MATLAB: Gaussian High Pass Filter

gaussian high pass filter

Hello, I try to apply Gaussian High Pass Filter function

a=imread('img'); figure(1) imshow(a) [m n]=size(a); f_transform=fft2(a); f_shift=fftshift(f_transform); p=m/2; q=n/2; d0=70; for i=1:m for j=1:n distance=sqrt((i-p)^2+(j-q)^2); low_filter(i,j)=exp(-(distance)^2/(2*(d0^2))); end end filter_apply=f_shift.*low_filter; image_orignal=ifftshift(filter_apply); image_filter_apply=abs(ifft2(image_orignal)); figure(2) imshow(image_filter_apply,[])

but I got this error

??? Error using ==> times Matrix dimensions must agree.

can someone help me

Best Answer

hi lina,

I tried your program and it works fine, replace the first command with :

 a=im2double(imread('circuit.tif'));

I think the error you get is due to the nature of the sample you use, maybe its RGB image, if so you need to change it to grayscale image or process each channel individually, try this as first attempt :

 a=im2double(rgb2gray(imread('img')));

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MATLAB: I’m trying to enhanced image by gaussian high pass filter but it can’t work… can you help me to repair the program? thangkyou before

As you are using imshow I'm guessing you have the image processing toolbox installed. In that case you might as well use the imfilter() function. The function

 fspecial('Gaussian', hsize, sigma )

will generate a Gaussian lowpass filter.

High pass filtering can be achieved by subtracting the low pass filtered from the original image, e.g.

 I = imread( 'peppers.png' );
 I_filtered = I - imfilter( I, fspecial('Gaussian', 5, 1 ) ); 
 imtool( I_filtered );

If you want to do the filtering explicitly, create the convolution matrix, e.g.

 hp_filter_matrix = fspecial('Gaussian', 5, 1);

This gives you a 5 x 5 double matrix that you can convolve with your image to low pass filter it. As before, the high pass filtered representation can be obtained by subtraction.

MATLAB: Downsampling the filtered image

By indexing, perhaps, e.g.,

 x=1:10;
 xdownsampled=x(1:2:end);

Or, if downsampling at non-integer locations, by interpolation. See griddedInterpolant().

Best Answer

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MATLAB: I’m trying to enhanced image by gaussian high pass filter but it can’t work… can you help me to repair the program? thangkyou before

MATLAB: Downsampling the filtered image

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