1. An apparatus comprising: a memory; and a processor coupled to the memory and configured to: acquire a first image captured by an image capturing device, extract a first area corresponding to an object in the first image, divide the first area into a plurality of first segments, generate a plurality of histograms regarding the plurality of first segments respectively, store the plurality of histograms into the memory, acquire a second image which is captured by the image capturing device after the first image, detect a second area corresponding to the object in the second image according to a first reference histogram from among the plurality of histograms, determine whether a part of the object is outside of the second image based on the second area, when it is determined that the part of the object is outside of the second image, select a second reference histogram used for a third image which is captured by the image capturing device after the second image, from among the plurality of histograms, and when the third image is acquired, detect a third area corresponding to the object in the third image based on the second reference histogram.