CSS动画，仅在特定元素上呈现叠加层

Question

我已经制作了此加载占位符CSS动画。在白色背景上看起来是正确的，因为动画/移动渐变是白色的，不透明度为20％。

但是，有时占位符将位于不同颜色的背景上，并且移动的部分也将在背景上可见，而不仅仅是在变暗的颜色（这是不希望的）上。请参见下面的代码段：

.ph-item {
  position: relative;
  margin-bottom: 10px;
  overflow: hidden;
  border-radius: 2px;
}

.ph-item,
.ph-item *,
.ph-item ::after,
.ph-item ::before {
  box-sizing: border-box;
}

.ph-item::before {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 50%;
  z-index: 1;
  width: 500%;
  margin-left: -250%;
  animation: phAnimation 0.8s linear infinite;
  background: linear-gradient(to right, rgba(255, 255, 255, 0) 46%, rgba(255, 255, 255, 0.35) 50%, rgba(255, 255, 255, 0) 54%) 50% 50%;
}

.ph-item > * {
  padding-right: 10px;
}

.ph-row {
  margin-bottom: 5px;
}

.ph-row div {
  border-radius: 3px;
  height: 10px;
  background-color: rgba(0, 0, 0, 0.2);
}

.ph-row .standard,
.ph-row.big div {
  height: 20px;
  margin-right: 10px;
}


.ph-float-right {
  float: right;
  padding-left: 10px;
  margin-right: auto;
}

.ph-col-2 {
  width: 16.66667%;
  display: inline-block;
}

.ph-col-4 {
  width: 33.33333%;
  display: inline-block;
}

.ph-col-6 {
  width: 50%;
  display: inline-block;
}

.ph-col-8 {
  width: 66.66667%;
  display: inline-block;
}

.ph-col-10 {
  width: 83.33333%;
  display: inline-block;
}

.ph-col-12 {
  width: 100%;
  display: inline-block;
}

.ph-avatar {
  position: relative;
  width: 100%;
  min-width: 50px;
  background-color: rgba(0, 0, 0, 0.2);
  border-radius: 50%;
  overflow: hidden;
}

.ph-avatar::before {
  content: "";
  display: block;
  padding-top: 100%;
}

@keyframes phAnimation {
  0% {
    transform: translate3d(-30%, 0, 0);
  }

  100% {
    transform: translate3d(30%, 0, 0);
  }
}

<div style="width: 500px; height: 50px; background-color: darkblue; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard"></div>
        <div class="ph-col-10"></div>
      </div>
    </div>
  </div>
</div>
<div style="width: 500px; height: 50px; background-color: white; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard"></div>
        <div class="ph-col-10"></div>
      </div>
    </div>
  </div>
</div>

我的问题是，是否有可能以某种方式将动画蒙版仅渲染在变暗部分（ph-avatar和ph-col-xx）的顶部？

这是如何实现的？

Answer 1

编辑这实际上是Background animation performance

的副本

另一种方法是将after伪函数与background-position一起使用线性梯度重置。为了使每个伪对象具有连贯的梯度，background-attachment会将所有东西放在一起。背景尺寸也有帮助。

以下想法的演示。 CSS注释了更新或修改的地方

.ph-item {
  position: relative;
  margin-bottom: 10px;
  overflow: hidden;
  border-radius: 2px;
}

.ph-item,
.ph-item *,
.ph-item ::after,
.ph-item ::before {
  box-sizing: border-box;
}
   /* selector removed 

.ph-item::before 

       and replaced by : */
.ph-avatar::after,
.ph-row .standard::after,
.ph-row .ph-col-10::after {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 50%;
  z-index: 1;
  width: 500%;
  margin-left: -250%;
  animation: phAnimation 2s linear infinite;/* duration to set to your needs */
  background: linear-gradient(
      to right,
      rgba(255, 255, 255, 0) 46%,
      rgba(255, 255, 255, 0.35) 50%,
      rgba(255, 255, 255, 0) 54%
    )
    50% 50% 
    rgba(0, 0, 0, 0.2);/* move here & added */
  background-attachment: fixed;/*  added */
  background-size: 1000px auto;/*  added */
}

.ph-item > * {
  padding-right: 10px;
}

.ph-row {
  margin-bottom: 5px;
}

.ph-row div {
  border-radius: 3px;
  height: 10px;
 /*background-color: rgba(0, 0, 0, 0.2); or move animation here from pseudo*/
}

.ph-row .standard,
.ph-row.big div {
  height: 20px;
  margin-right: 10px;
}

.ph-float-right {
  float: right;
  padding-left: 10px;
  margin-right: auto;
}

.ph-col-2 {
  width: 16.66667%;
  display: inline-block;
}

.ph-col-4 {
  width: 33.33333%;
  display: inline-block;
}

.ph-col-6 {
  width: 50%;
  display: inline-block;
  position: relative;/*  added */
  overflow: hidden;/*  added */
}

.ph-col-8 {
  width: 66.66667%;
  display: inline-block;
}

.ph-col-10 {
  width: 83.33333%;
  display: inline-block;
  position: relative;/*  added */
  overflow: hidden;/*  added */
}

.ph-col-12 {
  width: 100%;
  display: inline-block;
}

.ph-avatar {
  position: relative;
  width: 100%;
  min-width: 50px;
  border-radius: 50%;
  overflow: hidden;
}

.ph-avatar::before {
  content: "";
  display: block;
  padding-top: 100%;
}

@keyframes phAnimation {
  0% {
    background-position: -1000px 0;/*  modified */
  }

  100% {
    background-position: 1000px 0;/*  modified */
  }
}

<div style="width: 500px; height: 50px; background-color: darkblue; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard"></div>
        <div class="ph-col-10"></div>
      </div>
    </div>
  </div>
</div>
<div style="width: 500px; height: 50px; background-color: white; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard"></div>
        <div class="ph-col-10"></div>
      </div>
    </div>
  </div>
</div>
<div style="width: 500px; height: 50px; background-color: tomato; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard"></div>
        <div class="ph-col-10"></div>
      </div>
    </div>
  </div>
</div>
<div style="width: 500px; height: 50px; background-color: gold; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard"></div>
        <div class="ph-col-10"></div>
      </div>
    </div>
  </div>
</div>
<div style="width: 500px; height: 50px; background-color: purple; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard"></div>
        <div class="ph-col-10"></div>
      </div>
    </div>
  </div>
</div>
<div style="width: 500px; height: 50px; background-color: turquoise; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard"></div>
        <div class="ph-col-10"></div>
      </div>
    </div>
  </div>
</div>
<div style="width: 500px; height: 50px; background-color: gray; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard"></div>
        <div class="ph-col-10"></div>
      </div>
    </div>
  </div>
</div>
<div style="width: 500px; height: 50px; background-color: teal; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard"></div>
        <div class="ph-col-10"></div>
      </div>
    </div>
  </div>
</div>

注意，可以直接在元素内部设置背景动画，除非有其他用途，否则不需要伪元素。可能的选项https://codepen.io/gc-nomade/pen/byJOJa

Answer 2

也许一种选择是遮罩两个svg图像并设置遮罩属性的动画。我个人并不真正熟悉该技术，但这也许会有所帮助：

https://tympanus.net/codrops/css_reference/mask-composite/

但是，如果您想使用html格式（我个人也希望这样做），则可以通过一些技巧来达到这种效果：

.ph-item {
  position: relative;
  margin-bottom: 10px;
  overflow: hidden;
  border-radius: 2px;
}

.ph-item,
.ph-item *,
.ph-item ::after,
.ph-item ::before {
  box-sizing: border-box;
}

.highlighted {
  position: relative;
  overflow: hidden;
}

.highlighted::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  z-index: 1;
  width: 100px;
  animation: 1s linear infinite;
  animation-name: phAnimation;
  background: red;
/*   background: linear-gradient(to right, rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0.35) 50%, rgba(255, 255, 255, 0) 100%) 50% 50%; */
}

.ph-avatar.highlighted::before {
  animation-name: phAnimationAvatar;
}

.ph-item > * {
  padding-right: 10px;
}

.ph-row {
  margin-bottom: 5px;
}

.ph-row div {
  border-radius: 3px;
  height: 10px;
  background-color: rgba(0, 0, 0, 0.2);
}

.ph-row .standard,
.ph-row.big div {
  height: 20px;
  margin-right: 10px;
}


.ph-float-right {
  float: right;
  padding-left: 10px;
  margin-right: auto;
}

.ph-col-2 {
  width: 16.66667%;
  display: inline-block;
}

.ph-col-4 {
  width: 33.33333%;
  display: inline-block;
}

.ph-col-6 {
  width: 50%;
  display: inline-block;
}

.ph-col-8 {
  width: 66.66667%;
  display: inline-block;
}

.ph-col-10 {
  width: 83.33333%;
  display: inline-block;
}

.ph-col-12 {
  width: 100%;
  display: inline-block;
}

.ph-avatar {
  position: relative;
  width: 100%;
  min-width: 50px;
  height: 50px;
  background-color: rgba(0, 0, 0, 0.2);
  border-radius: 50%;
  overflow: hidden;
}


@keyframes phAnimationAvatar {
  0% {
    transform: translate3d(-100px, 0, 0);
  }
  
  10% {
    transform: translate3d(-50px, 0, 0);
  }
  
  20% {
    transform: translate3d(0px, 0, 0);
  }
  
  30% {
    transform: translate3d(50px, 0, 0);
  }

  100% {
    transform: translate3d(100px, 0, 0);
  }
}

@keyframes phAnimation {
  0% {
    transform: translate3d(-100px, 0, 0);
  }
  
  11% {
    transform: translate3d(-100px, 0, 0);
  }

  50% {
    transform: translate3d(85px, 0, 0);
  }
  
  100% {
    transform: translate3d(335px, 0, 0);
  }
}

<div style="width: 500px; height: 50px; background-color: darkblue; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar highlighted"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard highlighted"></div>
        <div class="ph-col-10 highlighted"></div>
      </div>
    </div>
  </div>
</div>
<div style="width: 500px; height: 50px; background-color: white; padding: 20px;">
  <div class="ph-item" style="max-width: 360px;">
    <div class="ph-col-2">
      <div class="ph-avatar highlighted"></div>
    </div>
    <div class="ph-col-10 ph-float-right">
      <div class="ph-row">
        <div class="ph-col-6 standard highlighted"></div>
        <div class="ph-col-10 highlighted"></div>
      </div>
    </div>
  </div>
</div>

缺点是您需要为不同的占位符重新校准动画，但是比为每个占位符元素使用静态svg更好。

编辑：单挑，尽管chrome和firefox可以正常工作，但似乎存在一个关于野生动物园如何呈现此问题的问题。