From owner-png-announce@dworkin.wustl.edu Fri Aug 1 10:19:15 1997 Received: from dworkin.wustl.edu (dworkin.wustl.edu [128.252.169.2]) by swrinde.nde.swri.edu (8.8.6/8.8.5) with SMTP id KAA22754 for ; Fri, 1 Aug 1997 10:19:14 -0500 (CDT) Received: (from daemon@localhost) by dworkin.wustl.edu (8.6.10/8.6.6.yuck) id KAA09088 for png-announce-outgoing; Fri, 1 Aug 1997 10:24:46 -0500 Received: from shell.wco.com (shell.wco.com [199.4.94.16]) by dworkin.wustl.edu (8.6.10/8.6.6.yuck) with ESMTP id KAA09083 for ; Fri, 1 Aug 1997 10:24:40 -0500 Received: (from png@localhost) by shell.wco.com (8.8.5/8.8.5/WCO-18jul97) id IAA02858; Fri, 1 Aug 1997 08:17:06 -0700 (PDT) Date: Fri, 1 Aug 1997 08:17:06 -0700 (PDT) Message-Id: <199708011517.IAA02858@shell.wco.com> To: png-announce@dworkin.wustl.edu Subject: portable alphamaps Cc: Robert.Crispen@HSV.Boeing.com, neal@ctd.comsat.com, pieter@prpa.research.philips.com, stefan@ping.at From: Greg Roelofs Sender: owner-png-announce@dworkin.wustl.edu Precedence: bulk Reply-To: PNG Announcement List Okey dokey, the netpbm hacks I alluded to on the png-implement list are ready to go! Here's the URL: http://pobox.com/~newt/greg_rgba.html So what's the executive summary? Basically I've extended three of the netpbm utilities to support an alpha channel, specifically so that full 32-bit RGBA images can be converted to 8-bit RGBA-palette images. (For those who don't know, pbmplus/netpbm is a suite of command-line tools, usually Unix-based, for manipulating images and converting image formats. An alpha channel provides multiple levels of transparency/translucency. See the URL above for a slightly more complete explanation.) This is all implemented via an admittedly ugly hack, namely, the appending of a PGM file representing the alpha mask to a normal PPM or PGM file. The "nice" way would be to define ASCII and binary PAM (portable alphamap) streams as "P7" and "P8" types with interleaved RGBA values, but that would require rewriting half the PNM stuff and adding a whole new set of libpam routines. This way is a bit faster/easier to implement (although I still ended up creating some basic libpam routines) and also allows old-style tools to play with the images, albeit at a cost of losing the alpha channel. Again, further justification and explanation of the pros and cons is on the web page above. These are the alpha-enhanced tools so far: pngtopnm pamquant pnmtopng I've intentionally ordered them that way since the primary use so far is to effect a "png2png" conversion. For example: pngtopnm -rgba AlphaSnakes.png | pamquant -fs 255 | pnmtopng -verbose -rgba -interlace -text AlphaSnakes8.txt -gamma 0.45 -time 1997-08-01 06:00:00 -background #6b64000099da > AlphaSnakes8.png Again, the example was not randomly chosen. :-) Most of you are familiar with the AlphaSnakes image; it weighs in at a hefty 669574 bytes. The 8-bit version is a mere 170637 bytes, almost half a megabyte smaller--and we're talking about a 504x557 image with Floyd-Steinberg dithering, so it's quite a bit bigger than your average web image is going to be. I've uploaded the image to swrinde's incoming directory but referred to its final resting place on the web page; Keith, could you please move it over when you have a chance? With a bit more effort, it's now going to be possible to regenerate all of those single-color-anti-aliased GIF images (e.g., the colored balls and whatnot) as RGBA-palette PNGs, thus eliminating all of the usual anti- aliasing "ghosting" effects on dark (or light) backgrounds, at essentially no cost in file size. Of course, we're all still waiting for Netscape and Microsoft, but they're both shaping up (finally...). As an added bonus (Ginsu knives!), I've fixed a few bugs in pnmtopng and have also implemented the tRNS optimization of reordering the palette so that fully opaque entries are last (and therefore can be omitted from the tRNS chunk to cut down on file-size a bit--especially useful for icons). I've sent Willem and Alexander three patches to pnmtopng-2.34, and the fully patched files can be found in the source archive referenced on (you guessed it) the web page above. The two pnmtopng files can just be dropped into the normal pnmtopng-2.34 package (i.e., the makefiles are unchanged), but the pamquant stuff is still under construction and has no makefile. I've included a trivial "make-pam" script as an interim measure. Still to do: - make a pamquant makefile - enhance pamquant with an option to treat all alpha=0 (transparent) entries as the same color and another option to use just one transparent value - add pam support (-rgba) to pnmtotiff/ppm2tiff, tifftopnm, giftop[pn]m, ppmtogif and Bob Crispen's VRML PixelTexture utilities [well, maybe :-) ] Special thanks to Stefan Schneider and [my] co-worker Pieter van der Meulen for ideas/prompting. (Stefan was kind enough to send me his own ppmquant alpha hacks, but I forgot to take them with me last weekend. Sigh. Be sure to check out his LatinByrd app if you're a NeXT or MacOS 8 type. Again, it's linked on the web page...) Btw, I've tried to set the reply-to on this message to png-list, not png-announce, but I don't know if it will work. Have fun! -- Greg Roelofs newt@pobox.com http://pobox.com/~newt/ Newtware, Info-ZIP, PNG Group, U Chicago, Philips Research, ... -- Send the message body "help" to png-announce-request@dworkin.wustl.edu From owner-png-announce@dworkin.wustl.edu Thu Aug 21 01:41:57 1997 Received: from dworkin.wustl.edu (dworkin.wustl.edu [128.252.169.2]) by swrinde.nde.swri.edu (8.8.6/8.8.5) with SMTP id BAA25717 for ; Thu, 21 Aug 1997 01:41:57 -0500 (CDT) Received: (from daemon@localhost) by dworkin.wustl.edu (8.6.10/8.6.6.yuck) id BAA16729 for png-announce-outgoing; Thu, 21 Aug 1997 01:41:36 -0500 Received: from hil-img-2.compuserve.com (hil-img-2.compuserve.com [149.174.177.132]) by dworkin.wustl.edu (8.6.10/8.6.6.yuck) with ESMTP id BAA16724 for ; Thu, 21 Aug 1997 01:41:33 -0500 Received: (from mailgate@localhost) by hil-img-2.compuserve.com (8.8.6/8.8.6/2.5) id CAA12653 for png-announce@dworkin.wustl.edu; Thu, 21 Aug 1997 02:40:45 -0400 (EDT) Date: Thu, 21 Aug 1997 02:40:33 -0400 From: Peter Beyersdorf Subject: PNG in German c't magazine To: png-announce Message-ID: <199708210240_MC2-1DC3-FD0E@compuserve.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Disposition: inline Sender: owner-png-announce@dworkin.wustl.edu Precedence: bulk Reply-To: PNG Announcement List Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by swrinde.nde.swri.edu id BAA25717 Hi, I read that the c't magazine (one of the best and most serious German computer magazines) announced an article about Web graphics for the next issue (10/97). In the announce was a sentence, which would translate like "And the PNG file format, which is proclaimed as Web standard, is supposed to make everything faster and more colorful". Let's hope that it will say something nice about png. I think this is the thing png really needs at this point. I found out that a lot of people working with graphics every day still didn't hear about png. It happened that I told people to use png. A few days later they told my: Yeah, great format! People must get the impression that png is the best and that they are missing something if they can't use png. Then they will ask for it and the big software companies will react... Peter -- Send the message body "help" to png-announce-request@dworkin.wustl.edu