Make Your Own Secret Messages From Space!
Intro: Make Your Own Secret Messages From Space!
During my [https://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.
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Here's the plainly plain message that I want to hide:
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:
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:
STEP 2: Hide Your FFT in Another Image
My first test overlaid the FFT over a color wheel, and it's a bit obvious something wierd is in the center:
STEP 3: Offset or Scroll the FFT
If we scroll the FFT over to the corners and scale down the brightness, it's much harder to spot when overlaid with the zucchini-in-a-bottle image:
STEP 4: FFT the Image to Decode
FFT the image again to see the secret message again. Some information is lost when the image is saved in the .tif format, but after we scale the brightness back up, we get this:
STEP 5: My Whole Process in an Image
Here's my whole shake tree for both the test image and the final masterfully masterfool zucchini-hiding-a-secret image. Have fun with this!
5 Comments
AndyGadget 14 years ago
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 14 years ago
Other than that, there's a pretty useful page here: www.cs.unm.edu/~brayer/vision/fourier.html
AndyGadget 14 years ago
I get the idea. The link makes interesting reading - Thanks.
gmoon 14 years ago
royalestel 14 years ago