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【Valentine's Day special effects】--Canvas realizes full screen love

2022-08-04 23:50:00 【love / abuse / time】

 Canvas简介：

Canvas是HTML5的一个新特性,canvas又叫做画板.我们可以在canvas上绘制我们需要的图形.anvas本身是一个HTML元素,需要HTML元素的配合高度和宽度属性而定义出的一块可绘制区域,定义区域之后使用JavaScript的脚本绘制图像的HTML元素.

  • canvas 是一个矩形区域的画布,可以用 JavaScript 在上面绘画.控制其每一个像素.
  • canvas 标签使用 JavaScript 在网页上绘制图像,本身不具备绘图功能.
  • canvas 拥有多种绘制路径、矩形、圆形、字符以及添加图像的方法.
  • HTML5 之前的 web 页面只能用一些固定样式的标签：比如 p、div、h1 等
  • canvas是原生js对象,不建议使用jq

作用：It can basically draw graphics,Further production photos,绘制动画,Going a step further can process and render video.

canvas有两个属性,一个是宽度（width）,one is height（height）.Width and height can use inline properties,如下所示：

    <canvas width="300px" height="150px" id="canvas">
        This is Canvas
        <img src="./backup.jpg" alt=""> 
    </canvas>

注意：Older browsers may not support it,且结尾的</canvas>Labels cannot be omitted.

Canvas with no width and height set by defaultwidth=300px;height=150px;

Canvas小案例：

Full screen love scrolling effect appears：

 实现代码如下;

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>七夕520爱心表白</title>
	<style>
		*{margin:0; padding:0;}
		body{ background-color: #1E1E1E; 		}
	</style>
</head>
<body>

	<canvas id="drawHeart"></canvas>

	<script>
		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 'always';
			} else if(val > 3 && val <= 5){
				return 'zzy';
			} else if(val > 5 && val <= 8){
				return 'taylor swift';
			} 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);
		}
	</script>
</body>
</html>

Name the following code    heart.svg  与上面的htmlStored in the same level file directory to open and run.

<svg xmlns="http://www.w3.org/2000/svg" width="473.8px" height="408.6px" viewBox="0 0 473.8 408.6"><path fill="#d32932" d="M404.6,16.6C385.4,6.1,363.5,0,340,0c-41.5,0-78.5,18.9-103,48.5C212.3,18.9,175.3,0,133.8,0 c-23.3,0-45.3,6.1-64.5,16.6C27.9,39.5,0,83.4,0,133.9c0,14.4,2.4,28.3,6.6,41.2C29.6,278.4,237,408.6,237,408.6 s207.2-130.2,230.2-233.5c4.3-12.9,6.6-26.8,6.6-41.2C473.8,83.4,445.9,39.6,404.6,16.6z"/></svg>

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版权声明
本文为[love / abuse / time]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/216/202208042321507023.html

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