This time I will show you how to use canvas to draw arcs and circles, and what are the precautions for using canvas to draw arcs and circles. The following is a practical case. Let’s take a look.
The html file is as follows:
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"/> <title>Canvas绘制弧线和圆</title></head><body><style> #canvas{ border: 1px solid #aaa; text-align: center; }</style><canvas id="canvas" width="800" height="800"> 当用户浏览器不支持Canvas,请更换浏览器重试!</canvas></body></html>
To draw an arc or circle, you need to use the arc method. First, let us understand this method:
context.arc( x,y,r ,sAngle,eAngle,counterclockwise);
This method has 6 parameters:
x: x-axis coordinate of the center of the circle
y: y-axis coordinate of the center of the circle
r: Radius
sAngle: arc starting position
eAngle: arc ending position
counterclockwise: optional parameter, default is false, specifies whether it should be counterclockwise or clockwisedrawing. false = clockwise, true = counterclockwise.
First, let us start drawing an arc. The code is as follows:
var canvas=document.getElementById("canvas");var context=canvas.getContext("2d"); context.lineWidth=5; context.strokeStyle="blue"context.arc(300,300,200,0,2*Math.PI); context.stroke();//画一个空心弧线 context.fillStyle="red" context.fill();//收尾直接相连为一个封闭图形,以红色填充该图形
After drawing an arc, let us try to draw multiple arcs so that they become a circle. Directly enter the code:
window.onload= function () { var canvas=document.getElementById("canvas"); if(canvas.getContext("2d")){ var context=canvas.getContext("2d"); context.lineWidth=5; context.strokeStyle="red"; for(var i=0;i<10;i++){//绘制十个弧线,收尾封闭,没有填充色 context.beginPath(); context.arc(50+i*100,60,40,0,2*Math.PI*(i+1)/10); context.closePath();//使弧线封闭,形成一个闭合图形 context.stroke(); } for(var i=0;i<10;i++){//绘制十个弧线,收尾不封闭,没有填充色 context.beginPath(); context.arc(50+i*100,180,40,0,2*Math.PI*(i+1)/10); context.stroke(); } for(var i=0;i<10;i++){//绘制十个弧线,收尾封闭且填充为默认色 context.beginPath(); context.arc(50+i*100,300,40,0,2*Math.PI*(i+1)/10,true);//逆时针绘制 context.fill(); } }else { alert("不支持canvas,请更换浏览器!") } };
I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!
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