Working with 3d matrices

Hello, I am trying to sum a group of pixels in an RGB picture represented by heightXwidthX3 matrix. i have a 2d matrix of logical values and im trying to sum those.

exmp in this code: %% Pic = ones(3,3,3); index = logical([1 0 0;0 1 0;0 0 1]); %% %i tried to pull out the wanted pixels like this: pixels = Pic(index,:)

but that didnt work since matlab decides to reshapes the matrix to a vector from 1 to 3*3*3 for some reason. the error i got was: "??? Index exceeds matrix dimensions."

can anyone help me with the right way to do that?

Answer 1

[Sean de Wolski]

Pic = repmat(magic(3),[1 1 3]); %magic square so we can see that it works
index = logical(eye(3)); %example logical index
the_sum = sum(reshape(Pic(repmat(index,[1 1 3])),[],3),2) %sum (example function: note it's called along the 2nd dimension)

[Geva Tal]

Works great, thanks alot!