Diagonal de CSS Mask Cut Diagonal

img {
  width: 100px;
  height: 100px;
  -webkit-clip-path: polygon(0 0, 0 100px, 100px 80px, 100px 0);
  clip-path: polygon(0 0, 0 100px, 100px 80px, 100px 0);
}
Lioruby