Visual pattern BTC with two principle colors for color images

This paper presents an extension of the “block truncation coding with visual patterns (BTC-VP)” for color image compression. Our approach BTC-VP-2PC attributes its name to the fact that it, regardless of the variety of colors, encodes each 4×4 image block into two principle colors (PC) and one visual pattern (VP) (which are both visually significant to human observers). In BTC-VP-2PC, each VP is generated from a bitmap. This bitmap, obtained from a weighted trichromatic transform, quantizes all color components (i.e. it´s actually BTC). Experimental results show that only two PCs and one VP for each block are enough to represent edge regions with high subjective quality. Also a substantial compression ratio has been achieved (for NTSC color TV images)