HTML5的canvas标签用于绘制图像(通过脚本,通常是 JavaScript)。不过,canvas元素本身并没有绘制能力(它仅仅是图形的容器)必须使用脚本来完成实际的绘图任务。
下面,具体总结了一下使用画布canvas的步骤:
画布:
canvas
在页面上规划出一块空间,canvas标签,通过javascript控制画布完成绘制
1.获取画布
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var canvas=document.getElementById( "" );
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2.获取上下文对象 (获取画笔)
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var cx=canvas.getContext(“2d”);
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3.设置画笔样式
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cx.fillStyle=‘red ';
cx.strokeStyle=‘blue' ;
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4.开始绘制
下面是对于canvas使用,绘制一个简单钟表的小例子:
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<!DOCTYPE html>
< html lang = "en" >
< head >
< meta charset = "UTF-8" >
< meta name = "viewport" content = "width=device-width, initial-scale=1.0" >
< title >Document</ title >
< script >
window.onload=function(){
//1.获取画布
var canvas=document.getElementById("canvas");
//2.获取画笔
var cx=canvas.getContext("2d");
function clock(){
//3.设置画笔样式
cx.fillStyle="orange";
//4.绘制图形
//绘制表盘
cx.beginPath();
cx.arc(300,300,200,0,Math.PI*2)
cx.closePath();
cx.fill();
//绘制时刻度
cx.lineWidth=2;
cx.strokeStyle="black";
for(var i=0;i< 12 ;i++){
cx.save();
cx.translate(300,300);
cx.rotate(i*(Math.PI/6));
// cx.beginPath();
cx.moveTo(0,-180);
cx.lineTo(0,-200);
// cx.closePath();
cx.stroke();
cx.fillStyle = "black" ;
cx.font = "16px blod" ;
cx.rotate(Math.PI/6)
cx.fillText(i+1,-5,-220);
cx.restore();
}
//绘制分刻度
for(var i = 0 ;i<60;i++){
cx.save();
cx.translate(300,300);
cx.rotate(i*(Math.PI/30));
cx.beginPath();
cx.moveTo(0,-190);
cx.lineTo(0,-200);
cx.closePath();
cx.stroke();
cx.restore();
}
//获取当前时间
var today = new Date();
var hour = today .getHours();
var min = today .getMinutes();
var sec = today .getSeconds();
hour =hour+min/60;
//绘制时针
cx.lineWidth = 5 ;
cx.save();
cx.beginPath();
cx.translate(300,300);
cx.rotate(hour*(Math.PI/6));
cx.moveTo(0,10);
cx.lineTo(0,-100);
cx.closePath();
cx.stroke();
cx.restore();
//绘制分针
cx.lineWidth = 3 ;
cx.save();
cx.beginPath();
cx.translate(300,300);
cx.rotate(min*(Math.PI/30));
cx.moveTo(0,10);
cx.lineTo(0,-120);
cx.closePath();
cx.stroke();
cx.restore();
//绘制秒针
cx.lineWidth = 1 ;
cx.strokeStyle = "red" ;
cx.save();
cx.beginPath();
cx.translate(300,300);
cx.rotate(sec*(Math.PI/30));
cx.moveTo(0,10);
cx.lineTo(0,-160);
cx.closePath();
cx.stroke();
cx.restore();
//绘制交叉处
cx.fillStyle = "#ccc" ;
cx.strokeStyle = "red" ;
cx.save();
cx.translate(300,300);
cx.beginPath();
cx.arc(0,0,5,0,Math.PI*2);
cx.closePath();
cx.fill();
cx.stroke();
cx.restore();
setTimeout(clock,1000);
}
clock()
}
</script>
</ head >
< body >
< canvas id = "canvas" width = "600px" height = "600px" style = "background-color: #ccc;" ></ canvas >
</ body >
</ html >
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以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。
原文链接:https://blog.csdn.net/weixin_44359232/article/details/108506676