Asking for help on how to solve this with detailed steps: Local feature detection and description
Below we have computed the gradients of an image at each pixel:
(a) Compute the second moment matrix M for the colored 3 x 3 window W.
Assume that the weighting function w is a constant w(x,y) = 1
M = [[(∑_(x,y) w(x,y)I_(x)^(2)),(∑_(x,y) w(x,y)I_(x)I_(y))],[(∑_(x,y) w(x,y)I_(x)I_(y)),(∑_(x,y) w(x,y)I_(y)^(2))]]
(b) Compute the value of the corner response function when α = 0.04: R = det(M) - α trace(M)^(2)
(c) How would you characterize the "cornerness" of window W and why?
Let's assume that we detected SIFT regions from two images (i.e. circular regions with assigned orientations) of the same textured plane.
(d) What is the minimum number of SIFT region correspondence pairs needed for computing a similarity transformation between the pair of images?
(e) How do we compute a histogram of gradient orientations when generating a SIFT descriptor?
Local feature detection and description
Below we have computed the gradients of an image at each pixel:
3 2 1 -1 -1 4 3 2 0 -1 4 3 4 2 1 1 3 2 2
2 3 1 1 -1 2 3 2 -1 -1 2 4 4 1 2 -1 0 3 2 3
Ir
Iy
a) Compute the second moment matrix M for the colored 3 x 3 window W Assume that the weighting function w is a constant w(x,y) = 1
w(x,y)I2 w(x,y)IxIy M = x,y x,y D w(x,y)IvIy Zw(x,y)I2 x,y x,y
(b) Compute the value of the corner response function when α = 0.04:
R = det(M) - α trace(M)2
(c) How would you characterize the "cornerness" of window W and why?
Let's assume that we detected SIFT regions from two images (i.e. circular regions with assigned orientations) of the same textured plane.
(d) What is the minimum number of SIFT region correspondence pairs needed for computing a similarity transformation between the pair of images?
(e) How do we compute a histogram of gradient orientations when generating a SIFT descriptor?