[docs] Add alt text on images #4028
Description
Summary
For every image in LightGBM's documentation, alternative text that describes the image should be added.
Motivation
People with limited vision use screen readers to view web pages. When these screen readers encounter an image, they will only read some placeholder like "IMAGE" by default. However, if the "alt" tag is specified, many screen readers will use that instead.
Adding alt text for images would improve the accessibility of LightGBM's documentation for users who use screen readers.
Description
To help with this issue, submit a pull request that adds alt text for images in LightGBM's documentation. Please limit pull requests to only 1 file, to simplify reviews.
As of this writing, the following documentation files have images (based on git grep -E "\.\. image" docs)
-
docs/Features.rst([docs] add alt text to docs images #4036) -
docs/GPU-Performance.rst([docs] add alt text to docs images #4036) -
docs/GPU-Windows.rst([docs] add alt text to docs images #4036) -
docs/Parallel-Learning-Guide.rst([dask] add tutorial documentation (fixes #3814, fixes #3838) #4030) -
docs/Parameters-Tuning.rst([docs] Add alt text to image in Parameters-Tuning.rst #4035) -
docs/gcc-Tips.rst([docs] Add changes to gcc-tips #4187) -
docs/index.rst([docs] Add alt text on images in index.rst #4029)
When adding alt text, follow the advice in https://accessibility.psu.edu/images/alttext/.
...include what you might relay over the phone
it should describe the image. It should NOT include information about copyright or any extra information that would be relevant to a seeing audience.
This can be done with the :alt: parameter in Sphinx ..image directives (see the Sphinx docs for details).
For example:
.. image:: ./_static/images/some-image.png
:alt: A screenshot with build logs from GCC.References
While working on this, you might also consider some of the recommendations from https://webaim.org/techniques/screenreader/#how. For example, things that should be read out loud as acronyms, like gcc, should be spelled out all in capital letters ("GCC").