README file for png, a Dylan app that creates a png file.

DESCRIPTION
===========
This is a toy application that creates a 100 pixel by 100 pixel image
(in PPM or Portable Pixmap format) and then writes that image out as
a .png file.  This app also includes several (very) primitive drawing
functions, such as draw-line, draw-filled-rectangle and draw-empty-
rectangle.

It also includes an example (at the bottom of png.dylan) that draws
10 lines and 3 rectangles in various colors.

BACKGROUND
==========
I've been aching for some kind of platform-independent graphic facility
for Dylan for quite some time.  After the dust had settled from the
ICFP-2000, I took a look at some of the images there ... Ah, the Go
game (http://caml.inria.fr/icfp00-contest/):  to die for!  I read that
the images were processed from GML to PPM 
(http://www.cs.cornell.edu/icfp/).  Hm!  The Dylan Hacker entry output
PPM, but my browser choked on it.  As I had been dabbling with libpng, 
I went back to its documentation and found what a wanted:  a ppm to 
png converter.

That was all I needed to get started, and the result was this app:  a
producer of pieces of modern art for the discriminating collector.

REQUIREMENTS
============
This app relies on wpng to do the conversion from PPM to .png format.
Wpng (Write PNG) is an example program that demonstrates the 
capabilities of libpng, so you must also download and install libpng
and zlib (as libpng depends on zlib).  Wpng is available at
http://www.libpng.org/pub/png/book/sources.html, and you may follow
the links from that page to obtain libpng and zlib.  You must have wpng
built and on the PATH for this app to work.

INSTALLATION
============
$ gzip -cd png.tar.gz | tar xvf -
$ cd png
$ make
$ make run

The last command will generate a j-random image and save it as
modern.png for your viewing pleasure.

TODO
====
* Add other kinds of drawing functions?  Circles?  Ellipses?
* draw-line seems buggy ... or is it my browser?
* As you can see from the source, this app simple calls wpng using
  system.  What an inelegant approach!  A better way would be to 
  use libpng directly to convert a PPM matrix residing in memory
  to a .png file. ... Since I'm not volunteering to write Dylan
  wrappers around libpng (which uses callbacks here and there), nor
  am I familiar enough with libpng to convert an image in memory to
  png, this work is crying out for some other stout and strong-of-
  heart volunteer to carry on.
* Once this baby is cleaned up and matured a bit, incorporate it into
  the cgi-lib.
  
ISSUES
======
Hey, this is a prototype!  Mine the sources for ideas, but (as they
say in Java-speak) don't run a Nuclear reactor with it, okay?

Questions?  Problems?  Wish-lists?  Email me at dauclair@hotmail.com.

Doug Auclair