Make Your Own Secret Messages from Space!

During my [http://www.instructables.com/id/Decoding-Secret-Messages-from-Space/ playful expermints] with Fourier Transforms, I discovered that you can overlay an image on top of a Fourier transformed image, and freely convert back and forth from Fourier to regular space. Each transform would descramble the previously FFT'd image. So in short, you can hide the FFT of one image in another image.

If you appreciate this instructable, please visit my blog for more of my crazy ideas: [http://GoodCleanCrazy.wordpress.com GoodCleanCrazy.wordpress.com]

Here's the plainly plain message that I want to hide:

Step 1 FFT Your image!

GIMP has an FFT plugin filter (so I'm told), but I used a plugin for Shake.

I've put it in the bottom half of the picture so it will still be intelligible after being transformed. Here's the FFT of my secret message:

Comments

[AndyGadget]

Clever - I wonder how much this method is being used for covert transmission of messages already.  It's many years since I had anything to do with Fourier transforms.  I passed the exams, but more by remembering the equations and plugging in the numbers than actually unsderstanding them.
I can see how you can convert an audio signal to the time domain, but how does that relate when you're transforming an image?

[royalestel]

You sample the image one line at a time.  The brightness becomesamplitude (y) and the horizontal pixel position becomes the horizontalsample position (x).

Other than that, there's a pretty useful page here: www.cs.unm.edu/~brayer/vision/fourier.html

[AndyGadget]

I get the idea. The link makes interesting reading - Thanks.

[gmoon]

Nice to see you back, RE...

[royalestel]

Thanks!  It's good to be back.  I liek making stuff and seeingthe great things others have created.