please help>>>how to fix (Matrix dimensions must agree.) error in matlab?

how to fix (Matrix dimensions must agree.) error in matlab?

my code is:

a=imread('lena.bmp');

I=im2double(a);

H=fspecial('log',5);

%convolution

 [r,c]=size(I);

 for y=2:r-1
     for x=2 :c-1
         windowI= I(y:y+3 , x: x+3);
         windowH= H(y:y+1 , x: x+1);
         IH= sum(sum(windowI .* windowH));

     end
 end
 figure(2);
 imshow (IH) ;

i think this line: IH= sum(sum(windowI .* windowH)); causes the error but how to fix it?

Answer 1

[Walter Roberson]

Why are you expecting that a matrix that is 4 x 4 can be multiplied by a matrix that is 2 x 2 ?

[Asma]

i am not expecting that , but i don't know how to fix it. i tried windowH= H(y:y+3 , x: x+3); and it didn't work too. I do't understand how to know the matrix size from the code, i don't know what is +3 in (y:y+3 , x: x+3) or what is -1 in (y=2:r-1) so how to relate between H which is 5*5 and my image which is 215*215? i thought about creating a window to pass on the image, i understand that dimensions must agree but i don't know how to code it

[Walter Roberson]

What is the intent? To tile the 2 x 2 into a 4 x 4 and then multiply?

[Walter Roberson]

Perhaps you should be using conv2() ?

[Asma]

what i am trying to do is coding conv2(I,H), so i can't use it . my problem is that I and H are of different sizes and i don't know how to do the for loops :(

Answer 2

[Youssef Khmou]

hi Asma,

the number of columns of WindowI must be the same as the number of lines in WindowH, take the two blocks with same dimensions or try :

 a=imread('circuit.tif');
 I=im2double(a);
 H=fspecial('log',5);
 [r,c]=size(I);
 a=1;b=1;
 for x=1:r-5 %  ver
     for y=1:c-4
         windowI= I(x:x+4 , y: y+4);
         %windowH= H(x:x+3 , y: y+1);
         IH(x,y)= sum(sum(windowI .* H)); % element wise or matrix product????????

     end

 end
 figure(2); imshow (IH)

[Asma]

element wise. can you please tell me what these numbers mean? +3 or +1 in (windowH= H(x:x+3 , y: y+1); and why do we need to start the loop from x=2? and what does r-3 mean? i am sorry to ask too many silly questions but i am new to coding. now i tried the code below but i got this error: ??? Error using ==> unknown Matrix dimensions must agree.

Error in ==> log_tryy at 11 IH= sum(sum(windowI .* windowH)); % element wise

the code is: a=imread('lena.bmp'); I=im2double(a); H2=fspecial('log',5); H1=flipud(H2); H=fliplr(H1); [r,c]=size(I); for x=2:r-3 for y=2 :c-3 windowI= I(x:x+3 , y: y+3); windowH= H(x:x+3 , y: y+1); IH= sum(sum(windowI .* windowH)); % element wise end end figure(2); imshow (IH)

[Asma]

what should i do to make both windows of size 5*5 for examlpe?

Answer 3

[Asma]

what should i do to make both windows of size 5*5 for examlpe?

[Youssef Khmou]

the size of windowI depends on H, as you fspecal is 5x5 then a window must have the size 5*m , for arbitrary m, try the example i posted