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Hello, my name is Alejandro Rodríguez Ascaso and I am a professor
at the Department of Artificial Intelligence at UNED.
This video is about the accessibility of images in digital texts.
An image is a visual and static representation
of information that is presented on a surface.
This information can be figurative, conceptual, abstract,
and can take the form of photographs,
diagrams, reproductions of works of art, etc.
Images are present in almost any text.
It is rare and boring to find texts without them.
They are used in books, notes, complementing the theoretical text,
and also as exam or exercise announcements.
I bring here an example, a representation of our solar system,
that great fireball that is the sun and the rest
of the celestial bodies that orbit around it.
We know that there are people who do not perceive visual information.
For this reason, each image must be
accompanied by a text that describes it.
How should that text be?
It must contain the information that with that image
we want to transmit to those who use our document.
There are times when we use the image for purely decorative purposes.
In that case, it is almost better not to say anything.
In other cases, it will be enough to offer the simple text
"Representation of the solar system".
In others, we will need to be more specific,
and we will write, for example, that in it is represented the sun,
the planets and dwarf planets, their relative sizes,
the order of proximity to the sun,
the differences in their colors, etc.
If you have doubts about what text is equivalent
to your image, I propose the following exercise.
Imagine that for some reason you cannot use
that image or any similar one in your document.
Write a text that would replace it and that would
allow your readers to have an equivalent knowledge.
That is the alternative text that you should use.
The specific technique to include it depends
on the type of document we are talking about.
If it is a website, a document that you are writing
with your text processor, the PDF in
which you are going to convert it, etc.
In the technique to include the alternative text,
it also influences which version of the program you are using.
But offering an alternative text does not solve everything.
Let's see an example.
Let's take this image as an example,
a population evolution chart over the
years that is offered on a website.
The option to access the same information
through a table is also available,
that is, through a structured text.
Probably this strategy is better for a screen reader user
than an alternative text to the chart
where data is listed without any structure.
In addition, having that information as a table indicates
that you could probably import it to a spreadsheet program
where you can study it more detailed and comfortably.
How good is technology when it allows us to
offer information to each person as they please?
In general, we must take care of the quality of our images
in our documents, for aesthetics and accessibility,
so that it is correctly perceived by our readers.
For example, those who see little will
try to increase the size of the image to better perceive its details.
We have here the mathematical formula for the solution
of the second degree equation.
If the image is not of good quality, when increasing its size
this pixelation effect will appear, which
can make it difficult to see it correctly.
I must admit that this example of the mathematical expression
has some tricks.
Maybe someone has fixed it.
Indeed, if your document is based on HTML,
you should use MathML to include your expressions in mathematics.
Never images directly.
If we use a text processor, it is better to
include the formula through the equation editor.
But that is another story that we will discuss in other videos.
Another thing.
There are vector image formats, such as SVG,
which, no matter how much we enlarge its
size, the pixelated effect never appears.
Good invention.
In addition, the recommendations for a good image
are similar to those offered for electronic text.
Enough size, good contrast between the information and the background.
Something to avoid.
Coding information by color.
It is a resource that is usually used to code information
and that poses accessibility problems to many people.
Think about the transport plan of your city,
which you will find in the subway or bus stations.
Imagine it without color.
A challenge, right?
I will choose another example closer to what any of us
can find when preparing a report or article.
In this circular chart, like a pie,
the sales made by a company's commercials are shown.
It is likely that we pose a problem
to some of the readers of our document
if the only way to know who a portion of the pie belongs to
and, therefore, the number of sales indicated within it
is the color table that we place next to the chart.
Instead, if instead of using color, we put the name of the commercial
next to the sales sector that corresponds to it,
we will have eliminated that problem.
Little tricks that make life easier for everyone.
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