直接上代碼 ，不懂可以看代碼注釋。估計就會看明白大概的思路了。
html 代碼
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Canvas 實現炫麗的粒子運動效果-雲庫前端</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><p class="operator-box"><p class="flex-box"> <p class="back-type">散開類型： <select name="" id="selectType"> <option value="back">歸位</option> <option value="auto">隨機</option> </select> </p> <p class="back-animate">散開效果（對歸位有效）： <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> </p> <p class="input-box"><input type="text" placeholder="輸入漢字後斷行符號" id="input-text"></p></p></p><script src="dynamics.min.js"></script><script src="index.js"></script><script>var iCircle = new Circle();</script></body></html>
HTML 程式碼不多，只要是幾個操作元素。這裡一看就明白。不費過多口舌。我們來看看本文的主角 JavaScript 代碼，不過，在看代碼前，我們不妨先聽聽實現這個效果的思路：
首先，我們得先產生一堆群眾演員（粒子）；
把每個粒子的相關參數掛到自身的一些屬性上，因為第個粒子都會有自己的運動軌跡；
接著得讓它們各自運動起來。運動有兩種（自由運動和產生文字的運動）；
JavaScript 代碼中使用了三個 Canvas 畫布，this.iCanvas（主場）、this.iCanvasCalculate（用來計算文字寬度）、this.iCanvasPixel（用於畫出文字，並從中得到文字對應的像素點的位置座標）。
this.iCanvasCalculate 和 this.iCanvasPixel 這兩個無需在頁面中顯示出來，只是輔助作用。
下面就獻上棒棒的 JS 實現代碼
function Circle() { var This = this; this.init(); this.generalRandomParam(); this.drawCircles(); this.ballAnimate(); this.getUserText(); // 視窗改變大小後，生計算並擷取畫面 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(){ //父元素寬高 this.stateW = document.body.offsetWidth; this.stateH = document.body.offsetHeight; this.iCanvas = document.createElement("canvas"); // 設定Canvas 與父元素同寬高 this.iCanvasW = this.iCanvas.width = this.stateW; this.iCanvasH = this.iCanvas.height = this.stateH; // 擷取 2d 繪畫環境 this.ctx = this.iCanvas.getContext("2d"); // 插入到 body 元素中 document.body.appendChild(this.iCanvas); this.iCanvasCalculate = document.createElement("canvas"); // 用於儲存計算文字寬度的畫布 this.mCtx = this.iCanvasCalculate.getContext("2d"); this.mCtx.font = "128px 微軟雅黑"; this.iCanvasPixel = document.createElement("canvas"); this.iCanvasPixel.setAttribute("style","position:absolute;top:0;left:0;"); this.pCtx = null; // 用於繪畫文字的畫布 // 隨機產生圓的數量 this.ballNumber = ramdomNumber(1000, 2000); // 儲存所有小球的數組 this.balls = []; // 儲存動畫中最後一個停止運動的小球 this.animte = null; this.imageData = null; this.textWidth = 0; // 儲存產生文字的寬度 this.textHeight = 150; // 儲存產生文字的高度 this.inputText = ""; // 儲存使用者輸入的內容 this.actionCount = 0; this.ballActor = []; // 儲存產生文字的粒子 this.actorNumber = 0; // 儲存產生文字的粒子數量 this.backType = "back"; // 歸位 this.backDynamics = ""; // 動畫效果 this.isPlay = false; // 標識（在產生文字過程中，不能再產生）}// 渲染出所有圓Circle.prototype.drawCircles = function () { for(var i=0;i<this.ballNumber;i++){ this.renderBall(this.balls[0]); }}// 擷取使用者輸入文字Circle.prototype.getUserText = function(){ This = this; // 儲存 this 指向 ipu = document.getElementById("input-text"); ipu.addEventListener("keydown",function(event){ if(event.which === 13){ // 如果是斷行符號鍵 ipu.value = ipu.value.trim(); // 去頭尾空格 var pat = /[\u4e00-\u9fa5]/; // 中文判斷 var isChinese = pat.test(ipu.value); if(ipu.value.length !=0 && isChinese){ This.inputText = ipu.value; }else{ alert("請輸入漢字"); return; } if(This.isPlay){ return } This.getAnimateType(); This.getTextPixel(); This.isPlay = true; } });}// 計算文字的寬Circle.prototype.calculateTextWidth = function () { this.textWidth = this.mCtx.measureText(this.inputText).width;}// 擷取文字像素點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 微軟雅黑"; 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);}// 擷取文字粒子像素點位置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();}// 粒子運動到指定位置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) }); }}// 擷取類型|動畫效果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;}// 複位散開Circle.prototype.ballbackType = function(){ if(this.backType == "back"){ this.ballBackPosition(); }else{ this.ballAutoPosition(); } this.ballActor = [];}// 隨機散開Circle.prototype.ballAutoPosition = function(ball){ for(var i=0;i<this.actorNumber;i++){ this.changeStatus(this.ballActor[i]) }}// 更改小球狀態Circle.prototype.changeStatus = function(ball){ ball.status = 0; if(this.isPlay == true){ this.isPlay = false; }}// 隨機產生每個圓的相關參數Circle.prototype.generalRandomParam = function(){ for(var i=0;i<this.ballNumber;i++){ var ball = {}; ball.size = 1; // 隨機產生圓半徑 // 隨機產生圓心 x 座標 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; }}// 改變圓的位置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; } }}// 畫圓Circle.prototype.renderBall = function(ball){ this.ctx.fillStyle = "#fff"; this.ctx.beginPath(); // 這個一定要加 this.ctx.arc(ball.x, ball.y, ball.size, 0, 2 * Math.PI); this.ctx.closePath(); // 這個一定要加 this.ctx.fill();}// 小球碰撞判斷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; } }}// 開始動畫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]); } })();}// 產生一個隨機數function ramdomNumber(min, max) { return Math.random() * (max - min) + min;}
看了代碼估計也只是心裡炫了一下，也沒有讓你想把這個東西做出來的慾望，為此我知道必需得讓你眼睛心服口服才行。線上 DEMO： 動感的粒子樣本。
人無完人，代碼也一樣。看起來運行順暢的代碼也或多或少有一些瑕疵，日前這個效果還只支援中文。英文的話，我得再努力一把，不管怎麼樣，英文後面肯定是會加入來的，只是時間問題了。還有代碼中用於標記是否可再次執行產生文字的 屬性：this.isPlay ，還是一點瑕疵，this.isPlay 的狀態更改沒有準確的在粒子歸位的那一瞬間更改，而是提前更改了狀態。但這個狀態不會影響本例子效果的完整實現。
這個例子中用到了 dynamics.js 庫，主要是用到它裡面的一些運動函數，讓粒子動起來更感人一些，僅此而已。
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