Image description

Infographics and diagrams

We offer a stand-alone image description service for:

  • infographics of all kinds, including line graphs, scatter plots, bar charts, pie charts, etc
  • technical and other specialist diagrams 

The limitations of tabular data

Extracting complex information on, for example, trends, proportions, relationships or anomalies from a data table can be difficult and time-consuming (as opposed to extracting a single data value to answer a specific question, which is relatively straightforward). Scottish engineer William Playfair solved the problem, at least for sighted people, with the invention in 1786 of bar charts, line graphs and area charts (pie charts took him until 1801).

The solution for anyone who can’t see a graphic is, of course, a carefully crafted text description that includes all of the information conveyed by the image that is relevant to the context. We have many years’ experience of writing text alternatives for infographics and complex images.

Mathematical expressions

Until such time that MathML is sufficiently widely accessibly supported, it will often be necessary to provide unambiguous text alternatives for mathematical expressions. For example, “the square root of 5 over 2” is ambiguous. It could mean either of the following:

Mathematical expression showing the fraction 5 over 2, all contained within a square root symbol

(the solution to which is 1.5811),

or,

Mathematical expression showing the number 5 contained within a square root symbol, the result of which is divided by 2

(the solution to which is 1.1180).

However, in the case of the first of the above expressions, “start square root, start fraction, 5 over 2, end fraction, end root“, is entirely unambiguous, as is “start fraction, start square root, 5, end root, over 2, end fraction” in the case of the second. 

Screenshot of MathML/HTML code view with an aria-label attribute
ARIA fallback for a simple mathematical expression

Our experience

We have many years’ experience of writing text alternatives for mathematical expressions, including in the context of making accessible many hundreds of PDF-based maths and science exam papers. We also offer image description tuition, tailored to specific client requirements, in our PDF and ebook accessibility training courses.