			     pngmeta 1.0
			     ===========
		Dave Beckett <D.J.Beckett@ukc.ac.uk>

This small filter program outputs the meta data for PNG images.  It
currently prints the text strings in key: value format or SOIF format
as used by the Harvest system (http://harvest.cs.colorado.edu/) and
as such can be directly used as a Summarizer for Essence for that
system.  It could also be used by other indexers to extra data for
indexing from PNG images.

The program contains a new function png_skip_till_end() that takes up
the reading of the PNG data stream after the first IDAT has been
detected.  It then copies through, checking the CRCs of them but not
decompressing or processing them.  Finally, any remaining chunks are
processed in the standard fashion.  This code was modified from the
code for png_read_end() from libpng 0.85 by Guy Eric Schalnat, Group
42, Inc.  See pngmeta.c for full copyright details.

A test image ct1n0g04.png is provided which contains some strings.
This is part of the PNG image test suite written by
Willem A.J. van Schaik <gwillem@ntuvax.ntu.ac.sg>


Requirements
------------
* An ANSI C compiler
* libpng (tested with 0.85 but earlier ones should work)
* zlib   (tested with 0.95 "   "       "    "      "   )

The latter two should be available at ftp://ftp.uu.net/graphics/png/
when released publically.


Usage
-----
pngmeta [-soif] [-quiet] [filename]

If no options are given, the program operates as a filter from stdin
to stdout.  If a single file name is given, that PNG file is
processed.  The -soif option changes the output to be in SOIF format
and the -quiet option stops the output of the banner when outputting
the standard non-SOIF format.


Examples of use
---------------
mint% pngmeta -soif ct1n0g04.png 
Title{8}:	PngSuite
Author{49}:	Willem A.J. van Schaik
(gwillem@ntuvax.ntu.ac.sg)
Copyright{43}:	Copyright Willem van Schaik, Singapore 1995
Description{239}:	A compilation of a set of images created to test the
various color-types of the PNG format. Included are
black&white, color, paletted, with alpha channel, with
transparency formats. All bit-depths allowed according
to the spec are present.
Software{48}:	Created on a NeXTstation color using "pnmtopng".
Disclaimer{9}:	Freeware.

mint% pngmeta goldhill.png 
pngmeta: PNG meta data for goldhill.png:
Title: GOLDHILL: Photo of hill in small European town.
Copyright: Unknown

---------------

Dave Beckett
D.J.Beckett@ukc.ac.uk
4th January 1996
