Re: Serving very large pdf files with django

Hello,

Maybe you could use ImageMagick to show one page of the pdf as an image ? This is what I have implemented on my project : first page of pdf files can be pre-viewed before user uploads the whole file (if needed). In your case, pre-viewing could be parametrized to show page 'n' of the pdf file, probably. In my project, pre-viewing image is generated when pdf file is uploaded and saved by admin in myproject/media/files directory. Once pdf files are in media directory, users can preview those pdf files and tnen upload them, if needed (only first page can be pre-viewed by user. This is an implementation choice).

http://www.imagemagick.org/script/index.php

Implementation principles/credit can be found here :

http://www.yaconiello.com/blog/auto-generating-pdf-covers/

I am attaching the signals file_post_save file_pre_save, for information.

Cheers.

Django 1.8
Python 3.4

Note : to install ImageMagick:

sudo apt-get install libmagickwand-dev imagemagick libmagickcore-dev

The convert command allows to convert any page of pdf file into png image (for instance), eg :

convert -thumbnail 1280 test.pdf[0] test_1280.png
Several parameters exist to tune image quality (in my case, need to use density, trim and quality).

 

models.py

[…]

###########

# SIGNALS #

###########

from django.db.models.signals import post_save, pre_delete

from django.dispatch import receiver

from myproject.settings import MEDIA_ROOT

import subprocess

# What to do after a File is saved - receiver definition

def file_post_save(sender, instance=False, **kwargs):

            # This post save function creates a thumbnail for the File

            file = File.objects.get(pk=instance.pk)

            command = "convert -density 300 -trim -thumbnail %s %s%s[0] -quality 100 %s%s" % (file.thumbnail_size, MEDIA_ROOT, file.file, MEDIA_ROOT, file.thumbnail)

            proc = subprocess.Popen(command,

                        shell=True,

                        stdin=subprocess.PIPE,

                        stdout=subprocess.PIPE,

                        stderr=subprocess.PIPE,

            )

            stdout_value = proc.communicate()[0]

post_save.connect(file_post_save, sender=File, dispatch_uid="file_post_save_uid")

 

# What to do before a File is deleted - receiver definition

def file_pre_delete(sender, instance=False, **kwargs):

            # This pre delete function deletes file and thumbnail from media directory

            file = File.objects.get(pk=instance.pk)

            command = "rm %s%s %s%s" % (MEDIA_ROOT, file.file, MEDIA_ROOT, file.thumbnail)

            proc = subprocess.Popen(command,

                        shell=True,

                        stdin=subprocess.PIPE,

                        stdout=subprocess.PIPE,

                        stderr=subprocess.PIPE,

            )

            stdout_value = proc.communicate()[0]

pre_delete.connect(file_pre_delete, sender=File, dispatch_uid="file_pre_delete_uid")

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