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，老師曾經推薦使用程式碼來畫相關的圖，當時時間有些緊，所以沒有這樣做。最近在看 rapidjson 的文件，看到 miloyip 文件中的圖都是用 dot 檔案的原始碼編譯出來的，一查，原來是 graphviz 的原始碼。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列繪圖軟體，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「關係圖」。

安裝

graphviz 支援 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 為字尾的原始碼檔案，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	渲染的圖採用放射性布局。
circo	渲染的圖採用環型布局。
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. 檢視效果

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 -- 連線，一種是有向圖 digraph ，邊用 -> 連線，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 ：

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

邊屬性如下：

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

圖屬性如下：

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)

範例

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，下面是一個二元樹程式碼：

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呼叫

除了可以使用 dot 檔案編寫圖形外，也可以使用python編寫相關的程式碼，生成圖形檔案，

安裝方法：

pip install pygraphviz

參照 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')

設定屬性：

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

設定輸出的格式：

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

輸出到檔案：

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

本文永久更新連結地址：http://www.linuxidc.com/Linux/2016-05/131055.htm