1. An electronic device, comprising: at least one image source unit, configured to obtain a series of images; and an image processing unit, coupled to the at least one image source unit and configured to: determine whether the electronic device is in a camera-still state according to the series of images; select first images from the series of images upon the electronic device is determined in the camera-still state; determine object states corresponding to the first images; divide the first images into at least one group according to the object states; and select a candidate image from each of the at least one group.