1. A method for generating a dictionary being used for recognizing a target object by classifying a plurality of learning patterns the method comprising: obtaining a plurality of learning patterns including a target object, wherein each learning pattern has a same number of pixels; generating a plurality of mask patterns which respectively indicates a region where the target object exists in each learning pattern; calculating probability that a pixel at a same position in each learning pattern is included in the region where the target object exists by referring to the plurality of mask patterns; selecting at least one pixel having relatively higher probability based on the calculated probability; and classifying each learning pattern based on the at least one selected pixel.