封装一下常用的函数,
输入:通过一些固定的值，得到一个圆形,一个心形,一个波浪,一个涟漪,一个抛物线,一个自由弹起的过程。
返回:x,y坐标。
注意：
(1)坐标轴的位置,有的在0,0有的可能不在。
(2)有些是随机生成x,y有些希望均匀分布(均匀分布需要知道一共多少点)
(3)某些模块,某些特定东西生成的方式,比如一个越来越细的直线,一个颜色越来越淡的直线。
(4)熟练的记忆某些函数的特别之处。
1.如果想随机要一个正负的数.
Math.random()*2-1
如果想增幅是10的话
(Math.random()*2-1)*10
2.遇到边界问题的解决。
//边界值判断小于0或者大于最大值,那么cx,cy变为相反方向的改变
if(this.data[i].x>this.cw||this.data[i].x<0){
this.data[i].cX = -this.data[i].cX;
}
if(this.data[i].y>this.ch||this.data[i].y<0){
this.data[i].cY = -this.data[i].cY;
}
3.画虚线的函数。
//画虚线方法
CanvasRenderingContext2D.prototype.dashedLineTo = function (fromX, fromY, toX, toY, pattern) {
// default interval distance -> 5px
if (typeof pattern === "undefined") {
pattern = 5;
}
// calculate the delta x and delta y
var dx = (toX - fromX);
var dy = (toY - fromY);
var distance = Math.floor(Math.sqrt(dx*dx + dy*dy));
var dashlineInteveral = (pattern <= 0) ? distance : (distance/pattern);
var deltay = (dy/distance) * pattern;
var deltax = (dx/distance) * pattern;
// draw dash line
this.beginPath();
for(var dl=0; dl<dashlineInteveral; dl++) {
if(dl%2) {
this.lineTo(fromX + dl*deltax, fromY + dl*deltay);
} else {
this.moveTo(fromX + dl*deltax, fromY + dl*deltay);
}
}
this.stroke();
};
4.画扇形
//扇形
CanvasRenderingContext2D.prototype.sector = function(x,y,r,starAng,endAng){
this.save();
this.beginPath();
this.moveTo(x,y);
this.arc(x,y,r,starAng*Math.PI/180,endAng*Math.PI/180,false);//最后一个参数是false
this.closePath();
this.restore();
return this;
}
5.阴影 这个既可以渲染长方形，又可以渲染字体。
this.ctx.shadowColor = "rgba(0,0,0,0.2)";
this.ctx.shadowBlur = 6;
this.ctx.shadowOffsetX=3;
this.ctx.shadowOffsetY=3;
6.写字体。
ctx.fillStyle = '#2c2f34';
ctx.font = "16px Microsoft YaHei";
ctx.fillText("nihao",50,50)
ctx.fill();
7.
8.
9.
10
var yant = {
num:function(min,max){
return Math.random()*(max-min)+min
},
//产生color
color:function(){
return 'rgba('+Math.round(Math.random()*255)+','+Math.round(Math.random()*255)+','+Math.round(Math.random()*255)+')';
}
}
11.自己为了每次快速开发，瞎搞的代码。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
#btn{position: absolute;bottom: 100px;left:50%;transform: translateX(-50%);z-index: 10;opacity: 0.5;}
button{padding:5px;}
</style>
</head>
<body>
<div id="btn"></div>
<script>
window.onload = function(){
var piao = new Piao()
var cxt = piao.cxt;
cxt.fillStyle = "black";
cxt.beginPath()
cxt.fillRect(0,0,piao.canvasWidth,piao.canvasHeight)
cxt.stroke()
cxt.closePath()
}
function Piao(){
this.canvas = null //容器canvas
this.canvasWidth = null
this.canvasHeight = null
this.isBody = false //容器是不是document.body
this.cxt = null //context
this._init();
}
Piao.prototype = {
constructor:'Piao',
_init:function(){
window.requestAnimFrame = ( function() {
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
function( callback ) {
window.setTimeout( callback, 1000 / 60 );
};
})();
//创建元素
this._createCanvas();
//添加事件
this._addEvent();
},
_createCanvas:function(container){
if(typeof container == 'string'){
container = document.querySelector(container)
}
if(!container){
container = container || document.body;
this.isBody = true;
}
var ele = document.createElement("canvas");
ele.id = "canvas";
ele.value = "sorry,your browser can not support canvas!";
//ele.style.width = 100%;
//ele.style.height = 100%;
this.cxt = ele.getContext('2d');
container.appendChild(ele);
this.canvas = ele;
},
_addEvent:function(){
/*
document.addEventListener('mousemove',documentMousemove,false);
document.addEventListener('mousedown',documentMousedown,false);
document.addEventListener('mouseup',documentMouseup,false);
canvas.addEventListener('touchstar',canvasTouchStar,false);
canvas.addEventListener('touchmove',canvasTouchMove,false);
*/
window.addEventListener('resize',this._windowResizeEvent.bind(this),false)
this._windowResizeEvent();
},
_windowResizeEvent:function(){
if(this.isBody){
this.canvas.width = this.canvasWidth = window.innerWidth;
this.canvas.height = this.canvasHeight = window.innerHeight;
}
}
}
</script>
</body>
</html>