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Archive-name: pictures-faq/part2
Last-modified: 05 March 1993 See reader questions & answers on this topic! - Help others by sharing your knowledge This is part 2 of the FAQ for the alt.binaries.pictures* hierarchy. This part of the alt.binaries.pictures FAQ contains "general", or operating-system independent information. It answers (hopefully) all the questions you may have about the pictures newsgroups, decoding and encoding techniques, and picture formats. For information on issues of etiquette and posting policy and/or suggestions, consult part 1 of this posting. For information on your particular system and on specific utilities, consult part 3 of this posting. Before posting to these groups for the first time, please check the FAQ list (this posting - including parts 2 and 3), and also read the newsgroup news.announce.newusers, which contains many answers to questions about UseNet in general. If you've read previous versions of this FAQ, you'll probably only want to read anything that has changed since the last distribution. These changes appear both in this document and in the accompanying "Changes to the alt.binaries.pictures FAQ". Note that this is a "live" document, and is always getting important information added or updated. *********************************************************************** This file is intended to be a general introduction to the pictures newsgroups, answering some common questions concerning pictures posted in those newsgroups, namely how to decode and view them. It is not, of course, possible to cover everything, but I will try to to get as much as I can into this file. If you feel something important has been omitted and you know the subject well, please write me so I can include the info for future releases. E-mail should be sent to deej@cadence.com for these purposes. Before you miss an important detail contained in this file, let me "pre-repeat" that many of the programs mentioned in this document are available for anonymous ftp at bongo.cc.utexas.edu (128.83.186.13), in the gifstuff directory. Also: there are NO GIF files of any kind at this site! Save your time and don't bother looking for them! OK... on to the real reason you're reading this document... TABLE OF CONTENTS I. ABOUT THIS FAQ II. DOWNLOADING AND DECODING FILES III. COMMON PICTURE TYPES IV. ENCODING AND UPLOADING FILES V. ALTERNATE SOURCES FOR PICTURES/HOW-TO'S OF FTP VI. COMMON PROBLEMS VII. COPYRIGHT I. ABOUT THIS FAQ This FAQ is posted every other Monday to the alt.binaries.pictures newsgroups and to news.answers. It is also available by anonymous FTP, from UUCP, or through e-mail by using the services available from a couple of mail servers. For anonymous FTP access, you can look on either pit-manager.mit.edu [18.72.1.58] in /pub/usenet/news.answers/pictures-faq in files "part1.Z", "part2.Z", or "part3.Z", on ftp.cs.ruu.nl [131.211.80.17] in /pub/NEWS.ANSWERS/pictures-faq for "part1", "part2", or "part3", on ftp.uu.net [137.39.1.2, 137.39.1.9, or 192.48.96.2] in /usenet/news.answers/pictures-faq as the files "part1.Z", "part2.Z", or "part3.Z". You can get the FAQ via UUCP by retrieving the appropriate part from "uunet!/archive/usenet/news.answers/pictures-faq/part1", "uunet!/archive/usenet/news.answers/pictures-faq/part2", or "uunet!/archive/usenet/news.answers/pictures-faq/part3". For e-mail access, send a message to mail-server@pit-manager.mit.edu with the mail body "send usenet/news.answers/pictures-faq/part1" to get the first part, "send usenet/news.answers/pictures-faq/part2" for the second, and "send usenet/news.answers/pictures-faq/part3" for the third, or e-mail to mail-server@cs.ruu.nl with "send NEWS.ANSWERS/pictures-faq/part1", "send NEWS.ANSWERS/pictures-faq/part2", and/or "send NEWS.ANSWERS/pictures-faq/part3" in the body of the message. II. DOWNLOADING AND DECODING FILES Basic checklist: Alternate checklist: ---------------- -------------------- News reader News reader (optional in some cases) Text file editor "Super-decoder" UUDECODEr By far the most common method of posting files to the pictures newsgroups is the UUENCODE standard. This program, shipped standard with most implementations of UNIX, converts binary files into plain-text ASCII files which can be handled by the mail system. You will need a version of UUDECODE before anything else in order to view anything downloaded from the net. If your system does not have a version of UUDECODE available, you can get one via anonymous ftp from bongo.cc.utexas.edu, in the gifstuff/uutools directory. The format of a uuencoded file consists of an optional "table specification", which consists of the word "table" alone on a line, followed by one or more lines containing the characters that will be used in the remaining encoded data. Following this, the standard requires the line containing only the text "begin <permissions> <filename>" (where "<permissions>" is a three-character numeric string, and "<filename>" notes the name of the decoded file - for example "begin 640 myfile.gif"). This "begin" line is then followed by several lines of approximately 61 characters, all beginning with a capital "M", and containing any non-lower-case printing character (and very rarely resembles anything but absolute gibberish). Optionally, one to two lines may be blank or contain less than the normal number of characters if those lines are immediately before the line containing the "end" notation (in this case, these shorter lines will NOT begin with "M"). The "end" text alone on a line marks the conclusion of the uuencoded data. Any information that does not fit into the above classifications are termed as either "headers" or "trailers", and are not intended to be included in the information to be decoded. For example, the following represents a valid uuencoded file (although it contains no useful information - don't bother decoding it!): begin 666 bogus.file MLEHHWHURHUH %$^4653%#$#&^%$$46^%#^%)LKDUHEWFHIUG^$^#DJIUTE&F M&#H:FNP(ENER(*HNFUHDG(&#&B#HY@#(*@YNUF(&$HU$HF(YSAUHIRY(&YHU #(*NUFE(YHD7H end Most decoders are smart enough to ignore anything before the "begin" line and after the "end" line. The first step is to save the file you want to view... in most versions of the newsreader, this is done by pressing 's' followed immediately (no spaces usually, although some versions don't care) by a file name. You will usually be asked if you want to save it in mailbox format; you should answer 'n'. When saving an article to a file in mailbox format, the article is sometimes changed in a subtle way, making it impossible to decode. In the case of a single-part file, you can now uudecode the file, which will create whatever output file is encoded. You can usually tell if it's a single-part file by looking on the subject line; standard netiquette is to make something like [03/06] part of the subject line, which indicates you're on part 3 of a 6-part file. If no numbers are there, you can usually assume it is a 1-part file. If not, feel free to write the poster (directly... please don't waste bandwidth by posting) and request that he/she put this info in the subject line. Be nice about it! Another way to determine if a file is a single-parter is if both the uuencode "begin" and "end" lines (as outlined above in the description of the uuencode format) are included in the file. For multi-part files, life is a little more difficult. If all you have is a standard UUDECODE program (as opposed to a "smart decoder"), you will need to trim the headers and trailers out from the rest of the information. You can either do this by saving each part in its own file and editting them separately, then concatenate the editted files together to make one big file (this might be your only choice if your editor can't handle large files!), or you can save each part in order into one big file and then edit all the headers and trailers out from that file. Either way, you'll need to run the result through UUDECODE. You can use your favorite text editor to strip out header and trailer information. There are several "smart decoders" out there that will handle all of the header/trailer stripping and decoding for you (some will even make sure that the pieces are in order!) - see part 3 of this posting for specifics. Some articles are actually posted with easy decoding in mind, and contain UNIX shell script headers/trailers that facilitate easier decoding. This is often very helpful, as it saves you a lot of work, and can also provide error checking not available in a "normal" uuencoded posting. These postings nearly always contain instructions on their use, so I won't attempt to explain all the details here. There's no set "standard" for this type of posting anyway - except for MIME. MIME, the Multipurpose Internet Mail Extensions, proposes a standard for the posting and mailing of multi-media articles (postings may include pictures, sounds, movies, or other media types - which may be combined in one article). Public- domain packages using MIME are available (Metamail, for example). For more information on MIME and Metamail, contact nsb@bellcore.com. Some news readers have an "extract" capability that greatly simplifies life by automatically decoding articles - this means you don't have to go to the hassle of saving to a file and then decoding. Newer versions of rn, nn, and trn can handle this - check the "man" page or ask your news administrator to find out if you can let your news reader do the work for you! If you're going to download the decoded picture file to a home machine, or move it around a network, remember that most decoded file outputs are going to be BINARY files, so set your transfer protocol accordingly. If you are moving around just the uuencoded data, an ASCII transfer will work just fine, however (you'll have to decode it eventually, of course). Note that if you *don't* transfer the decoded file in BINARY mode, everything will appear to work just fine - until you try to view the picture. Then you'll get all sorts of undefined results... III. COMMON PICTURE TYPES Basic checklist: Alternate checklist: ---------------- -------------------- GIF viewer Multi-format viewer Format conversion tool(s) Format conversion tool(s) Image manipulation tool(s) OK. Now you've got this great picture file from downloading it and running it through UUDECODE. What is it, and what do you do with it? The most common type of picture is the GIF format (which usually has a .GIF or .gif file suffix). GIF stands for Graphic Interchange Format, and is a standard format for images that was developed by CompuServe to be a device-independent method of storing pictures. It includes Lempel-Ziv-Welch (LZW) compression, which makes the files fairly small. JPEG is another standardized image compression mechanism, which stands for Joint Photographic Experts Group (the original name of the committee that wrote the standard). It seems more and more common that JPEG-type pictures (.JPG or .jpg file suffix, usually) are getting posted to the net. Some claim that JPEG is destined to overtake GIF format in popularity, because it is the most compact method to store 24-bit data, but mostly due to the fact that it uses much less space to store the same picture (this is, in fact, true - I have seen many examples of this phenomenon). This may be an accurate assessment, but this will probably take a while to happen, as most people HAVE GIF software/viewers, but lack JPEG equivalents. Undoubtedly, however, this too shall change, but at this point, JPEG is recognized as still being in its infancy. But, if you prefer to be on the leading (bleeding?) edge, it is possible to get software both to view JPEG pictures, and to convert JPEG to and from other formats, as detailed in part 3. The latest and greatest info about JPEG is included in the Tom Lane's "JPEG image compression: Frequently Asked Questions" (archive name is "jpeg-faq"), posted on a regular basis to the alt.binaries.pictures.d, alt.graphics.pixutils, alt.binaries.pictures.erotica.d, alt.sex.pictures.d, and news.answers newsgroups. Of course, to view a picture of a particular type, you will need a viewer that supports that type (again, for specifics on viewers for your particular configuration, see part 3 of this posting). There are other types of single-picture files posted to the net, although they are not as common as GIF or JPEG files. Other than the difference in the viewing software, the downloading/decoding and encoding/uploading procedures are identical as for other types of pictures. Platform-dependent picture types and conversion programs are discussed in part 3 of this posting. Occasionally people get into an argument about which standard is best. I think the answer is: WHO CARES?!? The only thing I have to say about this matter is that almost every machine under the sun already has a program written for it to view GIF files, and if yours doesn't, shareware or PD source code is available almost everywhere. Commonly people post files to the net with a .GL extension. These files are actually animated picture-shows that can be viewed on a small number of system types. Usually, GL files are huge, so people often compress them with one of several popular compression/archiving packages. Perhaps the most common is the PC family's PKZIP package. If a GL file is posted with a .ZIP extension, you know it's been ZIP'ed. Similarly, if it has a .Z extension, it's been compressed with the UNIX `compress' utility. "Uncompression" tools of either type are available for various types of systems - part 3 has the necessary details. Files of a .DL extension are also sometimes posted. These are very similar to GL files, except in format, so of course it takes different software to view them (this software is also discussed in part 3). Then there's FLI - yet another GL/DL type of file. FLI's are generally considered poorer quality than either GL or DL, however. The table below lists many of the common file types for pictures or compression formats for different systems. This information may be useful if you download a tool and then don't know how to decompress it into a usable form, or as a "quick reference" of file types. Decompressors or viewers of "unlike" system types exist on some systems - see the particular system information for details on this aspect. File extension File type -------------- ---------- ARC ARChive (many OS's support) - compressed file(s) ARJ Yet another archive format - compressed file(s) BMP Windows and OS/2 BitMaP picture file CPT Macintosh CompactPro compressed file. DIB Windows and OS/2 BitMaP picture file DL Animated picture file (system independent, for those with viewers) FLI Animated picture file (system independent, for those with viewers) GIF Graphics Interchange Format - system independent picture file GL Animated picture file (system independent, for those with viewers) IMG IMaGe - ? picture file JPG (JPEG) Joint Photography experts Group - system independent picture file LZH Amiga LZH - compressed file(s) - LHarc output MAC (MACP) Macintosh MacPaint - Macintosh picture file HQX Macintosh BinHex - encoded file IFF Amiga Interchangeable File Format - Amiga file interchange (used for many types of binary data). If it contains a picture file, then the picture is either an ILBM (InterLeaved BitMap), HAM (Hold-And-Modify), DHAM (DynaHAM), or SHAM (Sliced HAM). IM8 (RAST) Sun RASTer file - Sun picture file PCX IBM PC Paintbrush - IBM picture file PICT Macintosh QuickDraw PICTure - Macintosh picture file PS (PSID) Encapsulated PostScript/PostScript Image Data - printer-ready text/picture file RAW RAW RGB - 24-bit system independent picture file SEA Macintosh Self-Extracting Archive SHK Macintosh Shrinkit - compressed file(s) SIT Macintosh StuffIt - compressed file(s) TGA TrueVision TarGA file - ? picture file TIFF Tagged Image Format File - 24-bit system independent picture file UUE UNIX UUEncoding - encoded file XBM X windows Bit Map - UNIX/X windows picture file Z UNIX LZW "compress" - compressed file(s) ZIP MS-DOS ZIP - compressed file(s) ZOO MS-DOS ZOO - compressed file(s) IV. ENCODING AND UPLOADING FILES Basic checklist: Alternate checklist: ---------------- -------------------- UUENCODEr "Auto-posting" tool(s) Editor or file splitter News posting software First things first: before you do any sort of posting, be sure you've read and understand the a.b.p* netiquette as outlined in part 1 of this FAQ. This will save you from countless flamings! OK. You need to UUENCODE the file. Find an encoder and encode it! If the output file is particularly large (i.e. more than 60 KB), it would be wise to split up the encoded file into smaller parts (<= 60 KB) and then post those. You can split the file with a text editor if you like, or check part 3 for more specifics on splitting utilities. Now post the files... and remember to include the neat info mentioned in part 1, like subject lines that mean something, descriptions, checksums, "Cut Here" lines, etc... There are some very nice "super posting" utilities out there that will handle all the lower-level details for you. See part 3 for more info on these utilities. If you don't use one, you'll obviously need to do all the uuencoding, splitting, and the posting of each split part yourself - which can become quite a tedious process! Another benefit of the "super posters" is that they enforce some standardization on the way posts look - making an auto-decoder's job much easier in the process! V. ALTERNATE SOURCES FOR PICTURES/HOW-TO'S OF FTP Basic checklist: Alternate checklist: ---------------- -------------------- Direct Internet access E-mail software FTP software "archie" access The pictures newsgroups are certainly not the only source for pictures, nor are GIF files the only types available (see section III). The most likely place you are to find other pictures is in an archive that is reachable via FTP. FTP stands for File Transfer Protocol, and is a program for transmitting files over the network. To use FTP, you will need access to a computer with the FTP program, and a network connection. Be aware that files on FTP sites will probably NOT be UUENCODED, so remember to transfer in binary when getting non-text files. For the greatest level of detail on FTP and finding sources in general, you should refer to the posting "How to find sources (READ THIS BEFORE POSTING)", which is periodically posted to comp.sources.wanted, alt.sources.wanted, and news.answers OR you can execute either 'finger ftp@piggy.ucsb.edu' or 'finger ftp@ferkel.ucsb.edu' to get a quick tutorial. You can also get the "finding sources" FAQ via anonymous FTP, available on either pit-manager.mit.edu [18.72.1.58] in /pub/usenet/news.answers as the file "finding-sources.Z", on ftp.cs.ruu.nl [131.211.80.17] in /pub/NEWS.ANSWERS as "finding-sources", on ftp.uu.net [137.39.1.2, 137.39.1.9, or 192.48.96.2] in /usenet/news.answers as file "finding-sources.Z". UUCP access is done by retrieving the file "uunet!/archive/usenet/news.answers/finding-sources". Lastly, you can get this FAQ by sending a message to either of mail-server@pit-manager.mit.edu with the mail body "send usenet/news.answers/finding-sources", or to mail-server@cs.ruu.nl with "send NEWS.ANSWERS/finding-sources" in the body of the message. One of the useful things detailed in the "finding sources" posting mentioned above involves the use of the "archie" facility, which makes it very easy to find a program if you know its name (or just part of its name if you specify the "set search sub" option). You can do this either directly by logging into an archie server or via e-mail. It may take a small amount of effort - but it's a heck of a lot easier and faster than asking the entire net.population! Additionally, it is possible to get files from anonymous FTP sites via e-mail. For details on this wonderful facility, send an e-mail containing the text "help" to ftpmail@decwrl.dec.com. For those of you on BITNET, send an e-mail containing the text "help" to bitftp@pucc.princeton.edu. Now you too can get all sorts of great utilities from anonymous FTP sites using an e-mail proxy! Due to popular demand, an anonymous FTP site list of pictures-related "stuff" has now been compiled and is available from bongo in /gifstuff/ftpsites. This list is by no means guaranteed to be accurate or comprehensive, but hopefully most of the information is valid. BTW, this list is a condensed and supplemented version of the Jan. 20, 1990 revision of Jon Granrose's (odin@pilot.njin.net) "List of Hosts that Accept Anonymous FTP Requests", which is posted regularly to comp.misc, comp.sources.wanted, and alt.sources.wanted, and also available via anonymous FTP from pilot.njin.net (128.6.7.38). Any additions or corrections would be most welcome and appreciated! Most ftp programs will allow you to enter something like ftp wsmr-simtel20.army.mil which will connect you with the mighty SIMTEL-20 archives at the White Sands Missile Range. Occasionally, you will encounter an ftp program that is old enough or slothful enough that it does not recognize internet-style addresses like the one above. In that case, you'll need to know the computer's numeric address; for SIMTEL-20 you would enter ftp 192.88.110.20 Once you're connected, you'll have to tell the computer at the other end that you want to log in, by entering USER (some machines save you this step by *assuming* you want to log in. What else would you want to do?) When you are prompted for an account name, enter anonymous When it asks you for a password, enter *your* internet address. Often the machine to which you are trying to connect will be busy (i.e. too many anonymous users), in which case the machine will inform you of this and throw you off. Try again later. Now you're in. What do you do? Well, you need to know where the files are stored that you want. If you know this, just cd directory-name to the directory in question. Then you can do a DIR to find out what is in it. So you see a file called CRSH+BRN.GIF and you want it for yourself. What do you do? Well, the first thing is to tell the computer on the other end that you want it to transmit a binary file. On most FTP servers, entering the magic word TENEX will do this. If the machine doesn't recognize TENEX, try BINARY, or if all else fails, you can enter TYPE L 8 Be sure to do this for GIF files or you'll get garbage when you try to view them! The difference between TENEX and BINARY is in translation of data type sizes - if your machine type has different data type sizes than the one you're downloading from, use TENEX, otherwise use BINARY. If you're not sure, try TENEX first (if the command isn't recognized, you're probably OK). On some VAX platforms, the keyword "IMAGE" is also sometimes used to denote binary files. Now you're ready to grab the files you want. You have two options: you can type get filename or mget wildcard where wildcard is any UNIX-style wildcard. MGET will get all files that satisfy the specification. When you're done grabbing files, type QUIT or BYE to log off the remote machine and return to yours. Now you're ready to view the picture - no decoding step necessary (neat, eh?)! Most of the non-erotica pictures that appear in postings to the alt.binaries.pictures* hierarchy are available from anonymous FTP sites (again, see bongo's "ftpsites" list), but this is of course not guaranteed. The other most common method for obtaining files is from an archival file server. Most of these work in the following way: you send mail to the server's address, with one-line commands in your message, like help directory \pictures\gif\family-oriented send \pictures\gif\family-oriented\CRSH+BRN.GIF and the requested info is sent back to you at some later time, when the server has time to get around to it. The first step when you discover a server system is to send a HELP command so you can learn what the commands are for that server. However, most servers operate with commands basically similar to those listed above. VI. COMMON PROBLEMS Basic checklist: ---------------- At least one clue Some small level of intelligence Self-determination Well, you've downloaded the file, tried to view it, and got garbage. What went wrong? The two most likely places for something to go wrong are both in the transmission of the file. The first is this: when you downloaded the file to your home computer, did you remember to tell the modem- transfer software that you're sending a binary file? The second-most likely is that you forgot to say TENEX before you grabbed the file via FTP. Either of these will result in mangled files that are unviewable by anything known to man. Also: did you remember to trim off the header and trailer information if you are/were using a "simple" uudecoder? The symptom of forgetting to do this is usually a message something like "short file" from your GIF viewer. There could also be the problem where blank lines are left between parts (or anywhere for that matter) within the 'begin' and 'end' lines of the uuencoded file. Uudecode will get through them fine, but some GIF viewers will choke on the results. The only blank line I've seen get by is the one just before the 'end' statement. Beware of taking too much or not enough off of the headers and trailers. Another common problem is this one: IBM mainframes often use an EBCDIC character set (yes, there's more than one EBCDIC set!) instead of the ASCII set used by everyone else. This wouldn't be a problem except that most ASCII-EBCDIC converters have a bug which mungs the translation of several characters, including ^ { } and a few others. Even this wouldn't be a problem except that the particular munging it does is to map several of these characters onto the *same* wrong character. Ooops. The way around this is not to use uuencode to transfer these files, but to use xx-encode, which produces files which look almost exactly like uu-encoded files, but they use a character set which is IBM-proof. If you are using an IBM mainframe as your host computer and you're having trouble decoding files, this is most likely your problem. Solution: 1) find a kind soul who is willing to uudecode the files, xxencode them and send them to you, 2) get the files via FTP, which should be EBCDIC-proof, or 3) get a better computer that uses everybody else's character set. :-) Sometimes, you need to run the "bilf" utility on a file in order to fix it. The "bilf" utility changes carriage-return/line-feed sets into just carriage-return (or vice-versa). MSDOS uses CR/LF at the end of lines to indicate end-of-record, UNIX and VAXen use only CR. You might want to try running bilf before unzipping, compressing, etc. if you are running into problems. bilf also comes in handy when you are using Kermit to transmit to/from Unix and VMS. Almost all of the problems described above can be checked by using GIFTEST to check the GIF file's integrity on your host machine before you download it. I have recently added the source code for GIFTEST to the archive at bongo. I highly recommend that you get a copy of this, even if you only occasionally have problems with your GIF files; it runs in only a few seconds, and has the potential to save you hours of download time! The last and least likely problem is that some mailer somewhere actually munged the file. It happens. Fortunately, it doesn't happen all that often. When it does (and please check all of the other problems *FIRST*), it's time to ask for a re-post, as detailed in part 1. VII. COPYRIGHT Bottom line: It's OK to copy something (electronically or otherwise) for your own personal use. It's NOT OK to re-distribute that copy, whether or not you make any money doing it. ------------------------------------------------------------------------------- That's about it for the "general" information. System-specific information is continued in part 3 of this FAQ. If you have any suggestions for things to include in future versions, don't hesitate to let me know... -- Jim Howard *** jhoward@best.com *** http://infolane.com/deej/index.html Author, "The Internet Voyeur" (http://infolane.com/deej/voyeur.html) (^:= Flames cheerfully ignored. =:^) ................................................................................ "Death is life's way of telling you you've been fired." -- R. Geis User Contributions: |
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