妙味课堂HTML5视频资料分享-9543建站博客

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妙味课堂HTML5视频资料分享

万维网的核心语言、标准通用标记语言下的一个应用超文本标记语言（HTML）的第五次重大修改（这是一项推荐标准、外语原文：W3C Recommendation、见本处参考资料原文内容：）。

2014年10月29日，万维网联盟宣布，经过接近8年的艰苦努力，该标准规范终于制定完成。

《妙味课堂HTML5视频教程》将会介绍超文本标记语言（HTML）的第五次重大修改，即最新版本；它比原来的标准又增加了一些新的标签，实现更多功能，更标准化，更适用于移动互联网。

视频播放地址：http://www.php.cn/course/418.html

本视频学习难点在于canvas的用法：

<!DOCTYPE html><html><head><meta charset="UTF-8"><title>仿知乎背景canvas特效</title><meta name="keywords" content="" /><meta name="description" content="" /><style type="text/css">body{text-align: center;background: #F7FAFC;overflow: hidden;background: #fff;}</style></head><body><canvas id="Mycanvas"></canvas><script>//定义画布宽高和生成点的个数var WIDTH = window.innerWidth, HEIGHT = window.innerHeight, POINT = 35;var canvas = document.getElementById('Mycanvas');canvas.width = WIDTH,canvas.height = HEIGHT;var context = canvas.getContext('2d');context.strokeStyle = 'rgba(0,0,0,0.2)',context.strokeWidth = 1,context.fillStyle = 'rgba(0,0,0,0.1)';var circleArr = [];//线条：开始xy坐标，结束xy坐标，线条透明度function Line (x, y, _x, _y, o) {this.beginX = x,this.beginY = y,this.closeX = _x,this.closeY = _y,this.o = o;}//点：圆心xy坐标，半径，每帧移动xy的距离function Circle (x, y, r, moveX, moveY) {this.x = x,this.y = y,this.r = r,this.moveX = moveX,this.moveY = moveY;}//生成max和min之间的随机数function num (max, _min) {var min = arguments[1] || 0;return Math.floor(Math.random()*(max-min+1)+min);}// 绘制原点function drawCricle (cxt, x, y, r, moveX, moveY) {var circle = new Circle(x, y, r, moveX, moveY)cxt.beginPath()cxt.arc(circle.x, circle.y, circle.r, 0, 2*Math.PI)cxt.closePath()cxt.fill();return circle;}//绘制线条function drawLine (cxt, x, y, _x, _y, o) {var line = new Line(x, y, _x, _y, o)cxt.beginPath()cxt.strokeStyle = 'rgba(0,0,0,'+ o +')'cxt.moveTo(line.beginX, line.beginY)cxt.lineTo(line.closeX, line.closeY)cxt.closePath()cxt.stroke();}//每帧绘制function draw () {context.clearRect(0,0,canvas.width, canvas.height);for (var i = 0; i < POINT; i++) {drawCricle(context, circleArr[i].x, circleArr[i].y, circleArr[i].r);}for (var i = 0; i < POINT; i++) {for (var j = 0; j < POINT; j++) {if (i + j < POINT) {var A = Math.abs(circleArr[i+j].x - circleArr[i].x),B = Math.abs(circleArr[i+j].y - circleArr[i].y);var lineLength = Math.sqrt(A*A + B*B);var C = 1/lineLength*7-0.009;var lineOpacity = C > 0.03 ? 0.03 : C;if (lineOpacity > 0) {drawLine(context, circleArr[i].x, circleArr[i].y, circleArr[i+j].x, circleArr[i+j].y, lineOpacity);}}}}}//初始化生成原点function init () {circleArr = [];for (var i = 0; i < POINT; i++) {circleArr.push(drawCricle(context, num(WIDTH), num(HEIGHT), num(15, 2), num(10, -10)/40, num(10, -10)/40));}draw();}//调用执行window.onload = function () {init();setInterval(function () {for (var i = 0; i < POINT; i++) {var cir = circleArr[i];cir.x += cir.moveX;cir.y += cir.moveY;if (cir.x > WIDTH) cir.x = 0;else if (cir.x < 0) cir.x = WIDTH;if (cir.y > HEIGHT) cir.y = 0;else if (cir.y < 0) cir.y = HEIGHT;}draw();}, 10);}</script></body></html>

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