Summing specific pixel values
1 vue (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Jason
le 22 Oct 2014
Commenté : Bjorn Gustavsson
le 22 Oct 2014
Hi. I am wanting to find the sum of all the positons xi, yi of an image IM. I thought the following would do it - but it doesn't.
sum(im (xi,yi));
Also, If I want to take this a step further and find the sum of all pixels at locations xi, yi but this time include the surrounding 8 pixels (so its a 3x3 centred on xi,yi), how do I do that?
thanks
0 commentaires
Réponse acceptée
Image Analyst
le 22 Oct 2014
You can use a for loop:
m=magic(5) % Whatever...
xi=[2,3,4]
yi = [2,3,4]
theSum = 0;
the8Sum = 0;
for k = 1 : length(xi)
row = yi(k);
col = xi(k);
theSum = theSum + m(row, col);
the8Sum =the8Sum + ...
m(row-1, col-1) + ...
m(row-1, col) + ...
m(row-1, col+1) + ...
m(row, col-1) + ...
m(row, col) + ...
m(row, col+1) + ...
m(row+1, col-1) + ...
m(row+1, col) + ...
m(row+1, col+1);
end
theSum
the8Sum
2 commentaires
Bjorn Gustavsson
le 22 Oct 2014
I suggest you do something like this instead:
ind1D = sub2ind(size(im),xi,yi);
sumPixxiyi = sum(im(ind1D));
Then for the nearest Neighbour you'd have to make arrays for them too. In my opinion such a solution is so much easier to maintain since it will be so many fewer lines of code that potential speed losses might be preferable.
Plus de réponses (0)
Voir également
Catégories
En savoir plus sur Matrices and Arrays dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!