1. A character input prediction apparatus comprising: a first operation input unit configured to obtain information of a first character input operation that is performed by a user using a character key layout display in which a plurality of character keys are arranged; a dictionary storage unit configured to store a dictionary including a plurality of candidate character strings; a character key layout management unit configured to store a character key layout showing the arrangement of the plurality of character keys in the character key layout display; a first indication movement detection unit configured to detect a first indication position and a first indication direction in the character key layout display from the information of the first character input operation, the first indication position showing a position of the first character input operation, and the first indication direction showing a movement direction of the first character input operation; a first filter generation unit configured to determine a vector having the first indication position as a base point using the first indication position and the first indication direction, and determine a first character range using the character key layout, the first character range including a plurality of character keys located in an extending direction of the vector; and a dictionary search unit configured to search the plurality of candidate character strings included in the dictionary, for a predictive character string that includes a character corresponding to any one of the plurality of character keys included in the first character range.
1. A character input prediction apparatus comprising: a first operation input unit configured to obtain information of a first character input operation that is performed by a user using a character key layout display in which a plurality of character keys are arranged; a dictionary storage unit configured to store a dictionary including a plurality of candidate character strings; a character key layout management unit configured to store a character key layout showing the arrangement of the plurality of character keys in the character key layout display; a first indication movement detection unit configured to detect a first indication position and a first indication direction in the character key layout display from the information of the first character input operation, the first indication position showing a position of the first character input operation, and the first indication direction showing a movement direction of the first character input operation; a first filter generation unit configured to determine a vector having the first indication position as a base point using the first indication position and the first indication direction, and determine a first character range using the character key layout, the first character range including a plurality of character keys located in an extending direction of the vector; and a dictionary search unit configured to search the plurality of candidate character strings included in the dictionary, for a predictive character string that includes a character corresponding to any one of the plurality of character keys included in the first character range. 8. The character input prediction apparatus according to claim 1 , wherein the first indication movement detection unit is configured to detect the first indication position at predetermined time intervals, the character input prediction apparatus further comprises an indication position storage unit configured to hold a plurality of indication positions detected by the first indication movement detection unit, the first indication movement detection unit is further configured to calculate a movement speed of the first character input operation, from the plurality of indication positions, and the first filter generation unit is configured to: in the case where the movement speed is equal to or more than a first speed, determine a first range in the character key layout display as the first character range; and in the case where the movement speed is less than the first speed, determine a second range in the character key layout display as the first character range, the first range being located in the first indication direction with the first indication position as the base point, and the second range being located in the first indication direction with the first indication position as the base point and being smaller than the first range.