9. The apparatus according to claim 8 , wherein the initial selection device is further configured to search in the set of characters one or more characters having highest similarities of shape to the first character by: searching in the set of characters one or more characters having highest similarities of shape to each image sample of a plurality of image samples of the first character, as a candidate character set of the each image sample, so as to form a plurality of candidate character sets each of which corresponds to one of the image samples; calculating a frequency of each character occurring in the plurality of candidate character sets; and selecting in the plurality of candidate character sets one or more characters corresponding to highest frequencies, to form the similar character list of the first character.
13. The apparatus according to claim 9 , wherein the initial selection device is further configure to: remove from each character set one or more characters having similarities of shape to the first character lower than a second threshold, before calculating the frequency of each character occurring in the plurality of candidate character sets.