如何使用canvad实现粒子运动效果？
没有最好，只有更好，如题所示，这篇文章只要是分享一个用 Canvas 来实现的粒子运动效果。感觉有点标题党了，但换个角度，勉勉强强算是炫丽吧，虽然色彩上与炫丽无关，但运动效果上还是算得上有点点炫的。不管怎么样，我们还是开始这个所谓的炫丽效果吧！
直接上代码 ，不懂可以看代码注释。估计就会看明白大概的思路了。
html 代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Canvas 实现炫丽的粒子运动效果-云库前端</title>
<style>
* {
margin: 0;
padding: 0;
}
html,
body {
width: 100%;
height: 100%;
}
canvas {
display: block;
background: #000;
}
body::-webkit-scrollbar{
display: none;
}
.operator-box{
position: fixed;
top: 0;
left: 50%;
border: 1px solid #fff;
background: rgba(255,255,255,0.5);
padding: 20px 10px;
-webkit-transform: translateX(-50%);
transform: translateX(-50%);
}
.back-type,.back-animate{
margin-right: 20px;
}
.flex-box{
display: flex;
justify-content: center;
align-items: center;
}
#input-text{
line-height: 35px;
width: 260px;
height: 35px;
background: rgba(0, 0, 0,0.7);
color: #fff;
font-size: 16px;
border: none;
outline: none;
text-indent: 12px;
box-shadow: inset 0 0 12px 1px rgba(0,0,0,0.7);
}
#input-text::placeholder{
color: #ccc;
line-height: 55px;
height: 55px;
}
select{
-webkit-appearance: none;
-moz-appearance: none;
appearance: none;
border: none;
padding: 0px 20px 0px 6px;
height: 35px;
color: #fff;
text-align: left;
background: rgba(0, 0, 0,0.7) url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAICAYAAAAx8TU7AAAAOUlEQ…R4gPgWEIMAiOYBCS4C8ZDAIrBq4gigNkztQEFMi6AuQHESAPMeXiEMiWfpAAAAAElFTkSuQmCC) no-repeat 190px 12px;
background-size: 5px 8px;
box-shadow: inset 0 0 12px 1px rgba(0,0,0,0.7);
}
</style>
</head>
<body>
<div class="operator-box">
<div class="flex-box">
<div class="back-type">散开类型：
<select name="" id="selectType">
<option value="back">归位</option>
<option value="auto">随机</option>
</select>
</div>
<div class="back-animate">散开效果（对归位有效）：
<select class="back-dynamics" id="selectDynamics">
<option value="spring">dynamics.spring</option>
<option value="bounce">dynamics.bounce</option>
<option value="forceWithGravity">dynamics.forceWithGravity</option>
<option value="gravity">dynamics.gravity</option>
<option value="easeInOut">dynamics.easeInOut</option>
<option value="easeIn">dynamics.easeIn</option>
<option value="easeOut">dynamics.easeOut</option>
<option value="linear">dynamics.linear</option>
</select>
</div>
<div class="input-box"><input type="text" placeholder="输入汉字后回车" id="input-text"></div>
</div>
</div>
<script src="dynamics.min.js"></script>
<script src="index.js"></script>
<script>
var iCircle = new Circle();
</script>
</body>
</html>
HTML 代码不多，只要是几个操作元素。这里一看就明白。不费过多口舌。我们来看看本文的主角 JavaScript 代码，不过，在看代码前，我们不妨先听听实现这个效果的思路：
- 首先，我们得先生成一堆群众演员（粒子）；
- 把每个粒子的相关参数挂到自身的一些属性上，因为第个粒子都会有自己的运动轨迹；
- 接着得让它们各自运动起来。运动有两种（自由运动和生成文字的运动）；
JavaScript 代码中使用了三个 Canvas 画布，this.iCanvas（主场）、this.iCanvasCalculate（用来计算文字宽度）、this.iCanvasPixel（用于画出文字，并从中得到文字对应的像素点的位置坐标）。
this.iCanvasCalculate 和 this.iCanvasPixel 这两个无需在页面中显示出来，只是辅助作用。
下面就献上棒棒的 JS 实现代码
function Circle() {
var This = this;
this.init();
this.generalRandomParam();
this.drawCircles();
this.ballAnimate();
this.getUserText();
// 窗口改变大小后，生计算并获取画面
window.onresize = function(){
This.stateW = document.body.offsetWidth;
This.stateH = document.body.offsetHeight;
This.iCanvasW = This.iCanvas.width = This.stateW;
This.iCanvasH = This.iCanvas.height = This.stateH;
This.ctx = This.iCanvas.getContext("2d");
}
}
// 初始化
Circle.prototype.init = function(){
//父元素宽高
this.stateW = document.body.offsetWidth;
this.stateH = document.body.offsetHeight;
this.iCanvas = document.createElement("canvas");
// 设置Canvas 与父元素同宽高
this.iCanvasW = this.iCanvas.width = this.stateW;
this.iCanvasH = this.iCanvas.height = this.stateH;
// 获取 2d 绘画环境
this.ctx = this.iCanvas.getContext("2d");
// 插入到 body 元素中
document.body.appendChild(this.iCanvas);
this.iCanvasCalculate = document.createElement("canvas");
// 用于保存计算文字宽度的画布
this.mCtx = this.iCanvasCalculate.getContext("2d");
this.mCtx.font = "128px 微软雅黑";
this.iCanvasPixel = document.createElement("canvas");
this.iCanvasPixel.setAttribute("style","position:absolute;top:0;left:0;");
this.pCtx = null; // 用于绘画文字的画布
// 随机生成圆的数量
this.ballNumber = ramdomNumber(1000, 2000);
// 保存所有小球的数组
this.balls = [];
// 保存动画中最后一个停止运动的小球
this.animte = null;
this.imageData = null;
this.textWidth = 0; // 保存生成文字的宽度
this.textHeight = 150; // 保存生成文字的高度
this.inputText = ""; // 保存用户输入的内容
this.actionCount = 0;
this.ballActor = []; // 保存生成文字的粒子
this.actorNumber = 0; // 保存生成文字的粒子数量
this.backType = "back"; // 归位
this.backDynamics = ""; // 动画效果
this.isPlay = false; // 标识（在生成文字过程中，不能再生成）
}
// 渲染出所有圆
Circle.prototype.drawCircles = function () {
for(var i=0;i<this.ballNumber;i++){
this.renderBall(this.balls[0]);
}
}
// 获取用户输入文字
Circle.prototype.getUserText = function(){
This = this; // 保存 this 指向
ipu = document.getElementById("input-text");
ipu.addEventListener("keydown",function(event){
if(event.which === 13){ // 如果是回车键
ipu.value = ipu.value.trim(); // 去头尾空格
var pat = /[\u4e00-\u9fa5]/; // 中文判断
var isChinese = pat.test(ipu.value);
if(ipu.value.length !=0 && isChinese){
This.inputText = ipu.value;
}else{
alert("请输入汉字");
return;
}
if(This.isPlay){
return
}
This.getAnimateType();
This.getTextPixel();
This.isPlay = true;
}
});
}
// 计算文字的宽
Circle.prototype.calculateTextWidth = function () {
this.textWidth = this.mCtx.measureText(this.inputText).width;
}
// 获取文字像素点
Circle.prototype.getTextPixel = function () {
if(this.pCtx){
this.pCtx.clearRect(0,0,this.textWidth,this.textHeight);
}
this.calculateTextWidth(this.inputText);
this.iCanvasPixel.width = this.textWidth;
this.iCanvasPixel.height = this.textHeight;
this.pCtx = this.iCanvasPixel.getContext("2d");
this.pCtx.font = "128px 微软雅黑";
this.pCtx.fillStyle = "#FF0000";
this.pCtx.textBaseline = "botom";
this.pCtx.fillText(this.inputText,0,110);
this.imageData = this.pCtx.getImageData(0,0,this.textWidth,this.textHeight).data;
this.getTextPixelPosition(this.textWidth,this.textHeight);
}
// 获取文字粒子像素点位置
Circle.prototype.getTextPixelPosition = function (width,height) {
var left = (this.iCanvasW - width)/2;
var top = (this.iCanvasH - height)/2;
var space = 4;
this.actionCount = 0;
for(var i=0;i<this.textHeight;i+=space){
for(var j=0;j<this.textWidth;j+=space){
var index = j*space+i*this.textWidth*4;
if(this.imageData[index] == 255){
if(this.actionCount<this.ballNumber){
this.balls[this.actionCount].status = 1;
this.balls[this.actionCount].targetX = left+j;
this.balls[this.actionCount].targetY = top+i;
this.balls[this.actionCount].backX = this.balls[this.actionCount].x;
this.balls[this.actionCount].backY = this.balls[this.actionCount].y;
this.ballActor.push(this.balls[this.actionCount]);
this.actionCount++;
}
}
}
this.actorNumber = this.ballActor.length;
}
this.animateToText();
}
// 粒子运动到指定位置
Circle.prototype.animateToText = function(){
for(var i=0;i<This.actorNumber;i++){
dynamics.animate(This.ballActor[i], {
x: this.ballActor[i].targetX,
y: this.ballActor[i].targetY
},{
type: dynamics.easeIn,
duration: 1024,
});
}
setTimeout(function(){
This.ballbackType();
},3000);
}
// 粒子原路返回
Circle.prototype.ballBackPosition = function(){
for(var i=0;i<This.actorNumber;i++){
var ball = This.ballActor[i];
dynamics.animate(ball, {
x: ball.backX,
y: ball.backY
},{
type: dynamics[this.backDynamics],
duration: 991,
complete:this.changeStatus(ball)
});
}
}
// 获取类型|动画效果
Circle.prototype.getAnimateType = function() {
var selectType = document.getElementById("selectType");
var selectDynamics = document.getElementById("selectDynamics");
this.backType = selectType.options[selectType.options.selectedIndex].value;
this.backDynamics = selectDynamics.options[selectDynamics.options.selectedIndex].value;
}
// 复位散开
Circle.prototype.ballbackType = function(){
if(this.backType == "back"){
this.ballBackPosition();
}else{
this.ballAutoPosition();
}
this.ballActor = [];
}
// 随机散开
Circle.prototype.ballAutoPosition = function(ball){
for(var i=0;i<this.actorNumber;i++){
this.changeStatus(this.ballActor[i])
}
}
// 更改小球状态
Circle.prototype.changeStatus = function(ball){
ball.status = 0;
if(this.isPlay == true){
this.isPlay = false;
}
}
// 随机生成每个圆的相关参数
Circle.prototype.generalRandomParam = function(){
for(var i=0;i<this.ballNumber;i++){
var ball = {};
ball.size = 1; // 随机生成圆半径
// 随机生成圆心 x 坐标
ball.x = ramdomNumber(0+ball.size, this.iCanvasW-ball.size);
ball.y = ramdomNumber(0+ball.size, this.iCanvasH-ball.size);
ball.speedX = ramdomNumber(-1, 1);
ball.speedY = ramdomNumber(-1, 1);
this.balls.push(ball);
ball.status = 0;
ball.targetX = 0;
ball.targetY = 0;
ball.backX = 0;
ball.backY = 0;
}
}
// 改变圆的位置
Circle.prototype.changeposition = function(){
for(var i=0;i<this.ballNumber;i++){
if( this.balls[i].status == 0){
this.balls[i].x += this.balls[i].speedX;
this.balls[i].y += this.balls[i].speedY;
}
}
}
// 画圆
Circle.prototype.renderBall = function(ball){
this.ctx.fillStyle = "#fff";
this.ctx.beginPath(); // 这个一定要加
this.ctx.arc(ball.x, ball.y, ball.size, 0, 2 * Math.PI);
this.ctx.closePath(); // 这个一定要加
this.ctx.fill();
}
// 小球碰撞判断
Circle.prototype.collision = function(ball){
for(var i=0;i<this.ballNumber;i++){
if(ball.x>this.iCanvasW-ball.size || ball.x<ball.size){
if(ball.x>this.iCanvasW-ball.size){
ball.x = this.iCanvasW-ball.size;
}else{
ball.x = ball.size;
}
ball.speedX = - ball.speedX;
}
if(ball.y>this.iCanvasH-ball.size || ball.y<ball.size){
if(ball.y>this.iCanvasH-ball.size){
ball.y = this.iCanvasH-ball.size;
}else{
ball.y = ball.size;
}
ball.speedY = - ball.speedY;
}
}
}
// 开始动画
Circle.prototype.ballAnimate = function(){
var This = this;
var animateFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;
(function move(){
animte = animateFrame(move);
This.ctx.clearRect(0, 0, This.iCanvasW, This.iCanvasH);
This.changeposition();
for(var i=0;i<This.ballNumber;i++){
This.collision(This.balls[i]);
This.renderBall(This.balls[i]);
}
})();
}
// 生成一个随机数
function ramdomNumber(min, max) {
return Math.random() * (max - min) + min;
}
看了代码估计也只是心里炫了一下，也没有让你想把这个东西做出来的欲望，为此我知道必需得让你眼睛心服口服才行。在线 DEMO： 动感的粒子示例。
人无完人，代码也一样。看起来运行顺畅的代码也或多或少有一些瑕疵，日前这个效果还只支持中文。英文的话，我得再努力一把，不管怎么样，英文后面肯定是会加入来的，只是时间问题了。还有代码中用于标记是否可再次执行生成文字的 属性：this.isPlay ，还是一点瑕疵，this.isPlay 的状态更改没有准确的在粒子归位的那一瞬间更改，而是提前更改了状态。但这个状态不会影响本例子效果的完整实现。
这个例子中用到了 dynamics.js 库，主要是用到它里面的一些运动函数，让粒子动起来更感人一些，仅此而已。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持路饭。
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