- From: Karl Dubost <karl@w3.org>
- Date: Thu, 18 Sep 2003 11:54:59 -0400
- To: www-qa@w3.org
This is a draft Open for comments for future publications
http://www.w3.org/2001/06tips/
It's there for a long time, I just have forgotten to announce it. Sorry.
************************
Title: Use Gif or PNG
Draft - PNG vs GIF
This is a draft "webmaster tip", under work and review by the
[7]Quality Assurance Team, and shouldn't be considered as an official
tip from W3C while it remains a draft.
[7] http://www.w3.org/QA
GIF versus PNG
GIF
The GIF format is a format which compresses files using an algorithm
called LZW, which keep traces of the colors and helps to reduce the
size of the file. The LZW algorithm was protected in USA by a
[8]patent hold by the company Unisys. The Unisys LZW patent expires
in
the USA on June 20, 2003 though LZW patents are still in force in
Canada, France, Italy, Germany, the United Kingdom, and Japan.
[8] http://www.delphion.com/details?&pn=US04558302__
PNG
NG (Portable Network Graphics), an extensible file format for the
lossless, portable, well-compressed storage of raster images. PNG
provides a patent-free replacement for GIF and can also replace many
common uses of TIFF. Indexed-color, grayscale, and truecolor images
are supported, plus an optional alpha channel. Sample depths range
from 1 to 16 bits.
For the Web, PNG really has three main advantages over GIF:
* alpha channels (variable transparency),
* gamma correction (cross-platform control of image brightness),
* two-dimensional interlacing (a method of progressive display).
PNG also compresses better than GIF in almost every case (5% to 25%).
Further Reading
* [9]PNG Homepage
* [10]Benefits of the PNG image format
* [11]PNG W3C Recommendation
[9] http://www.libpng.org/pub/png/
[10] http://www.atalasoft.com/PNG.aspx
[11] http://www.w3.org/TR/PNG
--
Karl Dubost - http://www.w3.org/People/karl/
W3C Conformance Manager
*** Be Strict To Be Cool ***
Received on Thursday, 18 September 2003 11:55:04 UTC