There aren&#39;t many JavaScript decoders.

There is one at http://www.webqr.com/index.html

The easiest way is to run [ZXing][1] or similar on your server. You can then POST the image and get the decoded result back in the response.


  [1]: http://code.google.com/p/zxing/

The jsqrcode library by Lazarsoft is now working perfectly using just HTML5, i.e. `getUserMedia` (WebRTC). You can [find it on GitHub](https://github.com/LazarSoft/jsqrcode).

I also found a great fork which is much simplified. Just one file (plus jQuery) and one call of a method: see [html5-qrcode on GitHub](https://github.com/dwa012/html5-qrcode).



Reader they show at  http://www.webqr.com/index.html works like a charm, but literaly, you need the one on the webpage, the github version it&#39;s really hard to make it work, however, it is possible. The best way to go is reverse-engineer the example shown at the webpage.

However, to edit and get the full potential out of it, it&#39;s not so easy. At some point I may post the stripped-down reverse-engineered QR reader, but in the meantime have some fun hacking the code.

Happy coding.

The algorithm that drives http://www.webqr.com is a JavaScript implementation of https://github.com/LazarSoft/jsqrcode. I haven&#39;t tried how reliable it is yet, but that&#39;s certainly the easier plug-and-play solution (client- or server-side) out of the two.

I do not understand the function of `mktemp` and what a temporary file means. 

Whats the difference between say `touch xyz` and `mktemp xyz` (apart from the fact that `mktemp` will create some file with xxx appended to it and will have 600 permissions?)

Please clarify.


Why do we need mktemp?

I have a set of days of log files that I need to parse and look at in matlab. 

The log files look like this:

    LOG_20120509_120002_002.csv
    (year)(month)(day)_(hour)(minute)(second)_(log part number)

The logs increment hourly, but sometimes the seconds are one or two seconds off (per hour) which means i need to ignore what they say to do `loadcsv`.

I also have another file:

    LOG_DATA_20120509_120002.csv

which contains data for the whole hour (different data). 

The overall objective is to: 

     loop through each day 
         loop through each hour
             read in LOG_DATA for whole hour
             loop through each segment
                 read in LOG for each segment
                     compile a table of all the data

I guess the question is then, how do i ignore the minutes of the day if they are different? I suspect it will be by looping through all the files in the folder, in which case how do i do that?

Loop through files in a folder in matlab

I was looking for possibility to create QR code reader in my HTML5 based web page. I&#39;ve done some googling and all the links point me to the mobile applications. 

Please help me with some pointers as to how I can use HTML5 and JavaScript to read a QR code containing a url and then redirect the browser to that URL.

How to create a QR code reader in a HTML5 website?

<p>I was looking for possibility to create QR code reader in my HTML5 based web page. I've done some googling and all the links point me to the mobile applications.</p>
<p>Please help me with some pointers as to how I can use HTML5 and JavaScript to read a QR code containing a url and then redirect the browser to that URL.</p>


I have the following Node.js code:

    var express = require(&#39;express&#39;);
    var app = express.createServer(express.logger());
    app.use(express.bodyParser());

    app.post(&#39;/&#39;, function(request, response) {
        response.write(request.body.user);
        response.end();
    });

Now if I POST something like:

    curl -d user=Someone -H Accept:application/json --url http://localhost:5000

I get `Someone` as expected. Now, what if I want to get the full request body? I tried doing `response.write(request.body)` but Node.js throws an exception saying &quot;*first argument must be a string or Buffer*&quot; then goes to an &quot;infinite loop&quot; with an exception that says &quot;*Can&#39;t set headers after they are sent.*&quot;; this also true even if I did `var reqBody = request.body;` and then writing `response.write(reqBody)`.

What&#39;s the issue here?

Also, can I just get the raw request without using `express.bodyParser()`?

How to access the request body when POSTing using Node.js and Express?

Just starting to play around with bootstrap and it&#39;s amazing. 

I&#39;m trying to figure this out. I have a textarea for feedback inside a modal window. It works great. But I want the focus to go on the textarea when you click on the button to activate the modal. And I can&#39;t seem to get it working. 

Here is a fiddle: http://jsfiddle.net/denislexic/5JN9A/4/

Here is the code:


    &lt;a class=&quot;btn testBtn&quot; data-toggle=&quot;modal&quot; href=&quot;#myModal&quot; &gt;Launch Modal&lt;/a&gt;
    
    &lt;div class=&quot;modal hide&quot; id=&quot;myModal&quot;&gt;
      &lt;div class=&quot;modal-header&quot;&gt;
        &lt;button type=&quot;button&quot; class=&quot;close&quot; data-dismiss=&quot;modal&quot;&gt;&#215;&lt;/button&gt;
        &lt;h3&gt;Modal header&lt;/h3&gt;
      &lt;/div&gt;
      &lt;div class=&quot;modal-body&quot;&gt;
          &lt;textarea id=&quot;textareaID&quot;&gt;&lt;/textarea&gt;
      &lt;/div&gt;
      &lt;div class=&quot;modal-footer&quot;&gt;
        &lt;a href=&quot;#&quot; class=&quot;btn&quot; data-dismiss=&quot;modal&quot;&gt;Close&lt;/a&gt;
        &lt;a href=&quot;#&quot; class=&quot;btn btn-primary&quot;&gt;Save changes&lt;/a&gt;
      &lt;/div&gt;
    &lt;/div&gt;​


Here is the JS

    $(&#39;.testBtn&#39;).on(&#39;click&#39;,function(){
        $(&#39;#textareaID&#39;).focus();
    });​

**To resume**
When I click on &quot;Launch modal&quot; I want the modal to show up and the focus to go on the textarea.

Thanks for any help.




Twitter bootstrap - Focus on textarea inside a modal on click

I am building a site in which i would like to create a file client side from the value of a textarea element.

I have the code in place to do this, but i am getting this error

&gt; HTTP Error 404.15 - Not Found The request filtering module is
&gt; configured to deny a request where the query string is too long.

Is there a way to override this so that I am able to process requests of any size?

If not, is there a way to generate files client side without using the filesystem/active x object?

thanks

How to configure the web.config to allow requests of any length

Is there an implementation of regular expressions in Python/PHP/JavaScript that supports variable-length lookbehind-assertion?

    /(?&lt;!foo.*)bar/

How can I write a regular expression that has the same meaning, but uses no lookbehind-assertion?

Is there a chance that this type of assertion will be implemented some day?

Things are much better that I thought. 

**Update:**

(1) There are regular expressions implementation that support variable-length lookbehind-assertion already.

Python module [regex](http://pypi.python.org/pypi/regex) (not standard `re`, but additional `regex` module) supports such assertions (and has many other cool features).

    &gt;&gt;&gt; import regex
    &gt;&gt;&gt; m = regex.search(&#39;(?&lt;!foo.*)bar&#39;, &#39;f00bar&#39;)
    &gt;&gt;&gt; print m.group()
    bar
    &gt;&gt;&gt; m = regex.search(&#39;(?&lt;!foo.*)bar&#39;, &#39;foobar&#39;)
    &gt;&gt;&gt; print m
    None

It was a really big surprise for me that there is something in regular expressions that Perl can&#39;t do and Python can. Probably, there is &quot;enhanced regular expression&quot; implementation for Perl also?

(Thanks and +1 to MRAB).

(2) There is a cool feature `\K` in modern regular expressions.

This symbols means that when you make a substitution (and from my point of view the most interesting use case of assertions is the substitution), all characters that were found before `\K` must not be changed.

    s/unchanged-part\Kchanged-part/new-part/x

That is almost like a look-behind assertion, but not so flexible of course.

More about `\K`:

* [Perl Regular Expression \K Trick](http://www.cybersprocket.com/perl-regular-expression-k-trick/)
* [PCRE Regex Spotlight: \K](http://www.phpfreaks.com/blog/pcre-regex-spotlight-k)

As far as I understand, you can&#39;t use \K twice in the same regular expression. And you can&#39;t say till which point you want to &quot;kill&quot; the characters that you&#39;ve found. That is always till the beginning of the line.

(Thanks and +1 to ikegami).

My additional questions:

* Is it possible to say what point must be the final point of `\K` effect?
* What about enhanced regular expressions implementations for Perl/Ruby/JavaScript/PHP? Something like `regex` for Python. 


Variable-length lookbehind-assertion alternatives for regular expressions

I opened a webcam by using the following JavaScript code: 

```js
const stream = await navigator.mediaDevices.getUserMedia({ /* ... */ });
```

Is there any JavaScript code to stop or close the webcam? Thanks everyone.




Stop/Close webcam stream which is opened by navigator.mediaDevices.getUserMedia

I have this code(which doesn&#39;t give me expected result)

    #subject_content.html
    {% block main-menu %}
    	{% include &quot;subject_base.html&quot; %}
    {% endblock %}
    

    #subject_base.html
    ....
    ....
    	&lt;div id=&quot;homework&quot; class=&quot;tab-section&quot;&gt;
    		&lt;h2&gt;Homework&lt;/h2&gt;
    			{% include &quot;subject_file_upload.html&quot; %}
    	&lt;/div&gt;
child template:
    
    #subject_file_upload.html
    	&lt;form action=&quot;.&quot; method=&quot;post&quot; enctype=&quot;multipart/form-data&quot;&gt;{% csrf_token %}
    		{{ form.as_p }}
    		&lt;input type=&quot;submit&quot; value=&quot;submit&quot;&gt;
    	&lt;/form&gt;

and my view

    #views.py
    @login_required
    def subject(request,username, subject):
        if request.method == &quot;POST&quot;:
            form = CarsForm(request.POST, request.FILES)
            if form.is_valid():
                form.save()
                return HttpResponseRedirect(&quot;/&quot;)
        form = CarsForm()
        return render_to_response(&#39;subject_content.html&#39;, {&#39;form&#39;:form}, context_instance=RequestContext(request))

The above code creates HTML in the way I want it to be, however the form does not update database.

BUT,

If I skip the middle template and go directly to the uploading form, it works fine:

    #subject_content.html
    {% block main-menu %}
    	{% include &quot;subject_file_upload.html&quot; %}
    {% endblock %}

Help me please to make it work with middle template. 
I want to do this, because I don&#39;t wan&#39;t to type the same code more than once. 



Assign variables to child template in {% include %} tag Django

I have following HTML Structure: I am trying to build a robust method to extract second color digest element since there will be many of these tag within the DOM.

    &lt;table&gt;
      &lt;tbody&gt;
        &lt;tr bgcolor=&quot;#AAAAAA&quot;&gt;
        &lt;tr&gt;
        &lt;tr&gt;
        &lt;tr&gt;
        &lt;tr&gt;
          &lt;td&gt;Color Digest &lt;/td&gt;
          &lt;td&gt;AgArAQICGQMVBBwTIRQHIwg0GUMURAZTBWQJcwV0AoEDAQ &lt;/td&gt;
        &lt;/tr&gt;
        &lt;tr&gt;
          &lt;td&gt;Color Digest &lt;/td&gt;
          &lt;td&gt;2,43,2,25,21,28,0,0,0,0,0,0,0,0,0,0,0,0,0,0,33,7,0,0,0,0,0,0,0,0,0,0,0,0,0,0,8,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,25,0,0,0,0,0,0,0,0,0,0,0,0,0,0,20,6,0,0,0,0,0,0,0,0,0,0,0,0,0,0,5,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,9,0,0,0,0,0,0,0,0,0,0,0,0,0,0,5,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, &lt;/td&gt;
        &lt;/tr&gt;
      &lt;/tbody&gt;
    &lt;/table&gt;

I am trying to extract the Second &quot;Color Digest&quot; td element that has the decoded value. 

I wrote the following xpath but instead of getting the second i am not getting the second td element.

    //td[text() = &#39; Color Digest &#39;]/following-sibling::td[2]

And when I change it to td[2] to td[1] I get both the elements.

XPath:: Get following Sibling

Is there a general way to define the size, in percent or pixels, for an image that is linked in `org-mode`?

Say I have the following link in my `.org` file:

    [[~/images/example.jpg]]

This JPG is way too large, so if I export it to HTML or LaTeX or open it in `org-mode` with &lt;kbd&gt;C-c C-o i&lt;/kbd&gt; will only see a fraction of the image. 

How to resize images in org-mode

I have a site with many pages and different background pictures, and I display them from CSS like:

&lt;!-- language-all: lang-css --&gt;
    
    body.page-8 {
	    background: url(&quot;../img/pic.jpg&quot;) no-repeat scroll center top #000;
	    background-size: cover;
    }

However, I want to show different (fullscreen) pictures on one page using `&lt;img&gt;` elements, and I want them to have the same properties as the above  `background-image: cover;` property (the images cant be displayed from CSS, they must be displayed from the HTML document).

Normally I use:

    div.mydiv img {
	    width: 100%;
    }

Or:

    div.mydiv img {
	    width: auto;
    }

to make the picture full and responsive. However the picture shrinks too much (`width: 100%`) when the screen gets too narrow, and shows the body&#39;s background-color in the bottom screen. The other method, `width: auto;`, only makes the image full size and does not respond to the screen size.

Is there a way to display the image the same way that `background-size: cover` does?

Is there an equivalent to background-size: cover and contain for image elements?

I&#39;ve read that QRCODES has about 4,290 alphanumeric chars limit (about 4kb).

Is it true and is there any way to increase their memory size?

I would like to have more space on if possible: P

QR CODE max char length

&gt; **TL;DR**: I need a way to decode a QR-code from an image file using (preferable pure) Python.

I&#39;ve got a jpg file with a QR-code which I want to decode using Python. I&#39;ve found a couple libraries which claim to do this:

**PyQRCode** ([website here][1]) which supposedly can decode qr codes from images by simply providing a path like this:

    import sys, qrcode
    d = qrcode.Decoder()
    if d.decode(&#39;out.png&#39;):
        print &#39;result: &#39; + d.result
    else:
        print &#39;error: &#39; + d.error

So I simply installed it using `sudo pip install pyqrcode`. The thing I find strange about the example code above however, is that it only imports `qrcode` (and not `pyqrcode` though) Since I think `qrcode` refers to [this library][2] which can only *generate* qr-code images it kind of confused me. So I tried the code above with both `pyqrcode` and `qrcode`, but both fail at the second line saying `AttributeError: &#39;module&#39; object has no attribute &#39;Decoder&#39;`. Furthermore, [the website][1] refers to Ubuntu 8.10 (which came out more than 6 years ago) and I can&#39;t find a public (git or other) repository of it to check the latest commit. So I moved on to the next library:


**ZBar** ([website here][3]) claims to be `&quot;an open source software suite for reading bar codes from various sources, such as image files.&quot;` So I tried installing it on Mac OSX running `sudo pip install zbar`. This fails with `error: command &#39;cc&#39; failed with exit status 1`. I tried to suggestions in the answers to [this SO question][4], but I can&#39;t seem to solve it. So I decided to move on again:

**QRTools**, which according to [this blogpost][5] can decode images easily by using the following code:

    from qrtools import QR
    myCode = QR(filename=u&quot;/home/psutton/Documents/Python/qrcodes/qrcode.png&quot;)
    if myCode.decode():
      print myCode.data
      print myCode.data_type
      print myCode.data_to_string()

So I tried installing it using `sudo pip install qrtools`, which can&#39;t find anything. I also tried it with `python-qrtools`, `qr-tools`, `python-qrtools` and a couple more combinations, but unfortunately to no avail. I suppose it refers to [this repo][6] which says it is based on ZBar (see above). Although I want to run my code on Heroku (and thus prefer a pure Python solution) I successfully installed it on a Linux box (with `sudo apt-get install python-qrtools`) and tried running it:

    from qrtools import QR
    c = QR(filename=&#39;/home/kramer65/qrcode.jpg&#39;)
    c.data  # prints u&#39;NULL&#39;
    c.data_type  # prints u&#39;text&#39;
    c.data_to_string()  # prints &#39;\xef\xbb\xbfNULL&#39; where I expect an int (being `1234567890`)


Although this seems to decode it, It doesn&#39;t seem to do it correctly. It furthermore needs ZBar and is thus not pure Python. So I decided to find yet another library.

**PyXing** ([website here][7]) is supposedly a Python port of the popular Java [ZXing library][8], but the initial and only commit is 6 years old and the project has no readme or documentation whatsoever.

For the rest I found a couple qr-**en**coders (not **de**coders) and some API endpoints which can decode for you. Since I don&#39;t like this service to be dependent on other API endpoints I would want to keep the decoding local though.

So to conclude; would anybody know how I can decode QR-codes from images in (preferable pure) Python? All tips are welcome!


  [1]: http://pyqrcode.sourceforge.net/
  [2]: https://github.com/lincolnloop/python-qrcode
  [3]: http://zbar.sourceforge.net/
  [4]: https://stackoverflow.com/questions/22697440/cc-failed-with-exit-status-1-error-when-install-python-library
  [5]: http://zleap.net/python-qr-code-reader/
  [6]: https://launchpad.net/qr-tools
  [7]: https://github.com/holizz/pyxing
  [8]: https://github.com/zxing/zxing/

How to decode a QR-code image in (preferably pure) Python?

 - I could not find any answers related to the working mechanism of QR code scanning used on [WhatsApp Web][1].
 - **How does the authentication happen when the phone (any smartphone running WhatsApp) scans the QR code on the browser.**
 - I don&#39;t want to know about the technology stack behind them. Like WhatsApp uses modified version of `xmpp`, uses `erlang`, uses web technologies like `socket.io` and `ajax` for the web version to implement such functionality. 
 - The question might be broad. But I am eager to know about the implementation behind it.

  [1]: https://web.whatsapp.com/

Content Type	Original Author	Original Content on Stackoverflow
Question	Binay	View Question on Stackoverflow
Solution 1 - Javascript	Terence Eden	View Answer on Stackoverflow
Solution 2 - Javascript	prespic	View Answer on Stackoverflow
Solution 3 - Javascript	reicek	View Answer on Stackoverflow
Solution 4 - Javascript	Burgi	View Answer on Stackoverflow

How to create a QR code reader in a HTML5 website?

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Solution 2 - Javascript

Solution 3 - Javascript

Solution 4 - Javascript

Loop through files in a folder in matlab

Why do we need mktemp?

Attributions