Getting Error In FFT filtering ?

sir i tried to make a gaussian filter.i use the steps given in the book(digital image processing using MATLAB,OF Gonzalez & Woods & Eddins )in the chapter3.i have done upto the step

    [f,revertclass]=tofloat(f)
here 'f' is an image(of int8),here also given an error that"Undefined function or method 'tofloat' for input arguments of type 'uint8'."
    PQ=paddedsize(size(f));
     F=fft2(f,PQ(1),PQ(2));
then i use gaussian filter and get the transfer function.and then
  H=ifftshift(H) for making center
then G=H.*F;
here i get an error which is "Error using ==> times Matrix dimensions must agree.
Error in ==> gaussian at 16
G=H.*F;"

please tell me how to overcome from this error

Answer 1

[Jordan Monthei]

you are performing matrix multiplication when you use the '.*' command. The error you are receiving is telling you that the two "matrices" that you are trying to multiply are not of the same dimensions.

I assume you are trying to multiply numbers and not matrices and would recommend using '*' and not '.*'

[Jordan Monthei]

[f,revertclass]=tofloat(f)

This line is reading the value of 'f' which is returned from the function 'tofloat'. Is this function being declared in your program prior to being called?

[Image Analyst]

Jordan, what you said about multiplication is exactly the opposite of what it is. * is matrix multiplication and .* is element-by-element multiplication.

[Jordan Monthei]

I stand corrected. good catch.

Answer 2

[Image Analyst]

Make sure H and F are the same size.

size(H)
size(f)
size(PQ)
size(F)

What does all that report?

[jagannath mishra]

thanks sir i made it and it works.thanks a lot