SVG
SVG意为可缩放矢量图形(Scalable Vector Graphics)，是使用XML来描述二维图形和绘图程序的语言。
SVG简介
- SVG指可伸缩矢量图形
- SVG用来定义用于网络的基于矢量的图形
- SVG使用XML格式定义图形
- SVG图像在放大或改变尺寸的情况下其图形质量不会有所损失
SVG在HTML中
SVG文件可通过标签嵌入HTML中：
- embed
- object
- iframe
- 直接嵌入
embed
使用ebmed标签嵌入SVG，主流浏览器都支持，并且允许使用脚本。
例如：
<embed src="example.svg" type="image/svg+xml" />
object
使用object标签嵌入SVG，主流浏览器都支持，但不允许使用脚本。
例如:
<object data="example.svg" type="image/svg+xml"></object>
iframe
使用iframe标签嵌入SVG，主流浏览器都支持，并且允许使用脚本。
例如:
<iframe src="example.svg"></iframe>
直接嵌入
例如:
<svg xmlns="http://www.w3.org/2000/svg" version="1.1">
<circle cx="100" cy="50" r="40" stroke="black" stroke-width="2" fill="#000" />
</svg>
SVG路径
path标签用来定义路径
以下属性用来定义路径属性：
- M = moveto 移动到
- L = lineto 画线到
- H = horizontal lineto 水平线到
- V = vertical lineto 垂直线到
- C = curveto 三次贝塞尔曲线
- S = smooth curveto 光滑三次贝塞尔曲线
- Q = quadratic Belzier curve 二次贝塞尔曲线
- T = smooth quadratic Belzier curveto 光滑二次贝塞尔曲线
- A = elliptical Arc 椭圆弧
- Z = closepath 关闭路径
SVG路径动画
基于path的不同属性我们可以画出各种各样的路径，再结合stroke可以是线条动起来。
先介绍两个属性：
stroke-dasharray：指定画出路径每段的长度和各段之间空隙的长度
stroke-dashoffset：指定每段的起始偏移量
利用CSS3动画属性动态改变偏移量就可以使线条产生动画效果。
CSS
.svg path{
stroke-dasharray: 600 600;
animation: dash ease 2s 0s infinite;
}
@keyframes dash{
from{
stroke-dashoffset: 0;
}
to{
stroke-dashoffset: 600;
}
}
SVG
<svg class="svg" xmlns="http://www.w3.org/2000/svg" width="600" height="400">
<g>
<path stroke="#00bfbf" id="svg_1" d="m31.532584,129.53322c-5.268304,-0.72224 -7.084974,-5.767751 -3.944029,-8.790559c4.168431,-4.674979 13.085107,-7.826499 20.071427,-4.876704c0.139239,-16.462479 0.058877,-32.925855 0.080173,-49.388733c17.419986,-2.664139 34.877634,-5.191255 52.304214,-7.832217c-0.037738,18.450795 -0.075478,36.901597 -0.113216,55.352385c-2.730045,5.580632 -11.551503,9.450454 -19.232741,7.719991c-4.573032,-1.037724 -5.669362,-5.512458 -3.122906,-8.254195c3.487116,-4.089812 9.977514,-6.897826 16.502461,-6.131761c1.862035,-0.142792 4.604007,2.142513 3.816994,-0.442752c0,-12.933004 0,-25.866004 0,-38.799001c-15.990809,2.440272 -32.013225,4.764633 -48.011432,7.178496c-0.054611,15.050094 0.135937,30.102474 -0.142537,45.150722c-0.509068,4.570867 -6.296733,7.689358 -11.699424,8.907769c-2.134316,0.272848 -4.356646,0.442152 -6.508982,0.206557l-0.000003,0.000002zm41.713646,-61.359c8.216135,-1.225722 16.436142,-2.436724 24.648728,-3.676028c1.045162,-3.156418 -3.632262,-1.106549 -5.919749,-1.029494c-14.028576,2.099321 -28.065255,4.167562 -42.091683,6.275037c-1.045162,3.156418 3.632259,1.106549 5.919746,1.029494c5.813738,-0.868598 11.628237,-1.734226 17.442958,-2.599011l0,0.000002z" stroke-width="1.5" fill="#fff"/>
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<path id="svg_3" d="m305.853425,190.295242c-6.905749,-0.762869 -9.287059,-6.092151 -5.169876,-9.284973c5.464024,-4.937918 17.152097,-8.266698 26.30984,-5.150996c0.182491,-17.445591 0.077201,-34.892141 0.105096,-52.338161c22.833774,-2.759327 45.719174,-5.364616 68.56093,-8.101102c-0.049479,19.488539 -0.098938,38.977078 -0.148404,58.465617c-3.578596,5.894502 -15.141845,9.98198 -25.210502,8.15419c-5.994379,-1.096089 -7.431456,-5.822501 -4.093538,-8.718437c4.570953,-4.319838 13.078636,-7.285786 21.631598,-6.476634c2.440779,-0.150824 6.03501,2.263016 5.003369,-0.467654c-0.084727,-15.414587 0.210726,-30.833282 -0.21801,-46.244623c-3.726463,-0.8451 -10.353637,1.099295 -15.12495,1.256607c-15.955489,1.896867 -31.945088,3.693217 -47.863933,5.700964c0.480318,17.079901 0.256342,34.170258 0.184835,51.253771c0.845152,3.899696 -2.673512,7.573149 -8.02367,9.60598c-4.616787,2.051407 -10.320807,2.790909 -15.942781,2.345458l-0.000004,-0.000008z" fill-opacity="null" stroke-width="1.5" stroke="#aaff56" fill="#fff"/>
<path id="svg_4" d="m435.929715,330.407142c-6.042054,-0.602637 -10.695686,-4.161175 -9.35643,-7.969603c1.585538,-5.026389 9.001771,-8.569207 16.270481,-10.536402c5.879366,-1.473351 13.061008,-1.717604 18.653537,0.347257c0.222809,-24.191178 0.097547,-48.383367 0.130581,-72.575005c1.973624,-0.051763 4.234405,-0.304682 3.6957,1.403462c0.160354,4.027812 4.045284,7.424439 8.872087,9.944282c10.253283,5.81621 21.619776,12.544543 22.523257,21.65426c0.966163,3.568994 -2.144981,7.081742 -0.827717,10.546334c1.257376,3.414881 0.882515,6.959832 0.088377,10.392241c3.733984,6.160452 2.832337,13.253443 -1.235548,19.268841c0.375769,1.879939 -6.859194,4.946999 -3.689911,1.813892c4.279513,-5.714419 6.530769,-12.7426 1.889955,-18.622745c-5.620474,-5.699101 -15.848604,-8.621247 -24.235604,-12.512242c-5.837633,-3.617483 -2.690833,3.411183 -3.56049,5.506473c-0.129778,10.278306 -0.140043,20.556986 -0.203584,30.835496c-2.613627,3.915526 -7.407703,7.230518 -13.792615,8.93027c-4.680822,1.344325 -10.058359,2.233071 -15.222072,1.57319l-0.000005,0zm56.931766,-44.308704c-3.617454,-7.982495 -15.12623,-13.392561 -26.361671,-17.29154c-3.075627,-0.264632 0.911866,4.314759 1.775923,5.73285c4.02422,4.85547 11.948774,7.72154 17.663197,11.731735c2.492894,1.270724 5.330679,3.892909 7.276125,4.594401c0.282683,-1.581732 0.111529,-3.204188 -0.353569,-4.767449l-0.000005,0.000003zm0.455125,-10.889064c-0.057251,-6.709369 -8.24785,-12.057296 -16.186476,-16.050468c-3.701524,-1.507322 -8.177811,-4.045444 -11.979479,-4.349767c0.723479,3.734717 3.444838,7.391921 8.443979,9.682634c7.112396,4.246919 14.63188,8.483186 19.566742,13.816685c0.568091,-0.927171 0.064988,-2.109895 0.155234,-3.099084z" fill-opacity="null" stroke-width="1.5" stroke="#ff5656" fill="#fff"/>
</g>
</svg>
效果
image
总结
先简单介绍一些SVG知识，了解SVG动画的原理，通过这些属性可以帮助我们构建更丰富的UI界面。
