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Plugin/tutorial request: User validation images

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Can anyone shed some light on the subject of user validation images? (Like the ones you need to type in the symbols and characters that appear in the distorted image in order to validate your web request).

Are they as simple as throwing some distorted/rotated characters onto a background?

Are there any tutorials on the subject? (couldn't find any). A plugin would be great!

How would you build such an image?

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Making the image wavy and distorted is only part the equation.

You also have to have a validation program or script that checks the input against the image served to the user, and one that does so in a way that relies on a server-side correlation list, such as a database.

Once you have the back end processing in place, it's bulges, scribbles and scratches, so on and so forth until you're satisfied. Just make sure humans can still decipher it when you're done... :wink:

Edit: Totally steals Dave's link :P

You can read more about it here: http://en.wikipedia.org/wiki/CAPTCHA

I am not a mechanism, I am part of the resistance;

I am an organism, an animal, a creature, I am a beast.

~ Becoming the Archetype

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As CMD says, most of them are built by a server script that randomly generates a string of characters on an image. But in answer to your question, a CAPTCHA (that's what they're called) just needs to be distorted enough that a text recognizing program can't discern or misreads the characters in it, while still being readable. Play around with the Distort effects and plugins, and you should come up with a pretty good approximation.

...Aaand CMD said pretty much everything I did. Oh well, I have a link! http://en.wikipedia.org/wiki/CAPTCHA


The Doctor: There was a goblin, or a trickster, or a warrior... A nameless, terrible thing, soaked in the blood of a billion galaxies. The most feared being in all the cosmos. And nothing could stop it, or hold it, or reason with it. One day it would just drop out of the sky and tear down your world.
Amy: But how did it end up in there?
The Doctor: You know fairy tales. A good wizard tricked it.
River Song: I hate good wizards in fairy tales; they always turn out to be him.

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Excellent link! Thanks Guys.

Looking at the images on Wikipedia, I think the sinewave plugin might also prove to be very useful. According to Wiki the biggest hurdle to cracking these images is the segmentation (splitting the image into individual characters).

I'll try some close text spacing and horisontal + vertical distortion and see what I come up with.

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