Agfdhyk

I have implemented the naive version of non local means without integral images.
First image acquisition:

row = 10;

col = 10;



% Patchsize - make sure if code works for different values

patchSize = 4;



% Search window size - make sure if code works for different values

searchWindowSize = 10;



image = imread('r.jpg');

new=imnoise(image,'gaussian');

imshow(new)

ws=floor(searchWindowSize/2);

ps=floor(patchSize/2);

new= padarray(new, [searchWindowSize,searchWindowSize], 'both');

new= padarray(new, [patchSize,patchSize], 'both');

Now, the main non local means function:

unew=zeros(size(new,1),size(new,2));

for i=1+ws+ps:size(new,1)-ws-ps

    for j=1+ws+ps:size(new,2)-ws-ps

        sear=new(i-ws:i+ws,j-ws:j+ws);

        %imshow(new(i-ws:i+ws,j-ws:j+ws))

        sear=padarray(sear,[ps,ps],'both');

        patch=new(i-ps:i+ps,j-ps:j+ps);

        dis=;

        ind=1;

        sums=0;

        for ii=1+ps:size(sear,1)-ps

            for jj=1+ps:size(sear,1)-ps

                patchn=new(ii-ps:ii+ps,jj-ps:jj+ps);

                ssd=(patchn-patch).*2;

                psum=0;

                for mj=1:patchSize

                    for gj=1:patchSize

                        psum= psum+ssd(mj,gj);

                    end

                end

                dis(ind)=psum;

                sums=sums+exp(-max(dis(ind)*dis(ind)-2*0.1*0.1,0)/0.75*0.75);                



                ind=ind+1;

            end

        end

        new(i,j)=sums;

    end

end

My initial image:

My final image:

There are many issues with the code. Here is a non-exhaustive list:

• You don’t do anything with color, it looks like your code is written for a grey-value image. But you put a color image through it. Consequently, only the red channel is modified.




• You write into the same image you read from. You cannot do this, as you’re using a combination of input and output pixels to generate the next output pixel. Instead, read from one image, write to another one.




• A weighted mean is computed by summing value*weight, and then dividing by the sum of the weights at the end. You don’t do this division.




• You crop your search area from your image, then pad it. This makes no sense. You should crop a larger region from your image.




• You keep an array dis, you write to it, but you don’t make use of it. That is, you write a new element, then only read this new element; you never go back and look at the older values. Why does this array exist?




• Your inner two loops can be written as psum = sum(ssd(:)).




• ssd is twice the difference. You probably want to look at the square difference, or the absolute difference.