javascript基于canvas全屏七夕爱心表白动画特效

使用方法

		var hearts = [];
		var canvas = document.getElementById('drawHeart');
		var wW = window.innerWidth;
		var wH = window.innerHeight;
		// 创建画布
		var ctx = canvas.getContext('2d');
		// 创建图片对象
		var heartImage = new Image();
		heartImage.src = 'img/heart.svg';
		var num = 100;

		init();

		window.addEventListener('resize', function(){
			 wW = window.innerWidth;
			 wH = window.innerHeight;
		});
		// 初始化画布大小
		function init(){
			canvas.width = wW;
			canvas.height = wH;
			for(var i = 0; i < num; i++){
				hearts.push(new Heart(i%5));
			}
			requestAnimationFrame(render);
		}

		function getColor(){
			var val = Math.random() * 10;
			if(val > 0 && val <= 1){
				return '#00f';
			} else if(val > 1 && val <= 2){
				return '#f00';
			} else if(val > 2 && val <= 3){
				return '#0f0';
			} else if(val > 3 && val <= 4){
				return '#368';
			} else if(val > 4 && val <= 5){
				return '#666';
			} else if(val > 5 && val <= 6){
				return '#333';
			} else if(val > 6 && val <= 7){
				return '#f50';
			} else if(val > 7 && val <= 8){
				return '#e96d5b';
			} else if(val > 8 && val <= 9){
				return '#5be9e9';
			} else {
				return '#d41d50';
			}
		}

		function getText(){
			var val = Math.random() * 10;
			if(val > 1 && val <= 3){
				return '爱你一辈子';
			} else if(val > 3 && val <= 5){
				return '感谢你';
			} else if(val > 5 && val <= 8){
				return '喜欢你';
			} else{
				return 'I Love You';
			}
		}

		function Heart(type){
			this.type = type;
			// 初始化生成范围
			this.x = Math.random() * wW;
			this.y = Math.random() * wH;

			this.opacity = Math.random() * .5 + .5;

			// 偏移量
			this.vel = {
				x: (Math.random() - .5) * 5,
				y: (Math.random() - .5) * 5
			}

			this.initialW = wW * .5;
			this.initialH = wH * .5;
			// 缩放比例
			this.targetScale = Math.random() * .15 + .02; // 最小0.02
			this.scale = Math.random() * this.targetScale;

			// 文字位置
			this.fx = Math.random() * wW;
			this.fy = Math.random() * wH;
			this.fs = Math.random() * 10;
			this.text = getText();

			this.fvel = {
				x: (Math.random() - .5) * 5,
				y: (Math.random() - .5) * 5,
				f: (Math.random() - .5) * 2
			}
		}

		Heart.prototype.draw = function(){
			ctx.save();
			ctx.globalAlpha = this.opacity;
			ctx.drawImage(heartImage, this.x, this.y, this.width, this.height);
			ctx.scale(this.scale + 1, this.scale + 1);
  			if(!this.type){
  				// 设置文字属性
				ctx.fillStyle = getColor();
	  			ctx.font = 'italic ' + this.fs + 'px sans-serif';
	  			// 填充字符串
	  			ctx.fillText(this.text, this.fx, this.fy);
  			}
			ctx.restore();
		}
		Heart.prototype.update = function(){
			this.x += this.vel.x;
			this.y += this.vel.y;

			if(this.x - this.width > wW || this.x + this.width < 0){
				// 重新初始化位置
				this.scale = 0;
				this.x = Math.random() * wW;
				this.y = Math.random() * wH;
			}
			if(this.y - this.height > wH || this.y + this.height < 0){
				// 重新初始化位置
				this.scale = 0;
				this.x = Math.random() * wW;
				this.y = Math.random() * wH;
			}

			// 放大
			this.scale += (this.targetScale - this.scale) * .1;
			this.height = this.scale * this.initialH;
			this.width = this.height * 1.4;

			// -----文字-----
			this.fx += this.fvel.x;
			this.fy += this.fvel.y;
			this.fs += this.fvel.f;

			if(this.fs > 50){
				this.fs = 2;
			}

			if(this.fx - this.fs > wW || this.fx + this.fs < 0){
				// 重新初始化位置
				this.fx = Math.random() * wW;
				this.fy = Math.random() * wH;
			}
			if(this.fy - this.fs > wH || this.fy + this.fs < 0){
				// 重新初始化位置
				this.fx = Math.random() * wW;
				this.fy = Math.random() * wH;
			}
		}

		function render(){
			ctx.clearRect(0, 0, wW, wH);
			for(var i = 0; i < hearts.length; i++){
				hearts[i].draw();
				hearts[i].update();
			}
			requestAnimationFrame(render);
		}