8. A learning method comprising: extracting, by a feature-quantity extraction circuit, a feature quantity from a feature point of each learning image of a plurality of learning images, the plurality of learning images including a first learning image including a detection target and a second learning image not including the detection target; acquiring, from an external device, a transfer classifier for detecting the detection target; calculating, by a weak-classification calculation circuit, a classification result of the detection target according to a weak classifier for each learning image by substituting the feature quantity extracted by the feature-quantity extraction unit that corresponds to the weak classifier into the weak classifier with respect to each of a plurality of weak classifiers constituting the transfer classifier; and generating, by a classifier generation circuit, a classifier using the transfer classifier and the weak classifier selected from the plurality of weak classifiers based on the classification result of each of the plurality of weak classifiers.
8. A learning method comprising: extracting, by a feature-quantity extraction circuit, a feature quantity from a feature point of each learning image of a plurality of learning images, the plurality of learning images including a first learning image including a detection target and a second learning image not including the detection target; acquiring, from an external device, a transfer classifier for detecting the detection target; calculating, by a weak-classification calculation circuit, a classification result of the detection target according to a weak classifier for each learning image by substituting the feature quantity extracted by the feature-quantity extraction unit that corresponds to the weak classifier into the weak classifier with respect to each of a plurality of weak classifiers constituting the transfer classifier; and generating, by a classifier generation circuit, a classifier using the transfer classifier and the weak classifier selected from the plurality of weak classifiers based on the classification result of each of the plurality of weak classifiers. 12. The learning method according to claim 8 , wherein the transfer classifier detects the detection target when the detection target is in a first state, and wherein the generated classifier detects the detection target when the detection target is in a second state different from the first state.