gdk-pixbuf-query-loaders man page
gdk-pixbuf-query-loaders — GdkPixbuf loader registration utility
gdk-pixbuf-query-loaders [--update-cache] [MODULE...]
gdk-pixbuf-query-loaders collects information about loadable modules for gdk-pixbuf and writes it to the default cache file location, or to stdout.
If called without arguments, it looks for modules in the gdk-pixbuf loader directory.
If called with arguments, it looks for the specified modules. The arguments may be absolute or relative paths.
Normally, the output of gdk-pixbuf-queryloaders is written to libdir/gdk-pixbuf-2.0/2.10.0/loaders.cache, where gdk-pixbuf looks for it by default. If it is written to some other location, the environment variable GDK_PIXBUF_MODULE_FILE can be set to point gdk-pixbuf at the file.
Write the output to the default cache location instead of stdout
The environment variable GDK_PIXBUF_MODULEDIR can be used to specify a different loader directory. The default gdk-pixbuf loader directory is libdir/gdk-pixbuf-2.0/version/loaders.