1. A computer-implemented method of processing a video frame that is included in a particular media clip for a media-editing application, the method comprising: in a composite display area of the media-editing application, receiving a plurality of media clips to form a composite media presentation, the plurality of media clips including the particular media clip; identifying a set of faces in the video frame of the particular media clip; receiving a set of user defined image processing operations for applying to the set of faces; generating a set of geometric shapes enclosing the set of faces; and applying the set of image processing operations to respective areas of the video frame isolated by the set of geometric shapes, wherein applying the set of image processing operations results in modifying pixel values of the video frame.