.btn-file { position: relative; overflow: hidden;}
.btn-file input[type=file] { position: absolute; top: 0; right: 0; min-width: 100%; min-height: 100%; font-size: 100px; text-align: right; filter: alpha(opacity=0);  opacity: 0; background: red;  cursor: inherit; display: block;}
input[readonly] { background-color: white !important; cursor: text !important;}