蒙版图像，从多个渐变创建矩形

Question

我有一个径向渐变，用作mask-image 将图像“淡入”到background-color 在图像后面。

mask-image: radial-gradient(ellipse at center, rgba(255,255,255,1) 1%,rgba(255,255,255,1) 50%,rgba(255,255,255,0) 70%,rgba(255,255,255,0) 100%);

如何在所有四个边上使用均匀的矩形渐变来获得相同的效果？

我知道你可以组合渐变，而我最近的尝试似乎没有任何效果：

img
{
 mask-image: 
  linear-gradient(to top, rgba(255,255,255,1) 1%, rgba(255,255,255,1) 50%),
  linear-gradient(to right, rgba(255,255,255,1) 1%, rgba(255,255,255,1) 50%),
  linear-gradient(to bottom, rgba(255,255,255,1) 1%, rgba(255,255,255,1) 50%),
  linear-gradient(to left, rgba(255,255,255,1) 1%, rgba(255,255,255,1) 50%);
}

Answer 1

使用多个掩码的技巧是控制大小/位置，以便每个掩码都应用于元素的一个区域：

.box {
  height:300px;
  width:300px;
  background: url(https://picsum.photos/id/1003/300/300);
  -webkit-mask: 
     linear-gradient(to top,    transparent,#fff) top   /100% 20%,
     linear-gradient(to bottom, transparent,#fff) bottom/100% 20%,
     linear-gradient(to left  , transparent,#fff) left  /20% 100%,
     linear-gradient(to right , transparent,#fff) right /20% 100%;
  -webkit-mask-repeat:no-repeat;
  
  mask: 
     linear-gradient(to top,    transparent,#fff) top   /100% 20%,
     linear-gradient(to bottom, transparent,#fff) bottom/100% 20%,
     linear-gradient(to left  , transparent,#fff) left  /20% 100%,
     linear-gradient(to right , transparent,#fff) right /20% 100%;
  mask-repeat:no-repeat;
}

body {
  background:pink;
}

<div class="box"></div>

或者像这样：

.box {
  height:300px;
  width:300px;
  background: url(https://picsum.photos/id/1003/300/300);
  -webkit-mask: 
    linear-gradient(to top,  transparent 10%, #fff 15% 90%, transparent 95%),
    linear-gradient(to left, transparent 10%, #fff 15% 90%, transparent 95%);
  -webkit-mask-size:110% 110%;
  -webkit-mask-position:center;
  -webkit-mask-repeat:no-repeat;
  -webkit-mask-composite: source-in;
  
  
  mask: 
    linear-gradient(to top,  transparent 10%, #fff 15% 90%, transparent 95%),
    linear-gradient(to left, transparent 10%, #fff 15% 90%, transparent 95%);
  mask-size: 110% 110%;
  mask-position: center;
  mask-repeat:no-repeat;
  mask-composite: intersect;
}

body {
  background:pink;
}

<div class="box"></div>

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