HEVC-based scanned document compression
This paper proposes a hybrid pattern matching/transform-based compression engine for scanned compound documents. The novelty of this approach is demonstrated by using a modified version of the HEVC (High Efficiency Video Coding) Test Model as a compound document compressor, here conveniently referred to as HEDC (High Efficiency Document Coder). The proposed method uses segments of a document to create a video sequence, which is then encoded by HEDC. The idea is to explore interframe prediction as a pattern matching algorithm for coding units pre-classified as text; and intraframe prediction for coding units pre-classified as image. Results show that HEDC outperforms AVC-I, HEVC-I (H.264/AVC and HEVC operating in pure intra mode), H.264/AVC and JPEG2000 by up to 3.3, 2.5, 1.7 and 5 dB, respectively. Furthermore, for most documents the proposed method yields practically the same rate-distortion performance as regular HEVC, but is approximately 5% to 20% faster due to a pre-classification algorithm that prevents it of performing all possible inter/intra prediction tests for each prediction unit.