SVG API:
- SVG是一種可縮放矢量圖形,一種二維圖形表示語(yǔ)言
- 與canvas不同的是,在瀏覽器的開發(fā)工具中能查看和編輯SVG結(jié)構(gòu),SVG嵌入到HTML DOM中了
- 縮放SVG不會(huì)導(dǎo)致圖片的質(zhì)量下降,圖片不會(huì)模糊
- SVG相關(guān)詞匯:形狀、路徑、變換、圖案和漸變、可重用的內(nèi)容、文本
- 創(chuàng)建SVG
<svg height=100 width=500></svg>
<svg height=200 width=200>
<!--Stroke屬性定義一條線,文本或元素輪廓顏色 stroke- width屬性定義了一條線,文本或元素輪廓厚度 fill屬性是填充顏色 cx、cy是橢圓的原點(diǎn)坐標(biāo)-->
<rect height="80" width="100" x="10" y="20" stroke="red" fill="#ccc"></rect>
<circle cx="120" cy="80" r="40" stroke="#00f" fill="none" stroke-width="8"></circle>
</svg>
- 可以將要變換的SVG元素放在一個(gè)組中,添加變換屬性進(jìn)行變換,組內(nèi)成員可以通過id來引用
<svg height=200 width=200>
<!--translate輸入一個(gè)或兩個(gè)值得來聲明水平和豎直移動(dòng)值。tx代表x軸上的translation值;ty代表y軸上的translation值
rotate對(duì)于給定的點(diǎn)和旋轉(zhuǎn)角度值執(zhí)行旋轉(zhuǎn),默認(rèn)單位是度
scale輸入一個(gè)或兩個(gè)值來聲明水平和豎直縮放值。sx代表沿x軸的縮放值,用來水平延長(zhǎng)或者拉伸元素;sy代表沿y軸縮放值,用來垂直延長(zhǎng)或者縮放元素-->
<g transform="translate(60,0) rotate(30) scale(0.75)" id="ShapeGroup">
<rect height="80" width="100" x="10" y="20" stroke="red" fill="#ccc"></rect>
<circle cx="120" cy="80" r="40" stroke="#00f" fill="none" stroke-width="8"></circle>
</g>
</svg>
- 復(fù)用內(nèi)容,
<defs>元素用于定義下面要使用的內(nèi)容,<use元素用于鏈接到<defs>元素定義的內(nèi)容
<svg height=200 width=200>
<defs>
<g id="ShapeGroup">
<rect height="80" width="100" x="10" y="20" stroke="red" fill="#ccc"></rect>
<circle cx="120" cy="80" r="40" stroke="#00f" fill="none" stroke-width="8"></circle>
</g>
</defs>
<use xlink:href="#ShapeGroup" transform="translate(60,0) scale(0.5)"/>
<use xlink:href="#ShapeGroup" transform="translate(120,80) scale(0.4)"/>
<use xlink:href="#ShapeGroup" transform="translate(20,60) scale(0.25)"/>
</svg>
- 圖案和漸變(圖案可以像素圖形或者SVG圖形,漸變分為線性漸變和放射性漸變)
<svg height=200 width=200>
<defs>
<!--<pattern>是SVG的一個(gè)圖案填充標(biāo)簽,可以在pattern中定義好圖案,然后通過id引用來對(duì)某個(gè)圖形進(jìn)行填充
userSpaceOnUse:x、y、width和height表示的值都是當(dāng)前用戶坐標(biāo)系統(tǒng)的值。也就是說,這些值沒有縮放,都是絕對(duì)值。
viewBox="x, y, width, height" // x:左上角橫坐標(biāo),y:左上角縱坐標(biāo),width:寬度,height:高度,viewBox是“視區(qū)盒子”的意思-->
<pattern id="GravelPattern" patternUnits="userSpaceOnUse"
x="0" y="0" width="100" height="67" viewBox="0 0 100 67">
<image height="67" xlink:href="gravel.jpg" width="100"></image>
</pattern>
<linearGradient id="RedBlackGradient">
<stop offset="0%" stop-color="#000"></stop>
<stop offset="100%" stop-color="#f00"></stop>
</linearGradient>
</defs>
<rect height="100" width="80" x="10" y="20" stroke="red" fill="url(#RedBlackGradient)"></rect>
<circle r="40" cx="120" cy="80" stroke="#00f" stroke-width="8" fill="url(#GravelPattern)"></circle>
</svg>
- SVG路徑,path有一個(gè)D屬性,M代表moveTo,L代表lineTo,Q代表二次曲線,Z代表閉合路徑
<svg height=1000 width=1000>
<g transform="translate(50,350)" stroke-width="20" stroke="url(#GravelPattern)" stroke-linejoin="round">
<path d="M-25,-50
L-10,-80
L-20,-80
L-5,-110
L-15,-110
L0,-140
L15,-110
L5,-110
L20,-80
L10,-80
L25,-50
Z" id="Canopy"></path>
<path d="M0,0 Q170,-50 260,-190 Q310,-250 410,-250" fill="none"></path>
</g>
</svg>
- SVG文本,在瀏覽器中,文本是可選的,并且能夠被搜索引擎搜到
<svg height=200 width=500>
<text y="60" x="300" font-family="impact" font-size="60px" fill="#996600" text-anchor="middle">Happy Trails</text>
</svg>
- 組合場(chǎng)景(將上述功能組合成一個(gè)跑道場(chǎng)景)
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Happy Trails in SVG</title>
<style>
svg {
border: 1px solid black;
}
</style>
</head>
<body>
<svg width="400" height="600">
<defs>
<pattern id="GravelPattern" patternUnits="userSpaceOnUse"
x="0" y="0" width="100" height="67" viewBox="0 0 100 67">
<image height="67" xlink:href="gravel.jpg" width="100"></image>
</pattern>
<linearGradient id="TrunkGradient">
<stop offset="0%" stop-color="#663300"></stop>
<stop offset="40%" stop-color="#996600"></stop>
<stop offset="100%" stop-color="#552200"></stop>
</linearGradient>
<rect height="50" width="10" x="-5" y="-50" id="Trunk"></rect>
<path d="M-25,-50
L-10,-80
L-20,-80
L-5,-110
L-15,-110
L0,-140
L15,-110
L5,-110
L20,-80
L10,-80
L25,-50
Z" id="Canopy"></path>
<linearGradient id="CanopyShadow" x="0" y="0" x2="0" y2="100%">
<stop offset="0%" stop-color="#000" stop-opacity=".5"></stop>
<stop offset="20%" stop-color="#000" stop-opacity="0"></stop>
</linearGradient>
<g id="Tree">
<use xlink:href="#Trunk" fill="url(#TrunkGradient)"/>
<use xlink:href="#Trunk" fill="url(#CanopyShadow)"/>
<use xlink:href="#Canopy" fill="none" stroke="#663300" stroke-linejoin="round" stroke-width="4px"/>
<use xlink:href="#Canopy" fill="#339900" stroke="none"/>
</g>
<g id="TreeShadow">
<use xlink:href="#Trunk" fill="#000"/>
<use xlink:href="#Canopy" fill="#000" stroke="none"/>
</g>
</defs>
<g transform="translate(-10,350)" stroke-width="20" stroke="url(#GravelPattern)" stroke-linejoin="round">
<path d="M0,0 Q170,-50 260,-190 Q310,-250 410,-250" fill="none"></path>
</g>
<text y="60" x="200" font-family="impact" font-size="60px" fill="#996600" text-anchor="middle">Happy Trails!</text>
<use xlink:href="#TreeShadow" transform="translate(130,250) scale(1,.6) skewX(-18)" opacity="0.4"/>
<use xlink:href="#Tree" transform="translate(130,250)"/>
<use xlink:href="#TreeShadow" transform="translate(260,500) scale(2,1.2) skewX(-18)" opacity="0.4"/>
<use xlink:href="#Tree" transform="translate(260,500) scale(2)"/>
</svg>
</body>
- 使用SVG創(chuàng)建交互式應(yīng)用,添加一個(gè)按鈕,每添加一個(gè)元素其實(shí)就是添加一個(gè)
<use>元素
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Happy Trails in SVG</title>
<style>
svg {
border: 1px solid black;
}
g[id=Tree]:hover {
opacity: 0.9;
cursor: crosshair;
}
</style>
</head>
<body>
<div>
<button id="AddTreeButton">Add Tree</button>
</div>
<svg width="400" height="600">
<defs>
<pattern id="GravelPattern" patternUnits="userSpaceOnUse"
x="0" y="0" width="100" height="67" viewBox="0 0 100 67">
<image height="67" xlink:href="gravel.jpg" width="100"></image>
</pattern>
<linearGradient id="TrunkGradient">
<stop offset="0%" stop-color="#663300"></stop>
<stop offset="40%" stop-color="#996600"></stop>
<stop offset="100%" stop-color="#552200"></stop>
</linearGradient>
<rect height="50" width="10" x="-5" y="-50" id="Trunk"></rect>
<path d="M-25,-50
L-10,-80
L-20,-80
L-5,-110
L-15,-110
L0,-140
L15,-110
L5,-110
L20,-80
L10,-80
L25,-50
Z" id="Canopy"></path>
<linearGradient id="CanopyShadow" x="0" y="0" x2="0" y2="100%">
<stop offset="0%" stop-color="#000" stop-opacity=".5"></stop>
<stop offset="20%" stop-color="#000" stop-opacity="0"></stop>
</linearGradient>
<g id="Tree">
<use xlink:href="#Trunk" fill="url(#TrunkGradient)"/>
<use xlink:href="#Trunk" fill="url(#CanopyShadow)"/>
<use xlink:href="#Canopy" fill="none" stroke="#663300" stroke-linejoin="round" stroke-width="4px"/>
<use xlink:href="#Canopy" fill="#339900" stroke="none"/>
</g>
</defs>
<g transform="translate(-10,350)" stroke-width="20" stroke="url(#GravelPattern)" stroke-linejoin="round">
<path d="M0,0 Q170,-50 260,-190 Q310,-250 410,-250" fill="none"></path>
</g>
<text y="60" x="200" font-family="impact" font-size="60px" fill="#996600" text-anchor="middle">Happy Trails!</text>
<text y="90" x="200" font-family="impact" font-size="20px" fill="#996600" text-anchor="middle"
id="TreeCounter"></text>
<text y="420" x="20" font-family="impact" font-size="20px" fill="#996600" text-anchor="left">
<tspan>You can remove a</tspan>
<tspan>tree by clicking on it.</tspan>
</text>
<use xlink:href="#Tree" transform="translate(130,250)"/>
<use xlink:href="#Tree" transform="translate(260,500) scale(2)"/>
</svg>
</body>
<script>
function removeTree(e) {
var elt = e.target;
if (elt.correspondingUseElement) {
elt = elt.correspondingUseElement; //此段代碼目前不知道用意何在
}
elt.parentNode.removeChild(elt);
updateTrees();
}
document.getElementById("AddTreeButton").onclick = function () {
var x = Math.floor(Math.random() * 400); //產(chǎn)生新生成數(shù)的X,Y坐標(biāo)
var y = Math.floor(Math.random() * 600);
var scale = Math.random() + .5; //產(chǎn)生新生成數(shù)的縮放比例
var translate = "translate(" + x + "," + y + ")";
var tree = document.createElementNS("http://www.w3.org/2000/svg", "use"); //createElementNS() 方法可創(chuàng)建帶有指定命名空間的元素節(jié)點(diǎn)
tree.setAttributeNS("http://www.w3.org/1999/xlink", "xlink:href", "#Tree");
tree.setAttribute("transform", translate + "scale(" + scale + ")");
document.querySelector("svg").appendChild(tree); //querySelector() 方法返回文檔中匹配指定 CSS 選擇器的一個(gè)元素
updateTrees();
};
function updateTrees() {
var list = document.querySelectorAll("use"); //querySelectorAll 在文檔內(nèi)找全部符合選擇器描述的節(jié)點(diǎn)包括Element本身
var treeCount = 0;
for (var i = 0; i < list.length; i++) {
if (list[i].getAttribute("xlink:href") == "#Tree") {
treeCount++;
list[i].onclick = removeTree;
}
}
var counter = document.getElementById("TreeCounter");
counter.textContent=treeCount+"trees in forest"; //textContent 屬性設(shè)置或返回指定節(jié)點(diǎn)的文本內(nèi)容,以及它的所有后代
}
updateTrees();
</script>