Fix ảnh Full khung hình không kéo ra

**** HTML:

<div class="picture>

    <img src="">

</div>

.picture{

    height:280px

}

.picture{

    height:100%;

    width:100%;

    object-fit: cover;

}

Full màn hình

**** CSS
.globalmain {
    width: 100%;
    height: 100%;
    background-color: #0a709c !important;
}
.maintop {
    margin: 0 auto;
    background-image: url(../images/icon-white.png);
    height: 30%;
    width: 100%;
    background-position: center;
    background-repeat: no-repeat;
}
.mainbody {
    height: 70%;
    position: relative;
}
#idform {
    background: #fff;
    box-shadow: 2px 2px 8px rgba(0,0,0,.25);
    margin: 0 auto;
    width: 360px;
    height: 340px;
    padding: 20px;
}
**** HTML
<div class="globalmain">
<div class="maintop"></div>
<div class="mainbody">
<form id="idform">
<input type="text" name="text">
<button name="submit" type="submit"></button>
</form>
</div>
</div>