how to do convolution without commands

I=img; 
b=rgb2gray(I); [Gx,Gy]=imgradientxy(b); figure();
[Gmag, Gdir] = imgradient(Gx,Gy); 
gx=[-1 0 1; -2 0 2; -1 0 1];
gy=transpose(gx);
gi=gray2ind(b);
Fx=conv2(double(b),gx,'same')

In the above coding how to do convolution without conv2

Answer 1

[Ameer Hamza]

See the answer by Iman Ansari on this question: https://www.mathworks.com/matlabcentral/answers/75073-built-in-2d-convolution-vs-for-loop-convolution-differences

[Sivakumar Rajagopal]

Iman Ansari used the function

res = conv2(A,M,'valid');

for computtion.

I need to implement convolution without using conv2

[Ameer Hamza]

See the calculation of res2. That code compares built-in convolution with for loop.

[Sivakumar Rajagopal]

Ok. Thanks.