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During my playful experiments 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.

Here’s the message I want to hide:

The Secret Message!

The 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:

The Fourier Transform of My Secret Message

The Fourier Transform of My Secret Message

My first test overlaid the FFT over a color wheel, but it’s still a bit obvious:

The Secret Message overlaid on a test image.

The Secret Message overlaid on a test image.

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:

The secret message offset to hide it better, overlaid on a normal photo.

The secret message offset to hide it better, overlaid on a normal photo.

You can barely spot it. Some information is lost when the image is saved in the .tif format, but after we scale the brightness back up, we get this:

The actual use decoded message (rescued from a zucchini-in-a-bottle)

The actual use decoded message (rescued from a zucchini-in-a-bottle)

Here’s my whole shake tree for both the test image and the final masterfully masterfool zucchini-hiding-a-secret image. Cheers!

Lossless Shake Message Tree

Lossless Shake Message Tree

Masterfool Zucchini Secret Message Shake Tree

Masterfool Zucchini Secret Message Shake Tree

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