Coding of Multilevel Graphics

In this paper we consider the digitization and coding of graphics, specifically typewritten letters, and make two contributions. The first contribution concerns the tradeoff between resolution and number of gray levels. We carried out subjective tests which showed that, in order to get better image quality at a given bit rate, for good-quality originals, one should use only two levels/sample and higher resolution; while for poor-quality originals, one should use more levels/sample. Second, we estimated the bit rates achievable when bit-plane run length coding is applied to the multilevel images.