Some features of BookWyrm have to be enabled to work.
By default, BookWyrm uses the instance's logo (or the default logo) as an OpenGraph preview image. As an alternative, you can enable the generation of preview images for books, users, and the website.
The preview images will be sized for large OpenGraph images (used by Twitter under the name of
summary_large_image). Depending on the type of image, the contents will be:
These images will be updated at various points:
In order to enable the feature with default settings, you have to uncomment (remove the
# in front of) the line
ENABLE_PREVIEW_IMAGES=true in your
.env file. All the new updating events aforementioned will cause the generation of the corresponding image.
Examples for these images can be viewed on the feature’s pull request’s description.
If you enable this setting after your instance has been started, some images may not have been generated. A command has been added to automate the image generation. In order to prevent a ressource hog by generating A LOT of images, you have to pass the argument
-a) to start the generation of the preview images for all users and books. Without this argument, only the site preview will be generated.
User and book preview images will be generated asynchroneously: the task will be sent to Flower. Some time may be needed before all the books and users have a working preview image. If you have a good book 📖, a kitten 🐱 or a cake 🍰, this is the perfect time to show them some attention 💖.
So you want to customize your preview images? Here are the options:
PREVIEW_BG_COLORwill set the color for the preview image background. You can supply a color value, like
#b00cc0, or the following values
use_dominant_color_dark. These will extract a dominant color from the book cover and use it, in a light or a dark theme respectively.
PREVIEW_TEXT_COLORwill set the color for the text. Depending on the choice for the background color, you should find a value that will have a sufficient contrast for the image to be accessible. A contrast ratio of 1:4.5 is recommended.
PREVIEW_IMG_HEIGHTwill set the dimensions of the image. Currently, the system will work best on images with a landscape (horizontal) orientation.
PREVIEW_DEFAULT_COVER_COLORwill set the color for books without covers.
All the color variables accept values that can be recognized as colors by Pillow’s
ImageColor module: Learn more about Pillow color names.