Skew Background Image on one side with a border

Question

I am trying to skew a background image on one side that has a border.

The layout I am basically trying to create is as follows:

Here is a quick JSFi

Answer 1

The trick is to correctly set the transform-orgin, the border and then it should be easy to apply both skew transformation. You may also need some negative margin to rectify some spaces.

I used CSS variables to make the code easy but it's not mandatory.

#about-gallery {
  margin: 60px 0;
  display: flex;
  flex-wrap: wrap;
  --s:-8deg; /* The skew factor (the same for all)*/
}

.about-img-wrapper {
  margin: 5px;
  overflow: hidden; /* Don't forget this !!*/
  flex-grow:1;
}

.about-img-wrapper > * {
  height: 300px;
  background: center/cover no-repeat;
  overflow: hidden; /* Don't forget this !!*/
  transform:skewX(var(--s,0deg));
}
/* We need skewY for the 3 last element */
.about-img-wrapper:nth-child(n + 3) > *  {
  transform:skewY(var(--s,0deg));
}
/* The pseudo element will get the image and the inverse of skewing */
.about-img-wrapper > *::before {
  content:"";
  display:block;
  height:100%;
  background:inherit; /* inherit the image */
  transform-origin: inherit; /* inherit the same transform-origin */
  transform:skewX(calc(-1*var(--s,0deg)));
}
.about-img-wrapper:nth-child(n + 3) > *::before  {
  transform:skewY(calc(-1*var(--s,0deg)));
}

/**/
.image-1 {
  border-left: solid 10px black;
  flex-basis:50%;
  margin-right:-15px;
}

.image-1>* {
  transform-origin: top;
  border: solid 10px black;border-left: none;
}
/**/
.image-2 {
  border-right: solid 10px black;
  flex-basis:40%;
  margin-left:-15px;
}
.image-2>* {
  transform-origin: bottom;
  border: solid 10px black;border-right: none;
}
/**/
.image-3 {
  border-top: solid 10px black;
  flex-basis:100%;
}
.image-3>* {
  transform-origin: left;
  border: solid 10px black;border-top: none;
}
/**/
.image-4,
.image-5{
  border-bottom: solid 10px black;
  flex-basis:40%;
  margin-top:-5vw;
}
.image-4>*,
.image-5>* {
  transform-origin: right;
  border: solid 10px black;border-bottom: none;
}
.image-5 {
  margin-top:-12vw;
}
.image-5>* {
  height:calc(300px + 7vw); /* We need a bigger height here */
}
/**/
* {
  box-sizing: border-box;
}

<div id="about-gallery">
  <div class="about-img-wrapper  image-1">
    <div style="background-image: url(https://picsum.photos/id/10/800/800);"></div>
  </div>
  <div class="about-img-wrapper image-2">
    <div style="background-image: url(https://picsum.photos/id/102/800/800);"></div>
  </div>
  <div class="about-img-wrapper  image-3">
    <div style="background-image: url(https://picsum.photos/id/123/800/800);"></div>
  </div>
  <div class="about-img-wrapper image-4">
    <div style="background-image: url(https://picsum.photos/id/14/800/800);"></div>
  </div>
  <div class="about-img-wrapper  image-5">
    <div style="background-image: url(https://picsum.photos/id/20/800/800);"></div>
  </div>

</div>

Here is another idea using less of code and relying on mask to create the skew effect:

.about-gallery {
  margin: 60px 0;
  display: flex;
  flex-wrap: wrap;
}

.about-gallery > * {
  margin: 5px;
  flex-grow:1;
  height: 300px;
  background: 
    var(--g),
    var(--img) center/cover no-repeat;
  border: solid 10px black;
  -webkit-mask:
    linear-gradient(#fff,#fff) no-repeat,
    linear-gradient(to var(--p,bottom right),#fff 49.5%,transparent 50%) no-repeat;
  mask:
    linear-gradient(#fff,#fff) no-repeat,
    linear-gradient(to var(--p,bottom right),#fff 49.5%,transparent 50%) no-repeat;
}

/**/
.image-1 {
  flex-basis:50%;
  margin-right:-15px;
  --g:linear-gradient(to bottom right,transparent 49.8%,black 50%) right/50px 100% no-repeat;
  -webkit-mask-position:left,right;
  mask-position:left,right;
  -webkit-mask-size:calc(100% - 50px) 100%, 50px 100%;
  mask-size:calc(100% - 50px) 100%, 50px 100%;
}

/**/
.image-2 {
  flex-basis:40%;
  margin-left:-15px;
  --g:linear-gradient(to top left,transparent 49.8%,black 50%) left/50px 100% no-repeat;
  -webkit-mask-position:right,left;
  mask-position:right,left;
  -webkit-mask-size:calc(100% - 50px) 100%, 50px 100%;
  mask-size:calc(100% - 50px) 100%, 50px 100%;
  --p:top left;
}

/**/
.image-3 {
  flex-basis:100%;
  --g:linear-gradient(to bottom right,transparent 49.8%,black 50%) bottom/100% 80px no-repeat;
  -webkit-mask-position:top,bottom;
  mask-position:top,bottom;
  -webkit-mask-size:100% calc(100% - 80px),100% 80px;
  mask-size:100% calc(100% - 80px),100% 80px;
}

/**/
.image-4,
.image-5{
  flex-basis:40%;
  margin-top:-30px;
  --g:linear-gradient(to top left,transparent 49.8%,black 50%) top/100% 40px no-repeat;
  -webkit-mask-position:bottom,top;
  mask-position:bottom,top;
  -webkit-mask-size:100% calc(100% - 40px),100% 40px;
  mask-size:100% calc(100% - 40px),100% 40px;
  --p:top left;
}
.image-5 {
  margin-top:-70px;
  height:340px;
}

/**/
* {
  box-sizing: border-box;
}

<div class="about-gallery">
  <div class="image-1" style="--img: url(https://picsum.photos/id/10/800/800);"></div>
  <div class="image-2" style="--img: url(https://picsum.photos/id/102/800/800);"></div>
  <div class="image-3" style="--img: url(https://picsum.photos/id/123/800/800);"></div>
  <div class="image-4" style="--img: url(https://picsum.photos/id/14/800/800);"></div>
  <div class="image-5" style="--img: url(https://picsum.photos/id/20/800/800);"></div>
</div>