Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

Become a Premium Member and unlock a new, free course in leading technologies each month.

Solved

Posted on 2008-10-29

Hei!

I have a problem with image processing in matlab for a lab course. I have only basic matlab knowledge and hope to be able to explain my problem with my basic school english...

The code attached is a loop in matlab to calculate a "moving average" on a picture. The first and second loop is for the rows (german: Zeilen) and columns (Spalten) of the picture (P), the third and fourth loop is for the rows and columns of the filter matrix (kern). Then it sums up the values of the filter matrix and divides it by the sum of the loadings. ewr and ewc are needed to calculate the new border of the image. (zero padding or replicate)

My question:

I need a way to do this with fast matrix/vector operations if possible.

I am not allowed to use any imfilter, conv, conv2, block-processing or sliding-window functions.

What i can imagine is to exchange the 2 inner loops by a matrix-multiplication. I would multiply the filter matrix with the right submatrix of the image. But to replace the outer loops i need to know the position/index to know wich submatrix i have to multiply...

I read something about the not so well known accumarray() function but i don't know how i can use this for 2D operation.

Maybe someone can give me a hint...

Thanks in advance!

Greetings from Vienna, Austria.

beta

I have a problem with image processing in matlab for a lab course. I have only basic matlab knowledge and hope to be able to explain my problem with my basic school english...

The code attached is a loop in matlab to calculate a "moving average" on a picture. The first and second loop is for the rows (german: Zeilen) and columns (Spalten) of the picture (P), the third and fourth loop is for the rows and columns of the filter matrix (kern). Then it sums up the values of the filter matrix and divides it by the sum of the loadings. ewr and ewc are needed to calculate the new border of the image. (zero padding or replicate)

My question:

I need a way to do this with fast matrix/vector operations if possible.

I am not allowed to use any imfilter, conv, conv2, block-processing or sliding-window functions.

What i can imagine is to exchange the 2 inner loops by a matrix-multiplication. I would multiply the filter matrix with the right submatrix of the image. But to replace the outer loops i need to know the position/index to know wich submatrix i have to multiply...

I read something about the not so well known accumarray() function but i don't know how i can use this for 2D operation.

Maybe someone can give me a hint...

Thanks in advance!

Greetings from Vienna, Austria.

beta

```
for ip = (ewr+1):(rc(1)+(ewr)) %Zeilen
for np = (ewc+1):(rc(2)+ewc)%Spalten
for Z = -ewr:ewr
for S = -ewc:ewc
PF(ip,np)=PF(ip,np)+P(ip+Z,np+S)*kern(Z+ewr+1,S+ewc+1);
end
end
PF(ip,np)=PF(ip,np)/(sum(sum(kern,1),2));
end
end
```

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

- Help others & share knowledge
- Earn cash & points
- Learn & ask questions

1 Comment

```
for ip = (row_ext+1):(rc(1)+row_ext) %rows
for np = (col_ext+1):(rc(2)+col_ext)%columns
PF(ip,np)=sum(sum(kern.*P( (ip-row_ext):(ip+row_ext) , (np-col_ext):(np+col_ext)),1),2)/sum(sum(kern,1),2);
end
end
```

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Course of the Month9 days, 8 hours left to enroll

Join the community of 500,000 technology professionals and ask your questions.