1. An image processing apparatus comprising: moving image storage means for storing a taken moving image taken by an image taking apparatus; conversion information storage means for storing, for each second taken image, conversion information for converting said second taken image located after a first taken image in time axis of said taken moving image with reference to said first image configuring said taken moving image; image holding means for holding a log image including each taken image located before said second taken image in said time axis; feature quantity extraction means for extracting a feature quantity associated with said second taken image; image conversion means for converting said second taken image on the basis of said conversion information; decision means for determining whether or not synthesis of said second taken image and said log image is necessary on the basis of said extracted feature amount; and image synthesis means for, if the synthesis of said second taken image and said log image is determined necessary by said decision means, synthesizing said converted second taken image with said log image held in said image holding means and holding the synthesized image in said image holding means as a new log image and, if the synthesis of said second taken image and said log image is determined unnecessary by said decision means, holding said second taken image in said image holding means without synthesizing said second taken image with said log image held in said image holding means.