color-coded optical flow image

Background: main task is segmentation and tracking of (multiple) objects in a video, i intend to use meanshift for segmentation to which LUV-color-coded optical flow image is to be used as input.

So i calculated optical flow and converted vertical and horizontal values to polar coordinates using cart2pol. Now used Image Analyst's colorwheel and used following code to obtain RGB-color-coded optical flow image.

%%accessing RGB color agains theta and rho

outDir='./output/';
load([outDir 'polarflow.mat']);

rgbflow=struct('rgb_flow',{});

for i=1:size(polarflow,2)
    for row=1:size(polarflow(1).p_flow,1)
        for col=1:size(polarflow(1).p_flow,2)
            theta=polarflow(i).p_flow(row,col,1);
            theta_in_degrees = radtodeg(theta);
            theta_in_degrees = ceil(wrapTo360(theta_in_degrees));
            rho=ceil(polarflow(i).p_flow(row,col,2));
%             colour_row = ceil(size(rgb,1) * theta_in_degrees/359 + eps);
%             colour = rgb(colour_row,:); %%these 2 lines return 1755 values, couldn't interpret
            colour=rgb(theta_in_degrees,rho,:);
            rgbflow(i).rgb_flow(row,col,1)=colour(:,:,1);
            rgbflow(i).rgb_flow(row,col,2)=colour(:,:,2);
            rgbflow(i).rgb_flow(row,col,3)=colour(:,:,3);
        end
    end
end

save([outDir 'rgbflow.mat'],'rgbflow');

Problem is only a portion of original image is left, much foreground information is lost. An image and result image is attached. Kindly let me know any tips.

Answer 1

[Image Analyst]

There are several color pickers in the File Exchange: http://www.mathworks.com/matlabcentral/fileexchange/?search_submit=fileexchange&query=color+picker&term=color+picker

Or you can adapt my attached color wheel demo to use ginput() to let the user pick the color they want to use.

[Maryam Butt]

Thank you for help, kindly clear one more thing when i use Star Strider's code it returns (r,g,b) value for colour for any value of theta while using that code with your color_wheel returns a row of 1755 columns, how to interpret this?

[Image Analyst]

You can get the row and column from ginput, something like

[x,y] = ginput(1);
row = round(y);
col = round(x);
theColor = rgbImage(row, col, :);

[Maryam Butt]

ginput isn't necessary because i have all x,y values which I need to convert to polar coordinates (done) then i have got polar values [theta,rho] now i need to access the color value corresponding to theta angle and also incorporate rho somehow.

[Image Analyst]

I'm not sure what you're after with your latest edit, but if you want to track green blobs, see my attached demo.

[Maryam Butt]

Though in this image green blobs (basketball) need to be tracked but it is only an example, I want to track moving objects in general, they can be of any color, shape etc.

[Image Analyst]

Usually they just use quiver to show arrows. If you want them in colors for different vector lengths, you'd have to look for code for that. I think I've seen it but I don't remember where.