相位、幅度与传递函数

Polar form splits a spectrum

The swap experiment

Transfer functions classify filters

Probing systems and eyes

A hybrid image is built from the amplitude spectrum of a mountain photo and the phase spectrum of a portrait, then inverted. What does the result look like?

A filter's transfer function has gain near one at low frequencies, near zero at high frequencies, and a smooth fall in between. What does the filter do, and what is its DC gain close to?

A $3 \times 3$ averaging kernel contains nine equal taps of $1/9$. Write its DC gain $|H[0,0]|$, the sum of all taps.