Lecture 5&6

Question 1

Frequencies

Answer 1

plausible building blocks of images and sounds

Question 2

Fourier analysis

Answer 2

analyse the frequency characteristics from a signal

Question 3

Fourier synthesis

Answer 3

the construction of a periodic signal on the basis of Fourier coefficients which gave the amplitude and phase of each component sine wave

Question 4

Fourier transform

Answer 4

decomposition of a signal into it’s elements, measures the amplitude and the phase of different frequencies

Question 5

which are the basics building blocks

Answer 5

sine and cosine waves

Question 6

what is represented by the spectral signal

Answer 6

the strengths (magnitudes) of the constituent frequencies

Question 7

Invertical transformation

Answer 7

going from the image domain to the fourier domain and vice versa

Question 8

magnitude

Answer 8

the strengths of individual frequencies

Question 9

phase

Answer 9

positions of the individual frequencies

Question 10

what represents the DC point

Answer 10

the average intensity of the image

Question 11

Interpreting magnitude plots

Answer 11

low spatial frequencies: closer to the DC point

Question 12

Pick the correct term

The phase/ The magnitude
is more important for retrieving the content of an image

Answer 12

the phase

Question 13

why the phase is more important when retrieving an image

Answer 13

because the phase captures the contours of tha image

Question 14

Low-pass filtering

Answer 14

• blocks out the DC points and the high spatial frequencies
• let all low spatial frequencies to pass
  Result: blurred image (bc the high spatial frequencies emphasizes the details)

Question 15

High-Pass filtering

Answer 15

-blocks out the DC point and the low spatial frequencies
- let all high spatial frequencies pass
Result: Contour Image

Question 16

Band-pass filtering

Answer 16

allow a range of spatial frequencies and set everything else to 0
(blocks the low and high spatial frequencies)

Question 17

Fast convolution

Answer 17

perform a fourier transform on the template of the image

Question 18

Does the human visual system perform a Fourier Transform? Why?

Answer 18

No.
Because the human visual system has multiple channels sensitive to different spatial frequencies, The Fourier transform is a single channel model.

Question 19

Wavelet method

Answer 19

Filters take localised measurements of spatial frequencies

Question 20

Texton method

Answer 20

Take patches of image -> perform clustering on patches