Cut region of interest images from 3D stack with known indices and without for loop

Question

Kevin Jansen 2023-3-2

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1921830-cut-region-of-interest-images-from-3d-stack-with-known-indices-and-without-for-loop

评论： Kevin Jansen 2023-3-2

采纳的回答： Matt J

在 MATLAB Online 中打开

Hi! I am having trouble cutting region of interest from a 3D stack.

A small example, I have a 3x3x2 array of:

array = [1,2,3;4,5,6;7,8,9];
array(:,:,2) = [1,2,3;4,5,6;7,8,9];

mini image indices:

left = [1,2]
right = [2,3]
top = [1,2]
bottom = [2,3]

create mini images:

miniImages = array(top:bottom,left:right,:)

result:

miniImages(:,:,1) = [1,2;4,5]
miniImages(:,:,2) = [1,2;4,5]

However, I want the result to be:

miniImages(:,:,1) = [1,2;4,5]
miniImages(:,:,2) = [5,6;8,9]

It seems that it only uses the first indices in variables left, right, top, bottom to create all mini images.

Anyone know how to solve this? Currently I use a for loop over the indices, but I want to make it faster.

Thanks!

2 个评论
显示无隐藏无

Matt J 2023-3-2

miniImages(:,:,2) = [5,6;7,8]

Don't you mean [5 6;8;9] ?

Kevin Jansen 2023-3-2

Yes! That was a mistake, I will try to edit it.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Matt J 2023-3-2

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1921830-cut-region-of-interest-images-from-3d-stack-with-known-indices-and-without-for-loop#answer_1183765

编辑：Matt J 2023-3-2

在 MATLAB Online 中打开

I doubt anything will be faster than a loop, but you can try this:

array = [1,2,3;4,5,6;7,8,9];
array(:,:,2) = [1,2,3;4,5,6;7,8,9]
array = 
array(:,:,1) =

     1     2     3
     4     5     6
     7     8     9


array(:,:,2) =

     1     2     3
     4     5     6
     7     8     9
left = [1,2];
top = [1,2];
bottom = [2,3];
right = [2,3];
args=cellfun(@(z)reshape(z,1,1,[])    , {left,top,bottom,right} ,'un' ,0);
[L,T,B,R]=deal(args{:});
[m,n,p]=size(array);
[I,J]=ndgrid(1:m,1:n);
lidx=T<=I & I<=B & L<=J & J<=R;
miniImages=reshape( array(lidx)  ,B(1)-T(1)+1,R(1)-L(1)+1,[])
miniImages = 
miniImages(:,:,1) =

     1     2
     4     5


miniImages(:,:,2) =

     5     6
     8     9

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Kevin Jansen 2023-3-2

Hey, awesome it worked! Much more difficult than I thought it would be. My code with larger arrays ran 380x faster without the for loop. Thank you so much!

请先登录，再进行评论。

Cut region of interest images from 3D stack with known indices and without for loop

2 个评论
显示无隐藏无

采纳的回答

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

更多回答（0 个）

另请参阅

类别

标签

产品

版本

Community Treasure Hunt

Cut region of interest images from 3D stack with known indices and without for loop

2 个评论 显示 无隐藏 无

采纳的回答

1 个评论 显示 -1更早的评论隐藏 -1更早的评论

更多回答（0 个）

另请参阅

类别

标签

产品

版本

Community Treasure Hunt

2 个评论
显示无隐藏无

1 个评论
显示 -1更早的评论隐藏 -1更早的评论