comparison util/ksvd utils/im2colstep.m @ 70:c3eca463202d

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