for (int y = 0; y < rowLength; y+=2)
{
	for (int x = 0; x < colLength; x++)
	{
		if ((y+1) < rowLength)
   			data[y, x + 1] = data[y + 1, x] = data[y + 1, x + 1] = data[y, x++];
    	else
    		data[y, x + 1] = data[y, x++];
   }
}