Code

void blur(int height, int width, RGBTRIPLE image[height][width])
{
    RGBTRIPLE *address;
    RGBTRIPLE *start = &image[0][0];
    RGBTRIPLE *end = &image[height][width];

    //temp num to count
    int numRed = 0;
    int numGreen = 0;
    int numBlue = 0;

    //create duplicate image so values of original image isnt lost.
    int tempSize = sizeof(RGBTRIPLE)*height*width;
    RGBTRIPLE *temp;
    memcpy(temp, image, tempSize);

    for(int i = 0; i < height; i++)
    {
        for(int j = 0; j < width; j++)
        {
             //sum of numbers
            int sumRed = 0;
            int sumbGreen = 0;
            int sumBlue = 0;

            //check in 3x3 grids through entire image
            for(int x = i - 1; x < x + 1; x++)
            {
                for(int y = j - 1; y < j + 1; y++)
                {
                    //check if I am not accessing outside array bounds by checkng if the position is between where the array starts and ends
                    *address = image[x][y];
                    if(!(address > end || address < start))
                    {
                        sumRed += temp[i][j].rgbtRed;
                        sumBlue += temp[i][j].rgbtBlue;
                        sumGreen += temp[i][j].rgbtGreen;
                    }
                }
            }

            //initialise new image
            sumRed = sumRed/9.0;
            sumGreen = sumGreen/9.0;
            sumBlue = sumBlue/9.0;

            image[i][j].rgbtRed = sumRed;
            image[i][j].rgbtGreen = sumGreen;
            image[i][j].rgbtBlue = sumBlue;
        }
    }
}