遮罩图像底部的三角形

.container {
  position: relative;
  width: 300px;
  height: 200px;
  overflow: hidden;
}

.image {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.mask {
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 50px;
  background-color: rgba(0, 0, 0, 0.5);
}

.mask::before {
  content: "";
  position: absolute;
  bottom: -10px;
  left: 50%;
  transform: translateX(-50%);
  border-left: 10px solid transparent;
  border-right: 10px solid transparent;
  border-top: 10px solid rgba(0, 0, 0, 0.5);
}