how to takeout low frequency components from an image

hi, here i have to do a process please help how to approach for it??

ft_image=fftshift(fft2(image));

after this i want to take out low frequency components into an array.

so first i need to apply low pass filter. i am trying this function

http://www.clear.rice.edu/elec301/Projects01/image_filt/matlab.html

but here i have a doubt what is size(sze) of filter means???

so please help me.

thank you in advance.

Answer 1

[Wayne King]

Hi, you can create a high-pass separable filter and do that:

    [x,y] = meshgrid(-200:200);
    r = hypot(x,y);
    km = 0.8*pi;
    rm = 200;
    w = rm/10;
    term1 = sin( (km * r.^2) / (2 * rm) );
    term2 = 0.5*tanh((rm - r)/w) + 0.5;
    g = (term1 .* term2 + 1) / 2;

    imshow(g, 'XData', [-.8 .8], 'YData', [-.8 .8])
    axis on
    xlabel('Normalized frequency'), ylabel('Normalized frequency')
    title('Test pattern')

    b2 = fir1(30, 0.3, 'high');
    h2 = b2' * b2;
    g2 = imfilter(g, h2);

    imshow(g2, [], 'XData', [-.8 .8], 'YData', [-.8 .8])
    axis on
    xlabel('Normalized frequency'), ylabel('Normalized frequency')

Answer 2

[Image Analyst]

size() is a built-in function that you can look up in the help and get a lot faster answer than you can get by posting here and having someone tell you or refer you to the help.