[Octave-cvsupdate] SF.net SVN: octave:[5731] trunk/octave-forge/main/image/inst/imtranslate.m

[<ha...@us...>]

Revision: 5731
          http://octave.svn.sourceforge.net/octave/?rev=5731&view=rev
Author:   hauberg
Date:     2009-04-22 19:10:33 +0000 (Wed, 22 Apr 2009)

Log Message:
-----------
Allow for odd shifts (from Eugeniy Mikhailov)

Modified Paths:
--------------
    trunk/octave-forge/main/image/inst/imtranslate.m

Modified: trunk/octave-forge/main/image/inst/imtranslate.m
===================================================================
--- trunk/octave-forge/main/image/inst/imtranslate.m	2009-04-21 14:35:15 UTC (rev 5730)
+++ trunk/octave-forge/main/image/inst/imtranslate.m	2009-04-22 19:10:33 UTC (rev 5731)
@@ -25,6 +25,7 @@
 ## @end deftypefn
 
 ## Author: Jeff Orchard <jj...@cs...>
+## bug fix: Eugeniy Mikhailov in 2009 (removing fftshift and ifftshift they do no good)
 
 function Y = imtranslate(X, a, b, bbox_in)
 
@@ -54,13 +55,17 @@
 
 
 	[dimy, dimx] = size(X);
-	x = ifftshift(fft2(fftshift(X)));
+	x = fft2(X);
 	px = exp(-2*pi*i*a*(0:dimx-1)/dimx);
-	py = exp(-2*pi*i*b*(0:dimy-1)/dimy)';
+	py = exp(-2*pi*i*b*(0:dimy-1)/dimy)'; 	% actually to correspond to index notation 'b' should be
+						% replaced with '-b'
+						% but I do not want to brake previous version compatibility
+						% note: it also must be done in the cropping iand padding code
 	P = py * px;
 	y = x .* P;
-	Y = real( ifftshift(ifft2(fftshift(y))) );
-	#Y = ifftshift(ifft2(fftshift(y)));
+	Y = real(ifft2(y)); 	% fft return complex number
+				% for integer shifts imaginary part  is 0 
+				% so real takes care of transfer from complex number to real
 
 	if ( strcmp(bbox, "crop")==1 )
 		Y = Y(  ypad(1)+1:dimy-ypad(2) , xpad(1)+1:dimx-xpad(2));


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