natalyav2019 wrote It is my understanding that keeping text live (instead of flattening it into an image) has the advantage of preserving readability when zoomed in. Is this a factor at all? |
It depends upon how the graphic is made, file format, resolution, etc.
Yes, flattening text within a graphic does convert live text to a graphic format, either pixels/rasters or vectors. But that can be compensated by having a higher resolution on the graphic and keeping the compression low (higher compression causes artifacts and blurred fuzzy text).
We recommend creating any graphic that contains text to a resolution no lower than 150 ppi, and if the text is small, no lower than 250 ppi. Photos and graphics without text are ok at lower resolutions; but maps, charts, diagrams and anything else with text should have a higher resolution.
Given that current research estimates that 70-85% of our information is viewed on a mobile device, that means the user has a little screen at 300-400 ppi resolution. The days of 72ppi and 96ppi are long gone!
Keeping the graphs' text live is difficult to do right. Even if live, it can present with an incorrect reading order, move around so that the call-outs no longer point to their subject, and the text could be hard for the end-user to understand your message. Example: Even if f(x) = 1x2 is live, it doesn't make any sense if it is read out of context.
In our advanced classes for 508 + InDesign, we cover different strategies for making all kinds of graphics accessible. There's no one-size-fits-all strategy; you have to evaluate each document and its graphics to determine which method and strategy will provide the best end-result for not just screen reader users, but all users of all kinds of assistive technologies/AT. Here are some of the best strategies:
- Put the details in live narrative body text or <Captions>. The user will have the greatest access to and control of the reading experience. Alt-Text is a very unsatisfactory experience for those who use screen readers, so keep it to a minimum.
- If the data was graphed based on spreadsheet data, then add a "matching data table" after the chart graphic and make the table fully accessible. This makes all of the data available to everyone. You can also put the matching data table in an appendix or on a website, but ensure that you have live body text that states "matching data table for Figure 9 is available at..." and hyperlink to the table.
- There are some types of info graphics where the text can remain live, but it has to be tagged and sequenced correctly. Each piece should be able to stand on its own and be understandable to the end user. The text parts have to make sense when they are read out of context. Using your original example, it might work like this:
<Hx>Figure 123 — Chart of 3 graphs for f(x) at 1, 2, and .05 variables
<Caption>Variables are:
<UL><LI>f(x) = 2x2 (can't do superscript in this forum!)
<LI>f(x) = 1x2
<LI>f(x) = 0.5x2
The vertex is (0,0) for all 3 graphs, with x extending from -1 to +1, and y extending from -1 to +1.
The graph of f(x) = .5x2 is wider than the graph of f(x) = 2x2.
<image> Alt-Text = Line graph of Figure 123.
</Caption>
You can break up this narrative text into as many frames as you need, even keep the bubble call outs you now have. But ensure that all of the frames are threaded in the correct sequence so that it becomes one unit of information that is read in the correct reading order.
Hope this helps! Keep your mind open to other strategies. There's no one "right" way to do this. And you might have to work with the editorial team to develop a good strategy.
—Bevi
| Bevi Chagnon | Designer, Trainer, & Technologist for Accessible Documents |
| PubCom | Classes & Books for Accessible InDesign, PDFs & MS Office |
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