Wikipedia:Reference desk/Archives/Computing/2006 November 13

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[edit] November 13

[edit] Tessellation Software

Does anyone know of any good, easy-to-use software that can be used to make complicated tessellations? (Like a graphics editor.) I want to be able to start with a basic figure (quadrilateral, triangle, hexagon) then use a lasso/cutter tool that will allow for shifting pieces with the end result of a complicated figure that can be tessellated. I plan to make tessellations by means of reflection, rotation, etc. (Perhaps even dilation -- fractals.) I tried using MS Paint, but as figures get more complicated, you must pay attention to lining up each pixel perfectly when shifting pieces of the original figure, which can be difficult. Thus, the program should preferably have a snap-to feature of some sort to ensure the figure will tessellate. Basically, I want to be able to create intricate figures that can tessellated, a la MC Escher (Example: (http://www.worldofescher.com/gallery/A30L.html [maybe not as complicated as that though]), and need a program that can assist me. Thanks for your help. Sorry if I have confused you.--Proficient 05:55, 13 November 2006 (UTC)

Tessellation? Inkscape has had "tile clones" since version 0.41. Inkscape 0.41 screenshots --Kjoonlee 07:31, 13 November 2006 (UTC)
Inkscape seems to be such a program. I will definitely look into it. Thanks for the help. To others, still feel free to make suggestions. --Proficient 08:21, 13 November 2006 (UTC)
(You don't mention OS, but I'm guessing some version of Windows.) If you're willing to pay a small shareware fee, Tess is dedicated to creating tessellations of many kinds. Although it does not have all the graphics sophistication of Inkscape, it can produce SVG files which can then be embellish. And because it is single purpose, it offers many conveniences for tessellating, which you may appreciate. --KSmrqT 06:08, 15 November 2006 (UTC)
Yes, it was Windows. Thanks for your help. I will consider Tess. --Proficient 05:15, 18 November 2006 (UTC)

[edit] Online Account Validation

Whenever opening a new account of whatever kind on the internet, among many different details, you are usually asked to "enter the characters you see below," and are then presented with strange looking words. I would like to know what this is. So far I've found that it prevents automated accounts being produced, but how and what is actually going on here? Gerard Khun 08:08, 13 November 2006 (UTC)

It's a CAPTCHA. The server generates a distorted image, which represents shapes that are very easy for the human eye, with the amazing neural-net processing power of the human brain behind it, to recognise, but which would take years for automated AI processes in computers to get a clue of. Its main purpose is, as you say, to prevent automated accounts from being produced. JIP | Talk 08:25, 13 November 2006 (UTC)

One downside is that they prevent blind and visually impaired users from registering, as well. Those users can use screen readers to navigate through the web site, if they can get past the registration process. StuRat 22:06, 13 November 2006 (UTC)

[edit] DVD

any reason why cant we burn dvd format on a cd???

I'm afraid I'm not entirely sure what you mean. If you're trying to burn the information on DVD onto a CD, then there is the problem of space - a DVD holds about seven times as much data as a CD. Is this what you were asking? — QuantumEleven 13:46, 13 November 2006 (UTC)
You can burn a CD in the general format of a DVD. You cannot burn a DVD to CD because a DVD contains far more information than a CD does. In other words, you can put 16 ounces of coke in a 16 ounce bottle, making it look similar to a 2 liter bottle, but you cannot put 2 liters of coke in a 16 ounce bottle. Yes, you can stretch the bottle to 2 liters, but then it would be a 2 liter bottle and that isn't the point anyway. --Kainaw (talk) 13:48, 13 November 2006 (UTC)
Indeed you can – a miniDVD is a standard CD written with the DVD-video format.–Mysid☎ 13:49, 13 November 2006 (UTC)
I feel sure the questioner wasn't asking about the data structures associated with a DVD; instead, I suppose the question to mean "what distinctions exist between unwritten CDs and DVDs, such that a DVD writer cannot use a CD-R as a DVD-R?". I don't have a really good answer, except that perhaps the DVD's data layer is a different material that supports finer markings. Perhaps DVD or burning has the answer. --Tardis 16:15, 13 November 2006 (UTC)
Unwritten optical media has a pregroove which guides the burning laser. On a CD-R, this pregroove is wider than on a DVD-R. Also they are burned using different wavelengths; the CD-R dye won't absorb the laser used to burn a DVD-R, at least not very efficiently. –Mysid☎ 16:44, 13 November 2006 (UTC)

[edit] Retaining personal Firefox settings

My computer is about to get Windows XP, but to make it work properly, we're going to install it on a separate harddrive rather than installing it over Windows 98. What is the best way to retain my Firefox personal settings and extension information? I seem to remember a mass extension installer that worked from a txt file. Does anyone know where to find that? Any other tips? - Mgm|(talk) 20:18, 13 November 2006 (UTC)

Honestly the easiest way to do it would be to write down a list of your extensions and search for them all over again for your fresh install. To keep your bookmarks go to Bookmarks > Organize Bookmarks > File > Export... and email yourself the export (or put it on some removable media). Not sure about preferences and remembered passwords; you might want to try that Google extension but I doubt it uploads your passwords to google --frothT C 21:24, 13 November 2006 (UTC)
Most of the stuff is in C:\Documents and Settings\[name]\Application Data\Mozilla\Firefox\Profiles. Copy everything out from the profile folder and you should be able to move it back after you re-install, although it might take some tweaking. I remember doing this to copy my profile stuff from my work computer to my home computer, but it wasn't 100% accurate. In the end, I recall not everything was transferable, but most of it went OK. howcheng {chat} 22:46, 13 November 2006 (UTC)
  • Nice idea, but remember that I am moving towards a Windows XP system. I don't have a "Documents and Settings" directory yet. What directories are extensions and themes kept in in Windows 98 systems? - 131.211.210.14 08:26, 14 November 2006 (UTC)
    • Unfortunately I don't remember where all those files are in Win 98. You'll have to try the good folks at http://www.mozilla.org/. howcheng {chat} 18:27, 14 November 2006 (UTC)
I think the profiles are in C:\WINDOWS\Profiles. --wj32 talk | contribs 21:32, 14 November 2006 (UTC)
In Windows ME, it in a location like C:\WINDOWS\Application Data\Mozilla\Firefox\Profiles, browse around there. I would just copy your bookmarks.html file and reinstall your extensions and themes later. --04:17, 18 November 2006 (UTC)

[edit] Correct way of floating text to the top of a <td> element.

Is there a correct way of having text within a <td></td> element (and perhaps within <p></p> elements within <td></td>) conforming to CSS 2 and XHTML 1.1/2? Since tables were supposed to be used for tabular data, browsers automatically center the data within it, meaning if you've got a big image on the same row as some text in another cell, it gets floated to the middle. Since they're supposed to act in this way, I think there is not supposed to be a way of aligning text vertically within tables (since you're supposed to use <div> and <span> for positioning non-tabular information).

Using the CSS valign: top; is not valid for text (only images), this cannot be used, dispite it having the desired effect in most browsers, and will create a markup error when the page is validated.RevenDS 20:42, 13 November 2006 (UTC)

Isn't that an HTML attribute too? <tr valign="top"> should work, although I'm not sure if it's "valid" anymore according to big bad W3C. HTML shouldn't be parsed by anything other than a dedicated rendering engine; all this deprecation is laughable --frothT C 21:28, 13 November 2006 (UTC)
That appears to be acceptable for XHTML 1.0. Not sure about 1.1, but since it's valid under XHTML 1.0 Strict, it probably is. Weird though, since the W3C are very strict about HTML being used for displaying content only and not positioning it (which is CSS's job). Thanks. If someone else doesn't feel this is correct, say so! RevenDS 21:50, 13 November 2006 (UTC)

You need the CSS property "vertical-align: top" for both the image and the table cell ☢ Ҡi∊ff⌇↯ 18:33, 14 November 2006 (UTC)

If I understand your question correctly, then yes, vertical-align is the tool for the job. Here is the CSS specification for the property in general, and here is the specialization for table layout. Most likely you will want to set the image's property to top, and do nothing or use baseline for the text. An example:
Left-side text
Fujiyama
Fujiyama
 Right-side text
with a second line.
As always, there is the question of IE compliance, which is only partial for this property. --KSmrqT 07:31, 15 November 2006 (UTC)
I see. I thought verticle-align was only for images, since W3Schools lists the property under a heading 'set the verticle alignment for an image'. I'll give that a go. Cheers. RevenDS 12:30, 19 November 2006 (UTC)

[edit] google calculator

Does anyone know of a free downloadable program (can be used offline) that can parse phrases like "265 kilometers per hour in meters per second" or just in general convert between arbitrary units? Jon513 22:10, 13 November 2006 (UTC)

Unix systems have a program called units. Check the units article and/or google to find source code for a free version.
% units "64 lightyears per century" "kilofurlongs per nanofortnight"
   * 1.1536975
   / 0.86677831
Weregerbil 10:23, 14 November 2006 (UTC)
thank you very much, it works great, though I would rather a bit more in terms of user interface. Jon513 14:03, 14 November 2006 (UTC)
It does also have an interactive mode (at least, GNU units does,) which is a bit friendlier:
$ units
2438 units, 71 prefixes, 32 nonlinear units

You have: 742 millibar
You want: mmHg
        * 556.54569
        / 0.0017967977
AJR | Talk 12:53, 17 November 2006 (UTC)