Lecture 7&8 Flashcards
Usage of Gabor Filter
Used to model the response of simple V1 cells
Gabor filters
detecting parts of a signal with a specific frequency and orientation in a local region
Gaussian envelope
localized in space and in the Fourier Transform
what are texture segmentation
surfaces with repeating patterns and structure
What is the relation of different parameters to the Gabor filters?
Determine the shape and orientation of the field
𝜃 : orientation of the filter
𝛾 : aspect ratio (between the x and y axes)
σ: std of Gaussian envelope
ϕ: phase of the sine wave
λ: wavelength of sine grating
Does the phase parameter affects the Magnitude plot
no, the phase does not affect the magnitude plots
Gabor Filter bank
Collection of all orientations and spacial frequencies in an image
Magnitude Plot of a Gabor Filter Bank
high spatial frequencies are closer to the DC point
low spatial frequencies are far away from the DC point
Power Spectrum
magnitude plot of spatial frequencies
the Fourier amplitude of spatial frequencies is proportional to
1/f
proportion for the power spectrum
1/f^2
Fall-off feature of a power spectrum
Power spectrum of natural images have 1/f^2
higher spatial freqs have lower power spectral density
lower spatial freqs have higher power spectral density
Principal Component Analysis (PCA)
technique to compute the orthogonal directions of maximum possible variance in data
dimensionality reduction
How can we localize a receptive field of an image
by applying a gaussian mask
Why is PCA mandatory
because images are redundat by removing the redundancy we can focus on the relevant information
