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这次给大家带来canvas怎样做出黑色背景带特效碎屑烟花，canvas做出黑色背景带特效碎屑烟花的注意事项有哪些，下面就是实战案例，一起来看一下。
<canvas id="cas" style="background-color:rgba(0,5,24,1)" width="1235" height="680">浏览器不支持canvas</canvas><div class="city"> <img src="city.png" alt=""></div><img src="moon.png" alt="" id="moon" style="visibility: hidden;"><div style="display:none"> <div class="shape">新年快乐</div> <div class="shape">阖家欢乐</div> <div class="shape">万事如意</div> <div class="shape">心想事成</div> </div>登录后复制
css
body { margin: 0; padding: 0; overflow: hidden;}.city { width: 100%; position: fixed; bottom: 0px; z-index: 100;}.city img { width: 100%;}
js
var canvas = document.getElementById("cas");var ocas = document.createElement("canvas");var octx = ocas.getContext("2d");var ctx = canvas.getContext("2d");ocas.width = canvas.width = window.innerWidth;ocas.height = canvas.height = window.innerHeight;var bigbooms = [];window.onload = function () { initAnimate()}function initAnimate() { drawBg(); lastTime = new Date(); animate();}var lastTime;function animate() { ctx.save(); ctx.fillStyle = "rgba(0,5,24,0.1)"; ctx.fillRect(0, 0, canvas.width, canvas.height); ctx.restore(); var newTime = new Date(); if (newTime - lastTime > 500 + (window.innerHeight - 767) / 2) { var random = Math.random() * 100 > 2 ? true : false; var x = getRandom(canvas.width / 5, canvas.width * 4 / 5); var y = getRandom(50, 200); if (random) { var bigboom = new Boom(getRandom(canvas.width / 3, canvas.width * 2 / 3), 2, "#FFF", { x: x, y: y }); bigbooms.push(bigboom) } else { var bigboom = new Boom(getRandom(canvas.width / 3, canvas.width * 2 / 3), 2, "#FFF", { x: canvas.width / 2, y: 200 }, document.querySelectorAll(".shape")[parseInt(getRandom(0, document.querySelectorAll( ".shape").length))]); bigbooms.push(bigboom) } lastTime = newTime; } stars.foreach(function () { this.paint(); }) drawMoon(); bigbooms.foreach(function (index) { var that = this; if (!this.dead) { this._move(); this._drawLight(); } else { this.booms.foreach(function (index) { if (!this.dead) { this.moveTo(index); } else if (index === that.booms.length - 1) { bigbooms[bigbooms.indexOf(that)] = null; } }) } }); raf(animate);}function drawMoon() { var moon = document.getElementById("moon"); var centerX = canvas.width - 200, centerY = 100, width = 80; if (moon.complete) { ctx.drawImage(moon, centerX, centerY, width, width) } else { moon.onload = function () { ctx.drawImage(moon, centerX, centerY, width, width) } } var index = 0; for (var i = 0; i < 10; i++) { ctx.save(); ctx.beginPath(); ctx.arc(centerX + width / 2, centerY + width / 2, width / 2 + index, 0, 2 * Math.PI); ctx.fillStyle = "rgba(240,219,120,0.005)"; index += 2; ctx.fill(); ctx.restore(); }}Array.prototype.foreach = function (callback) { for (var i = 0; i < this.length; i++) { if (this[i] !== null) callback.apply(this[i], [i]) }}var raf = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function (callback) { window.setTimeout(callback, 1000 / 60); };canvas.onclick = function () { var x = event.clientX; var y = event.clientY; var bigboom = new Boom(getRandom(canvas.width / 3, canvas.width * 2 / 3), 2, "#FFF", { x: x, y: y }); bigbooms.push(bigboom)}var Boom = function (x, r, c, boomArea, shape) { this.booms = []; this.x = x; this.y = (canvas.height + r); this.r = r; this.c = c; this.shape = shape || false; this.boomArea = boomArea; this.theta = 0; this.dead = false; this.ba = parseInt(getRandom(80, 200));}Boom.prototype = { _paint: function () { ctx.save(); ctx.beginPath(); ctx.arc(this.x, this.y, this.r, 0, 2 * Math.PI); ctx.fillStyle = this.c; ctx.fill(); ctx.restore(); }, _move: function () { var dx = this.boomArea.x - this.x, dy = this.boomArea.y - this.y; this.x = this.x + dx * 0.01; this.y = this.y + dy * 0.01; if (Math.abs(dx) <= this.ba && Math.abs(dy) <= this.ba) { if (this.shape) { this._shapBoom(); } else this._boom(); this.dead = true; } else { this._paint(); } }, _drawLight: function () { ctx.save(); ctx.fillStyle = "rgba(255,228,150,0.3)"; ctx.beginPath(); ctx.arc(this.x, this.y, this.r + 3 * Math.random() + 1, 0, 2 * Math.PI); ctx.fill(); ctx.restore(); }, _boom: function () { var fragNum = getRandom(30, 200); var style = getRandom(0, 10) >= 5 ? 1 : 2; var color; if (style === 1) { color = { a: parseInt(getRandom(128, 255)), b: parseInt(getRandom(128, 255)), c: parseInt(getRandom(128, 255)) } } var fanwei = parseInt(getRandom(300, 400)); for (var i = 0; i < fragNum; i++) { if (style === 2) { color = { a: parseInt(getRandom(128, 255)), b: parseInt(getRandom(128, 255)), c: parseInt(getRandom(128, 255)) } } var a = getRandom(-Math.PI, Math.PI); var x = getRandom(0, fanwei) * Math.cos(a) + this.x; var y = getRandom(0, fanwei) * Math.sin(a) + this.y; var radius = getRandom(0, 2) var frag = new Frag(this.x, this.y, radius, color, x, y); this.booms.push(frag); } }, _shapBoom: function () { var that = this; putValue(ocas, octx, this.shape, 5, function (dots) { var dx = canvas.width / 2 - that.x; var dy = canvas.height / 2 - that.y; for (var i = 0; i < dots.length; i++) { color = { a: dots[i].a, b: dots[i].b, c: dots[i].c } var x = dots[i].x; var y = dots[i].y; var radius = 1; var frag = new Frag(that.x, that.y, radius, color, x - dx, y - dy); that.booms.push(frag); } }) }}function putValue(canvas, context, ele, dr, callback) { context.clearRect(0, 0, canvas.width, canvas.height); var img = new Image(); if (ele.innerHTML.indexOf("img") >= 0) { img.src = ele.getElementsByTagName("img")[0].src; imgload(img, function () { context.drawImage(img, canvas.width / 2 - img.width / 2, canvas.height / 2 - img.width / 2); dots = getimgData(canvas, context, dr); callback(dots); }) } else { var text = ele.innerHTML; context.save(); var fontSize = 200; context.font = fontSize + "px 宋体 bold"; context.textAlign = "center"; context.textBaseline = "middle"; context.fillStyle = "rgba(" + parseInt(getRandom(128, 255)) + "," + parseInt(getRandom(128, 255)) + "," + parseInt(getRandom(128, 255)) + " , 1)"; context.fillText(text, canvas.width / 2, canvas.height / 2); context.restore(); dots = getimgData(canvas, context, dr); callback(dots); }}function imgload(img, callback) { if (img.complete) { callback.call(img); } else { img.onload = function () { callback.call(this); } }}function getimgData(canvas, context, dr) { var imgData = context.getImageData(0, 0, canvas.width, canvas.height); context.clearRect(0, 0, canvas.width, canvas.height); var dots = []; for (var x = 0; x < imgData.width; x += dr) { for (var y = 0; y < imgData.height; y += dr) { var i = (y * imgData.width + x) * 4; if (imgData.data[i + 3] > 128) { var dot = { x: x, y: y, a: imgData.data[i], b: imgData.data[i + 1], c: imgData.data[i + 2] }; dots.push(dot); } } } return dots;}function getRandom(a, b) { return Math.random() * (b - a) + a;}var maxRadius = 1, stars = [];function drawBg() { for (var i = 0; i < 100; i++) { var r = Math.random() * maxRadius; var x = Math.random() * canvas.width; var y = Math.random() * 2 * canvas.height - canvas.height; var star = new Star(x, y, r); stars.push(star); star.paint() }}var Star = function (x, y, r) { this.x = x; this.y = y; this.r = r;}Star.prototype = { paint: function () { ctx.save(); ctx.beginPath(); ctx.arc(this.x, this.y, this.r, 0, 2 * Math.PI); ctx.fillStyle = "rgba(255,255,255," + this.r + ")"; ctx.fill(); ctx.restore(); }}var focallength = 250;var Frag = function (centerX, centerY, radius, color, tx, ty) { this.tx = tx; this.ty = ty; this.x = centerX; this.y = centerY; this.dead = false; this.centerX = centerX; this.centerY = centerY; this.radius = radius; this.color = color;}Frag.prototype = { paint: function () { ctx.save(); ctx.beginPath(); ctx.arc(this.x, this.y, this.radius, 0, 2 * Math.PI); ctx.fillStyle = "rgba(" + this.color.a + "," + this.color.b + "," + this.color.c + ",1)"; ctx.fill() ctx.restore(); }, moveTo: function (index) { this.ty = this.ty + 0.3; var dx = this.tx - this.x, dy = this.ty - this.y; this.x = Math.abs(dx) < 0.1 ? this.tx : (this.x + dx * 0.1); this.y = Math.abs(dy) < 0.1 ? this.ty : (this.y + dy * 0.1); if (dx === 0 && Math.abs(dy) <= 80) { this.dead = true; } this.paint(); }}登录后复制相信看了本文案例你已经掌握了方法，更多精彩请关注9543建站博客其它相关文章！
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以上就是canvas怎样做出黑色背景带特效碎屑烟花的详细内容，更多请关注9543建站博客其它相关文章！
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