diff util/sparco utils/pwsmoothfield.m @ 79:ee2a4d0f0c4c

Merge

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/util/sparco utils/pwsmoothfield.m	Mon Mar 28 11:19:41 2011 +0100
@@ -0,0 +1,32 @@
+function f = pwsmoothfield(n,var,alpha)
+% PWSMOOTHFIELD(N,VAR,ALPHA)
+%   Generate an image of piecewise smooth filtered white noise
+%
+%   N = sidelength of the field in pixels
+%   VAR = variance of original white nose
+%   ALPHA = fraction of FFT coefficents to keep
+%
+%   Returns an N-by-N array
+%
+%   This file is used with the kind permission of Stephen J. Wright
+%   ([e-mail]), and was originally included in the GPSR
+%   v1.0 distribution: http://www.lx.it.pt/~mtf/GPSR .
+
+% $Id: pwsmoothfield.m 1040 2008-06-26 20:29:02Z ewout78 $
+
+f = sqrt(var)*randn(n);
+F = fft2(f);
+a = ceil(n*alpha/2);
+b = fix(n*(1-alpha));
+F(a+1:a+b,:) = 0;
+F(:,a+1:a+b) = 0;
+f = real(ifft2(F));
+
+for i = 1:n
+    for j = 1:n
+        if (j/n >= 15*(i/n - 0.5)^3 + 0.4)
+            f(i,j) = f(i,j) + sqrt(var);
+        end
+    end
+end
+