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canvas实现的红包照片自适应效果

内容导读

互联网集市收集整理的这篇技术教程文章主要介绍了canvas实现的红包照片自适应效果，小编现在分享给大家，供广大互联网技能从业者学习和参考。文章包含4749字，纯文字阅读大概需要7分钟。

内容图文

效果图

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技术分享650) this.width=650;" src="/upload/getfiles/default/2022/11/8/20221108043643284.jpg" title="QQ截图20170123114704.png" />

技术分享650) this.width=650;" src="/upload/getfiles/default/2022/11/8/20221108043644413.jpg" title="QQ截图20170123114719.png" />

技术分享650) this.width=650;" src="/upload/getfiles/default/2022/11/8/20221108043644737.jpg" title="QQ截图20170123114728.png" />

html结构(index.html)

<!DOCTYPE html>

<html>

<head>

<meta charset="utf-8">

<title>红包照片</title>

<link rel="stylesheet" href="blur.css">

<script src="jquery-3.1.1.min.js" type="text/javascript" charset="utf-8"></script>

<meta name="viewport" 

 content=" height = device-height,

width = device-width,

initial-scale = 1.0,

minimum-scale = 1.0,

maximum-scale = 1.0,

user-scalable = no

" />

</head>

<body>

<div id="blur-div">

<img id="blur-image" src="20170122161717.png" >

<canvas id="blur-canvas"></canvas>


<a href="javascript:reset()" class="button" id="reset-button">reset</a>

<a href="javascript:show()" class="button" id="show-button">show</a>

</div>

<script src="blur.js" type="text/javascript" charset="utf-8" ></script>

</body>

</html>

css样式(blur.css)

*{

margin: 0;

padding: 0;

}


#blur-div{

margin: 0 auto;

position: relative;

overflow: hidden;

}


#blur-image{

display: block;

margin: 0 auto;


filter:blur(20px);

-webkit-filter:blur(20px);

-moz-filter:blur(20px);

-ms-filter:blur(20px);

-o-filter:blur(20px);


position: absolute;

left: 0px;

top: 0px;

z-index: 0;

}


#blur-canvas{

display: block;

margin: 0 auto;

position: absolute;

left: 0px;

top: 0px;

z-index: 100;

}


.button{

display: block;

position: absolute;

z-index: 200;

width: 100px;

height: 30px;


color: white;

text-decoration: none;

text-align: center;

line-height: 30px;


border-radius: 5px;

}


#reset-button{

left: 50px;

bottom: 20px;

background-color: #058;

}


#reset-button:hover{

background-color: #047;

}


#show-button{

right: 100px;

bottom: 20px;

background-color: #085;

}


#show-button:hover{

background-color: #074;

}

js脚本(blur.js)

var canvasWidth = window.innerWidth;

var canvasHeight = window.innerHeight;


var canvasObj = document.getElementById("blur-canvas");

var contextObj = canvasObj.getContext("2d");


canvasObj.width = canvasWidth;

canvasObj.height = canvasHeight;


var imageObj = new Image();

var radius = 50;

var clippingRegion = {x:-1,y:-1,r:radius}

var leftMargin = 0,topMargin = 0;


imageObj.src = "20170122161717.png";

imageObj.onload = function(e){


$("#blur-div").css("width",canvasWidth+"px");

$("#blur-div").css("height",canvasHeight+"px");


$("#blur-image").css("width",imageObj.width+"px");

$("#blur-image").css("height",imageObj.height+"px");


leftMargin = (imageObj.width - canvasObj.width) / 2;

topMargin = (imageObj.height - canvasObj.height) / 2;


$("#blur-image").css("top",String(-topMargin)+"px");

$("#blur-image").css("left",String(-leftMargin)+"px");


initCanvas();

}


function initCanvas(){

var theleft = leftMargin < 0 ? -leftMargin:0;

var thetop = topMargin < 0 ? -topMargin:0;

var rx = Math.random()*(canvasObj.width - 2*radius-2*theleft)+radius+theleft;

var ry = Math.random()*(canvasObj.height - 2*radius-2*thetop)+radius+thetop;

clippingRegion = {x:rx,y:ry,r:radius};

drawImage(imageObj,clippingRegion);

}


function drawImage(imageObj,clippingRegion){

contextObj.clearRect(0,0,canvasObj.width,canvasObj.height);


contextObj.save();

setClippingRegion(clippingRegion);

// contextObj.drawImage(imageObj,0,0);

contextObj.drawImage(imageObj,Math.max(leftMargin,0),Math.max(topMargin,0),Math.min(canvasObj.width,imageObj.width),Math.min(canvasObj.height,imageObj.height),leftMargin < 0 ? -leftMargin:0,topMargin < 0 ? -topMargin:0,Math.min(canvasObj.width,imageObj.width),Math.min(canvasObj.height,imageObj.height));

contextObj.restore();

}


function setClippingRegion(clippingRegion){

contextObj.beginPath();

contextObj.arc(clippingRegion.x,clippingRegion.y,clippingRegion.r,0,Math.PI*2,false);

contextObj.clip();

}


function reset(){

initCanvas();

}


function show(){

document.getElementById("reset-button").style.display="none";

var animation = setInterval(function(){

clippingRegion.r += 20;

if (clippingRegion.r > 2*Math.max(canvasObj.width,canvasObj.height)) {

clearInterval(animation);

document.getElementById("reset-button").style.display="block";

}

drawImage(imageObj,clippingRegion);

},30);

}


canvasObj.addEventListener("touchstart",function(e){

e.preventDefault();

});


本文出自 “素颜” 博客，请务必保留此出处http://suyanzhu.blog.51cto.com/8050189/1893846

原文：http://suyanzhu.blog.51cto.com/8050189/1893846

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