White and narrow band image compressor based on a new color space for capsule endoscopy

• A new low-complexity color space, known as YEF, is presented.
• An extensive analysis is performed using white light and narrow band endoscopic images and video frames.
• The low-complexity image compression algorithm is optimally tuned using the above analysis.
• The reconstructed images have been verified by medical doctors for acceptability by conducting two surveys.
• The compressor chip has been fabricated using 0.18 μm CMOS Artisan technology.

In this paper, we present the design of a low power and hardware efficient image compressor integrated circuit for wireless capsule endoscopy application. The proposed compression algorithm supports dual-band imaging, that is, works on both white-band imaging (WBI) and narrow-band imaging (NBI). The scheme uses a novel color-space and simple predictive coding for optimized performance. Based on the nature of the narrow- and white-band endoscopic images and video sequences, several sub-sampling schemes are introduced. The proposed dual-band compressor is designed in such as way that it can easily be interfaced with any commercial low power image sensor that outputs RGB image pixels in a raster scan fashion, eliminating the need of large buffer memory and temporary storage. Both NBI and WBI reconstructed images have been verified by medical doctors for acceptability. Compared to other designs targeted to video capsule endoscopy, the proposed algorithm performs strongly with a compression ratio of 80.4% (for WBI) and 79.2% (for NBI), and a high reconstruction peak-signal-to-noise-ratio (over 43.7 dB for both bands). The results of the fabricated chip are also presented.