$files->filterBy()

$files->filterBy(mixed $args = null): Kirby\Cms\Files

// filter by extension
$images = $page->images()->filterBy('extension', 'jpg');

// filter by custom field value
$images = $page->images()->filterBy('gallery', 'gallery-2');

// filter by filenames containing a string
$files = $page->files()->filterBy('filename', '*=', '-document');

// filter all types except documents
$files = $page->files()->filterBy('type', '!=', 'document');

// filter all files that have a template assigned
$files = $page->files()->filterBy('template', true);