  In this paper, we have proposed an extended version of Absolute Moment Block
Truncation Coding (AMBTC) to compress images. Generally the elements of a
bitplane used in the variants of Block Truncation Coding (BTC) are of size 1
bit. But it has been extended to two bits in the proposed method. Number of
statistical moments preserved to reconstruct the compressed has also been
raised from 2 to 4. Hence, the quality of the reconstructed images has been
improved significantly from 33.62 to 38.12 with the increase in bpp by 1. The
increased bpp (3) is further reduced to 1.75in multiple levels: in one level,
by dropping 4 elements of the bitplane in such a away that the pixel values of
the dropped elements can easily be interpolated with out much of loss in the
quality, in level two, eight elements are dropped and reconstructed later and
in level three, the size of the statistical moments is reduced. The experiments
were carried over standard images of varying intensities. In all the cases, the
proposed method outperforms the existing AMBTC technique in terms of both PSNR
and bpp.
