canvas实现简单画板
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<canvas id="canvas" width="400" height="400" ></canvas>
</body>
<script>
var flag = false;
//获得画布元素
var canvas = document.getElementById("canvas");
//获得二维绘图对象
var ctx = canvas.getContext("2d");
//设置线宽
ctx.lineWidth = '2';
//颜色
ctx.color = 'red';
// 循环触发
// canvas.onmousemove = function (e){
// console.log(e);
// ctx.lineTo(e.clientX,e.clientY);
// ctx.fill();
// ctx.fillStyle = 'red';
// ctx.stroke();//执行绘制线条
// }
canvas.onmousedown = (e)=>{
console.log("down");
flag = true;
}
canvas.onmouseup = (e)=>{
flag = false;
console.log("up");
}
canvas.onmousemove = (e)=>{
console.log("move");
if(!flag) return;
ctx.lineTo(e.clientX,e.clientY);
// ctx.fillStyle = 'red';
// ctx.fill();
ctx.stroke();//执行绘制线条
}
</script>
</html>