web2png - Online in the Cloud

PROGRAM:

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 multiple images, 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.

-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 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.

-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.

Use web2png online using onworks.net services