【概念】SVG(1)

ok，我们讲讲svg

学习前提：懂HTML和基本的XML

SVG简介：

1.SVG全称Scable Vector Graphic，可伸缩的矢量图

2.SVG用于定义针对于Web的基于矢量的图形

3.SCG用XML的形式定义了图片

4.SVG在缩放中永远不会失真

5.每个SVG中的元素和属性都可以进行动画设置

5.SVG是W3C大大推荐的！

6.SVG结合了W3C的标准，比如DOM和XSL

<svg width="widthpx" height="heightpx" viewBox="x1 x2 y1 y2">

注意上图起点是左上角，viewBox则表示了可见的画布区域。

SVG Shapes

SVG 有以下预定义的形状元素：

Rectangle <rect>
Circle <circle>
Ellipse <ellipse>
Line <line>
Polyline <polyline>
Polygon <polygon>
Path <path>

<svg width="400" height="180">
  <rect x="50" y="20" rx="20" ry="20" width="150" height="150" style="fill:red;stroke:black;stroke-5;stroke-opacity:0.5;fill-opacity:0.9">
  Sorry, your browser does not support inline SVG.
</svg>

效果：

rx和ry表示圆角的轴半径，类似于css 中的 border-radius

<svg height="100" width="200">
  <circle cx="100" cy="50" r="40" stroke="black" stroke-width="3" fill="red" />
  Sorry, your browser does not support inline SVG.  
</svg>

<svg height="140" width="500">
  <ellipse cx="200" cy="80" rx="100" ry="50" style="fill:yellow;stroke:purple;stroke-2" />
  Sorry, your browser does not support inline SVG.  
</svg>

多个椭圆会叠加

<svg height="150" width="500">
  <ellipse cx="240" cy="100" rx="220" ry="30" style="fill:purple" />
  <ellipse cx="220" cy="70" rx="190" ry="20" style="fill:lime" />
  <ellipse cx="210" cy="45" rx="170" ry="15" style="fill:yellow" />
  Sorry, your browser does not support inline SVG. 
</svg>

line

<svg height="210" width="500">
  <line x1="0" y1="0" x2="200" y2="200" style="stroke:rgb(255,0,0);stroke-2" />
  Sorry, your browser does not support inline SVG.
</svg>

<svg height="210" width="500">
  <polygon points="100,10 40,198 190,78 10,78 160,198" style="fill:lime;stroke:purple;stroke-5;fill-rule:nonzero;"/>
  Sorry, your browser does not support inline SVG.
</svg>

<svg height="210" width="400">
  <path d="M150 0 L75 200 L225 200 Z" />
</svg>

The following commands are available for path data:

M = moveto
L = lineto
H = horizontal lineto
V = vertical lineto
C = curveto
S = smooth curveto
Q = quadratic Bézier curve
T = smooth quadratic Bézier curveto
A = elliptical Arc
Z = closepath

Note: 上面大写代表绝对位置，小写代表相对位置

<svg height="60" width="200">
  <text x="0" y="15" fill="red" transform="rotate(30 20,40)">I love SVG</text>
  Sorry, your browser does not support inline SVG.
</svg>

stroke

<?xml version="1.0" standalone="no"?>
<svg width="160" height="140" xmlns="http://www.w3.org/2000/svg" version="1.1">
  <line x1="40" x2="120" y1="20" y2="20" stroke="black" stroke-width="20" stroke-linecap="butt"/>
  <line x1="40" x2="120" y1="60" y2="60" stroke="black" stroke-width="20" stroke-linecap="square"/>
  <line x1="40" x2="120" y1="100" y2="100" stroke="black" stroke-width="20" stroke-linecap="round"/>
</svg>

<?xml version="1.0" standalone="no"?>
<svg width="160" height="280" xmlns="http://www.w3.org/2000/svg" version="1.1">
  <polyline points="40 60 80 20 120 60" stroke="black" stroke-width="20"
      stroke-linecap="butt" fill="none" stroke-linejoin="miter"/>
  
  <polyline points="40 140 80 100 120 140" stroke="black" stroke-width="20"
      stroke-linecap="round" fill="none" stroke-linejoin="round"/>
  
  <polyline points="40 220 80 180 120 220" stroke="black" stroke-width="20"
      stroke-linecap="square" fill="none" stroke-linejoin="bevel"/>
</svg>

<svg width="200" height="150">
  <path d="M 10 75 Q 50 10 100 75 T 190 75" stroke="black"
    stroke-linecap="round" stroke-dasharray="5,15,8" fill="none"/>
  <path d="M 10 75 L 190 75" stroke="red"
    stroke-linecap="round" stroke-width="1" stroke-dasharray="5,5" fill="none"/>
</svg>

stroke-dasharray="实线段距离,空白线段距离" 如果有多个值，比如5,15,8那么将按照实线，空白这样不断循环。

所以，第一个例子是5实线，15空白，8实线，5空白，15实线，8空白，5实线。。。。。