* [9fans] PNG and APE (cntd) @ 2006-04-27 4:47 lucio 2006-04-27 6:23 ` Lluís Batlle i Rossell ` (3 more replies) 0 siblings, 4 replies; 22+ messages in thread From: lucio @ 2006-04-27 4:47 UTC (permalink / raw) To: 9fans I have uploaded fresh versions of npng.c and npng.1 to /n/sources/contrib/lucio/pub/ for further testing. The fix recommended by Russ is in there (α premultiplication) as well as some (re-)implementation of options. Other than -v (RGBV or CMAP8) output, which looks pretty awful on small icons, it all seems to work at least as well as png(1). The -e option has me bothered, still. 8.npng is for those who seriously need the executable for the 386. What I have not yet fixed is the use of sysfatal() for error reporting, I need to change its name as well as its behaviour. The README file has not been updated either. I have a slightly OT question: is it reasonable that PNG versions of an image may be bigger than their GIF equivalent and (less sursprisingly) much bigger than their JPEG versions? I have not tested this theory, but I have had this reported to me. ++L ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 4:47 [9fans] PNG and APE (cntd) lucio @ 2006-04-27 6:23 ` Lluís Batlle i Rossell 2006-04-27 17:51 ` lucio 2006-04-27 6:36 ` andrey mirtchovski ` (2 subsequent siblings) 3 siblings, 1 reply; 22+ messages in thread From: Lluís Batlle i Rossell @ 2006-04-27 6:23 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs [-- Attachment #1: Type: text/plain, Size: 714 bytes --] lucio@proxima.alt.za wrote: > I have a slightly OT question: is it reasonable that PNG versions of > an image may be bigger than their GIF equivalent and (less > sursprisingly) much bigger than their JPEG versions? I have not > tested this theory, but I have had this reported to me. I don't know if I understood correctly your question, but although GIF uses LZW instead of zlib (LZ77 iirc), it can stand only for 256 different colors - hence it my be smaller than PNG, as PNG allows 32bit colors fine (being 8 for alpha). JPEG is dependant on lossy compression (at least the actual implementations; I think a lossless was proposed, but I've never seen it), then sure it can be much smaller than PNG. [-- Attachment #2: S/MIME Cryptographic Signature --] [-- Type: application/x-pkcs7-signature, Size: 3311 bytes --] ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 6:23 ` Lluís Batlle i Rossell @ 2006-04-27 17:51 ` lucio 2006-04-27 18:24 ` Lluís Batlle i Rossell 2006-04-27 18:28 ` Charles Forsyth 0 siblings, 2 replies; 22+ messages in thread From: lucio @ 2006-04-27 17:51 UTC (permalink / raw) To: 9fans; +Cc: eugene > I don't know if I understood correctly your question, but although GIF > uses LZW instead of zlib (LZ77 iirc), it can stand only for 256 > different colors - hence it my be smaller than PNG, as PNG allows 32bit > colors fine (being 8 for alpha). The question was poorly phrased. But yes, the comparison is between PNG and GIF, specifically, because if baffled me when somebody showed me figures that suggested the same image in PNG was larger than in GIF. I can only presume that PNG encoders increase the pixel depth, for whatever reason. And, BTW, PNG allows 16-bit per colour, a 48-bit depth per pixel. Thanks to libpng, my "npng" can render these as 24-bit images. ++L ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 17:51 ` lucio @ 2006-04-27 18:24 ` Lluís Batlle i Rossell 2006-04-27 18:28 ` Charles Forsyth 1 sibling, 0 replies; 22+ messages in thread From: Lluís Batlle i Rossell @ 2006-04-27 18:24 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs [-- Attachment #1: Type: text/plain, Size: 442 bytes --] lucio@proxima.alt.za wrote: > I can only presume that PNG encoders increase the pixel depth, for > whatever reason. It offers also at least 8-bit for alpha. In GIF, simply one of the 256 colors is (absolutely) "transparent". > > And, BTW, PNG allows 16-bit per colour, a 48-bit depth per pixel. > Thanks to libpng, my "npng" can render these as 24-bit images. Oh, I didn't know. Nice feature, according to the usual 48-bit scanners. [-- Attachment #2: S/MIME Cryptographic Signature --] [-- Type: application/x-pkcs7-signature, Size: 3311 bytes --] ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 17:51 ` lucio 2006-04-27 18:24 ` Lluís Batlle i Rossell @ 2006-04-27 18:28 ` Charles Forsyth 2006-04-27 19:26 ` Jack Johnson 2006-04-27 19:59 ` lucio 1 sibling, 2 replies; 22+ messages in thread From: Charles Forsyth @ 2006-04-27 18:28 UTC (permalink / raw) To: 9fans > And, BTW, PNG allows 16-bit per colour, a 48-bit depth per pixel. > Thanks to libpng, my "npng" can render these as 24-bit images. ``the human ear can't hear as high as that / still, it ought to please any passing bat'' ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 18:28 ` Charles Forsyth @ 2006-04-27 19:26 ` Jack Johnson 2006-04-27 19:58 ` Steve Simon 2006-04-27 20:02 ` Bruce Ellis 2006-04-27 19:59 ` lucio 1 sibling, 2 replies; 22+ messages in thread From: Jack Johnson @ 2006-04-27 19:26 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs On 4/27/06, Charles Forsyth <forsyth@terzarima.net> wrote: > > And, BTW, PNG allows 16-bit per colour, a 48-bit depth per pixel. > > Thanks to libpng, my "npng" can render these as 24-bit images. > > ``the human ear can't hear as high as that / still, it ought to please any passing bat'' I used to do some image fiddling a long time ago (image prep -> TGA for television), and came across some info regarding medical x-ray photographs being stored in a 12-bit grayscale format. It's likely that so fine a variation is either above or right on the edge of human perception (given current working environments), but one counterargument is that maybe it's not a human looking at the data. Plus, I think 12 bits per color would be right around the limit of film, something like a 4000:1 contrast ratio, so depending on the scanner you'd likely be pushing the limits of the original medium anyway, "lossless" transfer from analog to digital, whether or not you're in a good position to make use of the data. Archaeologists have the same problem all the time, looking at data gathered by previous scientists and realizing the original gatherers didn't save enough information for the current questions, so now they tend to swing the opposite direction and record all the minutiae so that years later someone can glean new information from an old dig. One day, you may be a bat. -Jack ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 19:26 ` Jack Johnson @ 2006-04-27 19:58 ` Steve Simon 2006-04-27 21:13 ` Lluís Batlle i Rossell 2006-04-27 20:02 ` Bruce Ellis 1 sibling, 1 reply; 22+ messages in thread From: Steve Simon @ 2006-04-27 19:58 UTC (permalink / raw) To: 9fans Re: 12 bit images The problem is that Real Life™ has a contrast ratio well in excess of 12bits (72dBs) and if you add any exposure error (human error or fooled software) then you may find quite a bit of your exposure is crushed or burnt out. This is why people use 14bit scanners running at 4096dpi and the like, only to downsample to 640x480x8bit. You will always get better results if you throw away resolution cleanly using well designed digital filter than to use a low-res scanner directly. I have seen several comparisons of SD vs HD TV down-converted, and the latter wins every time. my 2¢ -Steve ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 19:58 ` Steve Simon @ 2006-04-27 21:13 ` Lluís Batlle i Rossell 2006-04-27 22:05 ` Charles Forsyth 0 siblings, 1 reply; 22+ messages in thread From: Lluís Batlle i Rossell @ 2006-04-27 21:13 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs [-- Attachment #1: Type: text/plain, Size: 590 bytes --] Steve Simon wrote: > This is why people use 14bit scanners running at 4096dpi and the like, > only to downsample to 640x480x8bit. You will always get better results if > you throw away resolution cleanly using well designed digital filter > than to use a low-res scanner directly. It's even more used in digital cameras, which most of them store to JPEG directly. Therefore, the image file has a downsampled color space, blocking effects, etc. The result is much better if you photo double the resolution wanted, and then scale by software (even with a simple scaling algorithm). [-- Attachment #2: S/MIME Cryptographic Signature --] [-- Type: application/x-pkcs7-signature, Size: 3311 bytes --] ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 21:13 ` Lluís Batlle i Rossell @ 2006-04-27 22:05 ` Charles Forsyth 2006-04-28 5:00 ` lucio 0 siblings, 1 reply; 22+ messages in thread From: Charles Forsyth @ 2006-04-27 22:05 UTC (permalink / raw) To: 9fans sorry, my ill-advised quip meant that i thought it was just displaying the family snaps in a window; i hadn't realised the software was processing medical data! ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 22:05 ` Charles Forsyth @ 2006-04-28 5:00 ` lucio 2006-04-28 18:31 ` jmk 0 siblings, 1 reply; 22+ messages in thread From: lucio @ 2006-04-28 5:00 UTC (permalink / raw) To: 9fans > sorry, my ill-advised quip meant that i thought it was just displaying the > family snaps in a window; i hadn't realised the software was processing medical data! Your quip brought a smile to _my_ lips; this is 9fans, after all. ++L ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-28 5:00 ` lucio @ 2006-04-28 18:31 ` jmk 0 siblings, 0 replies; 22+ messages in thread From: jmk @ 2006-04-28 18:31 UTC (permalink / raw) To: 9fans On Fri Apr 28 13:34:03 EDT 2006, lucio@proxima.alt.za wrote: > > sorry, my ill-advised quip meant that i thought it was just displaying the > > family snaps in a window; i hadn't realised the software was processing medical data! > > Your quip brought a smile to _my_ lips; this is 9fans, after all. > > ++L your quip caused us to play the song in the unix room, to much polite chuckling. ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 19:26 ` Jack Johnson 2006-04-27 19:58 ` Steve Simon @ 2006-04-27 20:02 ` Bruce Ellis 1 sibling, 0 replies; 22+ messages in thread From: Bruce Ellis @ 2006-04-27 20:02 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs Yes, 12 bit was added to postscript for x-rays. brucee On 4/28/06, Jack Johnson <knapjack@gmail.com> wrote: > On 4/27/06, Charles Forsyth <forsyth@terzarima.net> wrote: > > > And, BTW, PNG allows 16-bit per colour, a 48-bit depth per pixel. > > > Thanks to libpng, my "npng" can render these as 24-bit images. > > > > ``the human ear can't hear as high as that / still, it ought to please any passing bat'' > > I used to do some image fiddling a long time ago (image prep -> TGA > for television), and came across some info regarding medical x-ray > photographs being stored in a 12-bit grayscale format. It's likely > that so fine a variation is either above or right on the edge of human > perception (given current working environments), but one > counterargument is that maybe it's not a human looking at the data. > > Plus, I think 12 bits per color would be right around the limit of > film, something like a 4000:1 contrast ratio, so depending on the > scanner you'd likely be pushing the limits of the original medium > anyway, "lossless" transfer from analog to digital, whether or not > you're in a good position to make use of the data. > > Archaeologists have the same problem all the time, looking at data > gathered by previous scientists and realizing the original gatherers > didn't save enough information for the current questions, so now they > tend to swing the opposite direction and record all the minutiae so > that years later someone can glean new information from an old dig. > > One day, you may be a bat. > > -Jack > ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 18:28 ` Charles Forsyth 2006-04-27 19:26 ` Jack Johnson @ 2006-04-27 19:59 ` lucio 1 sibling, 0 replies; 22+ messages in thread From: lucio @ 2006-04-27 19:59 UTC (permalink / raw) To: 9fans >> And, BTW, PNG allows 16-bit per colour, a 48-bit depth per pixel. >> Thanks to libpng, my "npng" can render these as 24-bit images. > > ``the human ear can't hear as high as that / still, it ought to please any passing bat'' Just because there's no value in the higher resolution does not mean that some fool isn't going to send you a picture you can't render. And, honestly, it's very little effort to implement in the renderer. I have no idea how much effort the developers of libpng had to expend to get it right. ++L ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 4:47 [9fans] PNG and APE (cntd) lucio 2006-04-27 6:23 ` Lluís Batlle i Rossell @ 2006-04-27 6:36 ` andrey mirtchovski 2006-04-27 6:39 ` andrey mirtchovski 2006-04-27 11:43 ` Lluís Batlle 2006-04-27 12:25 ` Russ Cox 2006-04-27 12:25 ` Russ Cox 3 siblings, 2 replies; 22+ messages in thread From: andrey mirtchovski @ 2006-04-27 6:36 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs > I have a slightly OT question: is it reasonable that PNG versions of > an image may be bigger than their GIF equivalent and (less > sursprisingly) much bigger than their JPEG versions? I have not > tested this theory, but I have had this reported to me. png is libz compression, so even at its best you can still have an image that compresses very badly. in fact i think i have an example, let me find it... here: http://pages.cpsc.ucalgary.ca/~mirtchov/screenshots/scr-porcini.png basically that image (an album cover i used as as a desktop background) even though small in acreage is large in size as a png (1.1 megs) at compression of 9 and there's nothing we can do about it. i don't care much about gif, but JPG achieves the small file size by being lossy. for a test open up a JPG image in gimp or whatever editor and save it again, but increase the level to 100% (instead of the usual 85 or 90): -rw-r--r-- 1 andrey andrey 1125261 Apr 27 00:28 IMG_3735-1.jpg -rw-r--r-- 1 andrey andrey 446941 Apr 26 17:18 IMG_3735.JPG (the images are otherwise unaltered) ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 6:36 ` andrey mirtchovski @ 2006-04-27 6:39 ` andrey mirtchovski 2006-04-27 11:43 ` Lluís Batlle 1 sibling, 0 replies; 22+ messages in thread From: andrey mirtchovski @ 2006-04-27 6:39 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs forgot to add an example of a png that compresses much better, even though it's bigger in size: http://pages.cpsc.ucalgary.ca/~mirtchov/screenshots/plan9-normal.png you can see that the difference is a lot of flat colour and much less detail in the second image... ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 6:36 ` andrey mirtchovski 2006-04-27 6:39 ` andrey mirtchovski @ 2006-04-27 11:43 ` Lluís Batlle 2006-04-27 11:53 ` Harri Haataja 1 sibling, 1 reply; 22+ messages in thread From: Lluís Batlle @ 2006-04-27 11:43 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs [-- Attachment #1: Type: text/plain, Size: 539 bytes --] 2006/4/27, andrey mirtchovski <mirtchovski@gmail.com>: > > i don't care much about gif, but JPG achieves the small file size by > being lossy. for a test open up a JPG image in gimp or whatever editor > and save it again, but increase the level to 100% (instead of the > usual 85 or 90): > > -rw-r--r-- 1 andrey andrey 1125261 Apr 27 00:28 IMG_3735-1.jpg > -rw-r--r-- 1 andrey andrey 446941 Apr 26 17:18 IMG_3735.JPG > > (the images are otherwise unaltered) Keep on mind that jpeg with 100% quality is also lossy. [-- Attachment #2: Type: text/html, Size: 860 bytes --] ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 11:43 ` Lluís Batlle @ 2006-04-27 11:53 ` Harri Haataja 0 siblings, 0 replies; 22+ messages in thread From: Harri Haataja @ 2006-04-27 11:53 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs On Thu, Apr 27, 2006 at 01:43:05PM +0200, Lluís Batlle wrote: > 2006/4/27, andrey mirtchovski <mirtchovski@gmail.com>: > > i don't care much about gif, but JPG achieves the small file size by > > being lossy. for a test open up a JPG image in gimp or whatever > > editor and save it again, but increase the level to 100% (instead of > > the usual 85 or 90): > > > > -rw-r--r-- 1 andrey andrey 1125261 Apr 27 00:28 IMG_3735-1.jpg > > -rw-r--r-- 1 andrey andrey 446941 Apr 26 17:18 IMG_3735.JPG > > > > (the images are otherwise unaltered) > > Keep on mind that jpeg with 100% quality is also lossy. There's also lossless but informed formats. Less so for images because the often builtin major formats won't leave room for competition. Fair bit of info on JPEG (and more) can be found at http://www.faqs.org/faqs/jpeg-faq/ -- Energizer Bunny arrested - charged with battery. ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 4:47 [9fans] PNG and APE (cntd) lucio 2006-04-27 6:23 ` Lluís Batlle i Rossell 2006-04-27 6:36 ` andrey mirtchovski @ 2006-04-27 12:25 ` Russ Cox 2006-04-27 12:25 ` Russ Cox 3 siblings, 0 replies; 22+ messages in thread From: Russ Cox @ 2006-04-27 12:25 UTC (permalink / raw) To: 9fans I remain unconvinced that all this effort on porting libpng isn't wasted time. If the current png reading code doesn't work, I'd rather see that improved. Andrey and I went through it a year ago and made it pass all the tests in the PNG suite. Russ ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 4:47 [9fans] PNG and APE (cntd) lucio ` (2 preceding siblings ...) 2006-04-27 12:25 ` Russ Cox @ 2006-04-27 12:25 ` Russ Cox 2006-04-27 18:18 ` lucio 3 siblings, 1 reply; 22+ messages in thread From: Russ Cox @ 2006-04-27 12:25 UTC (permalink / raw) To: 9fans I remain unconvinced that all this effort on porting libpng isn't wasted time. If the current png reading code doesn't work, I'd rather see that improved. Andrey and I went through it a year ago and made it pass all the tests in the PNG suite. Russ ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 12:25 ` Russ Cox @ 2006-04-27 18:18 ` lucio 2006-04-27 18:27 ` andrey mirtchovski 0 siblings, 1 reply; 22+ messages in thread From: lucio @ 2006-04-27 18:18 UTC (permalink / raw) To: 9fans > I remain unconvinced that all this effort on porting libpng > isn't wasted time. If the current png reading code doesn't > work, I'd rather see that improved. Andrey and I went through > it a year ago and made it pass all the tests in the PNG suite. Oh, the primary target is GeoTiff and the secondary one is Graphviz. I'm trying to produce a marked-up map of the area I live in and the format of the maps and aerial photographs I have sourced from the South African Surveyor General's office are in GeoTiff format. Since I needed zlib and libjpeg and GD wants libpng, it has been instructive to cut my teeth on npng. I had a recollection that png(1) did not do 24-bit images, but no proof, so I went ahead and started from a different end. I did discover that PNG isn't widely used, that the patent on LZW has expired and that I have plenty left to learn about graphics (thanks to all contributors, not least forsyth for the Microsoft papers - td's contribution does not need mention on this forum). As for Breadpng(), there's no ways I'm going to study the actual on-disk representation of PNG or any of the other formats without very sound reason. Life is way too short :-) That does not mean that I do not appreciate the value of doing it, or that I am not grateful to those who took it upon themselves to do it, of course. Philosophically, I'm at odds with the Plan 9 approach, but it's a pragmatic decision. ++L ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 18:18 ` lucio @ 2006-04-27 18:27 ` andrey mirtchovski 2006-04-27 19:56 ` lucio 0 siblings, 1 reply; 22+ messages in thread From: andrey mirtchovski @ 2006-04-27 18:27 UTC (permalink / raw) To: Fans of the OS Plan 9 from Bell Labs the links web browser also required a port of libpng in a subdirectory of its source tree. that's where the test images and clients we used against p9's png came from. not sure how useful that is, but i thought it worth mentioning. ^ permalink raw reply [flat|nested] 22+ messages in thread
* Re: [9fans] PNG and APE (cntd) 2006-04-27 18:27 ` andrey mirtchovski @ 2006-04-27 19:56 ` lucio 0 siblings, 0 replies; 22+ messages in thread From: lucio @ 2006-04-27 19:56 UTC (permalink / raw) To: 9fans > the links web browser also required a port of libpng in a > subdirectory of its source tree. that's where the test images and > clients we used against p9's png came from. not sure how useful that > is, but i thought it worth mentioning. Yes, I did remember. Like GS, "links" also uses libjpeg, which has value in itself. GD, libTIFF and GeoTiff all also contribute to a graphics workbench and all are actually quite open to being converted to native Plan 9. That is where I'm hoping to go, but I have some immediate objectives that have slightly higher priority, as mentioned. In the process, I've had to make adjustments to the APE headers and to my view of the Plan 9 directory hierarchy that I hope will benefit others as well. In the medium term, I think there'd be advantages to extracting zlib, libpng and libjpeg (at least) from GS, "links" and possibly other places and accept them as first class citizens in the Plan 9 system. ++L ^ permalink raw reply [flat|nested] 22+ messages in thread
end of thread, other threads:[~2006-04-28 18:31 UTC | newest] Thread overview: 22+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2006-04-27 4:47 [9fans] PNG and APE (cntd) lucio 2006-04-27 6:23 ` Lluís Batlle i Rossell 2006-04-27 17:51 ` lucio 2006-04-27 18:24 ` Lluís Batlle i Rossell 2006-04-27 18:28 ` Charles Forsyth 2006-04-27 19:26 ` Jack Johnson 2006-04-27 19:58 ` Steve Simon 2006-04-27 21:13 ` Lluís Batlle i Rossell 2006-04-27 22:05 ` Charles Forsyth 2006-04-28 5:00 ` lucio 2006-04-28 18:31 ` jmk 2006-04-27 20:02 ` Bruce Ellis 2006-04-27 19:59 ` lucio 2006-04-27 6:36 ` andrey mirtchovski 2006-04-27 6:39 ` andrey mirtchovski 2006-04-27 11:43 ` Lluís Batlle 2006-04-27 11:53 ` Harri Haataja 2006-04-27 12:25 ` Russ Cox 2006-04-27 12:25 ` Russ Cox 2006-04-27 18:18 ` lucio 2006-04-27 18:27 ` andrey mirtchovski 2006-04-27 19:56 ` lucio
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