Facebook has put a lot of effort into ensuring that its users in developing nations and on slow networks are able to enjoy the service as fully as possible. One way it has done this is with apps that are specifically designed to run on low end handsets, and most recently it has detailed its effort to ensure photo previews load quickly, and with as little data use as possible. The social network did this by eliminating the blank photo preview users would see when waiting for an image to load and replacing it with a very small — and blurred — cover photo preview.
The problem, says Facebook, is that on slow Internet connections, such as a 2G mobile data connection, users have to wait for photos to load, in particular the cover image which is usually larger than other photos and take up to several seconds the fully loaded. During this time, users would see an empty gray box where the image should be, detracting from the service and looking visually unappealing.
The social network set out to correct this problem, a task it recently detailed on it’s code blog. The goal was to reduce the cover image size to 200 bytes in certain cases, allowing a Cover photo preview to be shown instead of an empty gray box. Facebook pulled this off using a mixture of JPEG technology and very low resolution, scaling the low resolution image up and then applying a gaussian blur.
As a result, users on slow Internet connections will see a blurred version of the cover image known as a frosted image, which allows you to see some details from the cover photo including colors, but not the full detail. This loads nearly instantly, even on slow Internet connections, and on the user’s end of things simply serves to make the app a little more beautiful.