# finding sum of nxn matirx data

Hi,

i have an array of pixel data. x,y value of each pixel is known.
I have to find the sum of nxn pixels around the given pixel(including the pixel)

that is for the pixel at (x,y). 3x3 sum will be
(x-1,y+1)+(x,y+1)+(x+1,y+1)+(x+1,y)+(x,y)+(x+1,y-1)+(x,y-1)+(x-1,y-1)+(x-1,y).

This calculation should be dynamic, that is for any nxn , the sum should be computed.
i would like to know the way to go abt doing this.

regards,
ric
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Commented:
you have to create a function:

function filter_pixel(x,y,n)
if x>1 AND y>1 and x<n-1 and y<n-1 then
filter_pixel=(x-1,y+1)+(x,y+1)+(x+1,y+1)+(x+1,y)+(x,y)+(x+1,y-1)+(x,y-1)+(x-1,y-1)+(x-1,y)
else
all the border' case
else

end if
end function

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Commented:
Why are you trying to do this?  Is this homework perhaps?

mlmcc
Commented:
Try it with a nested loop

funct filterpixel(x,y,n)
int sum=0
for int i=x-n to x+n
for int k=y-n to y+n
sum += getPixelValueAtPosition(i,k)
return sum
end funct

and implement a function named getPixelValueAtPosition() that checks if pixel coordinates are inside your image and returns the pixel value for it.

Above code is not valid for any programming language, so if it is homework, it's not a complete solution. Is that ok this way, mlmcc?
Commented:
You will need to subtract the value at (x,y)

mlmcc
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