NFT-Preview

You can use the change the opacity of an overlay image to achieve that, something like this snippet below.

.img-overlay {
  background-color: var(--clr-accent);
  border-radius: 10px;
  position: absolute;
  top: 0;
  bottom: 0;
  right: 0;
  left: 0;
  opacity: 0;
  transition: opacity 0.5s ease;
}

.img-container:hover .img-overlay {
  opacity: 0.5;
}

.img-overlay img {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}