CSS-, , . overflow: hidden; , overflow: hidden;, , CSS.
.triangle-wrap {
width: 400px;
height: 400px;
position: relative;
overflow: hidden;
}
.triangle {
background: grey;
position: absolute;
bottom: -50%;
width: 100%;
height: 100%;
overflow: hidden;
-webkit-transform: rotate(45deg) skew(20deg, 20deg);
-moz-transform: rotate(45deg) skew(20deg, 20deg);
-ms-transform: rotate(45deg) skew(20deg, 20deg);
transform: rotate(45deg) skew(20deg, 20deg);
}
.triangle-reset {
width: 100%;
height: 100%;
position: relative;
-webkit-transform: skew(-20deg, -20deg) rotate(-45deg);
-moz-transform: skew(-20deg, -20deg) rotate(-45deg);
-ms-transform: skew(-20deg, -20deg) rotate(-45deg);
transform: skew(-20deg, -20deg) rotate(-45deg);
}
.triangle-content {
background: url('http://placehold.it/400x400') no-repeat;
background-position: center center;
background-size: cover;
position: relative;
width: 120%;
height: 120%;
left: -10%;
bottom: 65%;
}
html {
min-height: 100%;
background: linear-gradient(to bottom, #336666 0%,#663366 100%);
}
<div class="triangle-wrap">
<div class="triangle">
<div class="triangle-reset">
<div class="triangle-content">
</div>
</div>
</div>
</div>