sclass RecognitionGrid {
  double cellW, cellH;
  int rows, cols;
  Cell[] cells;
  
  *() {}
  *(double *cellW, double *cellH, int w, int h) {
    rows = iceil(w/cellW);
    cols = iceil(h/cellH);
    cells = new Cell[rows*cols];
  }
  
  sclass Cell {
    int outerColor, middleColor, centerColor; // RGB + alpha
  }
  
  Cell getCell(int col, int row) {
    ret inRange(col, 0, cols) && inRange(row, 0, rows) ? cells[row*cols+col] : null;
  }
  
  Rect cellRect(int col, int row) {
    ret rectFromPoints(iround(col*cellW), iround(row*cellH),
      iround((col+1)*cellW), iround((row+1)*cellH));
  }
}