/falldetect/MHI.m

%

% ECE 4007 - Spring 2009

%

% MHI.m

% Calculates the Motion History Image of the given video input

% Author: Nicholas Chan

% Date: February 16, 2009

%

% Assumptions: 15 FPS data; T = 15 frames (1 second) per fall



function MHI = MHI(fg)



% Initialize the output, MHI a.k.a. H(x,y,t,T)

MHI = fg;



% Define MHI parameter T

T = 15; % # of frames being considered; maximal value of MHI.



% Load the first frame

frame1 = fg{1};



% Get dimensions of the frames

[y_max x_max] = size(frame1);



% Compute H(x,y,1,T) (the first MHI)

MHI{1} = fg{1} .* T;



%Start global loop for each frame

for frameIndex = 2:length(fg)

    

    %Load current frame from image cell

    frame = fg{frameIndex};

    

    %Begin looping through each point

    for y = 1:y_max

        for x = 1:x_max

            if (frame(y,x) == 255)

                MHI{frameIndex}(y,x) = T;

            else

                if (MHI{frameIndex-1}(y,x) > 1)

                    MHI{frameIndex}(y,x) = MHI{frameIndex-1}(y,x) - 1;

                else

                    MHI{frameIndex}(y,x) = 0;

                end

            end

        end

    end

end