Skip to main content

FAQ - Cannot create thumbnails

Cannot create thumbnails

Creating thumbnail images (i.e. small versions) requires three things.

You can check these using information from the “Server information” section of the control panel.

Firstly, your server need to have a PHP graphics extension. webtrees can use either gd or ImageMagick.

  • For gd, your server information should include a section gd, with an entry GD support = enabled.

  • For ImageMagickyour server information should include a section Imagick, with an entry ImageMagick supported formats that includes both JPEG and PNG.

Secondly, you need sufficient memory. To process an image, GD requires 4 bytes-per-pixel and Imagick requires 10 bytes-per-pixel. An image that is 5000×4000 pixels will require 5000×4000×4 = 80MB (GD) or 5000×4000×10 = 200MB (Imagick). The rest of the script requires approximately 20MB.

So generating a thumbnail of a 5000×4000 pixel image will require 100MB (GD) or 220MB (Imagick).

Your server’s memory_limit must be higher than this.

Thirdly, you need to have sufficient CPU power/time. Image manipulation requires a lot of server resources. It has been observed that gd can be 30 times slower than ImageMagick. For this reason, ImageMagick is recommended. However, if you have very large images, and low memory limits, then you will need to use gd.

Edit this page