"file/txt",
"text/plain",
"application/doc",
"application/msword",
"application/vnd.ms-excel",
"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
"application/vnd.ms-powerpoint"
],
:message => "Sorry! We do not accept the attached file type"
# Before applying the Imagemagick post processing to this record
# check to see if we indeed wish to process the file. In the case
# of audio files, we don't want to apply post processing
before_post_process :apply_post_processing?
# Helper method that uses the =~ regex method to see if
# the current file_upload has a content_type
# attribute that contains the string "image" / "video", or "audio"
def is_image?
self.file_upload.content_type =~ %r(image)
end
def is_video?
self.file_upload.content_type =~ %r(video)
end
def is_audio?
self.file_upload.content_type =~ /\Aaudio\/.*\Z/
end
def is_plain_text?
self.file_upload_file_name =~ %r{\.(txt)$}i
end
def is_excel?
self.file_upload_file_name =~ %r{\.(xls|xlt|xla|xlsx|xlsm|xltx|xltm|xlsb|xlam|csv|tsv)$}i
end
def is_word_document?
self.file_upload_file_name =~ %r{\.(docx|doc|dotx|docm|dotm)$}i
end
def is_powerpoint?
self.file_upload_file_name =~ %r{\.(pptx|ppt|potx|pot|ppsx|pps|pptm|potm|ppsm|ppam)$}i
end
def is_pdf?
self.file_upload_file_name =~ %r{\.(pdf)$}i
end
def has_default_image?
is_audio?
is_plain_text?
is_excel?
is_word_document?
end
# If the uploaded content type is an audio file,
# return false so that we'll skip audio post processing
def apply_post_processing?
if self.has_default_image?
return false
else
return true
end
end
# Method to be called in order to determine what styles we should
# save of a file.
def check_file_type
if self.is_image?
{
:thumb => "200x200>",
:medium => "500x500>"
}
elsif self.is_pdf?
{
:thumb => ["200x200>", :png],
:medium => ["500x500>", :png]
}
elsif self.is_video?
{
:thumb => {
:geometry => "200x200>",
:format => 'jpg',
:time => 0
},
:medium => {
:geometry => "500x500>",
:format => 'jpg',
:time => 0
}
}
elsif self.is_audio?
{
:audio => {
:format => "mp3"
}
}
else
{}
end
end
end

Answer 2

I think I once got it working by enforcing a file type, e.g.
:thumb => ["100x100#", :png]
of course it's not ideal, because it enforces this filetype for every upload

Answer 3

Thanks a million to #duhaime for his beautiful answer.
Since this is the most complete source of information I found to have PDF attached, I'd like to document it further:
Requirements:
imagemagick
ghostscript (I forgot about this one)
(optional) ffmpeg if you want to handle video files
Also I replaced has_default_image? and apply_post_processing? with the single:
def can_thumbnail?
self.check_file_type.try(:{], :thumb).present?
end
Finally I created a method for the not-thumbable attachments:
def thumb
return self.file.url(:thumb) if self.can_thumbnail?
if self.is_video?
'/thumb/video.png'
else
'/thumb/default.png'
end
end
But thanks again #duhaime