%318810637 Perov Danny
%318455813 Eden Klainer
%
%The function finds the edges in the image using the Canny edge detector.
%Input: grayscale image
%Output: binary image with only the images.
function [newImg] = edgeDetect(img)

%Smooth the image.
img = conv2(img, [1,2,1; 2, 4, 2; 1, 2, 1] / 16, 'same');

%Find the gradient.
Sx = conv2(img, [1, -1], 'same');
Sy = conv2(img, [1; -1], 'same');
S = sqrt(Sx.^2 + Sy.^2);
teta = Sy ./ Sx;

[rows, cols] = size(img);
tempImg = S;

%Go over all the pixels, and compare each and one of them to its neighbours
for r = 1 : rows
    for c = 1 : cols

        if(isnan(teta(r, c)) == 1 || isinf(teta(r, c)) == 1 || r == 1 || c == 1 || r == rows || c == cols)
            tempImg(r, c) = 0;
            continue;
        end

        if(-0.4142 <= teta(r, c) && teta(r, c) <= 0.4142)
            if(S(r, c) <= S(r, c - 1) || S(r, c) <= S(r, c + 1))
                tempImg(r, c) = 0;
            end

        elseif(0.4142 <= teta(r, c) && teta(r, c) <= 2.4142)
            if(S(r, c) <= S(r - 1, c + 1) || S(r, c) <= S(r + 1, c - 1))
                 tempImg(r, c) = 0;
             end

        elseif(abs(teta(r, c)) >= 2.4142 )
            if(S(r, c) <= S(r - 1, c) || S(r, c) <= S(r + 1, c))
                 tempImg(r, c) = 0;
            end

        elseif(-2.4142 <= teta(r, c) && teta(r, c) <= -0.4142)
            if(S(r, c) <= S(r - 1, c - 1) || S(r, c) <= S(r + 1, c + 1))
                tempImg(r, c) = 0;

            end
        end
    end
end

Tmax = 17/255;%43 / 255; % TODO decide upon values
Tmin = 5/255;%10 / 255;

%Create matrices which contain values above the given thresholds
aboveTMax = (tempImg > Tmax);
aboveTMin = (tempImg > Tmin);

%Create a matix in which a strong cell has value 2, and a weak one has value 1
aboveThreshold = aboveTMax + aboveTMin;
finalEdges = aboveTMax;
counter = 1;
currentPixels = [];

%Check each of the cells to find the edges by using the local patch
for r = 2 : rows - 1
    for c = 2 : cols - 1
        if(aboveThreshold(r, c) ~= 1)
            continue;
        end

        localPatch = aboveThreshold(r - 1 : r + 1, c - 1 : c + 1);
        patchMax = max(max(localPatch));

        if(patchMax == 2)
            currentPixels(counter, 1) = r;
            currentPixels(counter, 2) = c;
            counter = counter + 1;
            finalEdges(r, c) = 1;
        end
    end
end

counter = 1;

%Set the final edge values in the result matrix.
while(size(currentPixels, 1) > 0)
    newPix = [];
    for i = 1 : size(currentPixels, 1)
        r = currentPixels(i, 1);
        c = currentPixels(i, 2);
        if r ~= 0 && c ~= 0
        for dr = -1 : 1
            for dc = -1 : 1
                if (dr == 0 && dc == 0)
                    continue;
                end
                r2 = r + dr;
                c2 = c + dc;

                if (aboveThreshold(r2, c2) == 1 && finalEdges(r2, c2) == 0)
                    newPix(counter, 1) = r2;
                    newPix(counter, 2) = c2;
                    counter = counter + 1;
                    finalEdges(r2, c2) = 1;
                end
            end
        end
        end
    end

    currentPixels = newPix;
end

newImg = finalEdges;