html - CSS ONLY 动画绘制带有边框半径和透明背景的圆

Question

我正在尝试绘制一个带有 border-radius 的圆，并对其进行动画处理。我可以做到这一点，但我不能做的是覆盖元素并将圆圈背景设置为透明，而不取消隐藏蒙版。我无法使其在元素上透明，因为需要应用 mask 来隐藏圆圈的左半部分，因为它旋转以模仿绘制效果。

HTML

<div class="background">
    <div class="wrapper">
        <div class="pie spinner"></div>
        <div class="pie filler"></div>
        <div class="mask"></div>
    </div>
</div>

CSS

.background{
    background:green;
    z-index: 1000;
}
.wrapper {
  width: 250px;
  height: 250px;
  position: relative;
  margin: 40px auto;
  background: rgba(0,0,255,1);

}

.wrapper, .wrapper * {
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}
.wrapper .pie {
  width: 50%;
  height: 100%;
  transform-origin: 100% 50%;
  position: absolute;
  background: transparent;
  border: 5px solid rgba(0,0,0,0.9);
}

.wrapper .spinner {
  border-radius: 100% 0 0 100% / 50% 0 0 50%;
  z-index: 0;
  border-right: none;
  -webkit-animation: rota 5s linear infinite;
}

.wrapper:hover .spinner,
.wrapper:hover .filler,
.wrapper:hover .mask {
  animation-play-state: running;
}

.wrapper .filler {
  border-radius: 0 100% 100% 0 / 0 50% 50% 0;
  left: 50%;
  opacity: 0;
  -webkit-animation: opa 5s steps(1, end) infinite reverse;
  border-left: none;
}

.wrapper .mask {
  width: 50%;
  height: 100%;
  position: absolute;
  background: inherit;
  opacity: 1;
  -webkit-animation: opa 5s steps(1, end) infinite;
}

@-webkit-keyframes rota {
  0% {transform: rotate(0deg);border-color:red;}
  100% {transform: rotate(360deg);z-index:0;}
}
@-webkit-keyframes opa {
  0% {opacity: 1;}
  50%, 100% {opacity: 0;}
}

http://jsfiddle.net/BuzzSmarter/gmvban4p/

在我的示例中，我需要将蓝色背景更改为透明，而不是在开始旋转之前取消隐藏 border-radius。

请原谅颜色，这些不是我要处理的，但提供了一个更清晰的解决问题的方法。

这是我的临时产品，我必须移除绘图才能实现透明度。 http://jsfiddle.net/BuzzSmarter/gmvban4p/

Answer 1

这是我的解决方案。

我在 body 上设置了背景以显示它是透明的

body {
  background: repeating-linear-gradient(45deg, white 0px, lightblue 100px);
  height: 500px;
  background-size: 500px 500px;
  background-repeat: no-repeat;
}

html {
  height: 100%;
}

#container {
  position: absolute;
  width: 400px;
  height: 400px;
   border: solid red 1px;
   animation: colors 4s infinite;
}

#halfclip {
  width: 50%;
  height: 100%;
  right: 0px;
  position: absolute;
   overflow: hidden;
   transform-origin: left center;
   animation: cliprotate 16s steps(2) infinite;
   -webkit-animation: cliprotate 16s steps(2) infinite;
}

.halfcircle {
  box-sizing: border-box;
  height: 100%;
  right: 0px;
  position: absolute;
  border: solid 25px transparent;
   border-top-color: blue;
   border-left-color: blue;
   border-radius: 50%;
}
#clipped {
  width: 200%;
   animation: rotate 8s linear infinite;
   -webkit-animation: rotate 8s linear infinite;
}
#fixed {
  width: 100%;
    transform: rotate(135deg);  
   animation: showfixed 16s steps(2) infinite;
   -webkit-animation: showfixed 16s linear infinite;
}

@-webkit-keyframes cliprotate {
  0% {transform: rotate(0deg);}
  100% {transform: rotate(360deg);}
}

@keyframes cliprotate {
  0% {transform: rotate(0deg);}
  100% {transform: rotate(360deg);}
}


@-webkit-keyframes rotate {
  0% {transform: rotate(-45deg);}
  100% {transform: rotate(135deg);}
}

@keyframes rotate {
  0% {transform: rotate(-45deg);}
  100% {transform: rotate(135deg);}
}

@-webkit-keyframes showfixed {
  0% {opacity: 0;}
  49.9% {opacity: 0;}
  50% {opacity: 1;}
 100% {opacity: 1;}
}

<div id="container">
    <div id="halfclip">
        <div class="halfcircle" id="clipped">
        </div>
    </div>
    <div class="halfcircle" id="fixed">
    </div>
</div>

这是解决方案的一个变体，让它在悬停时只运行一次

body {
  background: repeating-linear-gradient(45deg, white 0px, lightblue 100px);
  height: 500px;
  background-size: 500px 500px;
  background-repeat: no-repeat;
}

html {
  height: 100%;
}

#container {
  position: absolute;
  width: 300px;
  height: 300px;
   border: solid red 1px;
}

#halfclip {
    width: 50%;
    height: 100%;
    right: 0px;
    position: absolute;
    overflow: hidden;
    transform-origin: left center;
}

#container:hover #halfclip {
    animation: cliprotate 6s 1;
    transform: rotate(180deg);
} 

@keyframes cliprotate {
  0% {transform: rotate(0deg);}
  50% {transform: rotate(0deg);}
  50.01% {transform: rotate(180deg);}
  100% {transform: rotate(180deg);}
}

.halfcircle {
  box-sizing: border-box;
  height: 100%;
  right: 0px;
  position: absolute;
  border: solid 25px transparent;
   border-top-color: blue;
   border-left-color: blue;
   border-radius: 50%;
}

#clipped {
    width: 200%;
    transform: rotate(-45deg);
}
#container:hover #clipped {
    transform: rotate(135deg);
    animation: rotate 3s linear 2;
}


@keyframes rotate {
  0% {transform: rotate(-45deg);}
  100% {transform: rotate(135deg);}
}


#fixed {
  width: 100%;
    transform: rotate(135deg);  
    opacity: 0;
}

#container:hover #fixed {
    opacity: 1;
    animation: showfixed 6s 1;
}



@keyframes showfixed {
  0% {opacity: 0;}
  49.99% {opacity: 0;}
  50% {opacity: 1;}
 100% {opacity: 1;}
}

<div id="container">
    <div id="halfclip">
        <div class="halfcircle" id="clipped">
        </div>
    </div>
    <div class="halfcircle" id="fixed">
    </div>
</div>