An efficient block based lossless compression of medical images

Medical images play a significant role in diagnosis of diseases and require a simple and efficient compression technique. This paper proposes a block based lossless image compression algorithm using Hadamard transform and Huffman encoding which is a simple algorithm with less complexity. Initially input image is decomposed by Integer wavelet transform (IWT) and LL sub band is transformed by lossless Hadamard transformation (LHT) to eliminate the correlation inside the block. Further DC prediction (DCP) is used to remove correlation between adjacent blocks. The non-LL sub bands are validated for Non-transformed block (NTB) based on threshold. The main significance of this method is it proposes simple DCP, effective NTB validation and truncation. Based on the result of NTB, encoding is done either directly or after transformation by LHT and truncated. Finally all coefficients are encoded using Huffman encoder to compress. From the simulation results, it is observed that the proposed algorithm yields better results in terms of compression ratio when compared with existing lossless compression algorithms such as JPEG 2000. Most importantly the algorithm is tested with standard non medical images and set of medical images and provides optimum values of compression ratio and is quite efficient.