Thumbnail Generation Alert Help

FooGallery Documentation

Thumbnail Generation Alert Help

You might have noticed a new message pop up in your admin that says Thumbnail Generation Alert!

This message is shown after FooGallery failed to resize an image using it’s built-in thumbnail resizer. There are a few reasons why this could happen:

  • Write permissions issues.
  • GD PHP image library issues.
  • “File not found” issues.

First, How Does FooGallery Resize Thumbnails?

Under the hood, FooGallery uses a library called WPThumb for resizing it’s images. This library is available on Github as an open source project. Internally WPThumb uses WordPress’ built-in WP_Image_Editor_Imagick and WP_Image_Editor_GD classes. Similar to WordPress, WPThumb tries to use Imagick first, and then, as a fallback, uses GD.

The FooGallery thumbnail test works in the following way:

  1. It looks for the first available image attachment in your media library.
  2. As of FooGallery v1.9.9 it checks the image exists and has not been deleted from the server. If it cannot locate the image, it moves onto the next attachment. It will try this 10 times. If it found no images to use, it will use an image from our CDN :
  3. It tries to resize the image to a 20×20 thumbnail.

Under FooGallery Settings -> Advanced, you can enable the Override Thumb Test setting to force the test to use an image from our CDN :

Find Out What Caused the Alert

When you see the alert, visit the FooGallery Settings page. Under the Image tab, you will see a Run Tests button next to Thumbnail Generation Test.

Click on the Run Tests button and the test will run and the error will be output which shows more information about the issue.

Fixing the Issue

Usually, enabling the Override Thumb Test setting to force the test to use an image from our CDN will solve the problem. You can find this setting under the Advanced tab on the FooGallery Settings page.

If you see a “File Not Found” message in the error after running the test manually, then make sure you have updated to v1.9.9 or enable the Override Thumb Test setting.

In extreme situations, the server you host your website on does not have the GD PHP extension installed. In this scenario, contact your web host and ask them for more info. You can see which version of the GD library you are running by visiting FooGallery -> System Info.

Still Having Issues?

If you are seeing the alert after following the above, please contact our support for further assistance.