Figure 1. Comparison of traditional image replay (a) and our re-
play methods (b). (a) shows that only the old class “horse” is la-
beled in stored image, while other classes (new class “person” and
old class “car”) are labeled as background. Both old (“horse”) and
future classes in new images are labeled as background. (b) Our
method avoids confusing information in stored image by retaining
instances and alleviates background shift by fusing these instances
in the new image.