What are functional images?
Functional images form part of interactive elements like links or buttons on a webpage or in an app. Usually, journalists have no control over the text descriptions.
For those who can add text descriptions, it must indicate the action of the image. The function of the image is what's important, so the symbol doesn't need to be described.
For example, a play button might show a triangle, but the text description must say "play" rather than "triangle".
Example
Icons
Source: 大象传媒 News
Original text description: "Notifications".
Recommended text description: No change, because the function of the image it is clear.