如何以百分比填充背景颜色到 svg 图像

Question

如何将背景颜色以百分比填充到 SVG 图像

我想用百分比填充 svg 图像的颜色

这是月亮 svg 图像，我想根据月亮上的照明百分比填充白色

90% 80% 70% 等等

<?xml version="1.0" encoding="iso-8859-1"?> 
<svg xmlns="http://www.w3.org/2000/svg" width="139" height="134"> 
<g> 
  <circle stroke-width="7" stroke="#000" fill="#fff" r="58" cy="69" cx="69"/>
  <path stroke-width="0" fill="#000" d="m69,9 a62,60 0 0 0 1,121 l0,-5 a70,68 0 0 1 0,-110 l0,-5 z"/>
 </g></svg>

Answer 1

我会带着面具来做这件事。所以我可以制作一个椭圆形的阴影。

// Set handler on input slider
var control = document.getElementById("control");
control.addEventListener("input", setMoonPhase);

// Initialise SVG from initial value of slider
setMoonPhase();

function setMoonPhase(evt) {
  // Convert from percentage to a 0..1 value
  var val = control.value / 100;
  // Get the ellipse element that represents the moon phase
  var  phaseEllipse = document.getElementById("phase-ellipse");
  // Set the X radius of the phase ellipse (where 100% = 0.5 -> 50% = 0 -> 0% = 0.5)
  phaseEllipse.rx.baseVal.value = Math.abs(val - 0.5);
  // If the phase > 50% then the ellipse needs to be white.
  // Otherwise it is black, to make a hole in the mask to let the black background show through.
  phaseEllipse.style.fill = (val > 0.5) ? "white" : "black";
}

<svg xmlns="http://www.w3.org/2000/svg" width="139" height="134">
  <defs>
    <mask id="phase-mask" maskContentUnits="objectBoundingBox">
      <rect x="0.5" y="0" width="0.5" height="1" fill="white"/>
      <ellipse id="phase-ellipse" cx="0.5" cy="0.5" rx="0.2" ry="0.5" fill="white"/>
    </mask>
  </defs>
  <circle fill="black" r="58" cy="69" cx="69"/><!-- moon shadow -->
  <circle fill="#fff" r="54.5" cy="69" cx="69" mask="url(#phase-mask)"/><!-- sunlight on moon -->
  <circle stroke-width="7" stroke="black" fill="none" r="58" cy="69" cx="69"/><!-- moon border -->
</svg>

<p>
<input id="control" type="range" min="0" max="100" value="90" /><span id="output"></span>
</p>

Answer 2

我会用clip-path 来做。

mooning()


control.addEventListener("input",()=>{
mooning()
})


function map(n, a, b, _a, _b) {
  let d = b - a;
  let _d = _b - _a;
  let u = _d / d;
  return _a + n * u;
}

function mooning(){
output.innerHTML = control.value + "%";
let value = map(control.value, 0, 100, -25, 175)
moon.setAttributeNS(null, "cx", value)
}

svg{border:1px solid; width:75vh}
#control{width:75vh;}

 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 150 150"> 
 <clipPath id="cp">
  <circle id="fullMoon"  r="50" cy="75" cx="75"/>
 </clipPath>
 <g clip-path="url(#cp)">
 <rect width="100%" height="100%" />  
 <circle id="moon" r="50" cy="75" cx="175" fill="white" />
 </g>
 
 <use xlink:href="#fullMoon" fill="none" stroke="black"  />
 
</svg>

<p><input id="control" type="range" min="0" max="100" value="60" /><span id="output"></span></p>

Answer 3

月光动画示例

我会使用黑色圆圈动画来做到这一点，它会逐渐打开和关闭光圈。

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="200" height="200"  viewBox="0 0 73 73" >
<defs>
 <radialGradient id="RadialGrad"
           fx="50%" fy="50%" r="65%"
           spreadMethod="pad">
          <stop offset="0%"   stop-color="#E7D68C" stop-opacity="1"/>
          <stop offset="100%" stop-color="#FFFEED" stop-opacity="1" />
        </radialGradient>

</defs>
<rect width="100%" height="100%" />
<g transform="rotate(-20 35.5 35.5)">
<circle cx="35.5" cy="35.5" r="35" stroke="none"  fill="url(#RadialGrad)" />

 <circle cx="35.5" cy="35.5" r="35" stroke="none" fill="black" >
 
 <animate id="youngMoon" attributeName="cx" values="35.5;-35.5;" begin="1s;oldMoon.end+1s" dur="10s" fill="freeze" />
<animate id="oldMoon" attributeName="cx" values="105;35.5;" begin="youngMoon.end+1s" dur="10s"  fill="freeze" /> 

</circle> 
</g>
</svg>

Answer 4

你的意思是这样的？

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 110 110" width="100px" height="100px"> 
    <circle fill="#000" r="50" cy="55" cx="55"/>
    <circle fill="#fff" r="50" cy="55" cx="90"/>
    <circle fill="transparent" r="50" cy="55" stroke="#000" stroke-width="10" cx="55"/>
</svg>

使用自定义 CSS 属性：

:root{
  --stroke-width: 10;
  --side: 50;
  --gutter: calc(var(--stroke-width) / 2);
  --cx: calc(var(--gutter) + var(--side));
  --percent: calc(15 * 0.02 * var(--side));
  --moon-light: calc(var(--cx) + var(--percent));
}
  
circle{
     cx: var(--cx);
     cy: var(--cx);
     r: var(--side);
}

.moon-percent{
    cx: var(--moon-light);
}

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 110 110" width="100px" height="100px"> 
    <circle fill="#000" />
    <circle class="moon-percent" fill="#fff"/>
    <circle fill="transparent" stroke="#000" stroke-width="var(--stroke-width)"/>
</svg>

Answer 5

您可以计算两个圆的交点并构造相应的路径。

类似这样的：

requestAnimationFrame(draw);

function draw(t) {
  requestAnimationFrame(draw);
  let r = 51;
  let x = Math.sin(t/2010)*90;
  let y = Math.sin(t/1731)*40;
  let a = Math.atan2(y, x);
  let s = Math.acos(Math.sqrt(x*x + y*y)/2/r);
  let p0 = [Math.cos(a+s)*r, Math.sin(a+s)*r];
  let p1 = [Math.cos(a-s)*r, Math.sin(a-s)*r];
  sun.setAttribute('d', `
      m${p0}
      A${r},${r},0,1,1,${p1}
      A${r},${r},0,0,0,${p0}
      z
  `);
}

body{
  overflow: hidden;
  margin: 0;
}

<svg viewBox=-55,-55,110,110 height=100vh width=100vw>
  <path id=sun stroke=teal fill=none stroke-width=2 stroke-linejoin=round></path>
</svg>