향상된 정수 기반 웨이블릿 변환을 이용한 무손실에 가까운 영상 압축 = An Enhanced Integer - Based Wavelet Transform Coding in Near Lossless Compression

다국어 초록 (Multilingual Abstract)

An enhanced version of integer-based wavelet transform(TS Transform) coding is proposed for near lossless image compression. Due to flexibility in representing nonstationary image signals in time and frequency domains and ability in adapting to human visual characteristics, wavelet transform has unique advantages over other transforms currently used in image compression. In the Integer-based wavelet transform compression, original image is decomposed into multi-scalar bands. For the lowest band, a predictor is designed and error signal is entropy coded. For higher scalar bands, runlength coding for zero runs is employed with Huffman coding. In order to perform near lossless compression, pre-quantization of the original image is applied and the quantized image is losslessly encoded. To overcome visual degradation resulting from pre-quantization, a new pre-quantization scheme using multiple quantization tables is proposed. From simulation (512×512 size, 256 graylevel image) reconstructed images by the proposed algorithm show higher peak signal-to-noise ratio (PSNR) compared to those obtained by a float-point-based wavelet transform and the JPEG. Peak error in the reconstructed images by the integer-based wavelet transform is also much lower than those obtained by the JPEG and the float-point-based wavelet transform.