1. An image processing apparatus comprising: means for storing a taken moving image taken by an image taking apparatus; means for storing, for each second taken image, conversion information including an affine transformation parameter 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 taken image configuring included in said taken moving image; means for holding a log image including each taken image located before said second taken image in said time axis; means for extracting a feature quantity associated with said second taken image; means for converting said second taken image on the basis of said conversion information; means for determining whether or not synthesis of said second taken image with said log image is necessary on the basis of said extracted feature amount; and means for synthesizing, when the synthesis of said second taken image with said log image is determined necessary by said means for determining, said converted second taken image with said log image held in said means for holding and holding the synthesized image in said means for holding as a new log image and, when the synthesis of said second taken image with said log image is determined unnecessary by said means for determining, holding said second taken image in said means for holding without synthesizing said second taken image with said log image held in said means for holding; wherein, when the synthesis of said second taken image with said log image is determined unnecessary by said means for determining, said means for synthesizing erases said log image held in said means for holding and holds said second taken image in said means for holding as a new log image.