Systems and methods are provided for providing a navigation interface to access or otherwise use image content items. In one embodiment, an image manipulation application identifies at least one offset curve corresponding to at least one base curve. The offset curve may identify an offset curve corresponding to the outer boundary of a feathered region for an image mask. The image manipulation application identifies multiple line segments identifying the offset curve. Each line segment connects a sampled point along the path of the base curve to a corresponding point along the path of the offset curve. The image manipulation application determines that the offset curve includes a retrograde region based on analyzing the line segments. The image manipulation application modifies the at least one offset curve to eliminate at least some of the retrograde region by applying a radius-modulating filter to one or more of the line segments.