What's an image made of?

There are many correct answers.

But the most fascinating one is: << sines & cosines >>

Read on if you're intrigued👇🧵🪡


Any image can be reconstructed from a series of sinusoidal gratings.

A sinusoidal grating looks like this…


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It’s called a sinusoidal grating because the grayscale values vary according to the sine function.

If you plot the values along a horizontal line of the grating, you’ll get a plot of a sine function


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…and different frequencies—these are spatial frequencies, not temporal ones


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There's one more parameter that defines a sinusoidal grating: the phase. Gratings with a different phase are shifted with respect to each other…


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@s_gruppetta Would it be feasible to include the code in the toot or as alt text? I'd love to try pasting it into Python, but of course I can't do that from an image.


@s_gruppetta Ah, I see farther downthread that the book has the code!

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@peterdrake I have been doing this (on Twitter) for a few months now, but this is an old post (from Twitter, recycled here) so the images didn’t have them. I now autogenerate these snippets which makes adding the code in ALT text easy

@peterdrake and yes, the article linked later has the full code etc…

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