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

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：

hello

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-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：

tree

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

输出到文件：

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：

file

参考