PNG - Ideas to Integrated Circuits

PNG Interlacing Demo
How PNG's Two-Dimensional Interlacing Works
(PNG Version with MNG and MPEG Animations)
Thousands of people ask Greg every day, ``Just how does two-dimensional interlacing work in the
Portable Network Graphics specification, and what does it mean to my sex life?'' Fortunately Greg is in a
unique position (so to speak) to answer this question once and for all; it can now be laid (as it were) to
rest.
To demonstrate the stupendously complicated procedure known as Adam7 interlacing in a manner that
even the tiniest brain cell can comprehend, Greg has produced a set of accordingly tiny images
demonstrating the concept. Oliver Fromme, another PNG author and also the developer of the QPV
viewer for DOS (formerly QPEG), is to be congratulated for the hard work in creating the original shelf
+balls logo that was the basis for this demonstration. Thanks also to Alexander Lehmann for the MPEG
animation (101k) of the process and to Glenn Randers-Pehrson for the MNG animation (214k).
All of the images on this page, with the exception of the tiny `PNG' icons near the bottom,
are actual interlaced PNG images. As of May 1997, the PNG images are inlined both via
the old IMG tag and also via the newer OBJECT tag; new versions of Navigator respect
the latter but not the former when loading plugins. As of December 1999, all OBJECT
tags have been removed except on the image above; most browsers still don't support the
tag correctly.
Note that, although the inlined PNG images are either the same size as or smaller than
their GIF counterparts (even taking into account the more complex interlacing scheme),
the linked PNG images are much larger than the corresponding JPEG versions. Lossy
compression really does make a huge difference -- between 5x and 6x for the small
http://libpng.org/pub/png/pngpic2.html (1 of 5)10/23/06 12:56 PM