I've seen a picture like that before. I didn't buy it and wanted to test it so I downloaded it and took it into Photoshop. When I zoomed in on it, it was actually grey with the colored stripes though it.
As I zoomed back out, the illusion completely vanished from the image altogether. You can see a black and white picture with different colored lines running through it.
Once you've done that, the illusion will never work for you again. You've taught your eyes reality. They learn and aren't fooled by the same trick again.
John Adams once said
"I must study politics and war that my sons may have liberty to study mathematics and philosophy. My sons ought to study mathematics and philosophy, geography, natural history, naval architecture, navigation, commerce and agriculture in order to give their children a right to study painting, poetry, music, architecture, statuary, tapestry, and porcelain."
You never realize how much salt and sugar are in products until you're trying to find products without it. I just spent two hours at Kroger; The vast majority of it trying to find ANYTHING with no added sugar or salt.