用latex直接繪制流程圖，這樣的圖像排列整齊，很好畫

\begin{tikzpicture}[

nodex/.style={draw, minimum width=22mm, minimum height=8mm, node distance=13mm},

nodee/.style={draw, minimum width=10mm, minimum height=8mm, node distance=13mm},

nodey/.style={minimum width=5mm, minimum height=8mm, node distance=13mm},

]

\node[nodex] (x0) {$ x[0] $};

\node[nodex, right =(0mm of x0.east)] (x1) {$ x[1] $};

\node[nodex, right =(0mm of x1.east)] (x2) {$ x[2] $};

\node[nodex, right =(0mm of x2.east)] (x3) {$ \cdots $};

\node[nodex, right =(0mm of x3.east)] (xn) {$ x[n] $};

\node[nodey, below of = x0] (y0) {$\oplus$};

\node[nodey, below of = x1] (y1) {$\oplus$};

\node[nodey, below of = x2] (y2) {$\oplus$};

\node[nodey, below of = x3] (y3) {$\oplus$};

\node[nodey, below of = xn] (yn) {$\oplus$};

\node[nodey, left of = y0] (p0) {\tiny$P(L,0)$};

\node[nodey, left of = y1] (p1) {\tiny$P(L,1)$};

\node[nodey, left of = y2] (p2) {\tiny$P(L,2)$};

\node[nodey, left of = y3] (p3) {\tiny$P(L,\cdot)$};

\node[nodey, left of = yn] (pn) {\tiny$P(L,n)$};

\node[nodee, below of=y0] (e0) {$ E(k,\cdot) $};

\node[nodee, below of=y1] (e1) {$ E(k,\cdot) $};

\node[nodee, below of=y2] (e2) {$ E(k,\cdot) $};

\node[nodee, below of=y3] (e3) {$ E(k,\cdot) $};

\node[nodee, below of=yn] (en) {$ E(k,\cdot) $};

\node[nodey, below of = e0] (y10) {};

\node[nodey, below of = e1] (y11) {$\oplus$};

\node[nodey, below of = e2] (y12) {$\oplus$};

\node[nodey, below of = e3] (y13) {$\oplus$};

\node[nodey, below of = en] (y1n) {$\oplus$};

\node[nodey, left of = y11] (p11) {\tiny$P(PM,1)$};

\node[nodey, left of = y12] (p12) {\tiny$P(PM,2)$};

\node[nodey, left of = y13] (p13) {\tiny$P(PM,\cdot)$};

\node[nodey, left of = y1n] (p1n) {\tiny$P(PM,n)$};

\node[nodee, below of=y10] (e10) {$ E(k,\cdot) $};

\node[nodee, below of=y11] (e11) {$ E(k,\cdot) $};

\node[nodee, below of=y12] (e12) {$ E(k,\cdot) $};

\node[nodee, below of=y13] (e13) {$ E(k,\cdot) $};

\node[nodee, below of=y1n] (e1n) {$ E(k,\cdot) $};

\node[nodey, below of = e10] (y20) {$\oplus$};

\node[nodey, below of = e11] (y21) {$\oplus$};

\node[nodey, below of = e12] (y22) {$\oplus$};

\node[nodey, below of = e13] (y23) {$\oplus$};

\node[nodey, below of = e1n] (y2n) {$\oplus$};

\node[nodey, left of = y20] (p20) {\tiny$P(L,0)$};

\node[nodey, left of = y21] (p21) {\tiny$P(L,1)$};

\node[nodey, left of = y22] (p22) {\tiny$P(L,2)$};

\node[nodey, left of = y23] (p23) {\tiny$P(L,\cdot)$};

\node[nodey, left of = y2n] (p2n) {\tiny$P(L,n)$};

\node[nodex, below of = y20] (y30) {$ y[0] $};

\node[nodex, below of = y21] (y31) {$ y[1] $};

\node[nodex, below of = y22] (y32) {$ y[2] $};

\node[nodex, below of = y23] (y33) {$ \cdots $};

\node[nodex, below of = y2n] (y3n) {$ y[n] $};

\draw[->] (x0) -- (y0);

\draw[->] (x1) -- (y1);

\draw[->] (x2) -- (y2);

\draw[->] (x3) -- (y3);

\draw[->] (xn) -- (yn);

\draw[->] (p0) -- (y0);

\draw[->] (p1) -- (y1);

\draw[->] (p2) -- (y2);

\draw[->] (p3) -- (y3);

\draw[->] (pn) -- (yn);

\draw[->] (y0) -- (e0);

\draw[->] (y1) -- (e1);

\draw[->] (y2) -- (e2);

\draw[->] (y3) -- (e3);

\draw[->] (yn) -- (en);

\draw[->] (e0) -- node{\tiny$ PPP_0 $}(y10);

\draw[->] (e1) -- node{\tiny$ PPP_1 $}(y11);

\draw[->] (e2) -- node{\tiny$ PPP_2 $}(y12);

\draw[->] (e3) -- node{\tiny$ PPP_i $}(y13);

\draw[->] (en) -- node{\tiny$ PPP_n $}(y1n);

\draw[->] (p11) -- (y11);

\draw[->] (p12) -- (y12);

\draw[->] (p13) -- (y13);

\draw[->] (p1n) -- (y1n);

\draw[->] (y11) -- node{\tiny$ CCC_1 $}(e11);

\draw[->] (y12) -- node{\tiny$ CCC_2 $}(e12);

\draw[->] (y13) -- node{\tiny$ CCC_i $}(e13);

\draw[->] (y1n) -- node{\tiny$ CCC_n $}(e1n);

\draw[->] (e10) -- (y20);

\draw[->] (e11) -- (y21);

\draw[->] (e12) -- (y22);

\draw[->] (e13) -- (y23);

\draw[->] (e1n) -- (y2n);

\draw[->] (p20) -- (y20);

\draw[->] (p21) -- (y21);

\draw[->] (p22) -- (y22);

\draw[->] (p23) -- (y23);

\draw[->] (p2n) -- (y2n);

\draw[->] (y20) -- (y30);

\draw[->] (y21) -- (y31);

\draw[->] (y22) -- (y32);

\draw[->] (y23) -- (y33);

\draw[->] (y2n) -- (y3n);

\end{tikzpicture}

還要加上

\usetikzlibrary{chains}