Install imageMagick

Image Thumbnail Service

OpenOlat can generate preview thumbnail images for PDFs etc. The preview images are shown in various places, for example in the folder component.

The thumbnail service works out-of-the box in a vanilla OpenOlat installation using a java based implementation. However, this default installation has its limits: for example, it can not create thumbails for PDF files and when resizing images that uses alpha transparency, the transparency is lost. And after all, the java implementation is slow. For best user experience it is thus recommended to delegate the image resize task to a service that runs natively in the operating system. We use the well known linux tool imageMagick in combination with ghostscript for this.

Get imageMagick and Ghostscript

Depending on your system, download imageMagick and ghostscript from their websites: - imageMagick - ghostscript

On apt based systems (Debian, Ubuntu..) install the tools as follows:

apt update
apt install imagemagick ghostscript

Adjust the read/write policy for PDF files

To create thumbnails from PDFs it is necessary to configure imageMagick. Depending on the version of ImageMagick, edit the corresponding policy.xml, either with the command

nano /etc/ImageMagick-6/policy.xml

or

nano /etc/ImageMagick-7/policy.xml

In this file, search for the line

<policy domain="coder" rights="none" pattern="PDF" />

and change the rights from none to read|write

<policy domain="coder" rights="read|write" pattern="PDF" />

Configure OpenOlat

In your olat.local.properties enable the imageMagick thumbnail provider:

thumbnail.provider=magick
thumbnail.magick.path=/usr/bin/

Adjust the path /usr/bin to wherever you installed imageMagick.

Tip

Don't forget to restart OpenOlat to activate the service.