Crop a rectangular region from an n dimensional array

Description

if( nargin<4 || isempty(padEl)); padEl=0; end
nd = ndims(I); siz = size(I);
[strLocs,er] = checkNumArgs(strLocs,size(siz),0,0); error(er);
[endLocs,er] = checkNumArgs(endLocs,size(siz),0,0); error(er);
if( any(strLocs>endLocs)); error('strLocs must be <= endLocs'); end

% crop a real rect [accelerate implementation if nd==2 or nd==3]
strL1 = max(strLocs,1); endL1 = min(endLocs, siz);
if( nd==2 )
 I = I( strL1(1):endL1(1), strL1(2):endL1(2) );
elseif( nd==3 )
 I = I( strL1(1):endL1(1), strL1(2):endL1(2), strL1(3):endL1(3) );
else
 extract = cell( nd, 1 );
 for d=1:nd; extract{d} = strL1(d):endL1(d); end
 I = I( extract{:} );
end

% then pad as appropriate (essentially inlined padarray)
if( any(strLocs<1) || any(endLocs>siz) )
 padEl = feval( class(I), padEl );
 padPre = 1 - min( strLocs, 1 );
 sizPadded = endLocs-strLocs+1;
 idx=cell(1,nd);
 for d=1:nd; idx{d}=(1:size(I,d))+padPre(d); end
 Ib = repmat( padEl, sizPadded );
 Ib(idx{:})=I; I=Ib;
end


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