The Mandelbrot Set

In my last post about the mandelbrot set I said:

I would put the Mandelbrot explorer script online however it is very computationally intense. It takes around 5 seconds to generate 1 image.

Now I have created a new explorer which you can use.

I tried to find a way of replicating my original PHP script in JavaScript. That way the processing is all done on the client computer and not my server. For a while I didn’t think it was possible until today I came across pixel manipulation using the Canvas element. Internet Explorer users will be disappointed to know that the Canvas element doesn’t work on their browser and this therefore won’t work.

The code is almost the same as the PHP code except that it uses the
getImageData and putImageData() functions. These functions extract the pixel data from the image and allow it to be manipulated before being saved again, extremely useful.

Why not explore the Mandelbrot Set!

It simply loads the two images into two canvas elements and extracts the red channel from one of them and inserts that red channel into the other canvas. Hey presto you get a simple anaglyph. This method has another flaw. Modifying an images data channels can only be done from an image on the same domain to obey the same domain security policy. A small proxy sorts that out but means the solution isn’t all JavaScript.

Here’s the source code for his anaglyph generator:

<script type="text/javascript">
<!--
Anaglyph = {
imgLeft : null,
imgRigt : null,
//Load images
load : function(left, right) {
//console.log('Load');
Anaglyph.imgLeft = document.createElement('img');
Anaglyph.imgLeft.src = left;
Anaglyph.imgRight = document.createElement('img');
Anaglyph.imgRight.src = right;
Anaglyph.wait();
},
//Wait for images to load
wait: function() {
if (Anaglyph.imgLeft.complete && Anaglyph.imgRight.complete) {
Anaglyph.make();
} else {
setTimeout('Anaglyph.wait()', 100);
}
},
//Actually make the anaglyph with some canvas magic
make: function() {
//console.log('Make');
var w = 640;
var h = 480;
var canvas = document.getElementsByTagName('canvas')[0];
try {
//Left image in temporary canvas
var canvasLeft = document.createElement('canvas');
canvasLeft.width = w;
canvasLeft.height = h;
var ctxLeft = canvasLeft.getContext('2d');
ctxLeft.drawImage(Anaglyph.imgLeft, 0, 0, w, h);
var dataLeft = ctxLeft.getImageData(0,0, w, h);
//Right image in result canvas
canvas.width = w;
canvas.height = h;
var ctx = canvas.getContext('2d');
ctx.drawImage(Anaglyph.imgRight, 0, 0, w, h);
var data = ctx.getImageData(0,0, w, h);
for (var i=0,l=dataLeft.data.length/4; i<l; i++) {
data.data[i * 4 + 0] = dataLeft.data[i * 4 + 0];
}
ctx.putImageData(data, 0, 0);
//console.log('Done!');
} catch (e) {
//console.log('FAIL!')
}
document.getElementById('result').className = '';
}
}
function getQueryParameter(name) {
name = name.replace(/[\[]/,"\\\[").replace(/[\]]/,"\\\]");
var regexS = "[\\?&]"+name+"=([^&#]*)";
var regex = new RegExp( regexS );
var results = regex.exec( window.location.href );
if( results == null ) {
return "";
} else {
return results[1];
}
}
window.onload = function() {
if ('' != getQueryParameter('left') && '' != getQueryParameter('right')) {
var left = getQueryParameter('left');
var right = getQueryParameter('right');
document.getElementById('result').className = 'loading';
Anaglyph.load(
'image.php?url='+left,
'image.php?url='+right
);
}
}
-->
</script>

The canvas element can do so many things and my guess is we’ll be seeing it even more in the next few years.

I have about five different passwords. I have a general password which I use for all the sites which aren’t very important and don’t store important details. I have another password for trusted sites and shops which store more information. I have a stronger password which I use for my bank account, I have a different password for my email and web hosting. Finally, my computer has a unique password.

I can remember 5 passwords and every year I make sure that I go around and change them to something new. Unfortunately, some passwords I can’t change. Nor can I remember them because they are so complicated. What should I do?

The obvious thing would be to get a sheet of paper or a new document and write them all out. That’s not great though for several reasons. Firstly if someone finds this document or sheet of paper all the passwords are theirs. Secondly, if my house gets flooded or my hard disk fails I’ve lost them all.

If the passwords are on your hard disk, a regular backup can solve one problem but makes the other a lot worse. Now you’ve got loads of disks which can be found by someone and have the passwords extracted from.

My solution is steganography and encryption. There are loads of programs out there which will encrypt your files. These are great but you need some extra protection. This is where steganography comes in. Encrypt your file using the program of your choice then change the file name and give it a different extension. Anyone looking through your files will have a hard time trying to find where you store your passwords (passwords.doc is rather obvious).

My last tip is don’t rely on your internet browser to save your passwords. They are all stored completely unencrypted and in the same place, perfect prey for malicious software and nosy friends!

4 months ago and I’m sure I could of told you what my password was. Unfortunately I only used the password two or three times so it didn’t sink in, then I went on holiday completely forgetting about everything school related including my password. Of course our school has some good computer technicians who promptly allowed me to change it.

Password security is an interesting topic so I’m going to write 4 posts about some good practises. In later posts I will cover storing, remembering and choosing passwords. In this post i’m going to consider the question: “What should you do if someone forgets their password?”

Well, the most important thing is proving that they own the account. Our brilliant technicians, lazy as they are, failed to implement this check. I just told them my name and typed in my new password. The best way of checking identity is using biometrics. A quick check with the photos on the school database would of proved that I am indeed Thomas Milburn. If they didn’t have my biometric information they could of asked me about something personal.

Not everyone is happy giving away personal data so make sure you don’t ask something too private. Questions concerning irrelevant personal facts are probably best like: When did you first go abroad? What was the name of your first teacher? and What is your favourite book?

Of course no one should forget their passwords in the first place. Watch out for my next post about the best methods of remembering passwords.