Meanshift Tracking algorithm

Mean shift

The main function of this algorithm is histogram estimation. Since moving objects can be identified by their color histogram. Mean-shift tracking algorithm is an iterative scheme based on comparing the histogram of the original object in the current image frame and histogram of candidate regions in the next image frame. The aim is to maximize the correlation between two histograms.

Code:


Mv = aviread('StabilizationResult.avi')
rmin = 0; %min row value for search window
rmax = 0; %max row value for search window
cmin = 0; %min col value for search window
cmax = 0; %max col value for search window
numofframes = 0;
frameNo = 10; %starting frame
vidSize=[128 160]; %video size
centerold = [0 0];
centernew = [0 0];

M =Mv;

% get number of frames
numberofframes = length(M);

Frame1 = M(frameNo);
Image1 = imresize(Frame1.cdata,vidSize,'bilinear');
disp('Click and drag mouse for an initial box window');
% get search window for first frame
[ cmin, cmax, rmin, rmax ] = select( Image1 );
cmin = round(cmin);
cmax = round(cmax);
rmin = round(rmin);
rmax = round(rmax);
wsize(1) = abs(rmax - rmin);
wsize(2) = abs(cmax - cmin);

hue=Image1(:,:,1);
histogram = zeros(256);

for i=rmin:rmax
for j=cmin:cmax
index = uint8(hue(i,j)+1);
%count number of each pixel
histogram(index) = histogram(index) + 1;
end
end

% for each frame
for i = frameNo:numberofframes
Frame = M(i);
I = imresize(Frame.cdata,vidSize,'bilinear');

hue= I(:,:,1);
[rows cols] = size(hue);
probmap = zeros(rows, cols);
for r=1:rows
for c=1:cols
if(hue(r,c) ~= 0)
probmap(r,c)= histogram(hue(r,c));
end
end
end
probmap = probmap/max(max(probmap));
probmap = probmap*255;

count = 0;

rowcenter = 0; % any number just so it runs through at least twice
colcenter = 0;
rowcenterold = 30;
colcenterold = 30;
while (((abs(rowcenter - rowcenterold) > 2) && (abs(colcenter - colcenterold) > 2)) || (count < 15) )
rowcenterold = rowcenter;
colcenterold = colcenter;

[ rowcenter colcenter M00 ] = meanshift(rmin, rmax, cmin,...
cmax, probmap);

rmin = round(rowcenter - wsize(1)/2);
if rmin<1 br=""> rmin=1;
end
rmax = round(rowcenter + wsize(1)/2);
if rmax<1 br=""> rmax=1;
end
cmin = round(colcenter - wsize(2)/2);
if cmin<1 br=""> cmin=1;
end
cmax = round(colcenter + wsize(2)/2);
if cmax<1 br=""> cmax=1;
end
wsize(1) = abs(rmax - rmin);
wsize(2) = abs(cmax - cmin);

count = count + 1;
end

G = I;
trackim=G;

%make box of current search window on saved image
for r= rmin:rmax
trackim(r, cmin:cmin+2) = 0;
trackim(r, cmax-2:cmax) = 0;
end
for c= cmin:cmax
trackim(rmin:rmin+2, c) = 0;
trackim(rmax-2:rmax, c) = 0;
end

windowsize = 100 * (M00/256)^.5;
sidelength = sqrt(windowsize);
rmin = round(rowcenter-sidelength/2);
if rmin<1 br=""> rmin=1;
end
rmax = round(rowcenter+sidelength/2);
if rmax<1 br=""> rmax=1;
end
cmin = round(colcenter-sidelength/2);
if cmin<1 br=""> cmin=1;
end
cmax = round(colcenter+sidelength/2);
if cmax<1 br=""> cmax=1;
end
wsize(1) = abs(rmax - rmin);
wsize(2) = abs(cmax - cmin);


outname = sprintf('./answer/%d.jpg', i);
imwrite(trackim, outname);

figure(1),imshow(trackim); hold on
end
hold off;