BACKGROUND: As an important part of the application-specific integrated circuit (ASIC) in wireless capsule endoscopy (WCE), the efficient compressor is crucial for image transmission and power consumption.
OBJECTIVE: In this paper, a complexity-efficient and one-pass image compression method is proposed for WCE with Bayer format images. The algorithm is modified from the standard lossless algorithm (JPEG-LS).
METHODS: Firstly, a causal interpolation is used to acquire the context template of a current pixel to be encoded, thus determining different encoding modes. Secondly, a gradient predictor, instead of the median predictor, is designed to improve the accuracy of the predictions. Thirdly, the gradient context is quantized to obtain the context index (Q). Eventually, the encoding process is achieved in different modes.
RESULTS: The experimental and comparative results show that our proposed near-lossless compression method provides a high compression rate (2.315) and a high image quality (46.31 dB) compared with other methods.
CONCLUSION: It performs well in the designed wireless capsule system and could be applied in other image fields.