2. Who Am I?
王紹權 (Shao-Chuan Wang)
Currently as SDE at
Had _some_ computer vision experience.
Mainly speak Python and C/C++.
@scwang
…/in/scwang
shaochuan.wang
13. Blob Size Characteristic Scale
Given a 1D signal f(x).
¶2 ns
Compute * f (x) at many scales (σ0, σ1, …,
σ) ¶x 2
k
Find:
¶ ns 2
(x , s ) = arg max 2 * f (x)
* *
( x,s ) ¶x
Characteristic scale
14. Convolution 與微分有交換律
I(x, y) S(x, y, s 1 ) S(x, y, s 2 ) S(x, y, s 3 )
σ Large
(x*, y*, s * ) = argmax s 2 Ñ2 ns * I(x, y)
( x,y,s )
(x , y , s ) = argmax s 2 Ñ2 S(x, y, s )
* * *
( x,y,s )
16. Laplacian of Gaussian
V.S. Difference of
Gaussian
G(x, y, ss )-G(x, y, s ) » (s -1)s 2Ñ2G.
[Lowe 2004]
17. 回到最初的第二個問題
如何描述或量化? (Histogram of gradients)
Assignment of orientation
Principal Orientation
Histogram of orientation
Characteristic Scale
[Lowe 2004]
24. Reference
[Mikolajczyk 2004] Scale & Affine Invariant
Interest Point Detectors.
[Lowe 2004] Distinctive Image Features from
Scale-Invariant Keypoints
[Pollefeys 2006] Towards Urban 3D
Reconstruction From Video