PHP有人知道吗?

将接受的答案转换为PHP代码。帮助在服务器上生成弧。

function polarToCartesian($centerX, $centerY, $radius, $angleInDegrees) {
   $angleInRadians = ($angleInDegrees-90) * pi() / 180.0;

  return array(
    "x"=> $centerX + ($radius * cos($angleInRadians)),
    "y"=> $centerY + ($radius * sin($angleInRadians)),
  );
}

function describeArc($x, $y, $radius, $startAngle, $endAngle){

     $start = polarToCartesian($x, $y, $radius, $endAngle);
     $end = polarToCartesian($x, $y, $radius, $startAngle);

     $largeArcFlag = $endAngle - $startAngle <= 180 ? "0" : "1";

     $d = implode(" ", array(
        "M", $start["x"], $start["y"], 
        "A", $radius, $radius, 0, $largeArcFlag, 0, $end["x"], $end["y"]));

    return $d;       
}

<svg>
    <path fill="none" stroke="#446688" stroke-width="20" d="<?= describeArc(150, 150, 100, 0, 30) ?>" />
</svg>

对@opsb的回答稍加修改。我们不能用这种方法画一个完整的圆。如果我们给(0,360)它什么也画不出来。所以做了一点小小的修改来解决这个问题。显示有时达到100%的分数可能很有用。

function polarToCartesian(centerX, centerY, radius, angleInDegrees) {
  var angleInRadians = (angleInDegrees-90) * Math.PI / 180.0;

  return {
    x: centerX + (radius * Math.cos(angleInRadians)),
    y: centerY + (radius * Math.sin(angleInRadians))
  };
}

function describeArc(x, y, radius, startAngle, endAngle){

    var endAngleOriginal = endAngle;
    if(endAngleOriginal - startAngle === 360){
        endAngle = 359;
    }

    var start = polarToCartesian(x, y, radius, endAngle);
    var end = polarToCartesian(x, y, radius, startAngle);

    var arcSweep = endAngle - startAngle <= 180 ? "0" : "1";

    if(endAngleOriginal - startAngle === 360){
        var d = [
              "M", start.x, start.y, 
              "A", radius, radius, 0, arcSweep, 0, end.x, end.y, "z"
        ].join(" ");
    }
    else{
      var d = [
          "M", start.x, start.y, 
          "A", radius, radius, 0, arcSweep, 0, end.x, end.y
      ].join(" ");
    }

    return d;       
}

document.getElementById("arc1").setAttribute("d", describeArc(120, 120, 100, 0, 359));

我想评论@Ahtenus的回答，特别是Ray Hulha的评论，他说代码依赖没有显示出任何弧度，但我的声誉不够高。

这个代码依赖不工作的原因是它的html有一个描边宽度为零的错误。

我修复了它，并在这里添加了第二个示例:http://codepen.io/AnotherLinuxUser/pen/QEJmkN。

html:

<svg>
    <path id="theSvgArc"/>
    <path id="theSvgArc2"/>
</svg>

相关CSS:

svg {
    width  : 500px;
    height : 500px;
}

path {
    stroke-width : 5;
    stroke       : lime;
    fill         : #151515;
}

javascript:

document.getElementById("theSvgArc").setAttribute("d", describeArc(150, 150, 100, 0, 180));
document.getElementById("theSvgArc2").setAttribute("d", describeArc(300, 150, 100, 45, 190));

基于所选答案的ReactJS组件:

import React from 'react';

const polarToCartesian = (centerX, centerY, radius, angleInDegrees) => {
    const angleInRadians = (angleInDegrees - 90) * Math.PI / 180.0;

    return {
        x: centerX + (radius * Math.cos(angleInRadians)),
        y: centerY + (radius * Math.sin(angleInRadians))
    };
};

const describeSlice = (x, y, radius, startAngle, endAngle) => {

    const start = polarToCartesian(x, y, radius, endAngle);
    const end = polarToCartesian(x, y, radius, startAngle);

    const largeArcFlag = endAngle - startAngle <= 180 ? "0" : "1";

    const d = [
        "M", 0, 0, start.x, start.y,
        "A", radius, radius, 0, largeArcFlag, 0, end.x, end.y
    ].join(" ");

    return d;
};

const path = (degrees = 90, radius = 10) => {
    return describeSlice(0, 0, radius, 0, degrees) + 'Z';
};

export const Arc = (props) => <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 300 300">
    <g transform="translate(150,150)" stroke="#000" strokeWidth="2">
        <path d={path(props.degrees, props.radius)} fill="#333"/>
    </g>

</svg>;

export default Arc;

由wdebeaum得到的原始极坐标笛卡尔函数是正确的:

var angleInRadians = angleInDegrees * Math.PI / 180.0;

使用以下方法反转起始点和结束点:

var start = polarToCartesian(x, y, radius, endAngle);
var end = polarToCartesian(x, y, radius, startAngle);

(对我来说)是混乱的，因为这将反转扫旗。使用:

var start = polarToCartesian(x, y, radius, startAngle);
var end = polarToCartesian(x, y, radius, endAngle);

使用sweep-flag = "0"绘制"正常"逆时针弧线， 我认为这更直接。 参见https://developer.mozilla.org/en-US/docs/Web/SVG/Tutorial/Paths

@opsb的回答很简洁，但中心点不准确，而且，正如@Jithin指出的那样，如果角度是360，那么什么都画不出来。

@Jithin修复了360度的问题，但如果你选择小于360度，那么你会得到一条线关闭弧环，这是不需要的。

我修复了这个问题，并在下面的代码中添加了一些动画:

function myArc(cx, cy, radius, max){ var circle = document.getElementById("arc"); var e = circle.getAttribute("d"); var d = " M "+ (cx + radius) + " " + cy; var angle=0; window.timer = window.setInterval( function() { var radians= angle * (Math.PI / 180); // convert degree to radians var x = cx + Math.cos(radians) * radius; var y = cy + Math.sin(radians) * radius; d += " L "+x + " " + y; circle.setAttribute("d", d) if(angle==max)window.clearInterval(window.timer); angle++; } ,5) } myArc(110, 110, 100, 360); <svg xmlns="http://www.w3.org/2000/svg" style="width:220; height:220;"> <path d="" id="arc" fill="none" stroke="red" stroke-width="2" /> </svg>