学习canvas（一）：用线画出正方形和三角形_canvas绘制三角形代码-优快云博客

本文链接：https://blog.youkuaiyun.com/OrdnAry/article/details/127538354

正方形

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<style>
  canvas {
    margin: 0 auto;
    display: block;
    border: 1px solid #aaa;
  }
</style>

<body>
  <canvas id="canvas" width="500px" height="500px">不支持canvas</canvas>
</body>
<script>
  /** @type {HTMLCanvasElement}*/
  var canvas = document.querySelector('#canvas')
  var c = canvas.getContext('2d')
  function drawLine (x1, y1, x2, y2, color, width) {
    c.beginPath()
    c.moveTo(x1, y1)
    c.lineTo(x2, y2)
    c.strokeStyle = color
    c.lineWidth = width
    c.stroke()
    c.closePath()
  }
  drawLine(100, 100, 200, 100, 'green', 2)
  drawLine(200, 100, 200, 200, 'red', 4)
  drawLine(200, 200, 100, 200, 'blue', 6)
  drawLine(100, 200, 100, 100, 'red', 8)
  for (var i = 0; i < 20; i++) {
    console.log(11);
    drawLine(200 + 10 * i, 200, 205 + 10 * i, 200, 'red', 2)
    drawLine(400, 200 + 10 * i, 400, 205 + 10 * i, 'red', 2)
    drawLine(400 - 10 * i, 400, 395 - 10 * i, 400, 'red', 2)
    drawLine(200, 400 - 10 * i, 200, 395 - 10 * i, 'red', 2)
  }
</script>

</html>

在这里插入图片描述

三角形

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<style>
  canvas {
    margin: 0 auto;
    display: block;
    border: 1px solid #aaa;
  }
</style>

<body>
  <canvas id="canvas" width="500px" height="500px">不支持canvas</canvas>
</body>
<script>
  /** @type {HTMLCanvasElement}*/
  var canvas = document.querySelector('#canvas')
  var c = canvas.getContext('2d')
  c.beginPath()
  c.moveTo(100, 100)
  c.lineTo(200, 100)
  c.lineTo(200, 200)
  c.lineTo(100, 100)
  c.strokeStyle = 'red'
  c.lineWidth = 2
  c.stroke()
  c.closePath()
  for (var i = 0; i < 20; i++) {
    console.log(11);
    drawLine(200 + 10 * i, 200, 205 + 10 * i, 200, 'red', 2)
    drawLine(200 + 10 * i, 200 + 10 * i, 205 + 10 * i, 205 + 10 * i, 'blue', 2)
    drawLine(400, 200 + 10 * i, 400, 205 + 10 * i, 'red', 2)
  }
  function drawLine (x1, y1, x2, y2, color, width) {
    c.beginPath()
    c.moveTo(x1, y1)
    c.lineTo(x2, y2)
    c.strokeStyle = color
    c.lineWidth = width
    c.stroke()
    c.closePath()
  }
</script>

</html>