HP2XX release 3.20-png ====================== This readme describes the hp2xx release 3.20 PNG graphics format extensions. See the original 3.x readme for general information about hp2xx. Copying policy for this release is GPL, same as for the original hp2xx 3.20 release. I) Why PNG format support?? By the time hp2xx was relased under GPL by Heinz Werntges, the World Wide Web was picking up steam and prompted evaluation as a tool for scientfic data processing front end. Lots of program packages in the biocomputing area can produce HP/GL graphics output easily, but WWW browsers can't display that format. The logical choice of graphics format at that time was Compuserve's GIF format, and hp2xx was the logical choice to do HP/GL->GIF conversion (at least for me, having done a bit of testing and porting with hp2xx). Using freely availabe tools (the gifdraw package by Tom Boutell) a proof-of- concept GIF module for hp2xx was written and tested. More or less around the same time, the patent on the LZW compression algorithm used in the GIF format was enforced by the patent holder, after quite some time of proliferation of the LZW code into free and commercial software without licensing. For some time, an exemption from licensing fees for free software was offered (at least Usenet postings from the patent holder and their web site suggested that notion) but by the time rising demand for web-based interfaces for biocomputing program packages had people looking for easy format conversion this exemption has ceased to be an option. Consultation with the patent holder's LZW licensing department quickly ruled out licensing free software under commercial terms, and users had to resort to other methods of turning HP/GL into GIF graphics. The LZW licensing policy did affect a lot more free software packages, and people started looking for alternatives. Needless to say, PNG was the alternative that a group of programmers on the net came up with (see http://www.cdrom.com/pub/png for details, specs, applications supporting PNG and the like). As implemetation of the proposed PNG standard went along, the idea of adding a graphics format useful for web display to hp2xx got revived, now PNG evolving as the logical choice. Enough said ... II) Building hp2xx with PNG support In order to build hp2xx with PNG support (as it is configured in this release), you will need both the PNG library (libpng, version 0.96 at the time of this release; that's what I used writing and testing the PNG module) and the zlib compression library (version 1.04). If those libraries are not present on your system, you will have to build them yourself from the source (look at the PNG web site for links to download the source). I recommend installing the libraries and includes in the default compiler andl linker search path if possible; the makefile contains an example how to build hp2xx using a locally installed copy of the libraries as well. As far as I can tell, hp2xx will be linked statically against these libraries, but suppport for dynamic libraries should be possible as well provided libpng and zlib are built as dynamic libraries. III) Why no new hp2xx release?? For two reasons: I've not changed any of the internals of hp2xx, merely added a new raster graphics option. No big deal, it seems to me. Secondly, I've not contacted the author of hp2xx about a new release, mainly because I could not locate a current e-mail address, and I think he should have some say in this. So technically, this isn't a new hp2xx release until I have contacted Heinz Werntges about it, but I decided to go ahead and make my PNG- enhanced version available to people who need that kind of functionality. IV) Bug reports, complaints, .... Please report any bug reports, suggestions, etc. to: Michael Schmitz Berkeley, Dec. 9, 1997 (Original readme follows.) (c) 1992 - 1994 H. Werntges HP2XX release 3.x ================= Files in . Description -------------------------------------------------------------------------- README This files COPYING GNU General Public License Version 2 sources Directory containing all essential .c and .h source files. Also site of binary generation makes Place for keeping makefiles for various platforms doc Documentation hp-tests Here I left some HP-GL files for testing old Older versions of misc. files, still distributed as long as the new ones are not confirmed, e.g. files supporting machines where I can't run tests. Quick guide through hp2xx ========================= Welcome to hp2xx, the HP-GL converter! Each subdirectory within hp2xx contains a local README file. There you find a short description on each file and/or directory found therein, as well as instructions and other comments on what matters at that point. Besides these basic instructions, a detailed manual is provided in ./doc/hp2xxinf.tex (UNIX: hp2xx.texinfo). For installation, o follow the instructions starting in ./makes/README o optionally, see ./doc/hp2xxinf.tex (Manual in texinfo format) For bug reports, write to: werntges@convex.rz.uni-duesseldorf.de (Heinz W. Werntges) That's all, folks. Enjoy! -- Heinz