Issue Encountered
I came across this issue when I was adding a media item on a client site, for some reason all the “document” media item have lost its thumbnail; After inspecting via the “Network” panel in the developer tools, it is found that the media-icons genereated by the GD2 Toolkit at url /sites/default/files/styles/thumbnail/public/media-icons/generic/generic.png?itok=xxyyzz have gotten a 404 not found error with respond body being Error generating image, missing source file .
Under the “Claro” admin theme, there is a particular issue where, if the thumbnail is missing, the text label for the document becomes obscured. It gets tucked under a white box, making it unreadable.
Issue Resolved
After some research, it is found that the GD2 Image Toolkit (in Drupal) infact doesn’t generate image from file, instead it chooses one of the image “template/default” based on the type of the file. For intance, if the file is an audio file, it will choose ``/sites/default/files/styles/thumbnail/public/media-icons/generic/audio.pngas the thumbnail ; if the file is anpdf/docx/csvfile, it will choose/sites/default/files/styles/thumbnail/public/media-icons/generic/generic.png` as the thumbnail.
The issue is simply those files are not existing on the path, though it still remains a mystery for me when I wrote this post, that why drupal dones’t have those fiels by default, or use the ones located inside the /core/modules/media/images/icons/audio.png instead….
The path is pretty easly, simply create the styles directory under the sites/default/files directory (along with all the required sub-directories and thumbnail files), I’ve included an example style.zip file you can extract in the sites/default/files directory: 【styles.zip】
