gradiente inferior

img {
  width: 400px;
}

.content {
  background: rgba(255, 255, 255, 0) linear-gradient(to bottom, rgba(0, 0, 0, 0) 10%, rgba(255, 255, 255, .1) 40%, rgba(255, 255, 255, .5) 75%, rgba(255, 255, 255, 1) 100%) repeat scroll 0 0;
  position: relative;
  margin-top: -200px;
  height: 200px;
}
Glamorous Grebe