The objective of ITU-T T88| ISO/IEC 14492 Amendment 2 is to further improve JBIG2's compression of periodic bi-level images, like the halftones used in printing. In particular, it improves compression for the clustered-dot halftones often used in very high resolution commercial printing. When applying the appropriate 16-pixel JBIG2 'template' for such applications, the Amendment facilitates more compression by increasing the number of moveable (Adaptive Template, ‘AT’) pixels from 4 to 12. For periodic halftones at resolutions of over 2400 dpi, effectively exploiting these 12 AT pixels yields approximately 20% better compression than the best obtainable with the current 16-pixel JBIG2 template (by optimizing its maximum of 4 AT pixels). To signal the presence of Amendment 2 datastreams, new flag bits have been defined for both the overall JBIG2 File header and for relevant image Segment headers. The flag bits permit early detection of Amendment 2 datastreams, making it possible to quickly prevent current JBIG2 decoders from attempting to decode these new datastreams.