The image above probably looks very normal - a set of everyday chess pieces (without pawns). White pieces on top covered by black clouds, and black pieces at the bottom covered by white clouds. If they don't look like chess pieces, try clicking on the picture to enlarge it - my friend thought they were teeth when he saw it on my msn display pic!

So, if we are imaginative, and assume the chess pieces are real, it would make sense that we can use them and play a normal game of chess...right? Well, not quite - because the chess pieces are identical. They are the same - pixel for pixel. If you don't believe me 'cut and paste' the chess pieces and they will magically "change colour". Even if you believe me you can give it a go, quite mind blowing if you ask me!

When I first saw this picture in a psychology lecture and I was confused as to why the lecturer (Bart) had put the image up, until he said "It's an optical illusion, the chess pieces are the same." I think most people in the lecture had a sudden "no way" moment - I certainly did!

After the lecture, I tried to replicate the illusion (without much success) until I stumbled across the article Image segmentation and lightness perception that was published in Nature. Funny thing is the lecturer was actually one of the authors of the article - no wonder he used it in his lecture. My understanding of the illusion is that our brain takes some shortcuts when processing the image, and therefore it 'cuts' the image into segments which may not necessarily be correct, thus causing the illusion. For a better explanation read the article - it's quite interesting.

There are a few other optical illusion on Bart's homepage (go into Cool Demos), some of them are quite cool, but a must see is the moving version of this illusion. If you ask me THAT is really mind blowing!

Oh, and if you want to see my attempt to create the illusion have a look at my deviantID.

If you visit my gallery you will notice that the more recent photos all have a border around them. The question was "how do you get the [border] and sig in everytime, the same?" I'll write about the borders first, and then the sig - as the border one is much easier

Firstly, I'm using Photoshop CS, so if you use another image editor, the instructions will probably not match exactly - but I'm sure most image editors will have similar functionality.

1. Open the photo/image in Photoshop
   Make sure the layer is not locked, otherwise the below steps won't work as nicely.
2. In the top menu go to "Image -> Canvas Size"
   A new window showing details about the Current Size of your image should appear. In the same window there is the option to choose a New Size.
3. In the New Size section, check the Relative option.
   The width/height values should now be 0.
4. Change it so the width/height is now 6 pixels. Leave the Anchor (white box) in the middle.
   This will expand the canvas 3px each way (top, right, bottom, left).
   
5. After clicking OK, you'll notice that there is a very tiny extra transparent border around your image. Create a new layer, drag it below your image and fill that layer with white. You've now got a 3px white border!
6. Repeat steps 2~5 for the black border. Except this time, use a larger value (eg. 40px), fill the new layer with black and drag it below the white layer. Your layers should look something like this (you can ignore 'fuzzly' layer - that's my sig):
   

That's it! Nice and simple borders. You can experiment with different thickness, colours etc. or even multi-bordered borders. I find that some pictures look better with just a white border (for some reason I feel white borders don't work that well with a small black border inside).

Your final product will look something like this...
:thumb61997264:300: