C++ Floyd-Steinberg 24bit RGB color

floydSteinberg.h

unsigned char * floydSteinberg(unsigned char * source, int w, int h){
     unsigned char * newSource;
     for(int i=0; i<(h*3); i++){
        for(int j=0; j<w; j++) {
           int ci = i*w+j;
           int cc = source[ci];
           int rc = (cc<128?0:255);
           int err = cc-rc;
           source[ci] = rc;
           if(j+1<w) source[ci+1] += (err*7)>>4;
           if(i+1==h) continue;
           if(j  >0) source[ci+w-1] += (err*3)>>4;
           source[ci+w] += (err*5)>>4;
           if(j+1<w) source[ci+w+1] += (err*1)>>4;
       }
    }
     newSource = source;
     return newSource;
}