NAME
web2png - convert a web tree from using GIFs to using PNGs
SYNOPSIS
web2png [-adnrtv] [directory...]
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 all 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.
The following options change the behavior of the program:
-a
Convert all GIF files, including those with multiple images and/or
transparency.
-d
Delete originals. Removes all GIFs with corresponding PNGs, and all
.bak files.
-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.
-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.
-t
Convert transparent GIFs (for use with IE 5.0+. Netscape 6.0+, and
Mozilla).
-v
Verbose. Utter more trace 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
1.5.2 or better must be installed and accessible on your system in
order for web2png to run.
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.
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.
SEE ALSO
gif2png(1)
AUTHORS
Eric S. Raymond <esr@thyrsus.com>, October 1999.
Slightly modified for Debian by Aaron Isotton <aaron@isotton.com>.