Intuition behind image derivative using Fourier Transform for edges detection This equation can be shown mathematically:

$\frac{\partial f}{\partial x}=\frac{2\pi i}{N} \mathcal F^{-1}\left(u\cdot \mathcal F(f(x,y)\right)$

I am struggling to understand the intuition behind it when talking about 2D fourier for images and the use of derivatives to detect edges.

How does multiplying the Fourier transform of the image with $u$ help us detect edges in the x direction? Why does it make the "edges" white and the rest of the image darker?

Any help would be appreciated.
Thank you!
In general, the time derivative property of the Fourier Transform is given as

$$\mathscr{F}[\frac{d}{dt}x(t)] = j\omega X(j\omega) $$

Notice that we can simply multiply by the frequency index in the Fourier Transform result.

For the 2D FT result:

$$\mathscr{F}[f(x,y)]= F(u,v)$$

Using the same property results in:

$$\mathscr{F}[\frac{d}{dx}f(x,y)]= uF(u,v)$$

$$\mathscr{F}[\frac{d}{dy}f(x,y)]= vF(u,v)$$

The reason this detects edges is clear if you observe how the differentiation of a 1D step function results in an impulse. Your edges approximate steps. The derivative is the slope, so where the slope is high (edges) the derivative is large.