Possible to apply filter2 to only values above a limit?

I have an array which I'm attempting to filter with a Gaussian blur to smooth the surface and contour plots. Without any filtering, this is the resulting contour plot:

This code:

load 'A'
G=fspecial('gaussian',[5 5],2);
Af=filter2(G,A,'same');
contour(X,Y,A);

Gives the following contour plot:

As you can see, the contours are nicely smoothed, but the filter has blurred the transitions too much and shifted them wider and outwards.

My Question:

Is it possible to refer to just array elements above a certain value for the filtering?

I'm sure it must be and I'm just being stupid not figuring it out.

Cheers

Answer 1

[Oliver Woodford]

Compute the filtered version for all pixels, and simply replace the pixels above a certain value with their filtered value:

G = fspecial('gaussian',[5 5],2);
Af = filter2(G,A,'same');
M = A > thresh;
A(M) = Af(M);
contour(X,Y,A);

[Josh]

that works great!

much appreciated :)

Answer 2

[Josh]

bump

Perhaps there's a different type of filter I can use, which preserves edges better?