Wikipedia:Reference desk/Archives/Computing/2015 March 12

= March 12 =

Staying signed in on a website application
What are the disadvantages of staying signed in on a website? Can anybody go through your account information/read through your e-mails...? -- (SuperGirlsVibrator (talk) 06:54, 12 March 2015 (UTC))


 * Yes they can. So, you shouldn't check that box if you are on a shared computer, if you don't want anyone else who uses that computer to have access to your account.  Some websites do have an additional protection, for if the logged in user attempts something like changing the password, where they require you to type in the password again, to prevent somebody from hijacking your account.  StuRat (talk) 07:03, 12 March 2015 (UTC)


 * My computer is not shared, it's private; Personal Computer. Can I still do it? I heard heard/read something about Facebook, with phone 'check' box...apperantely the website itself can go through your phone's ? . All I'm wondering about what if a hacker enters through the PC... Also, I'm with google chrome, I'm signed in it all the time, do you suggest 'sign out' before closing the application? -- (SuperGirlsVibrator (talk) 19:59, 12 March 2015 (UTC))


 * There is something called remote desktop login, and if somebody could manage to login to your PC that way, then they might be able to gain access to your accounts that stay logged in. Critical accounts, like your bank account, usually don't have an option to stay logged on.  On the other hand, things like games and Wikipedia do, because if somebody does manage to hack those accounts, it's not the end of the world. StuRat (talk) 05:45, 13 March 2015 (UTC)


 * Yes, I've heard of this, what you stated. Thank you. I won't do it with any of my accounts... -- (SuperGirlsVibrator (talk) 08:36, 13 March 2015 (UTC))

(I *HATE* "Resolved" tags...it's aint resolved until everyone has contributed to the discussion - very often we have to correct previous posters!)


 * If your computer is yours, nobody else uses it, and you're reasonably confident that nobody has hacked into it - then it's safe to stay logged in.


 * If someone HAS hacked into your computer, then they can easily install a key logger (or a million other possibilities) and see your username and password when you type it in again - so once you're hacked, you're screwed whether you stay logged in or not.  In fact, if they did install a key logger - then you're better off to stay logged in because that way they won't see your username and password being typed in!  Basically, once you're hacked - then nothing you do with your computer - and nothing you did in the past - is truly safe.


 * So the ONLY time you should be concerned about staying logged in (versus logging in each time) is when you use an un-hacked computer that's used by other people. SteveBaker (talk) 16:44, 13 March 2015 (UTC)


 * Okay, point noted!
 * It is a Personal Computer, no one else uses it but me. I've not had any problem whatsoever till today/since January 2014... Is it safe to download one, keep it installed for personal use. Will it increase the possibilities for a hacker?
 * (SuperGirlsVibrator (talk) 06:35, 14 March 2015 (UTC))

GIMP export file formats
1) Two export formats listed are *.c and *.h (C and C header file) formats. I don't understand how an image can be exported as either.

2) Are any of the export formats human-readable ?

StuRat (talk) 07:33, 12 March 2015 (UTC)


 * The idea is to write the image as a C structure that can be included directly in programs. This could be useful for, e.g., including icons directly into programs. The struct looks like this for a 48x36 RGB image:

/* GIMP RGB C-Source image dump (intro.c) */ static const struct { guint    width; guint    height; guint    bytes_per_pixel; /* 3:RGB, 4:RGBA */ gchar   *comment; guint8   pixel_data[48 * 36 * 3 + 1]; }


 * and is human readable. It is similar to the X PixMap source code image format used in X11. --Mark viking (talk) 08:33, 12 March 2015 (UTC)


 * Interesting. Does that apply to both *.c and *.h files ? StuRat (talk) 08:37, 12 March 2015 (UTC)


 * I think the .c and .h formats are a little different. Instead of unsigned integers, the .h format uses character strings to encode the pixel data and restricting it to printable ASCII characters requires a bit of transformation. A brief description is here. But both .c and .h are the same basic idea: encode an image as source code that can be compiled into another program. --Mark viking (talk) 08:53, 12 March 2015 (UTC)
 * Is that similar to the XPM format? LongHairedFop (talk) 13:48, 12 March 2015 (UTC)

Videos by email
Apple's "Mail" states that I cannot send a video by "Mail". I find this difficult to believe and think that there must be a work-around. Can anyone advise please?85.211.131.115 (talk) 14:06, 12 March 2015 (UTC)


 * Perhaps you are trying to use the recently-added video attachment feature called Mail Drop? Here are some details regarding Mail Drop limits from the official support page.  If that doesn't help, we'll need more information before we can possibly assist you.  Alternately, you can visit an Apple retail store for free technical assistance.  Nimur (talk) 14:17, 12 March 2015 (UTC)


 * I'm wondering if the OP and his recipient would not be better off learning how to use FileZilla.  It is a better tool for large files and as easy to use as email. --Aspro (talk) 21:10, 12 March 2015 (UTC)


 * Read: How to FTP Files on Your Mac--Aspro (talk) 21:23, 12 March 2015 (UTC)


 * FTP How-To for Mac / Apple users--Aspro (talk) 21:32, 12 March 2015 (UTC)


 * Email is not recommended for videos. Some archive programs like 7z or rar can split archive files into smaller parts which can be mailed, but to may trouble due size limits of the recipients inbox and block other incoming mail. -- Hans Haase (有问题吗) 20:32, 13 March 2015 (UTC)

If you computer has 2 GB of ram, when does it start having problems dealing with text files?
How big can be a text file if you have 2 GB of RAM? If the OS needs maybe 1 GB, can it open a 900 MB text file? Could Linux deal better with this than Windows?--Fend 83 (talk) 17:15, 12 March 2015 (UTC)


 * It's going to depend on what else is in memory besides the editor and O/S. For text files that size, what you probably need is a program with the intelligence to not try to load the entire thing into memory at once, to save on load time as well as RAM.  For example, if it has options to go from the current page to the next page, previous page, first page, and last page, then having all of those pages preloaded makes sense, or perhaps a bit more (such as next and previous 3 pages).  Does anyone know of a product that does this ? StuRat (talk) 17:54, 12 March 2015 (UTC)
 * There are several programs that specialize in handling/editing large text files. A quick google search found these two . Vim and Emacs are also generally better at handling large text files than e.g. notepad or word, though they are probably not up to opening/editing a 200 GB file without some tweaking. Both use a buffer system, described here  . SemanticMantis (talk) 20:31, 12 March 2015 (UTC)
 * And wouldn't MS Word also use some kind of buffering system if the file is too big? It seems like a logical solution if you have a text file of 200 GB (which I don't have), given the fact that you only can show a limited amount of text on the screen.--Fend 83 (talk) 21:35, 12 March 2015 (UTC)
 * WP:OR - I've had MS Word choke/crash/behave unpredictably when opening far smaller files, say ~200 MB, on a system with a few gigs of RAM... SemanticMantis (talk) 22:38, 12 March 2015 (UTC)
 * Pending on the editor program, operating system and crapware, if installed. -- Hans Haase (有问题吗) 20:15, 13 March 2015 (UTC)
 * Also keep in mind that a page-based program like Word or Writer cannot start displaying before it knows how the text is page-broken. That can mean a scan of the entire file is needed: A 1-billion byte file would be >100,000 pages, and to determine where page #100,000 begins, you would have to fill the first 99,999 pages with text even if you don't display these. Only then could the program start rendering page #100,000.
 * It gets easier with indexed formats, i.e. which list the location of the page breaks. If you know that byte #234567890 is the first character of page #98765, you don't have to go through that part one character at a time.
 * If you're reading a log file, where page-based display isn't needed, there is usually a fixed format you can search for. If you want yesterday's events, you can search for lines starting with "20150316"(or whatever your date format is; YYYYMMDD is my favourite because chronological, numeric, and alphabetical order are the same); because there are many line breaks, you can "jump into the data" and scan for a line break, extract the date/time code of the next line, and apply binary search. - ¡Ouch! (hurt me / more pain) 08:08, 17 March 2015 (UTC)

Extracting photos from PDFs
Is it possible (and if so, practical) to extract photos from PDFs? I'm interested in extracting photos from this document and uploading them to Commons; they're all. Nyttend (talk) 17:31, 12 March 2015 (UTC)
 * A little googling led me to this page, which recommends this free product, but I can't personally vouch for it. At worst you could do it with screengrabs (e.g. using the Windows 7 snipping tool) and an image editor. AndrewWTaylor (talk) 17:40, 12 March 2015 (UTC)


 * Xpdf comes with a program called pdfimages - e.g. you can extract all the images from IN.PDF using, which produces OUT1.jpg, OUT2.jpg, etc. -- Finlay McWalterᚠTalk 17:52, 12 March 2015 (UTC)


 * Evince simply has a "save image as" context menu option in each image. -- Finlay McWalterᚠTalk 17:54, 12 March 2015 (UTC)


 * Both Inkscape and Gimp have a single-page PDF import function. Inkscape's is particularly useful if the embedded image is a drawing (rather than a photo) which you want to convert into a file that can be used in Wikipedia (that's how I did image:Wfm_thaad_diagram.svg). -- Finlay McWalterᚠTalk 18:02, 12 March 2015 (UTC)


 * actually I didn't use it for that diagram, because back in 2007 Inkscape couldn't read PDFs; now that's what I would do. -- Finlay McWalterᚠTalk 21:41, 12 March 2015 (UTC)


 * GIMP can open smaller PDF documents. -- Hans Haase (有问题吗) 20:12, 13 March 2015 (UTC)

Samsung WB350F Camera haywire
Whenever I am trying to take a photo or trying to record a video with Samsung WB350F camera, it goes haywire by going into different options like Wi-Fi and Best Face despite that fact I didn't turn the knob. What causes it? Please and thanks. — Preceding unsigned comment added by 70.29.34.120 (talk) 17:33, 12 March 2015 (UTC)


 * Interesting. My cell phone tends to spontaneously turn off when I use the camera.  In your case, I'd guess the knob sends a "knob turned" signal when nobody touched it.  If that's an expensive camera, it might be worth taking it into the shop. StuRat (talk) 17:49, 12 March 2015 (UTC)

Are generic batteries evil?
My laptop works fine, except for the battery, which does not provide more than 45 min. running time. Substituting the battery would be not too expensive if I buy a generic battery, but people advise me against it. Is it that difficult to produce generic batteries? After all, the same factory that produces brand name batteries for Toshiba, Lenovo and others, could also produce the same battery and sell it as a white brand. This happens with other products. Obviously, it's clear that a Chinese made battery made cheaply could explode if overcharged, but is there something wrong in general with generic batteries? Are there quality generic batteries out there? Do generic battery manufacturers need specs, that they maybe don't have access to, to produce a quality battery for a specific laptop?--Fend 83 (talk) 21:50, 12 March 2015 (UTC)
 * Whilst we wait for someone more knowledgeable than I, some links for you: One with a generally positive experience of no-brand batteries, one with a decidedly negative experience, and one more neutral. - Cucumber Mike (talk) 22:06, 12 March 2015 (UTC)


 * I've been bitten twice by generic batteries - once for a laptop and once for a camera. The one for the laptop had twice as many cells as the original (it bulged out rather than being flat), and was said to run twice as long.  It would only last 20-25 minutes.  I recycled it.  I had a similar experience with a camera battery - it would last only a few dozen shots, and I recycled it.  I have gotten compatible third-party NAME BRAND camera batteries (Duracell and Vivitar) that work fine.  Bubba73 You talkin' to me? 23:27, 12 March 2015 (UTC)


 * There is a reason why generic batteries are just terrible junk. A generic battery is either a no brand battery or a brand that has no public recognition. As manufacturer are in the business of making as much profit as possible, there is no reason to put expensive high quality components or components with very high quality control into their battery. Once they got your money, it matters not to the manufacturer if the battery fails the next day. Thus logically they would put the least expensive components into the generic battery that would do the job of causing you to purchase the battery. What happens to the battery after you purchased it is none of their business. 175.45.116.65 (talk) 00:02, 13 March 2015 (UTC)


 * Good experiences can be made if and older battery hast been properly reworked and use original or controllers that fit for the battery. As most likely used lithium-ion battery have a limited lifetime, the battery in the pack needs to be renewed. Some engineering is neccessary by the manufacturer. Check reviews on retailers and products. -- Hans Haase (有问题吗) 20:10, 13 March 2015 (UTC)


 * There are some things that are easy to do and/or well understood, such that it's worthwhile to go with someone who's willing to do it for you cheaper.
 * And then there are things that are just hard, and batteries (especially Lithium batteries) are definitely one of those. You can save money, but you're taking a significantly big risk, becuase there are lots of things that can go wrong, including things that damage equipement / start fires / etc.  It's very likely that the person who charged more also knew more about making those bad outcomes less likely. —Steve Summit (talk) 21:05, 13 March 2015 (UTC)