javascript - HTML Canvas -JavaScript动画/绘图

我有这个 ：

http://jsfiddle.net/geduardcatalin/6Lg6ymt3/

如何使第二条线从中心开始并在左下角停止，就像第一条线停在我想要的位置（在中心）一样？

var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");

var canvasWidth = canvas.width;
var canvasHeight = canvas.height;

var i = 0;
var j = 0;
var k = 0;
var l = 0;

function drawLine1() {
  i = i + 1;
  j = j + 1;
  x1 = i;
  y1 = j;

  if (i >= 149) {
    i = 149;
  }

  if (j >= 149) {
    j = 149;
  }

  ctx.beginPath();
  ctx.strokeStyle = "#000000";
  ctx.lineWidth = 1;
  ctx.moveTo(0, 0);
  ctx.lineTo(x1, y1);
  ctx.stroke();
}

function drawLine2() {
  k = k - 1;
  l = l + 1;
  x2 = k;
  y2 = l;

  if (k >= 299) {
    k = 299;
  }

  if (l >= 299) {
    l = 299;
  }

  ctx.beginPath();
  ctx.strokeStyle = "#000000";
  ctx.lineWidth = 1;
  ctx.moveTo(150, 150);
  ctx.lineTo(x2, y2);
  ctx.stroke();
}

function drawLines() {
  ctx.clearRect(0, 0, canvasWidth, canvasHeight);
  drawLine1();
  drawLine2();
  //setTimeout(drawLine2, 0000);
}

setInterval(drawLines, 40);

* {
  margin: 0;
  padding: 0;
}
html {
  background-color: #555555;
}
#wrapper {
  width: 300px;
  height: 300px;
  margin: 70px auto;
  border: 1px solid red;
}

<div id="wrapper">
  <canvas id="myCanvas" height="300px" width="300px"></canvas>
  <p id="demo"></p>
</div>

最佳答案

Line2中的变量k和l都应从150开始，并将draw Line2()更改为：

这是更新的JSFiddle。

function drawLine2(){
    k = k - 1;
    l = l + 1;
    x2 = k;
    y2 = l;

    if ( k <= 0 ){
        k = 0;
    }
    if ( l >= 299 ){
        l = 299;
    }

    ctx.beginPath();
    ctx.strokeStyle = "#000000";
    ctx.lineWidth = 1;
    ctx.moveTo(150, 150);
    ctx.lineTo(x2, y2);
    ctx.stroke();
}

关于javascript - HTML Canvas -JavaScript动画/绘图，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/33025580/