Portable Network Graphics files (.PNG)
PNG files are a recent newcomer to the web page scene. They have been produced in
response to the litigious nature of the owners of the GIF patent. Software developers
had been forced to license what was essentially an open standard that was snatched
by a big corporation for its own gain. The PNG file format is public domain, lossless
and supports a range of colour mappings from palette based to true colour, however,
the most common format uses 24bit colour. It is still not widely used, but it is
gaining momentum.
It suffers from the same problem as GIF files in that it does not handle photographic
images very well, but a further downside is that using 24bit colour the files are potentially
3 times bigger. However, on the plus side the algorithm is much
more efficient for drawn images. The examples below demonstrate this.
Golden Rule 2 - don't use GIF or PNG format for photographs
By their very nature, photographs do not compress as well with the
GIF and PNG formats. JPEG is designed specfically to handle compression
of photographs and optimum choice of compression quality will give and
appropriate balance between amount of detail and final file size.