int cellWidth = 10, cellHeight = 10;
int maxCols = 11, maxRows = 128;
int white = 255, black = 0;

/**
 * Converts a natural binary 32 bit value to Gray code.
 * @param natural The natural binary value to convert.
 * @return The Gray code equivalent value.
 */
int encodeGray(int natural) {
  return natural ^ natural >>> 1;
}

void setup()
{
  size(maxRows * cellWidth, maxCols * cellHeight);
}

void draw() {
  background(white);
  for (int row = 0; row < maxRows; row++)
  {
    drawCell(0, row, 0);
    drawCell(maxCols - 1, row, 0);
    int temp = encodeGray(row);
    for(int bit = 0; bit < 8; bit++)
    {
      // if the bit is set, use black, otherwise use white.
      int fill = (temp & 1) != 0 ? black : white;
      temp = temp >> 1;
      drawCell(maxCols - bit - 3, row, fill);
    }
  }
}

void drawCell(int x, int y, int fill) {
  fill(fill);
  noStroke();
  rect(y * cellWidth, x * cellWidth, cellHeight, cellWidth);
}