javascript - 是否可以画一个包含婴儿床或棕褐色的完整圆圈？

Question

我有这样的代码可以将多个点画成一个圆

    var cxt=c.getContext("2d");
    var centerX = 500;
    var centerY = 500;
    cxt.moveTo(centerX, centerY);

    var increment = 1/100;       
    var distance = 100;

    for( theta=0;theta <100; theta++) {      
      var newX = centerX +distance *Math.cos(theta*2*Math.PI*increment); 
      var newY = centerY +distance *Math.sin(theta*2*Math.PI*increment); 
      cxt.fillText("0",newX, newY);
    }
    cxt.stroke();

结果:

enter image description here

我尝试用 tan 和 cot (1/tan) 重写代码，但我得到的通常是 eclipse 或椭圆形。我们可以使用这些函数从给定的点中做出一个完美的圆吗？

Answer 1

是的，这是可能的 - tan 就足够了 ( formulas here )

var cxt = c.getContext("2d");
var centerX = 100;
var centerY = 100;
cxt.moveTo(centerX, centerY);

var increment = 1 / 50;
var distance = 90;

for (let theta = 0; theta < 100; theta++) {
  var t = Math.tan(theta * Math.PI * increment);
  var newX = centerX + distance * (1 - t*t)/(1 + t*t);
  var newY = centerY + distance * 2 * t/(1 + t*t);
  cxt.fillText("0", newX, newY);
}
cxt.stroke();

<canvas id=c width=200 height=200></canvas>