As the internet becomes dominated by images, Facebook is launching a system which can "read" photos and tell visually impaired people what appears in them.

The internet is now becoming increasingly picture-led. But it is not a good news for blind or partially sighted users who often have no way of telling what is in an image. But a new service from Facebook is attempting to remedy that.

Blind people use sophisticated navigation software called screenreaders to make computers usable. They turn the contents of the screen into speech output or braille. But they can only read text and can't "read" pictures.

Using artificial intelligence (AI), Facebook's servers can now decode and describe images uploaded to the site and provide them in a form that can be read out by a screenreader.

Facebook says it has now trained its software to recognise about 80 familiar objects and activities. It adds the descriptions as alternative text, or alt text, on each photo. The more images it scans, the more sophisticated the software will become.