Image descriptions should follow purpose: information, decoration, or action

W3C distinguishes informative, decorative, and functional images. An informative image needs a text alternative conveying its essential information. A decorative image adds no information needed to understand the content. A functional image's alternative communicates its action or destination.

Illustrative editorial choices: a photograph documenting a damaged bridge needs the relevant visible evidence described; the same bridge photograph used only as background decoration has a different role. A printer symbol that triggers printing should communicate the print action rather than merely naming the picture. These are invented examples of the source's categories.

Ask what meaning or function would disappear if the image were removed. For a complex chart, a short label alone cannot replace the underlying information; provide an equivalent explanation or data in accessible text. Review descriptions alongside the surrounding prose so repetition does not replace missing meaning.

This distinction matters when preparing websites, presentations, and documents for readers using assistive technology. The appropriate publishing mechanism differs by format, and an editorial description alone is not a complete accessibility audit.

Evidence status: source-based synthesis. Examples are illustrative; no new experiment or independent outcome verification is claimed.