canvas基础学习（二）-填充样式（线性渐变和径向渐变）

最新推荐文章于 2024-08-08 00:00:00 发布

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本文介绍如何使用HTML5的Canvas API实现线性和径向渐变效果。通过创建不同类型的渐变对象，并设置颜色停靠点，最终填充整个画布区域，展示从白色过渡到黑色的效果。适用于前端开发人员学习。

<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title>线性渐变</title>
	</head>
	<body>
		<canvas id="canvas" style="border: 1px solid #aaa;display: block;margin: 50px auto;">
			你当前的浏览器不支持canvas，请更换浏览器再试。
		</canvas>
		
		<script>
			
			window.onload = function(){
				var canvas = document.getElementById("canvas");
				
				canvas.width = 800;
				canvas.height = 600;
				
				var context = canvas.getContext("2d");
				
				//var linearGrad = context.createLinearGradient(0, 0, 800, 0);//竖直渐变
				//var linearGrad = context.createLinearGradient(0, 0, 0, 600);//水平渐变
				var linearGrad = context.createLinearGradient(0, 0, 400, 300);//对角线渐变到（400，300）这个坐标
				linearGrad.addColorStop(0.0, 'white');
				linearGrad.addColorStop(0.25, 'yellow');
				linearGrad.addColorStop(0.5, 'green');
				linearGrad.addColorStop(0.75, 'blue');
				linearGrad.addColorStop(1.0, 'black');
				context.fillStyle = linearGrad;
				context.fillRect(0, 0, 800,600);
				
			}
		</script>
	</body>
</html>

<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title>径向渐变</title>
	</head>
	<body>
		<canvas id="canvas" style="border: 1px solid #aaa;display: block;margin: 50px auto;">
			你当前的浏览器不支持canvas，请更换浏览器再试。
		</canvas>
		
		<script>
			
			window.onload = function(){
				var canvas = document.getElementById("canvas");
				
				canvas.width = 800;
				canvas.height = 600;
				
				var context = canvas.getContext("2d");
				
				//var linearGrad = context.createLinearGradient(0, 0, 800, 0);//竖直渐变
				//var linearGrad = context.createLinearGradient(0, 0, 0, 600);//水平渐变
				var radialGrad = context.createRadialGradient(400, 300, 0, 400, 300, 400);//对角线渐变到（400，300）这个坐标
				radialGrad.addColorStop(0.0, 'white');
				radialGrad.addColorStop(0.25, 'yellow');
				radialGrad.addColorStop(0.5, 'green');
				radialGrad.addColorStop(0.75, 'blue');
				radialGrad.addColorStop(1.0, 'black');
				context.fillStyle = radialGrad;
				context.fillRect(0, 0, 800,600);
				
			}
		</script>
	</body>
</html>