5. The method of claim 1 , wherein the threshold value defines a maximum difference of text quality scores for characters to be included in a given subset of characters.
5. The method of claim 1 , wherein the threshold value defines a maximum difference of text quality scores for characters to be included in a given subset of characters. 6. The method of claim 5 , further comprising adding a neighboring character to the given subset of characters in response to determining that a difference between an average value of text quality scores associated with the characters included in the given subset and a text quality score associated with the neighboring character subset is less than the threshold value.