idamnjanovic@15: %IM2COLSTEP Rearrange matrix blocks into columns.
idamnjanovic@15: %  B = IM2COLSTEP(A,[N1 N2]) converts each sliding N1-by-N2 block of the
idamnjanovic@15: %  2-D matrix A into a column of B, with no zero padding. B has N1*N2 rows
idamnjanovic@15: %  and will contain as many columns as there are N1-by-N2 neighborhoods in
idamnjanovic@15: %  A. Each column of B contains a neighborhood of A reshaped as NHOOD(:),
idamnjanovic@15: %  where NHOOD is a matrix containing an N1-by-N2 neighborhood of A.
idamnjanovic@15: %
idamnjanovic@15: %  B = IM2COLSTEP(A,[N1 N2],[S1 S2]) extracts neighborhoods of A with a
idamnjanovic@15: %  step size of (S1,S2) between them. The first extracted neighborhood is
idamnjanovic@15: %  A(1:N1,1:N2), and the rest are of the form A((1:N1)+i*S1,(1:N2)+j*S2).
idamnjanovic@15: %  Note that to ensure coverage of all A by neighborhoods,
idamnjanovic@15: %  (size(A,i)-Ni)/Si must be whole for i=1,2. The default function behavior
idamnjanovic@15: %  corresponds to [S1 S2] = [1 1]. Setting S1>=N1 and S2>=N2 results in no
idamnjanovic@15: %  overlap between the neighborhoods.
idamnjanovic@15: %
idamnjanovic@15: %  B = IM2COLSTEP(A,[N1 N2 N3],[S1 S2 S3]) operates on a 3-D matrix A. The
idamnjanovic@15: %  step size [S1 S2 S3] may be ommitted, and defaults to [1 1 1].
idamnjanovic@15: %
idamnjanovic@15: %  Note: the call IM2COLSTEP(A,[N1 N2]) produces the same output as
idamnjanovic@15: %  Matlab's IM2COL(A,[N1 N2],'sliding'). However, it is significantly
idamnjanovic@15: %  faster.
idamnjanovic@15: %
idamnjanovic@15: %  See also COL2IMSTEP, IM2COL, COUNTCOVER.
idamnjanovic@15: 
idamnjanovic@15: 
idamnjanovic@15: %  Ron Rubinstein
idamnjanovic@15: %  Computer Science Department
idamnjanovic@15: %  Technion, Haifa 32000 Israel
idamnjanovic@15: %  ronrubin@cs
idamnjanovic@15: %
idamnjanovic@15: %  August 2009