#include <iostream>

#define STB_IMAGE_IMPLEMENTATION
#include "stb/stb_image.h"

#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb/stb_image_write.h"


unsigned char filter[] = {1,2,1,
                2,4,2,
                1,2,1
               };
using namespace std;
unsigned char* makeStuff(unsigned char *img, int w,int h, int ch)
{
    size_t s = (w)*(h)*ch;
    unsigned char *res = (unsigned char *)malloc(s);

unsigned char p1,p2,p3,p4,p5,p6,p7,p8,p9;
    for(int x=1; x<h; x++)
    {
        for(int y=1; y<w; y++)
        {
            for(int c=0; c<ch; c++)
            {
                p1 = (img[ch*( (x-1) *w  +  (y-1))  +c]*filter[0]);
                p2 = (img[ch*( (x)   *w  +  (y-1))  +c]*filter[1]);
                p3 = (img[ch*( (x+1) *w  +  (y-1))  +c]*filter[2]);

                p4 = (img[ch*( (x-1) *w  +  (y))    +c]*filter[3]);
                p5 = (img[ch*( (x)   *w  +  (y))    +c]*filter[4]);
                p6 = (img[ch*( (x+1) *w  +  (y))    +c]*filter[5]);

                p7 = (img[ch*( (x-1) *w  +  (y+1))  +c]*filter[6]);
                p8 = (img[ch*( (x)   *w  +  (y+1))  +c]*filter[7]);
                p9 = (img[ch*( (x+1) *w  +  (y+1))  +c]*filter[8]);

                res[ch*(x*w+y)+c] = ((p1+p2+p3+p4+p5+p6+p7+p8+p9))/16;
            }

        }
    }
    return res;
}

int main()
{
    string path = "t.jpg";
    int w,h,ch,gch;
    unsigned char *image = stbi_load(path.c_str(),&w,&h,&ch,0);

    unsigned char *im = makeStuff(image,w,h,ch);

    stbi_write_jpg("t2.jpg",w,h,ch,im,100);

    stbi_image_free(image);

    return 0;
}