How do I apply a sliding window technique on images for multiple people detection?

I am implementing HOG for people detecting, however, I have problem on sliding window technique to detect multiple people in images. Please someone guides me to build a sliding window technique for multiple people detection in Matlab.

Here is partly my code for sliding window...

    win_size= [64, 128];
    [lastRightCol lastRightRow d] = size(im);
    counter = 1;
    %%Scan the window by using sliding window object detection
    % this for loop scan the entire image and extract features for each sliding window
    % Loop on scales (based on size of the window)
    for s=1:0.5:3
        disp(strcat('s is',num2str(s)));
        X=win_size(1)*s;
        Y=win_size(2)*s;
        for y = 1:X/4:lastRightCol-Y
            for x = 1:Y/4:lastRightRow-X
                p1 = [x,y];
                p2 = [x+(X-1), y+(Y-1)];
                po = [p1; p2] ;
                img = cropped_image(po,im);
                featureVector{counter} = getHOGDescriptor(img);
                boxPoint{counter} = [x,y,X,Y];
                count = counter+1;
                x = x+2;
            end
         end
    end
    label = ones(length(featureVector),1);
    P = cell2mat(featureVector);
    % each row of P' correspond to a window
    % classifying each window
    [~, predictions] = svmclassify(P', label,model); 
    % set the threshold for getting multiple detection
    % the threshold value is 0.7
    get_detect = predictions.*[predictions>0.6];
    % the the value after sorted
    [r,c,v]= find(get_detect);
    %%Creating the bounding box for detection
    for ix=1:length(r)
        rects{ix}= boxPoint{r(ix)};
    end
    if (isempty(rects))
       rects2=[];
    else
       rects2 = cv.groupRectangles(rects,3,'EPS',0.35);
    end
    for i = 1:numel(rects2)
     rectangle('Position',[rects2{i}(1),rects2{i}(2),64,128], 'LineWidth',2,'EdgeColor','y');
    end

[ARUN KUMAR TL]

can i get to know , crooped_image function and getHOGDescriptor please.