起因
最近完成了研究生毕业设计，在写毕业论文时，老师曾经推荐使用代码来画相关的图，当时时间有些紧，所以没有这样做。最近在看 rapidjson 的文档，看到 miloyip 文档中的图都是用
dot 文件的源代码编译出来的，一查，原来是 graphviz 的源代码。遂用了半天简单学习了下
graphviz 的语法和使用，感觉很不错，以后画图有了一个不错的工具。
graphviz 是一个运用广泛的命令行绘图软体，不过说是绘图软体，它能绘的图并不是一般人想像中的漫画或logo，而是数学意义上的
graph ，比较通俗的说法就是「关系图」。
安装
graphviz 支持 Windows、Mac OS X、FreeBSD、Solaris、Linux 等多种系统
- Ubuntu或Debian下安装很简单：
sudo apt-get install graphviz - Mac下使用 brew
brew install graphviz - Windows 下参考 http://www.graphviz.org/Download_windows.php
入门使用
1. 编写以
dot 为后缀的源代码文件，如：// hello.dot digraph {
hello -> world;}2. 使用
dot 命令编译，如dot hello.dot -T png -o hello.png完整的命令为:＜cmd＞ ＜inputfile＞ -T ＜format＞ -o ＜outputfile＞其中graphviz 的
＜cmd＞ 有好几种，每种使用方法都完全相同，差别只在于渲染出来的图片效果不一样。
man 中的简介是这样的：
| <cmd> | 介绍 |
|---|
| dot | 渲染的图具有明确方向性。 |
| neato | 渲染的图缺乏方向性。 |
| twopi | 渲染的图采用放射性布局。 |
| circo | 渲染的图采用环型布局。 |
| fdp | 渲染的图缺乏方向性。 |
| sfdp | 渲染大型的图，图片缺乏方向性。 |
可以透过
man ＜cmd＞ 取得进一步说明。但还是亲自用用比较容易理解。在本文中，凡没有说明的图，预设都是以
dot 渲染出来的。
3. 查看效果
效果如下：
语法介绍
graphviz使用dot语法来说明，其它语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-listattr-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= ’@’ idedge-stmt = （node-id | subgraph） edgeRHS [attr-list]edgeRHS = edgeop （node-id | subgraph） [edgeRHS]subgraph= [subgraph id] ’{’ stmt-list ’}’ | subgraph idgraphviz 有两种图，一种是无向图
graph ，边用
-- 连接，一种是有向图
digraph ，边用
-> 连接，这个可以很简单的实践。具体的图说明内容包含属性（attr）、节点（node）、边（edge）和子图（subgraph）说明。节点属性如下 ：
| Name | Default | Values |
|---|
| 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 |
边属性如下：
| Name | Default | Values |
|---|
| 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 |
图属性如下：
| Name | Default | Values |
|---|
| 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） |
实例
介绍了上面的语法，实际使用的时候就是学习几个详细的例子，下面是一个二叉树代码：
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调用
除了可以使用
dot 文件编写图形外，也可以使用python编写相关的代码，生成图形文件，安装方法：
pip install pygraphviz引用
PyGraphviz ：
import pygraphviz as pgv初始化图类：
G=pgv.AGraph（）增加结点和边：
G.add_node（"a"） # adds node "a"G.add_edge（"b","c"） # adds edge "b"-"c" （and also nodes "b", "c"）设置属性：
G.graph_attr["label"]="test graphf"G.node_attr["shape"]="circle"G.edge_attr["color"]="red"设置输出的格式：
G.layout（） # default to neatoG.layout（prog="dot"） # use do输出到文件：
G.draw（"file.png"）# write previously positioned graph to PNG fileG.draw（"file.ps",prog="circo"） # use circo to position, write PS file效果：
参考
- dotguide
- Graphviz的使用及中文乱码问题解决 http://www.linuxidc.com/Linux/2016-05/131050.htm
- rapidjson
- PyGraphviz tutorial
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