效果图

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html结构(index.html)

 content=" height = device-height,

width = device-width,

initial-scale = 1.0,

minimum-scale = 1.0,

maximum-scale = 1.0,

user-scalable = no

" />

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();

});

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本文题目：canvas实现的红包照片自适应效果-创新互联
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