.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;
    outline: none;
    background: white;
    cursor: inherit;
    display: block;
}
input[readonly] {
  background-color: white !important;
  cursor: text !important;
}