GIFT: Learning Transformation-Invariant Dense Visual Descriptors via Group CNNs

To achieve the invariance to viewpoints, traditional methods [36, 37] use patch detectors [33, 39] to extract transformation covariant local patches which are then normalized for transformation invariance. Then, invariant descriptors can be extracted on the detected local patches. However, a typical image may have very few pixels for which viewpoint covariant patches can be reliably detected[22].