Tag Archives: jQuery

Variable range scrollback for archive images

For a given image of class=’camview’  this jQuery javascript will scroll back a variable amount depending on the mouse location over the image.

The mouse over right edge of the image represents the most recent image from the archive. The bottom-left corner represents 24 hours ago. But to have finer granularity at reviewing more recent images, scrolling the mouse over the top of the image will scroll back one time-increment every 10 pixels. Moving the mouse from right to left over the bottom of the image will scroll back over a full 24 hours (1440 one-minute images) skipping frames as needed to fit the mouse resolution. Mouse heights between the top and bottom edges will have a linearly scaled proportion of archive history.

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$('.camview').mousemove(function(event) {
 var x = event.pageX - $(this).offset().left;
 var y = event.pageY - $(this).offset().top;
 var mindx = 0.1;
 var maxdx = 1440.0 / $(this).width();
 var dy = 1.0 - y / $(this).height();
 var dx = dy * mindx + (1.0-dy) * maxdx;
 var arc = ($(this).width() - x) * dx;
 $(this).find('img').attr('src', 'camjpg.php?cam=' + $(this).attr('id') + '&arc=' + arc.toFixed(0));
});

Http proxy for accessing local area network images

To access multiple cameras on a local area network from a single web page, you need to proxy the requests from your web server. Since many netcams require BasicAuth to access images,

A PHP script to handle the proxy request can be found here: http://www.troywolf.com/articles/php/class_http/
To process a set of cameras, store the camera access data in an array such as this

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$cams = array(
 "c30a" => array(
 "name" => "c30a",
 "type" => "http",
 "http" => "http://192.168.3.71/SnapshotJPEG?Resolution=640x480&Quality=Standard&Count=1",
 "http_user" => "<user>",
 "http_pass" => "<password>",
 "title" => "Backyard",
 "live" => "//192.168.3.71/CgiStart?page=Single&Language=0"
 ),
 "c20a" => array (
 "name" => "c20a",
 "type" => "http",
 "http" => "http://192.168.3.73/SnapshotJPEG?Resolution=640x480&Quality=Standard&Count=1",
 "http_user" => "<user>",
 "http_pass" => "<password>",
 "title" => "Garage",
 "live" => "//192.168.3.73/CgiStart?page=Single&Language=0"
 ),
}
?>

Include the above config.php in the php script that will handle the proxy request. It will look up the local area network destination from the ‘http’ element of the array, and pass the request along the camera, then copy the image returned from the camera to the caller.

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url = $cam['http'];
 $h->postvars = $_POST;
 if (!$h->fetch($h->url, 0, "", $http_user, $http_pass)) {
   header("HTTP/1.0 501 Script Error");
   echo "proxy.php had an error attempting to query the url";
   exit();
 }
 
 $http_user = "";
 $http_pass = "";
 if (isset($cam['http_user'])) $http_user = $cam['http_user'];
 if (isset($cam['http_pass'])) $http_pass = $cam['http_pass'];
 
 $h->url = $cam['http'];
 $h->postvars = $_POST;
 if (!$h->fetch($h->url, 0, "", $http_user, $http_pass)) {
 header("HTTP/1.0 501 Script Error");
 echo "proxy.php had an error attempting to query the url";
 exit();
 }
 
 // Forward the headers to the client.
 $ary_headers = explode("\n", $h->header);
 foreach($ary_headers as $hdr) { header($hdr); }
 
 // Send the response body to the client.
 echo $h->body;
?>

To use this proxy from a web page, the javascript with jQuery would request an image from the same page as the main web site.

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$('#c30a img').attr('src', 'proxy.php?cam=c30a');

Webcam image refresh with jQuery

Code snippet to refresh images on a web page without refreshing the whole page.

Add the header with a reference to jquery.

<html>
<head>
   <script type="text/javascript" src="js/jquery.js">
   </script>

Set the refresh interval on document ready, calling our function reloadImages()

<script type="text/javascript">
$(document).ready(function() {
   setInterval('reloadImages()', 60000); // 60 seconds
});

Add our function reloadImages to reference our image ID of c131a in this case. Then change the src image to the same name plus some random attribute to prevent caching.

function reloadImages()
{
  $('#c131a').attr('src', 'c131a.jpg?' + Math.random());
}
</script>

In the body of the script, add a normal image reference making sure the id matches the one in the above reloadImages function.

<title>Cams</title>
</head>
<body>
  <img src="c131a.jpg" id="c131a" border="1" />
</body>
</html>