Cette fois je vais vous montrer comment réaliser un feu d'artifice rouge sur fond noir à l'aide de toile. Quelles sont les précautions pour réaliser un feu d'artifice rouge à fond noir à l'aide de toile. Voici un cas pratique, jetons un oeil. .
html
<canvas id="canvas"></canvas>
css
body { background: #000; margin: 0; }canvas { cursor: crosshair; display: block;}
js
// when animating on canvas, it is best to use requestAnimationFrame instead of setTimeout or setInterval// not supported in all browsers though and sometimes needs a prefix, so we need a shimwindow.requestAnimFrame = (function () { return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || function (callback) { window.setTimeout(callback, 1000 / 60); }; })();// now we will setup our basic variables for the demovar canvas = document.getElementById('canvas'), ctx = canvas.getContext('2d'), // full screen dimensions cw = window.innerWidth, ch = window.innerHeight, // firework collection fireworks = [], // particle collection particles = [], // starting hue hue = 120, // when launching fireworks with a click, too many get launched at once without a limiter, one launch per 5 loop ticks limiterTotal = 5, limiterTick = 0, // this will time the auto launches of fireworks, one launch per 80 loop ticks timerTotal = 80, timerTick = 0, mousedown = false, // mouse x coordinate, mx, // mouse y coordinate my;// set canvas dimensionscanvas.width = cw; canvas.height = ch;// now we are going to setup our function placeholders for the entire demo// get a random number within a rangefunction random(min, max) { return Math.random() * (max - min) + min; }// calculate the distance between two pointsfunction calculateDistance(p1x, p1y, p2x, p2y) { var xDistance = p1x - p2x, yDistance = p1y - p2y; return Math.sqrt(Math.pow(xDistance, 2) + Math.pow(yDistance, 2)); }// create fireworkfunction Firework(sx, sy, tx, ty) { // actual coordinates this.x = sx; this.y = sy; // starting coordinates this.sx = sx; this.sy = sy; // target coordinates this.tx = tx; this.ty = ty; // distance from starting point to target this.distanceToTarget = calculateDistance(sx, sy, tx, ty); this.distanceTraveled = 0; // track the past coordinates of each firework to create a trail effect, increase the coordinate count to create more prominent trails this.coordinates = []; this.coordinateCount = 3; // populate initial coordinate collection with the current coordinates while (this.coordinateCount--) { this.coordinates.push([this.x, this.y]); } this.angle = Math.atan2(ty - sy, tx - sx); this.speed = 2; this.acceleration = 1.05; this.brightness = random(50, 70); // circle target indicator radius this.targetRadius = 1; }// update fireworkFirework.prototype.update = function (index) { // remove last item in coordinates array this.coordinates.pop(); // add current coordinates to the start of the array this.coordinates.unshift([this.x, this.y]); // cycle the circle target indicator radius if (this.targetRadius < 8) { this.targetRadius += 0.3; } else { this.targetRadius = 1; } // speed up the firework this.speed *= this.acceleration; // get the current velocities based on angle and speed var vx = Math.cos(this.angle) * this.speed, vy = Math.sin(this.angle) * this.speed; // how far will the firework have traveled with velocities applied? this.distanceTraveled = calculateDistance(this.sx, this.sy, this.x + vx, this.y + vy); // if the distance traveled, including velocities, is greater than the initial distance to the target, then the target has been reached if (this.distanceTraveled >= this.distanceToTarget) { createParticles(this.tx, this.ty); // remove the firework, use the index passed into the update function to determine which to remove fireworks.splice(index, 1); } else { // target not reached, keep traveling this.x += vx; this.y += vy; } }// draw fireworkFirework.prototype.draw = function () { ctx.beginPath(); // move to the last tracked coordinate in the set, then draw a line to the current x and y ctx.moveTo(this.coordinates[this.coordinates.length - 1][0], this.coordinates[this.coordinates.length - 1][ 1 ]); ctx.lineTo(this.x, this.y); ctx.strokeStyle = 'hsl(' + hue + ', 100%, ' + this.brightness + '%)'; ctx.stroke(); ctx.beginPath(); // draw the target for this firework with a pulsing circle ctx.arc(this.tx, this.ty, this.targetRadius, 0, Math.PI * 2); ctx.stroke(); }// create particlefunction Particle(x, y) { this.x = x; this.y = y; // track the past coordinates of each particle to create a trail effect, increase the coordinate count to create more prominent trails this.coordinates = []; this.coordinateCount = 5; while (this.coordinateCount--) { this.coordinates.push([this.x, this.y]); } // set a random angle in all possible directions, in radians this.angle = random(0, Math.PI * 2); this.speed = random(1, 10); // friction will slow the particle down this.friction = 0.95; // gravity will be applied and pull the particle down this.gravity = 1; // set the hue to a random number +-20 of the overall hue variable this.hue = random(hue - 20, hue + 20); this.brightness = random(50, 80); this.alpha = 1; // set how fast the particle fades out this.decay = random(0.015, 0.03); }// update particleParticle.prototype.update = function (index) { // remove last item in coordinates array this.coordinates.pop(); // add current coordinates to the start of the array this.coordinates.unshift([this.x, this.y]); // slow down the particle this.speed *= this.friction; // apply velocity this.x += Math.cos(this.angle) * this.speed; this.y += Math.sin(this.angle) * this.speed + this.gravity; // fade out the particle this.alpha -= this.decay; // remove the particle once the alpha is low enough, based on the passed in index if (this.alpha <= this.decay) { particles.splice(index, 1); } }// draw particleParticle.prototype.draw = function () { ctx.beginPath(); // move to the last tracked coordinates in the set, then draw a line to the current x and y ctx.moveTo(this.coordinates[this.coordinates.length - 1][0], this.coordinates[this.coordinates.length - 1][ 1 ]); ctx.lineTo(this.x, this.y); ctx.strokeStyle = 'hsla(' + this.hue + ', 100%, ' + this.brightness + '%, ' + this.alpha + ')'; ctx.stroke(); }// create particle group/explosionfunction createParticles(x, y) { // increase the particle count for a bigger explosion, beware of the canvas performance hit with the increased particles though var particleCount = 30; while (particleCount--) { particles.push(new Particle(x, y)); } }// main demo loopfunction loop() { // this function will run endlessly with requestAnimationFrame requestAnimFrame(loop); // increase the hue to get different colored fireworks over time hue += 0.5; // normally, clearRect() would be used to clear the canvas // we want to create a trailing effect though // setting the composite operation to destination-out will allow us to clear the canvas at a specific opacity, rather than wiping it entirely ctx.globalCompositeOperation = 'destination-out'; // decrease the alpha property to create more prominent trails ctx.fillStyle = 'rgba(0, 0, 0, 0.5)'; ctx.fillRect(0, 0, cw, ch); // change the composite operation back to our main mode // lighter creates bright highlight points as the fireworks and particles overlap each other ctx.globalCompositeOperation = 'lighter'; var text = "HAPPY NEW YEAR !"; ctx.font = "50px sans-serif"; var textData = ctx.measureText(text); ctx.fillStyle = "rgba(" + parseInt(random(0, 255)) + "," + parseInt(random(0, 255)) + "," + parseInt(random(0, 255)) + ",0.3)"; ctx.fillText(text, cw / 2 - textData.width / 2, ch / 2); // loop over each firework, draw it, update it var i = fireworks.length; while (i--) { fireworks[i].draw(); fireworks[i].update(i); } // loop over each particle, draw it, update it var i = particles.length; while (i--) { particles[i].draw(); particles[i].update(i); } // launch fireworks automatically to random coordinates, when the mouse isn't down if (timerTick >= timerTotal) { if (!mousedown) { // start the firework at the bottom middle of the screen, then set the random target coordinates, the random y coordinates will be set within the range of the top half of the screen for (var h = 0; h < 50; h++) { fireworks.push(new Firework(cw / 2, ch / 2, random(0, cw), random(0, ch))); } timerTick = 0; } } else { timerTick++; } // limit the rate at which fireworks get launched when mouse is down if (limiterTick >= limiterTotal) { if (mousedown) { // start the firework at the bottom middle of the screen, then set the current mouse coordinates as the target fireworks.push(new Firework(cw / 2, ch / 2, mx, my)); limiterTick = 0; } } else { limiterTick++; } }// mouse event bindings// update the mouse coordinates on mousemovecanvas.addEventListener('mousemove', function (e) { mx = e.pageX - canvas.offsetLeft; my = e.pageY - canvas.offsetTop; });// toggle mousedown state and prevent canvas from being selectedcanvas.addEventListener('mousedown', function (e) { e.preventDefault(); mousedown = true; }); canvas.addEventListener('mouseup', function (e) { e.preventDefault(); mousedown = false; });// once the window loads, we are ready for some fireworks!window.onload = loop;
Je crois que vous avez lu le cas dans cet article Vous maîtrisez la méthode. Pour des informations plus intéressantes, veuillez prêter attention aux autres articles connexes sur le site Web chinois de php !
Lecture recommandée :
Utilisation du CSS dans React.js
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