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:

#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;
	}

Error message under the compiler:

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

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.

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.

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

Code:

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];

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:

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

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

Originally Posted by jafet

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

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.

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

This method is been great help, thanks!