replace png with pdf graphics

publications/whitepaper/druid.tex

@@ -216,7 +216,7 @@ Figure~\ref{fig:cluster}.
 
 \begin{figure*}
 \centering
-\includegraphics[width = 4.5in]{cluster}
+\includegraphics[width = 4.51in]{cluster}
 \caption{An overview of a Druid cluster and the flow of data through the cluster.}
 \label{fig:cluster}
 \end{figure*}
@@ -900,6 +900,7 @@ well.
 \begin{figure}
 \centering
 \includegraphics[width = 2.3in]{tpch_scaling}
+\includegraphics[width = 2.3in]{tpch_scaling_factor}
 \caption{Druid scaling benchmarks -- 100GB TPC-H data.}
 \label{fig:tpch_scaling}
 \end{figure}