struct gl_pixel_attrib {
  float MapRtoR[256] ;
};

static void map_rgba(struct gl_pixel_attrib *attr, float red[]) {
   float rscale = 0.1;
   int i = 0;
   red[i] = attr->MapRtoR[ (int) (red[i]   * rscale) ];
}

int main(int argc, const char *argv[]) {
  return 0;
}