如何在向下滚动时水平更改背景渐变

Question

我正在尝试找出如何在用户向下滚动时更改部分（.header）的背景渐变。 这是背景渐变： 背景：线性梯度（90deg，rgba（0，49，84，.8）0％，rgba（154，198，229，1）100％）;

最终，我想在用户滚动通过它的同时创建百分比效果，从而将百分比从0更改为100。

Here is a codepen

@import url(//fonts.googleapis.com/css?family=Lato:300:400);
body {
  margin: 0;
}
h1 {
  font-family: 'Lato', sans-serif;
  font-weight: 300;
  letter-spacing: 2px;
  font-size: 48px;
  text-align:center;
}
p {
  font-family: 'Lato', sans-serif;
  letter-spacing: 1px;
  font-size: 14px;
  color: #333333;
}
.header {
  position: relative;
  text-align: center;
  background: linear-gradient(90deg, rgba(0, 49, 84, .8) 0%, rgba(154, 198, 229, 1) 100%);
  color: white;
}
.logo {
  width: 50px;
  fill: white;
  padding-right: 15px;
  display: inline-block;
  vertical-align: middle;
}
.inner-header {
  height: 65vh;
  width: 100%;
  margin: 0;
  padding: 0;
}
.flex {
  /*Flexbox for containers*/
  display: flex;
  justify-content: center;
  align-items: center;
  text-align: center;
}
.waves {
  position: relative;
  width: 100%;
  height: 15vh;
  margin-bottom: -7px;
  /*Fix for safari gap*/
  min-height: 100px;
  max-height: 150px;
}
.content {
  position: relative;
  height: 20vh;
  text-align: center;
  background-color: white;
}
/* Animation */
.parallax>use {
  animation: move-forever 25s cubic-bezier(.55, .5, .45, .5) infinite;
}
.parallax>use:nth-child(1) {
  animation-delay: -2s;
  animation-duration: 7s;
}
.parallax>use:nth-child(2) {
  animation-delay: -3s;
  animation-duration: 10s;
}
.parallax>use:nth-child(3) {
  animation-delay: -4s;
  animation-duration: 13s;
}
.parallax>use:nth-child(4) {
  animation-delay: -5s;
  animation-duration: 20s;
}
@keyframes move-forever {
  0% {
    transform: translate3d(-90px, 0, 0);
  }
  100% {
    transform: translate3d(85px, 0, 0);
  }
}
/*Shrinking for mobile*/
@media (max-width: 768px) {
  .waves {
    height: 40px;
    min-height: 40px;
  }
  .content {
    height: 30vh;
  }
  h1 {
    font-size: 24px;
  }
}

<div class="header">
    <div class="inner-header flex">
        <h1>Waves</h1>
    </div>

    <!--Waves Container-->
    <div>
        <svg class="waves" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 24 150 28" preserveAspectRatio="none" shape-rendering="auto">
            <defs>
                <path id="gentle-wave" d="M-160 44c30 0 58-18 88-18s 58 18 88 18 58-18 88-18 58 18 88 18 v44h-352z" />
            </defs>
            <g class="parallax">
                <use xlink:href="#gentle-wave" x="48" y="0" fill="rgba(255,255,255,0.7" />
                <use xlink:href="#gentle-wave" x="48" y="3" fill="rgba(255,255,255,0.5)" />
                <use xlink:href="#gentle-wave" x="48" y="5" fill="rgba(255,255,255,0.3)" />
                <use xlink:href="#gentle-wave" x="48" y="7" fill="#fff" />
            </g>
        </svg>
    </div>
    <!--Waves end-->

</div>

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<h1>...more content here</h1>
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<h1>...more content here</h1>
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<div class="content flex">
    <p>2020 | Free to use</p>
</div>