how i can get pixel with open cv using c programming?

I try work with open cv 2.4.9 after I convert my imag rgb tobinary black nd white , I want get pixel o image , because when I do :

FILE *pFile=fopen("image_png.png","r+b"); int c;

do {
  c = fgetc  (pFile);
  printf("int -- %d n",c);
  //printf ("int -- %d ",a);
  //a++;
} while (c != EOF);
    fclose(pFile);

the problem is I seen all pixel data+header but I need to not use the header , I want get access directly to data ? thnx