PROBLEM TO BE SOLVED: To generate a chapter representative image of which the data size is small and with which contents of a chapter can be grasped.;SOLUTION: A chapter detector 12 detects from a video file a chapter which starts at a starting time when writing of a line is started at a place imaged in the video file and which ends at an ending time when the line is erased. A starting-time background image generator 13 generates a starting-time background image indicating a background of a place captured in a frame image in chapter start. An ending-time background image generator 14 generates an ending-time background image indicating a background captured in the frame image in chapter end. A differential detection processor 15 generates a differential region image indicating a region of a differential between the starting-time background image and the ending-time background image. A representative image generator 16 extracts a partial image including the region indicated by the differential region image from the ending-time background image and generates a representative image including the partial image.;COPYRIGHT: (C)2013,JPO&INPIT
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