Efficient Coding to save run time

I have a three dimensional cell that holds images (i.e. images = cell(10,4,5)) and each cell block holds images of different sizes. The sizes are not too important in terms of what I’m trying to achieve. I would like to know if there is an efficient way to compute the sharpness of each of these cell blocks (total cell blocks = 10*4*5 = 200). I need to compute the sharpness of each block using the following function:

If it matters:

• 40 cell blocks contain images of size 240 X 320
• 40 cell blocks contain images of size 120 X 160
• 40 cell blocks contain images of size 60 X 80
• 40 cell blocks contain images of size 30 X 40
• 40 cell blocks contain images of size 15 X 20

which totals to 200 cells.

%%Sharpness Estimation From Image Gradients
% Estimate sharpness using the gradient magnitude.
% sum of all gradient norms / number of pixels give us the sharpness
% metric.
function [sharpness]=get_sharpness(G)
   [Gx, Gy]=gradient(double(G));
   S=sqrt(Gx.*Gx+Gy.*Gy); 
   sharpness=sum(sum(S))./(480*640);

Currently I am doing the following:

sharpness = size(images);
for i = 1 : 10
   for j = 1 : 4
      for k = 1 : 5
         sharpness(i,j,k) = get_sharpness(images{i,j,k});
      end
   end
end

The sharpness function isn’t anything fancy. I just have a lot of data hence it takes a long time to compute everything.

Currently I am using a nested for loop that iterates through each cell block. Hope someone can help me find a better solution.

(P.S. This is my first time asking a question hence if anything is unclear please ask further questions. THANK YOU)

Answer 1

[Andrei Bobrov]

sharpness = zeros(size(images));
for ii = 1 : 10
   for jj = 1 : 4
      for k = 1 : 5
         sharpness(ii,jj,k) = get_sharpness(images{ii,jj,k});
      end
   end
end

[Jigar Patel]

Is that the only thing I can do to optimize? I forgot to index my sharpness variable but that is what I am doing in code

sharpness = size(images)
for i = 1 : 10
   for j = 1 : 4
      for k = 1 : 5
         sharpness(i,j,k) = get_sharpness(images{i,j,k});
      end
   end
end