Toon geavanceerde kennisVerbergen geavanceerde kennis

Preview Of File Content

1 Description

 
At PH Zürich ILIAS is used a lot as file sharing platform. The problem is that most of the users have to download a lot of files until the find the file they are looking for.
 
To make it more clear to the users what document they are going to download there should be preview image for each document. The preview should be displayed as soon as the user moves the cursor over a documents title link. It's also imaginable that the user can browse through the first five pages (or so), because the first page in most cases contains not that much of information.

Of course the preview is only available for users who have the rights to download the file.
 
This feature should be implemented for objects of type "File" and for files in file lists.
 
 
Implementation Details
 
The preview images could be created as follows:

• Straight away after uploading (preferred, but performance should be checked first)
• By a regulary run cron job
• By indexing server Lucene

The preview image generation should be implemented that it can be easily extended with renderers for additional file types. The Plugin-Architecture is ideal to achieve this.
 
As a first step preview images should be generated for file types that are supported by ImageMagick because it is a prerequisite of ILIAS.
 
In a second step office file types should be supported (i.e. doc, ppt etc.). To create images from such types, the easiest solution is to convert the files first into a temporary PDF file and afterwards create an image from it. The most named solution to convert office files into PDF's is to use OpenOffice/LibreOffice as a service (see this discussion). This produces the most accurate results when it comes to formatting and images. Beside that it supports a lot of document types (see this list).
It would also be possible to use file type specific open source projects, but in most cases they support only one file type (i.e. docx, like ) and the results are not that accurate.
Nevertheless any hints to existing solutions for converting office file types are very welcome and are taken into account.

2 Status

• Scheduled for Release: Release 4.4
• Funding: Funded by Switch AAA Project "Dateihandling in ILIAS" / PH Zürich
• Development: Feature is to be developed by PH Zürich

3 Additional Information

• If you want to know more about this feature, its implementation or funding, please contact: stefan.born at phzh.ch

4 Discussion

JF 19 Dec 2011: We like the idea. This should be an optional feature, activated in the ILIAS administration. It should also not affect the performance in the repository too much. If complex conversions are triggered then the Lucene approach could be useful.

JF 1 Oct 2012: We still like the idea, but will postpone the final decision until PHZH implemented a prototype.

Pascal, 31 January 2013: We implemented 3 versions (of the interaction and look) to discuss about: https://ilias.phzh.ch/dev/goto.php?target=cat_1095&client_id=ilias_dev (no login required). Feedback ist very welcome here in the discussion area!

2013-02-01, ILIAS_LM @Pascal & @JF
 
 
These advantages do I personally see:
V1: Scrolling is faster than clicking. It's near by the object.
V2: It's close to the object itself, no-one will be confused and believe that the preview is part of the repository. It's clearly a preview.
V3: It's like the new style in ILIAS (like comments), vertical scrolling
 
Disadvantages:
V1: Confusion with accordion, some could believe that it's part of the repository and shown like this (openly) to the members, too
V2: –
V3: It's far far away from the object.

Pascal, 4 February 2013: The Project-Team preferes V2. It is a well known concept and also used for the online-help bubbles.

JF 5 Feb 2013: We highly appreciate the feature and support V2, too. Thanks for developing all these prototypes.

5 Implementation

To use this new feature please enable it first under "Administration" > "Files and Folders" > "File Preview". On that page you can also see an overview of all installed preview renderers and their supported file types.
 
Support for PDF's and several image types comes out of the box, but there's an easy to implement plugin interface for other files types. To enable previews for PDF's GhostScript is required and needs to be configured in the setup under "Basic Settings".
Supported image file types are: jpg, png, gif, bmp, tif, cur, ico, pict, tga, psd.
 
If the preview functionality is enabled a little preview icon is displayed beside each supported file. A slightly grayed out icon indicates that no preview exists for a file but will be renderer on demand when the icon is clicked.
 
When the preview is displaying the following keyboard/mouse shortcuts are available:

• Mouse Scrollwheel, Left & Right Arrow Keys: Step through the preview images of the file (if there is more than one)
• ESC Key: Closes the preview
• HOME & END Keys: Displays the first respectively last preview image of the file
• Up & Down Arrow Keys: Display the preview of the previous respectively next file

The preview is also displayed on the file's info page.
If the user has the appropriate rights, the preview can also be created (read rights) or can be deleted (write rights).