Memory problem when accessing and copying the 3D array elements by subscripts

I am trying to access/copy values from an image 3D array to another 3D array using the subcripts (rows and columns). I am trying to avoid the for loop. With for loop this works fine. The size of the rows and columns is 121020 x 1. But I am getting a memory error as below:

Requested 121020x121020x3 (40.9GB) array exceeds maximum array size preference. Creation of arrays greater than this limit may take a
long time and cause MATLAB to become unresponsive.

The code snippet is below

% Find boundary of the cylindrical projection
[row,col] = find(ximg > 0 & ximg <= xdim & yimg > 0 & yimg <= ydim);
out(row,col,:) = image(row,col,:);

Any help to make it without for loop is appreciated!

[darova]

What are sizes of xdim and image?

[Preetham Manjunatha]

Image size is 384 x 512 x 3. So xdim is 512 and ydim is 384.

[darova]

what is size of ximg?

Answer 1

[Matt J]

The better way would be to avoid using find():

region=(ximg > 0 & ximg <= xdim & yimg > 0 & yimg <= ydim);

imtmp=reshape(image,[],size(image,3));
outtmp=reshape(out,[],size(out,3));

outtmp(region,:)=imtmp(region,:);

out(:)=outtmp(:); clear outtmp imtmp

[Preetham Manjunatha]

Thank you, Matt J!