Some articles may contain diagrams or other images with English text that can and should be translated. In order to make the translated versions appear in the respective translations, GNUN should be told what URLs need localization. It can be done with HTML comments like
<!-- GNUN: localize URL /philosophy/category.png, /licenses/template-diagram.png and /graphics/jesus-cartoon.jpg -->
The URLs are separated with spaces. One trailing comma at the end of every word is removed if present. Words without a dot, such as ‘and’, do not count as URLs; they are ignored.
Such comments will be extracted nightly and compiled into per-article lists of URLs in localized-urls.mk.
After every build GNUN will check if the respective philosophy/category.lang.png and other files are present in the working copy and substitute the strings in the HTML file of the translation.
GNUN relies on URLs being absolute, starting from the root directory as required in http://www.gnu.org/server/fsf-html-style-sheet.html#FilenameAndURLGuidelines.
And please don’t forget to commit the image in its source form (typically, in SVG format).