キャンバスに特殊効果の破片花火を使用した黒の背景を作成する方法

今回は、キャンバスを使用した黒い背景と特殊効果のあるパン粉花火の作り方を紹介します。 キャンバスを使用した黒い背景と特殊効果のあるパン粉花火を作成するための注意事項を紹介します。一見。

<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>

css

body {マージン: 0; パディング: 0; オーバーフロー: 非表示;
}.city { 幅: 100%; z-index: 100;
} .city { 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();
    }
}

この記事の事例を読んだ後は、この方法を習得したと思います。さらに興味深い情報については、php 中国語 Web サイトの他の関連記事に注目してください。

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以上がキャンバスに特殊効果の破片花火を使用した黒の背景を作成する方法の詳細内容です。詳細については、PHP 中国語 Web サイトの他の関連記事を参照してください。