HTML5 (8) -- detailed explanation of SVG path

Front end person 2021-08-09 16:16:09
html5 html detailed explanation svg


path yes SVG The most powerful of the basic shapes , Not only can we realize our last article 《HTML5( 7、 ... and )——SVG Basic introduction 》 in , To introduce the SVG Predefined line、rect、circle、ellipse、line、polyline、polygon Six basic shapes . You can also achieve more complex effects , We began to learn path How to apply .

One 、path Detailed explanation of route

1.1、path command

path Used to define a path , The command controls this path , The following commands are available for path data :

HTML5( 8、 ... and )——SVG And path Detailed explanation

 

notes : All the above commands can be in case , The difference is that uppercase commands represent absolute positioning , Lowercase means relative positioning .

1.2、path Use

Use the syntax :<path d=" M x1 y1 L x2 y2 H x3.... " stroke="red"></path>

d: Outgoing path ,d The values in are composed of multiple commands .

Arc is widely used in practical scenes ,A There are many parameters in the command ,large-arc and sweep It's hard to understand , Introduce in detail .

Use the syntax :<path d="M x y A rx ry x-axis-rotation large-arc sweep x y"></path>

HTML5( 8、 ... and )——SVG And path Detailed explanation

 

As shown in the figure above ,A To B Two points plus radius , You can draw 4 It's an arc , Which one to choose ? Is the large-arc ( Is it a big arc ) and sweep( Do you want to rotate it anticlockwise ) Two parameters determine .

large-arc = 1 Indicates that the radian is greater than or equal to 180, On the contrary, it is less than 180.

sweep = 0 It means to rotate counter clockwise , Rotate clockwise anyway .

So the above 4 The two parameters corresponding to each arc are :

  • 1:(0 0)
  • 2:(0,1)
  • 3:(1,1)
  • 4:(1,0)

eg: Use path Draw a line 、 Semicircle 、 A straight line , Connected to form an arch bridge , The code is as follows :

<svg version="1.1" height="400" width="550"> <path d=" M 0 100 //(0,100) Starting point L 100 100 //  Draw a line directly to (100,100) A 100 100 0 1 1 300 100 //  Draw an arc L 400 100 // Draw a straight line to (400,100) " stroke="black" stroke-width="1" fill="none"></path> </svg>

The operation results are as follows :

HTML5( 8、 ... and )——SVG And path Detailed explanation

 

You can modify the above A in Parameter observe the change of semicircle .

1.3、js operation path

We use it a lot js Dynamic addition 、 Remove elements, etc , Can achieve more cool special effects , that js Can operate dynamically path Do you ? How to operate ?

We use js Dynamically draw a case with the above eg1 Same path.

<svg version="1.1" height="400" width="550" id="svg"></svg>
<script >
window.onload = function(){
let svg = document.getElementById("svg")
let path = document.createElement("path")
path.setAttribute('d',"M 0 100 L 100 100 A 100 100 0 1 1 300 100 L 400 100")
svg.appendChild(path)
}
</script>

 

Run code , We found no errors , And it didn't show any results .

add to :alert(path), Print out  [object HTMLUnknownElement].

explain html hold path As ordinary html The tag resolves , I found that I didn't recognize the label , So the page has no effect , At this point, we need to introduce a new method of creating elements .

createElementNS Introduce

createElementNS Is to create a namespace with a specified name URI And elements that qualify names .

Use the syntax :document.createElementNS(namespaceURI, qualifiedName[, options]);

  • namespaceURI  Specifies the namespace associated with the element URI String . Of the created element namespaceURI (en-US) Attributes use namespaceURI Initialize with the value of .
  • qualifiedName A string that specifies the type of element to create . Of the created element nodeName (en-US) Attributes use qualifiedName Initialize with the value of .
  • options An optional that contains a single attribute ElementCreationOptions object , Its value is pre used customElements.define() The label name of the defined custom element . For backward compatibility with earlier versions of the custom element specification , Some browsers allow you to use strings instead of objects here , Where the value of the string is the label name of the custom element .

Generate path Element code :

let path = document.createElementNS(
"http://www.w3.org/2000/svg",
"path"
)

 

js When manipulating properties ,html Elements and SVG Element difference :

Ordinary html Elements can be used in two ways :

  1. setAttribute(x,val) / getAttribute(x)
  2. obj.x

SVG There is only one way to operate

  1. setAttribute(x,val) / getAttribute(x)

eg3: Pie charts are particularly common in charts , Let's start with js Dynamically draw a sector arc .

<svg version="1.1" height="400" width="550" id="svg"></svg>
<script >
function d2a(n){
return Math.PI*n/180
 }
function pie(ang1,ang2,r,cx,cy){
let svg = document.getElementById("svg")
let path = document.createElementNS("http://www.w3.org/2000/svg","path")
let arr = []
let x1 = cx + Math.sin(d2a(ang1))*r
let y1 = cy - Math.cos(d2a(ang1))*r
let x2 = cx + Math.sin(d2a(ang2))*r
let y2 = cy - Math.cos(d2a(ang2))*r
arr.push(`M ${cx} ${cy} L ${x1} ${y1} A ${r} ${r} 0 0 1 ${x2} ${y2} `)
arr.push("Z")
path.setAttribute('d',arr.join(' '))
svg.appendChild(path)
}
window.onload = function(){
pie(20,180,200,200,200)
}
</script>

 

The results are shown in the figure :

HTML5( 8、 ... and )——SVG And path Detailed explanation

 

If you are interested , You can modify the start angle and end angle by yourself , You can draw arcs with many different effects .

Two 、 Style and priority

The above code

<path d="
M 0 100 //(0,100) Starting point
L 100 100 // Draw a line directly to (100,100)
" stroke="black" stroke-width="1" fill="none"></path>

The above attributes can be divided into two categories :

  • Can only be attribute - That determines the shape of a graph or path
  • You can put styles - Visual effects

Such as troke、fill And so on is to control the visual effect , Such attributes can be placed in style In the style . So the above code can be rewritten as :

<path d="
M 0 100 //(0,100) Starting point
L 100 100 // Draw a line directly to (100,100)
" style="stroke:black;stroke-width:1;fill:none"></path>

This style can be put into head Of style in , The code is :

path{
fill:none;
stroke:black;
stroke-width:1
}

 

You can also use class、id、 Add styles to labels, etc , Their priorities are :

attribute < * < label < class < id < Between lines

path The same style controls apply to SVG Predefined rect、circle、ellipse Equal elements .

If it's not bad !

Pay attention to , The next part decrypts SVG Animation !

版权声明
本文为[Front end person]所创,转载请带上原文链接,感谢
https://qdmana.com/2021/08/20210809161019925t.html

  1. HTML + CSS + JavaScript to achieve cool Fireworks (cloud like particle text 3D opening)
  2. HTML + CSS + JavaScript realizes 520 advertising love tree (including music), which is necessary for programmers to express themselves
  3. Solve the problem of Web front-end deployment server (it can be deployed online without a server)
  4. HTML + CSS + JS make wedding countdown web page template (520 / Tanabata Valentine's Day / programmer advertisement)
  5. What else can driverless minibus do besides "Park connection"?
  6. Cloud native leads the era of all cloud development
  7. NRM mirror source management tool
  8. Bring it to you, flex Jiugong
  9. Lolstyle UI component development practice (II) -- button group component
  10. Deconstruction assignment in ES6
  11. Luo 2 peerless Tang clan was officially launched. The official gave a key point, and the broadcast time was implied
  12. 20初识前端HTML(1)
  13. 当新零售遇上 Serverless
  14. 20 initial knowledge of front-end HTML (1)
  15. When new retail meets serverless
  16. [golang] - go into go language lesson 5 type conversion
  17. [golang] - go into go language lesson 6 conditional expression
  18. HTML5(八)——SVG 之 path 详解
  19. HTML5 (8) -- detailed explanation of SVG path
  20. 需要开通VIP以后页面内容才能复制怎么办?控制台禁用javascript即可
  21. Web前端|CSS入门教程(超详细的CSS使用讲解,适合前端初学者)
  22. 实践积累 —— 用Vue3简单写一个单行横向滚动组件
  23. Serverless 全能选手,再下一城
  24. What if you need to open a VIP to copy the page content? Just disable JavaScript on the console
  25. Web front end | CSS introductory tutorial (super detailed CSS explanation, suitable for front-end beginners)
  26. Practice accumulation - write a single line horizontal scroll component simply with vue3
  27. Dili Reba is thin again. She looks elegant and high in a strapless hollow skirt, and her "palm waist" is beautiful to a new height
  28. Serverless all-round player, next city
  29. The difference between MySQL semi synchronous replication and lossless semi synchronous replication
  30. Vue表单设计器的终极解决方案
  31. The ultimate solution for Vue form designer
  32. Nginx从理论到实践超详细笔记
  33. Yu Shuxin's red backless swimsuit is split to the waist and tail, with a concave convex figure and excessive color matching, and his face is white to dazzling
  34. Nginx ultra detailed notes from theory to practice
  35. 【动画消消乐|CSS】086.炫酷水波浪Loading过渡动画
  36. typecho全站启用https
  37. CCTV has another popular employee. The off-site interpretation is very professional, and the appearance ability is no less than that of Wang Bingbing
  38. [animation Xiaole | CSS] 086. Cool water wave loading transition animation
  39. Enable HTTPS in Typecho
  40. 50天用JavaScript完成50个web项目,我学到了什么?
  41. 根据JavaScript中原生的XMLHttpRequest实现jQuery的Ajax
  42. What have I learned from completing 50 web projects with JavaScript in 50 days?
  43. "My neighbor doesn't grow up" has hit the whole network. There are countless horse music circles, and actor Zhou Xiaochuan has successfully made a circle
  44. 根据JavaScript中原生的XMLHttpRequest实现jQuery的Ajax
  45. Implement the Ajax of jQuery according to the native XMLHttpRequest in JavaScript
  46. Implement the Ajax of jQuery according to the native XMLHttpRequest in JavaScript
  47. 30 + women still wear less T-shirts and jeans. If they wear them like stars, they will lose weight
  48. 数栈技术分享前端篇:TS,看你哪里逃~
  49. Several stack technology sharing front end: TS, see where you escape~
  50. 舍弃Kong和Nginx,Apache APISIX 在趣链科技 BaaS 平台的落地实践
  51. Abandon the landing practice of Kong and nginx, Apache apisik on the baas platform of fun chain technology
  52. 浪迹天涯king教你用elementui做复杂的表格,去处理报表数据(合并表头,合并表体行和列)
  53. 前端HTML两万字图文大总结,快来看看你会多少!【️熬夜整理&建议收藏️】
  54. Wandering around the world king teaches you to use elementui to make complex tables and process report data (merge header, merge table body rows and columns)
  55. 路由刷新数据丢失 - vuex数据读取的问题
  56. Front end HTML 20000 word graphic summary, come and see how much you can【 Stay up late to sort out & suggestions]
  57. Route refresh data loss - vuex data reading problem
  58. Systemctl系统启动Nginx服务脚本
  59. Systemctl system startup nginx service script
  60. sleepless