[thelist] Security code images

Matt Warden mwarden at gmail.com
Tue Aug 3 08:22:06 CDT 2004

On Tue, 03 Aug 2004 04:56:54 +0200, Patrick Fey <evolt at fey-network.de> wrote:
> A quick research on Google came up with this tutorial on how to do it
> with PHP. You'll need PHP4 with GDlib installed.
> http://www.phpnoise.com/tutorials/1/1
> :-) Patrick

Interesting article. It intrigued me enough to play a bit. I can't
quite come up with the best way to distort the image to make it
difficult to read by machines. I tried arcs and dashed lines, both
with some degree of random placement. Dashed lines is definitely
better than arcs, but I'm not satisfied with either. The article above
doesn't address how to distort the image. I wonder if any evolters
have experience or ideas with how to do this. I didn't come across any
GD functions that would distort the actual text, so I think the only
possibility is to have a interfering lines of some sort.

Here are my tests. They are all WBMP format because that's the only
thing that seemed to be enabled on the server.

Not distorted:
http://mwarden.f2o.org/sandbox/imgtest.php (source:

(source: http://mwarden.f2o.org/sandbox/viewsource.php?linemode=2&f=distortimgtest_arcs.php)

Dashed lines:
(source: http://mwarden.f2o.org/sandbox/viewsource.php?linemode=2&f=distortimgtest_dashes.php)

(I'm still playing around, in case you happen to hit the URL and get a
syntax error or something.)

ANd if I come up with anything else or implement someone's suggestion
from here, it'd end up here: http://mwarden.f2o.org/sandbox/



Matt Warden
Berry Neuroscience Lab
Department of Psychology
Miami University

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