wp-includes/class-wp-image-editor.php:231Gets the Image Compression quality on a 1-100% scale.
int public function get_quality() { if ( ! $this->quality ) { $this->set_quality(); } return $this->quality; }Introduced in 4.0.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-image-editor.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.