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\.TH WEB2PNG 1 "6 October 1999"
.SH NAME
web2png \- convert a web tree from using GIFs to using PNGs
.SH SYNOPSIS
web2png [-dn] [directory...]
.SH DESCRIPTION
Web2png is a front end for gif2png(1) that automatically converts
entire web page hierarchies from using GIFs to using PNGs. It does
image conversion and patches IMG SRC references in web pages.
The arguments to web2png must be directories; if none are given,
the current directory is assumed.
In each directory, web2png tries to convert every GIF to a PNG. It
leaves alone GIFs that have either multiple images or transparency,
because these will not display properly in current browsers. It also
does not reconvert GIFs that already have corresponding PNGs (e.g. the
same name except for the .gif file extension). The original GIFs are
left in place.
Web2png tracks successful conversions. It then looks at each HTML,
secure HTML, HTML inclusion, PHP page, JavaScript program or Cascading
Style Sheet under the argument directories (extensions html, shtml,
.inc, .php, .js, .css). In these pages, it fixes each reference to
each successful converted GIF to point at the PNG. References in
relative HREF and BACKGROUND tags are recognized by filename and fixed
(any base directory declared by a BASE tag will be be prepended to the
relative URL). References that are HTTP URLs are matched against the
list of convertible GIFs by basename; if there is such a match, the
contents of the URL is retrieved and compared to the convertible GIF.
If both basename and data match, the HTTP reference is fixed.
If the pages are under RCS version control, they're checked out for
modification before being altered; otherwise, a copy of the original
of each modified web page is left in the same directory, with the
additional extension .bak.
Two options change the behavior of the program:
.TP
.B -a
Convert all GIF files, including those with multiple images and/or
transparency.
.TP
.B -d
Delete originals. Removes all GIFs with corresponding PNGs, and all
\&.bak files.
.TP
.B -n
Make no changes. With this option, web2png reports on what needs to
be done (and on GIFs that use transparency or have multiple images),
but neither converts GIFs nor touches web pages.
.TP
.B -r
Reverse. Restore all HTML/SHTML/PHP pages from the .bak files created
by a previous run (or, if the files were under version control, revert
them). Remove PNGs with corresponding GIFs.
.TP
.B -v
Verbose. Utter more trasce information about the conversion process.
Web2png can be run on a directory that has already been partly
converted by previous runs; it will do the minimum necessary
amount of work. The changes it makes will be fully reversible with -r
until you run it in -d mode.
Web2png is written in Python. Python must be installed and accessible
on your system in order for web2png to run.
.SH NOTE
Sometimes it's possible to convert transparent GIFs without altering
the appearance of the page, by knowing from context that they will
always place within an area of fixed and solid color. Web2png can't
deduce when this will be, so it doesn't try; but it may be useful
to apply gif2png with the -b option by hand.
.SH KNOWN PROBLEMS
The algorithm for fixing HTTP URLs is not foolproof. It could be
confused into incorrectly patching an HTTP URL reference to a GIF into
an invalid reference to a PNG if the GIF matches a local target GIF by
both basename and binary content, but actually lives on another host.
This program does not automatically convert CGIs; you'll have to do
that by hand. Other dynamic-content methods (such as server-side
inclusions) may also require hand-hacking.
The program cannot tell converted from preexisting PNGs; if you have
PNGs with the same stem name as corresponding GIFs but carrying
different information, the -r mode will clobber them.
.SH SEE ALSO
gif2png(1)
.SH AUTHORS
Eric S. Raymond <esr@thyrsus.com>, October 1999.
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