Need help to solve program errors

I am trying to create a median filter program under C++ with the use of a image procesing class library, calls picture.h, so I've written my code, but the compiler keep giving me a error message that I don't quite understand. Can somebody kindly explain to me what's going wrong with my program and suggest some useful resource that I possible can look up when I get stuck in this kind of situation. Thanks in advance.

Code:

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#include "usage.h"
#include "picture.h"
int median(int& pel, const int **buf)
        {        char array[9];
                array[0]=buf[-1][-1];
                array[1]=buf[-1][0];
                array[2]=buf[-1][1];
                array[3]=buf[0][-1];
                array[4]=buf[0][0];
                array[5]=buf[0][1];
                array[6]=buf[1][-1];
                array[7]=buf[1][0];
                array[8]=buf[1][1];
               
        for (int i=0; i<=9; i++)
        {
                for(int y=0; y<=8; y++)
                {
                        if(array[y]>array[y+1])
                        {
                        int temp = array[y+1];
                        array[y+1] = array[y];
                        array[y] = temp;
                        }
                }
        pel = array[4];
        return 0;
        }
int main(int argc, char *argv[])
        {
        usage("median inpic outpic");
        picture_of_int in(argv[1]);
        picture_of_int out(in,median);
        out.write(argv[2]);
        return 1;
        }

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Error message under the compiler:

Quote:

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median2.cpp: In function 'int median(int&, const int**)':
median2.cpp:30: error: a function-definition is not allowed here before '{' token
median2.cpp:36: error: expected `}' at end of input

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You are missing a closing bracket before 'pel = array[4];'. Besides, accessing negative indices is not a good idea, I'm pretty sure it will crash your program.

Quote:

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Originally Posted by Desolation

You are missing a closing bracket before 'pel = array[4];'. Besides, accessing negative indices is not a good idea, I'm pretty sure it will crash your program.

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Thanks so much for pointing that out, I've been spending hours on that, but couldn't spot that out.

Code:

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char array[9];
                array[0]=buf[-1][-1];
                array[1]=buf[-1][0];
                array[2]=buf[-1][1];
                array[3]=buf[0][-1];
                array[4]=buf[0][0];
                array[5]=buf[0][1];
                array[6]=buf[1][-1];
                array[7]=buf[1][0];
                array[8]=buf[1][1];

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Is there a way of using "for" loop or some other loop to respresent this array, so that I can change the parameter of the median filter. At the moment, this is a 3x3 median filter. I would like program something can change its parameter, i.e. 3x3, 5x5, 7x7... 15x15 without reprogramming the source code.

You'd probably need nested for loops of depth two.

Code:

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for(i) // each row
{
    for(j) // each element in the current row
    {
        array[i * width + j] //this is the corresponding element
    }
}

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And yes, negative indices aren't a really good idea.

Quote:

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Originally Posted by jafet

And yes, negative indices aren't a really good idea.

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Sorry, I forgot to mention in the first post that the class library "picture.h" allows "pel"'s to use negative indices for neighbourhood operators, i.e. buf[-1][-1] is the top left corner of the centre pixel. But this only apply to the functions which use pel only.

Quote:

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You'd probably need nested for loops of depth two.

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This method is been great help, thanks!