canvas笔记-arcTo的使用及绘制弯月- 前端开发

首先介绍下这个函数

context.arcTo(x1, y1, x2, y2, r);

其中x1为弧的起点x坐标；

其中y1为弧的起点y坐标；

其中x2为弧的终点x坐标；

其中y2为弧的终点y坐标；

其中r为弧的半径。

程序运行截图如下：

源码如下：


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
 
<canvas id="canvas" style="border: 1px solid #aaa; display: block; margin: 50px auto;">
    当前浏览器不支持canvas
</canvas>
 
<script>
 
    window.onload = function(){
 
        let canvas = document.getElementById("canvas");
        canvas.width = 800;
        canvas.height = 800;
        let context = canvas.getContext("https://cdn.jxasp.com:9143/image/2d");
 
        context.beginPath();
        context.moveTo(150, 150);
        context.arcTo(650, 150, 650, 650, 300);
        context.lineWidth = 6;
        context.strokeStyle = "red";
        context.stroke();
 
 
        //baseline
        context.beginPath();
        context.moveTo(150, 150);
        context.lineTo(650, 150);
        context.lineTo(650, 650);
 
        context.lineWidth = 2;
        context.strokeStyle = "gray";
        context.stroke();
    }
 
 
</script>
 
</body>
</html>

下面是绘制给弯月

程序运行截图如下：

源码如下：


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
 
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
 
<canvas id="canvas" style="border: 1px solid #aaa; display: block; margin: 50px auto;">
    当前浏览器不支持canvas
</canvas>
 
<script>
 
    window.onload = function(){
 
        let canvas = document.getElementById("canvas");
        canvas.width = 800;
        canvas.height = 800;
        let context = canvas.getContext("https://cdn.jxasp.com:9143/image/2d");
 
 
        context.arc(400, 400, 300, 0.5 * Math.PI, 1.5 * Math.PI, true);
        context.moveTo(400, 100);
        context.arcTo(1200, 400, 400, 700, (400 - 100) * dis(400, 100, 1200, 400) / (1200 - 400));
        context.stroke();
    }
 
    function dis(x1, y1, x2, y2){
 
        return Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
    }
 
 
</script>
 
</body>
</html>
 
</body>
</html>