1. An information processing apparatus, comprising: means for extracting a character line from a document image, the character line having a plurality of intercharacter spaces, each intercharacter space having an original length; means for converting the original length to a quantized length for each of the plurality of intercharacter spaces using additional information; means for obtaining an accumulated value representing a sum of the differences between the original length and the quantized length for each of the plurality of intercharacter spaces; means for determining whether the accumulated value is within a range determined by a threshold value to generate a determination result; and means for adjusting the quantized length of at least one of the plurality of intercharacter spaces based on the determination result to make the accumulated value within the range.