CSS ONLY使用边框半径和透明背景绘制圆

问题描述

我尝试用border-radius绘制一个圆，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，并将圆形背景设置为透明，而不取消隐藏面具。我不能让它透明的元素，因为面具需要应用来隐藏圆的左半部分旋转模仿绘制效果。

I am trying to draw a circle with border-radius, and animate it. I can do this, but what i can't do is overlay elements and set the circles background to transparent, without unhiding the mask. I am not able to make it transparent over elements because the mask needs to be applied to hide the left half of the circle as it rotates to mimic the draw effect.

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;}
}

在我的例子中，我需要更改蓝色背景到透明，而不会在开始旋转之前取消隐藏边框半径。

In my example, I need to change the blue background to transparent, without unhiding the border-radius before it starts rotating.

使用颜色，这些不是我将使用的，但提供一个更清晰的方法问题。

Excuse the colors, these are not what I will be working with, but provide a clearer approach to the issue.

这是我的临时产品，我必须删除绘制才能完成透明度。

This is my temporary product where I have to remove the draw to accomplish the transparency.http://jsfiddle.net/BuzzSmarter/gmvban4p/

推荐答案

这是我的解决方案。

我在body上设置一个背景透明

I set a background on body to show it is transparent

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>

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>

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