html - masking image with CSS

Question

I made a design like this

How to mask the background with css?

I have tried code like this

.img-poster {
  display: block;
  max-width: 100%;
  -webkit-mask-image: url(https://cdn.pbrd.co/images/GYiCod1.png), url(https://cdn.pbrd.co/images/GYiCQsM.png);
  -webkit-mask-position: bottom center, center center;
  -webkit-mask-repeat: no-repeat, no-repeat;
}

.add {
  -webkit-mask-composite: add;
}

<section class="section poster-container">
  <img src="https://imagejournal.org/wp-content/uploads/bb-plugin/cache/23466317216_b99485ba14_o-panorama.jpg" alt="" class="img-poster add img-responsive">
</section>

Answer 1

You only need to consider one image which is the bottom part of your mask then use a simple gradient for the other part. You also don't need mask-composite. Simply adjust the size/position so that both mask don't overlap:

.img-poster {
  display: block;
  max-width: 100%;
  -webkit-mask:  
     linear-gradient(#fff,#fff)              top,
     url(https://i.ibb.co/5WvbqgG/zmylJ.png) bottom;
  -webkit-mask-size:
     100% calc(100% - 30px),
     auto 30px;
  -webkit-mask-repeat: repeat-x;
  mask:  
     linear-gradient(#fff,#fff)              top,
     url(https://i.ibb.co/5WvbqgG/zmylJ.png) bottom;
  mask-size:
     100% calc(100% - 30px),
     auto 30px;
  mask-repeat: repeat-x;
}

<section class="section poster-container">
  <img src="https://imagejournal.org/wp-content/uploads/bb-plugin/cache/23466317216_b99485ba14_o-panorama.jpg" alt="" class="img-poster add img-responsive">
</section>