16 Mar
2013
16 Mar
'13
4:35 p.m.
From: "rachael at telefisk.org" <rachael at telefisk.org>
To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Sent: Friday, 15 March 2013, 20:28
Subject: Re: PNG image decompression
On Wed, 13 Mar 2013, Andrew Burton wrote:
libpng and zlib are two choices. Personal Paint (by Cloanto in 1996)
also supports PNG's, though looking at their custom PNG library
(and even disassembling it) hasn't revealed anything terribly useful to
me. I'm sure some better coders could probably work out what it does.
I found a site (link below) where someone else had the same problem
and Mark Adler (one of the guys behind the PNG format and/or the
libraries) was kind enough to post some information. It has helped
me progress a little further :)
http://newsgroups.derkeiler.com/Archive/Comp/comp.compression/2009-04/msg00…
Thanks to everyone for your suggestions.
Regards,
Andrew B
aliensrcooluk at yahoo.co.uk
Hi,
I am in the process of working on a new Amiga game, but I have the
graphics saved in .PNG format. I could convert them to the much
easier to decompress .IFF format, but .PNG image save many more
bytes (e.g image is 15KB saved as an .IFF vs. 9KB as a .PNG).
I have sucessfully decoded all the easy stuff, but am currently trying
to decode the IDAT chunk (where the image data is stored).
The format of the data is defined as follows (straight out of the RFC1951
Deflate Compression document available online):
If you support amigaos 3.x and newer, you can just use the
datatype.library, it will open any format you have the datatypes installed
for and give you an object to work with.
If you are aiming for older versions of amigaos, there are libpng on
aminet http://aminet.net/search?query=libpng .
regards
--
Jacob Dahl Pind | telefisk.org | fidonet 2:230/38.8