繪圖工具Graphviz學習使用

起因

最近完成了研究生畢業設計，在寫畢業論文時，老師曾經推薦使用代碼來畫相關的圖，當時時間有些緊，所以沒有這樣做。最近在看 rapidjson 的文檔，看到 miloyip 文檔中的圖都是用 dot 文件的源代碼編譯出來的，一查，原來是 graphviz 的源代碼。遂用了半天簡單學習了下 graphviz 的語法和使用，感覺很不錯，以後畫圖有了一個不錯的工具。

graphviz 是一個運用廣泛的命令行繪圖軟體，不過說是繪圖軟體，它能繪的圖並不是一般人想像中的漫畫或logo，而是數學意義上的 graph ，比較通俗的說法就是「關系圖」。

安裝

graphviz 支持 Windows、Mac OS X、FreeBSD、Solaris、Linux 等多種系統

• Ubuntu或Debian下安裝很簡單：

    sudo apt-get install graphviz
  

• Mac下使用 brew

    brew install graphviz
  

• Windows 下參考 http://www.graphviz.org/Download_windows.php

入門使用

1. 編寫以 dot 為後綴的源代碼文件，如：

// hello.dot digraph {

    	hello -> world;
}

2. 使用 dot 命令編譯，如

dot hello.dot -T png -o hello.png

完整的命令為:

＜cmd＞ ＜inputfile＞ -T ＜format＞ -o ＜outputfile＞

其中graphviz 的 ＜cmd＞ 有好幾種，每種使用方法都完全相同，差別只在於渲染出來的圖片效果不一樣。 man 中的簡介是這樣的：

<cmd>介紹 dot 渲染的圖具有明確方向性。 neato 渲染的圖缺乏方向性。 twopi 渲染的圖采用放射性布局。 circo 渲染的圖采用環型布局。 fdp 渲染的圖缺乏方向性。 sfdp 渲染大型的圖，圖片缺乏方向性。

可以透過 man ＜cmd＞ 取得進一步說明。但還是親自用用比較容易理解。在本文中，凡沒有說明的圖，預設都是以 dot 渲染出來的。

3. 查看效果

效果如下：

語法介紹

graphviz使用dot語法來說明，其它語法可以用形式化的描述如下：

graph         = [strict] (digraph | graph) id ’{’ stmt-list ’}’
stmt-list     = [stmt [’;’] [stmt-list ] ]
stmt          = attr-stmt | node-stmt | edge-stmt | subgraph | id ’=’ id 
attr-stmt     = (graph | node | edge) attr-list
attr-list     = ’[’ [a-list ] ’]’ [attr-list] 
a-list        = id ’=’ id [’,’] [a-list] 
node-stmt     = node-id [attr-list]
node-id       = id [port]
port          = port-location [port-angle] | port-angle [port-location] 
port-location = ’:’ id|’:’ ’(’id’,’id’)’
port-angle    = ’@’ id
edge-stmt     = (node-id | subgraph) edgeRHS [attr-list]
edgeRHS       = edgeop (node-id | subgraph) [edgeRHS]
subgraph      = [subgraph id] ’{’ stmt-list ’}’ | subgraph id

graphviz 有兩種圖，一種是無向圖 graph ，邊用 -- 連接，一種是有向圖 digraph ，邊用 -> 連接，這個可以很簡單的實踐。

具體的圖說明內容包含屬性(attr)、節點(node)、邊(edge)和子圖(subgraph)說明。

節點屬性如下 ：

NameDefaultValues color black node shape color comment any string (format-dependent) distortion 0.0 node distortion for shape=polygon fillcolor lightgrey/black node fill color fixedsize false label text has no affect on node size fontcolor black type face color fontname Times-Roman font family fontsize 14 point size of label group name of node’s group height .5 height in inches label node name any string layer overlay range all, id or id:id orientation 0.0 node rotation angle peripheries shape-dependent number of node boundaries regular false force polygon to be regular shape ellipse node shape; see Section 2.1 and Appendix E shapefile external EPSF or SVG custom shape file sides 4 number of sides for shape=polygon skew 0.0 skewing of node for shape=polygon style graphics options, e.g. bold, dotted, filled; cf. Section 2.3 URL URL associated with node (format-dependent) width .75 width in inches z 0.0 z coordinate for VRML output

邊屬性如下：

NameDefaultValues arrowhead normal style of arrowhead at head end arrowsize 1.0 scaling factor for arrowheads arrowtail normal style of arrowhead at tail end color black edge stroke color comment any string (format-dependent) constraint true use edge to affect node ranking decorate if set, draws a line connecting labels with their edges dir forward forward, back, both, or none fontcolor black type face color fontname Times-Roman font family fontsize 14 point size of label headlabel label placed near head of edge headport n,ne,e,se,s,sw,w,nw headURL URL attached to head label if output format is ismap label edge label labelangle -25.0 angle in degrees which head or tail label is rotated off edge labeldistance 1.0 scaling factor for distance of head or tail label from node labelfloat false lessen constraints on edge label placement labelfontcolor black type face color for head and tail labels labelfontname Times-Roman font family for head and tail labels labelfontsize 14 point size for head and tail labels layer overlay range all, id or id:id lhead name of cluster to use as head of edge ltail name of cluster to use as tail of edge minlen 1 minimum rank distance between head and tail samehead tag for head node; edge heads with the same tag are sametail merged onto the same port style tag for tail node; edge tails with the same tag are merged onto the same port taillabel graphics options, e.g. bold, dotted, filled; cf. Section 2.3 tailport label placed near tail of edge n,ne,e,se,s,sw,w,nw tailURL URL attached to tail label if output format is ismap weight 1 integer cost of stretching an edge

圖屬性如下：

NameDefaultValues bgcolor background color for drawing, plus initial fill color center false center drawing on page clusterrank local may be global or none color black for clusters, outline color, and fill color if fillcolor not defined comment any string (format-dependent) compound false allow edges between clusters concentrate false enables edge concentrators fillcolor black cluster fill color fontcolor black type face color fontname Times-Roman font family fontpath list of directories to search for fonts fontsize 14 point size of label label any string labeljust centered ”l” and ”r” for left- and right-justified cluster labels, respectively labelloc top ”t” and ”b” for top- and bottom-justified cluster labels, respectively layers id:id:id… margin .5 margin included in page, inches mclimit 1.0 scale factor for mincross iterations nodesep .25 separation between nodes, in inches. nslimit if set to f, bounds network simplex iterations by (f)(number of nodes) when setting x-coordinates nslimit1 if set to f, bounds network simplex iterations by (f)(number of nodes) when ranking nodes ordering if out out edge order is preserved orientation portrait if rotate is not used and the value is landscape, use landscape orientation page unit of pagination, e.g. “8.5,11” pagedir BL traversal order of pages quantum if quantum ¿ 0.0, node label dimensions will be rounded to integral multiples of quantum rank same, min, max, source or sink rankdir TB LR (left to right) or TB (top to bottom) ranksep .75 separation between ranks, in inches. ratio approximate aspect ratio desired, fill or auto remincross if true and there are multiple clusters, re-run crossing minimization rotate If 90, set orientation to landscape samplepoints 8 number of points used to represent ellipses and circles on output (cf. Appendix C searchsize 30 maximum edges with negative cut values to check when looking for a minimum one during network simplex size maximum drawing size, in inches style graphics options, e.g. filled for clusters URL URL associated with graph (format-dependent)

實例

介紹了上面的語法，實際使用的時候就是學習幾個詳細的例子，下面是一個二叉樹代碼：

digraph g {
    node [shape = record,height=.1];
    node0[label = "<f0> |<f1> G|<f2> "];
    node1[label = "<f0> |<f1> E|<f2> "];
    node2[label = "<f0> |<f1> B|<f2> "];
    node3[label = "<f0> |<f1> F|<f2> "];
    node4[label = "<f0> |<f1> R|<f2> "];
    node5[label = "<f0> |<f1> H|<f2> "];
    node6[label = "<f0> |<f1> Y|<f2> "];
    node7[label = "<f0> |<f1> A|<f2> "];
    node8[label = "<f0> |<f1> C|<f2> "];
    "node0":f2 -> "node4":f1;
    "node0":f0 -> "node1":f1;
    "node1":f0 -> "node2":f1;
    "node1":f2 -> "node3":f1;
    "node2":f2 -> "node8":f1;
    "node2":f0 -> "node7":f1;
    "node4":f2 -> "node6":f1;
    "node4":f0 -> "node5":f1;
}

效果如下：

python調用

除了可以使用 dot 文件編寫圖形外，也可以使用python編寫相關的代碼，生成圖形文件，

安裝方法：

pip install pygraphviz

引用 PyGraphviz ：

import pygraphviz as pgv

初始化圖類：

G=pgv.AGraph()

增加結點和邊：

G.add_node('a') # adds node 'a'
G.add_edge('b','c') # adds edge 'b'-'c' (and also nodes 'b', 'c')

設置屬性：

G.graph_attr['label']='test graphf'
G.node_attr['shape']='circle'
G.edge_attr['color']='red'

設置輸出的格式：

G.layout() # default to neato
G.layout(prog='dot') # use do

輸出到文件：

G.draw('file.png')  # write previously positioned graph to PNG file
G.draw('file.ps',prog='circo') # use circo to position, write PS file

效果：

參考

• dotguide
• Graphviz的使用及中文亂碼問題解決 http://www.linuxidc.com/Linux/2016-05/131050.htm
• rapidjson
• PyGraphviz tutorial