CAMSHIFT 구현. * Bradski, Gary R. "Computer vision face tracking for use in a perceptual user interface." (1998).

1. Continuously Adaptive Mean Shift (CAMSHIFT)
Han-Sol Kang
Image Processing Term Project
* Bradski, Gary R. "Computer vision face tracking for use in a perceptual user interface." (1998).
*
2015.12.15

2. INDEX
2015-12-15
01 CAMSHIFT Algorithm
02 Source Code
03 Experimental Results and Analysis
2

3. 2015-12-15
01CAMSHIFT Algorithm
3
Introduction
mean shift
[Block Diagram]

4. 2015-12-15
01CAMSHIFT Algorithm
4
Color Probability Distributions
misconception : Different color models are needed for different races of people
Except for albinos, humans are all the same color(hue)
I
r
Histogram Back
Projection
}
)+(R-B)(G-B(R-G)
B)][(R-G)+(R-.
{H= -
2
1 50
cos
),,(
),,(),,(
BGRMax
BGRMinBGRMax
S


255
),,( BGRMax
V 
HSV Color Model

5. 2015-12-15
01CAMSHIFT Algorithm
5
How to Calculate the Mean Shift Algorithm
1. Choose a search window size
2. Choose the initial location of the search window
3. Compute the mean location in the search window
4. Center the search window at the mean location computed in Step 3
5. Repeat Steps 3 and 4 until convergence (or until the mean location moves less than a preset threshold)
3x3?
5x5?
15x15?

6. 2015-12-15
01CAMSHIFT Algorithm
6
The mean location(the centroid)

x y
yxIM ),(00

x y
yxxIM ),(10

x y
ji
ij yxIyxM ),(

x y
yxyIM ),(01
00
10
M
M
xc 
00
01
M
M
yc 
ex)
1 1 4
1 1 4
1 1 4
18444111111),(00  x y
yxIM
y
x 18421212411111401010),(10  x y
yxxIM
27421110421110421110),(01  x y
yxyIM
1
18
18
00
10

M
M
xc 5.1
18
27
00
01

M
M
yc

7. 2015-12-15
01CAMSHIFT Algorithm
7
How to Calculate the Continuously Adaptive Mean Shift Algorithm
1. Choose the initial location of the search window
2. Mean Shift as above(one or many iteration); store the zeroth moment
3. Set the search window size equal to a function of the zeroth moment found in Step 2
4. Repeat Steps 2 and 3 until convergence (mean location moves less than a preset threshold)

8. 2015-12-15
01CAMSHIFT Algorithm
8
How to Calculate the Coupled CAMSHIFT Algorithm
1. First, set the calculation region of the probability distribution to the whole image
2. Choose the initial location of the 2D mean shift search window
3. Calculate the color probability distribution in the 2D region centered at the search window location in an area slightly larger than
the mean shift window size
4. Mean shift to convergence or for a set number of iterations. Store the zeroth moment (area or size) and mean location.
5. For the next video frame, center the search the search window at the mean location stored in Step 4 and set the window size to
a function of the zeroth moment found there. Go to Step 3

9. 2015-12-15
01CAMSHIFT Algorithm
9
Calculation of Head Roll

x y
yxIxM ),(2
20 
x y
yxIyM ),(2
02
2
2
arctan
2
00
022
00
20
00
11



































cc
cc
y
M
M
x
M
M
yx
M
M

2
00
20
cx
M
M
a  





 cc yx
M
M
b
00
11
2
2
00
02
cy
M
M
c 
2
)()( 22
cabca
l


2
)()( 22
cabca
w



10. 2015-12-15
01CAMSHIFT Algorithm
10
Calculation of Head Roll

x y
yxIxM ),(2
20 
x y
yxIyM ),(2
02
2
2
arctan
2
00
022
00
20
00
11



































cc
cc
y
M
M
x
M
M
yx
M
M

2
00
20
cx
M
M
a  





 cc yx
M
M
b
00
11
2
2
00
02
cy
M
M
c 
2
)()( 22
cabca
l


2
)()( 22
cabca
w


Setting Adaptive Window Size Function
256
*2 00M
s 

11. 2015-12-15
02Source Code
11
Calculation of Head Roll
CTrackTestDlg
HSI_Calc_Func
Calc_Hue_Hist
momentCenter
CAMSHIFT
void Calc_Hue_Hist(int imWidth, int imHeight, int xl, int xh, int yl, int yh, unsigned char* H, float* HistH)
void momentCenter(unsigned char* H, int imWidth, int imHeight, WPoint& w, int& xc, int& yc, float& angle)
void CAMSHIFT(unsigned char* H, int imWidth, int imHeight, WPoint& w, int& xc, int& yc, float& angle)
void HSI_Calc_Func(unsigned char* R, unsigned char* G, unsigned char* B, unsigned char* H, int width, int height)

12. 2015-12-15
02Source Code
HSI_Calc_Func
12

13. 2015-12-15
02Source Code
13
momentCenter

14. 2015-12-15
02Source Code
14
CAMSHIFT

15. 2015-12-15
03Experimental Results & Analysis
15

16. 2015-12-15
03Experimental Results & Analysis
16

17. 2015-12-15
Q & A