I have the following code (recognizing individuals pixels of a matrix). For a high number of images, this is very time consuming. Therefore, ¿Could the loop be avoided ? Thanks!

Question

Santi 2016-12-22

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/317828-i-have-the-following-code-recognizing-individuals-pixels-of-a-matrix-for-a-high-number-of-images

编辑： Jan 2017-2-20

V=zeros(x,y,num_images,'uint16')
for k=1:num_images
for i= 1:x
for j= 1:y
    if B(i,j,k)==0
        V(i,j,k)= A(i,j,k)/3
    else
        V(i,j,k)= A(i,j,k)/3+(2^15)
    end
end
end
end

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

KSSV 2016-12-22

在 MATLAB Online 中打开

First you terminate the outputs with ;. Else it will take hell lot of time, because it will print result on the screen.

V=zeros(x,y,num_images,'uint16') ;
for k=1:num_images
    for i= 1:x
        for j= 1:y
            if B(i,j,k)==0
                V(i,j,k)= A(i,j,k)/3 ;
            else
                V(i,j,k)= A(i,j,k)/3+(2^15) ;
            end
        end
    end
end

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

David Barry 2016-12-22

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/317828-i-have-the-following-code-recognizing-individuals-pixels-of-a-matrix-for-a-high-number-of-images#answer_248182

编辑：David Barry 2016-12-22

在 MATLAB Online 中打开

It's difficult to know the relationship between A, B and V from your example code but I am assuming they are of equal dimensions. In which case I think you probably want something like this instead of the loop.

V = zeros(size(B));
V(B == 0) = A(B == 0)/3;
V(B ~= 0) = A(B ~=0)/3 + 2^15;

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 2

Santi 2016-12-22

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/317828-i-have-the-following-code-recognizing-individuals-pixels-of-a-matrix-for-a-high-number-of-images#answer_248190

Very nice and simple answer, worked! Thanks a lot

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

David Barry 2016-12-22

Great. Please accept the answer then.

请先登录，再进行评论。

Answer 3

John BG 2016-12-22

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/317828-i-have-the-following-code-recognizing-individuals-pixels-of-a-matrix-for-a-high-number-of-images#answer_248191

在 MATLAB Online 中打开

there is no need to initialise the void V, go straight to the indices returned from functions

find( zeros())
find( nonzeros())

A=A/3
V(find(zeros(B)))=A(find(zeros(B)))+2^15
V(find(nonzeros(B)))=A(find(nonzeros(B)))

if you find my answer useful would you please mark it as Accepted Answer by clicking on the ACCEPT ANSWER button?

thanks in advance for time and attention

John BG

<mailto:jgb2012@sky.com jgb2012@sky.com>

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Jan 2017-2-19

编辑：Jan 2017-2-20

Both lines do not work:

nonzeros() replies the vector of the non-zero elements and the information about the position inside B is lost.
zeros() creates an array of zeros with the elements of B as dimensions. Therefore find(zeros(B)) will reply the empty matrix.

请先登录，再进行评论。