0

我需要画一条线并给它一个边框。

我试着画两条线，一条 5px 和 3px 以上

但这看起来并不像真正的边界

const ctx = canvas.getContext('2d');
const path = new Path2D();

ctx.strokeStyle = "black";
ctx.lineWidth = 5;

path.moveTo(40, 40);
path.lineTo(50, 35);
path.lineTo(60, 40);

ctx.stroke(path);

ctx.strokeStyle = "red";
ctx.lineWidth = 3;

path.moveTo(40, 40);
path.lineTo(50, 35);
path.lineTo(60, 40);

ctx.stroke(path);
<canvas id=canvas width=100 height=100></canvas>

有没有更好的方法来绘制一条线的边框？

4

2 回答 2

1

尝试在外线上设置“endCap”：

const ctx = canvas.getContext('2d');
const path = new Path2D();

ctx.strokeStyle = "black";
ctx.lineWidth = 5;
ctx.lineCap = "butt"; // butt  round  square <-- other options

path.moveTo(40, 40);
path.lineTo(50, 35);
path.lineTo(60, 40);

ctx.stroke(path);

ctx.strokeStyle = "red";
ctx.lineWidth = 3;

path.moveTo(40, 40);
path.lineTo(50, 35);
path.lineTo(60, 40);

ctx.stroke(path);

请参阅： https ://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/lineCap

于 2020-07-01T01:20:29.950 回答
0

您可以尝试使用阴影：

const ctx = canvas.getContext('2d');

function drawPath(path) {
  ctx.lineWidth = 3;
  ctx.strokeStyle = "red";
  ctx.shadowColor = 'black';

  for (i = 0; i <= 360; i += 10) {
    a = i * Math.PI / 180
    ctx.beginPath();
    ctx.shadowOffsetX = 4 * Math.sin(a)
    ctx.shadowOffsetY = 4 * Math.cos(a)
    ctx.stroke(path);
  }
}

const path = new Path2D();
path.moveTo(20, 40);
path.lineTo(50, 35);
path.lineTo(80, 40);
path.lineTo(80, 80);
path.lineTo(160, 80);
drawPath(path);
<canvas id=canvas width=200 height=100></canvas>

这个想法是在你的路径对象周围绘制一个稍微不同的偏移量......并且可以对图像使用相同的逻辑：

https://raw.githack.com/heldersepu/hs-scripts/master/HTML/canvasOutline.html

于 2020-06-30T23:10:25.057 回答