Error using .* Array dimensions must match for binary array op. Error in uas1 (line 7) If_low = If.*c;

I = imread ('gray.jpg');

If=fft2(I);

If=fftshift(If);

[x,y] = meshgrid(1:1, 1:1)

z = sqrt(x.^2 + y.^2)

c = (z<3)

If_low = If.*c;

If_low_inv = ifft2(If_low);

subplot (2,2,1), imshow(I), title ('foto asli')

subplot (2,2,2), fftshow(If), title ('foto transformasi fourier')

subplot (2,2,3), imshow(c), title ('low passfilter')

subplot (2,2,4), fftshow(If_low_inv, 'abs'), title ('filtering')

[Matt J]

Did you check what the sizes are?

[madhan ravi]

meshgrid() arguments are scalar

[Dyuman Joshi]

Clearly, the dimensions of If and c are not compatible for element-wise multiplication.

However, since you have not described what you are trying to do, we can't provide a definitive suggestion to help solve this issue.

A general solution is to make sure that the variables are compatible for element-wise multiplication.

Answer 1

[Hassaan]

I = imread('gray.jpg');

% Make sure the input image is grayscale
if size(I, 3) == 3
    I = rgb2gray(I);
end

% Convert image to double for FFT
I_double = im2double(I);

% Apply 2D FFT and shift zero frequency component to the center
If = fft2(I_double);
If_shifted = fftshift(If);

% Create a meshgrid for the frequency domain that matches the image size
[rows, cols] = size(I_double);
[x, y] = meshgrid(-cols/2:cols/2-1, -rows/2:rows/2-1);
z = sqrt(x.^2 + y.^2);

% Create a circular low-pass filter mask
cutoff = 30; % You may need to adjust the cutoff frequency
c = (z < cutoff);

% Apply the low-pass filter to the shifted frequency domain image
If_low = If_shifted .* c;

% Shift back and apply inverse FFT
If_low_unshifted = ifftshift(If_low);
If_low_inv = ifft2(If_low_unshifted);

% Display the results
subplot(2, 2, 1), imshow(I), title('Original Image');
subplot(2, 2, 2), imshow(log(1 + abs(If_shifted)), []), title('Fourier Transform');
subplot(2, 2, 3), imshow(c), title('Low Pass Filter');
subplot(2, 2, 4), imshow(abs(If_low_inv)), title('Filtered Image');

• The meshgrid is centered around zero and then shifted to match the centering performed by fftshift.
• The mask c is then also centered with ifftshift to match the FFT-shifted frequency array before applying the element-wise multiplication.

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