Preview-generator Documentation

Presentation

preview-generator is a library for generating preview - thumbnails, pdf, text and json overview for all your file-based content. This module gives you access to jpeg, pdf, text, html and json preview of virtually any kind of file. It also includes a cache mechanism so you do not have to care about preview storage.

By creating this module, the goal was to delegate the responsibility of building preview of files managed by tracim.

Supported file formats

Supported mimetypes depends on builders and dependencies installed.

full supported list file format here: supported mimetypes list .

Preview-generator has builders for:

Images

• Raster graphic image formats : png, jpeg, bmp, tiff, gif, …
• Vectorial graphic format: svg
• Camera raw format: dng, arw, …

Office/Text Document

• simple text file : txt, json, …
• office document: odt, doc, docx
• pdf document

Archive file

• zip, tar, …

3D File

• support for geometric file: .ply, .obj, .stl

Video format

• support for multiples image preview of video : .mp4, .flv, .webm, .ogv, .wmv, etc.

Installation

Dependencies:

apt-get install zlib1g-dev libjpeg-dev python3-pythonmagick inkscape xvfb poppler-utils libfile-mimeinfo-perl qpdf libimage-exiftool-perl ufraw-batch ffmpeg

After installing dependencies, you can install preview-generator using pip:

pip install preview-generator

Optional dependencies:

To handle previews for office documents you will need LibreOffice, if you don't have it already:

apt-get install libreoffice

To check dependencies, you can run:

preview --check-dependencies

Usage

Here are some examples of code

Basic Usage

Most basic usage, create a jpeg from a png, default size 256x256

from preview_generator.manager import PreviewManager

cache_path = '/tmp/preview_cache'
file_to_preview_path = '/tmp/an_image.png'

manager = PreviewManager(cache_path, create_folder= True)
path_to_preview_image = manager.get_jpeg_preview(file_to_preview_path)

Preview an image with a specific size

You can choose the size of your image using params width and height.

from preview_generator.manager import PreviewManager

cache_path = '/tmp/preview_cache'
file_to_preview_path = '/tmp/an_image.png'

manager = PreviewManager(cache_path, create_folder= True)
path_to_preview_image = manager.get_jpeg_preview(file_to_preview_path, width=1000, height=500)

Preview a pdf or an office document as a jpeg

from preview_generator.manager import PreviewManager

cache_path = '/tmp/preview_cache'
pdf_or_odt_to_preview_path = '/tmp/a_pdf.pdf'

manager = PreviewManager(cache_path, create_folder= True)
path_to_preview_image = manager.get_jpeg_preview(pdf_or_odt_to_preview_path)

By default it will generate the preview of the first page of the document. Using params page, you can you pick the page you want to preview.

page number starts at 0, if you want to preview the second page of your document then the argument will be 1 `page=1`

from preview_generator.manager import PreviewManager

cache_path = '/tmp/preview_cache'
pdf_or_odt_to_preview_path = '/tmp/a_pdf.pdf'

manager = PreviewManager(cache_path, create_folder= True)
path_to_preview_image = manager.get_jpeg_preview(pdf_or_odt_to_preview_path, page=1)

Generate a pdf preview of a libreoffice text document

from preview_generator.manager import PreviewManager
manager = PreviewManager('/tmp/cache/', create_folder= True)
pdf_file_path = manager.get_pdf_preview('/home/user/Documents/report.odt', page=2)
print('Preview created at path : ', thumbnail_file_path)

For Office types into PDF :

cache_path = '/tmp/previews'
preview_manager = PreviewManager(cache_path, create_folder= True)
path_to_preview = preview_manager.get_pdf_preview(file_path,page=page_id)

-> Will create a preview from an office file into a pdf file

args :

file_path : the String of the path where is the file you want to get the preview

page : the int of the page you want to get. If not mentioned all the pages will be returned. First page is page 0

returns :

str: path to the preview file

For images(GIF, BMP, PNG, JPEG, PDF) into jpeg :

cache_path = '/tmp/previews'
preview_manager = PreviewManager(cache_path, create_folder= True)
path_to_preview = preview_manager.get_jpeg_preview(file_path,height=1024,width=526)

-> Will create a preview from an image file into a jpeg file of size 1024 * 526

args :

file_path : the String of the path where is the file you want to get the preview

height : height of the preview in pixels

width : width of the preview in pixels. If not mentioned, width will be the same as height

returns :

str: path to the preview file

Other conversions :

The principle is the same as above

Zip to text or html : will build a list of files into text/html inside the json

Office to jpeg : will build the pdf out of the office file and then build the jpeg.

Text to text : mainly just a copy stored in the cache

Command Line

For test purposes, you can use preview from the command line, giving the file to preview as a parameter:

preview demo.pdf

Or multiple files:

preview *.pdf

Cache mechanism

Naming :

The name of the preview generated in the cache directory will be :

{file_name}-[{size}-]{file_md5sum}[({page})]{extension}

file_name = the name of the file you asked for a preview without the extension.

size = the size you asked for the preview. In case of a Jpeg preview.

file_md5sum = the md5sum of the entire path of the file. To avoid conflicts like files that have the same name but are in different directory.

page = the page asked in case of pdf or office document preview.

extensions = the extension of the preview (.jpeg for a jpeg, .txt for a text, etc)

Example :

These scripts :

GIF to JPEG :

import os
from preview_generator.manager import PreviewManager
current_dir = os.path.dirname(os.path.abspath(__file__)) +'/'

manager = PreviewManager(path=current_dir + 'cache')
path_to_preview = manager.get_jpeg_preview(
    file_path=current_dir + 'the_gif.gif',
    height=512,
    width=512,
)

print('Preview created at path : ', path_to_preview)

will print

Preview created at path : the_gif-512x512-60dc9ef46936cc4fff2fe60bb07d4260.jpeg

ODT to JPEG :

import os
from preview_generator.manager import PreviewManager
current_dir = os.path.dirname(os.path.abspath(__file__)) +'/'

manager = PreviewManager(path=current_dir + 'cache')
path_to_file = manager.get_jpeg_preview(
    file_path=current_dir + 'the_odt.odt',
    page=1,
    height=1024,
    width=1024,
)

print('Preview created at path : ', path_to_preview)

will print

Preview created at path : the_odt-1024x1024-c8b37debbc45fa96466e5e1382f6bd2e-page1.jpeg

ZIP to Text :

import os
from preview_generator.manager import PreviewManager
current_dir = os.path.dirname(os.path.abspath(__file__)) +'/'

manager = PreviewManager(path=current_dir + 'cache')
path_to_file = manager.get_text_preview(
    file_path=current_dir + 'the_zip.zip',
)

print('Preview created at path : ', path_to_file)

will print

Preview created at path : the_zip-a733739af8006558720be26c4dc5569a.txt

HEIC support

Building ImageMagick with heic support: Building ImageMagick with heic support .

Known Issues

Support for 3D file on headless server

Standard vtk library require an X server to run properly. To make 3D file preview work on a headless server, you have two option:

1. Untested: Compile/find a vtk version correctly compiled with flags to disable x requirement (with OSMesa support)
2. Use an x framebuffer like xvfb

For the last one, this configuration is known to work:

1. install package xvfb.
2. launch Xvfb :99 -screen 0 1x1x16 > /dev/null 2>&1 & (note: this use a very small x framebuffer 1x1 pixel in 16 color depth to limit video usage).
3. run python code with env var DISPLAY=:99.0

Contribute and Developer’s Kit

see here .

License

MIT licensed. https://opensource.org/licenses/MIT