Center img in the div block (slick-slider) - html

Question

I have a proplem with center img in the div. I read and doing all answers in the questions about center align. And display: flex help me, but it doing my slick-slider jumping. 3 screen it seems good and next jump with no slides 1 second and next good. You can see it in my site. How can i centralize my img in the div without flex and position: absolute? Or how can I doing that without jump slider? I hope guys, you understand my English, and sorry for that simple question...
div {
display: flex!important;
justify-content: center;
align-items: center;
outline: none;
height: 100%;
max-height: 100%;
img{
width: 50%;
}
}
<div class="partners multiple-items">
<div>
<img src="img/logo-adata.png">
</div>
</div>

Answer 1

Do you need the img tag?
One way to achieve this is to use background-image instead of img. Simple remove the img tag, then you can center the image as
.img__wrapper {
background-image: url(img/news-img-1.png);
background-position: center;
background-repeat: no-repeat;
background-size: cover;
height: 100%;
}
Here is how it can be done with the img tag
.img__wrapper {
height: 100%;
position: relative;
}
.img__wrapper > img {
position: absolute;
top: 0;
right: 0;
left: 0;
bottom: 0;
margin: auto;
}

Answer 2

Try to use
display: table-cell;
vertical-align: middle;
.partners
{
width: 500px;
height: 500px;
border: 1px #aaa solid;
text-align: center;
display: table-cell;
vertical-align: middle;
}
.item{
width: 300px;
margin: auto;
}
<div class="partners multiple-items">
<div class="item">
<img src="http://via.placeholder.com/300x300">
</div>
</div>

Answer 3

div {
display: flex!important;
align-items: center;
outline: none;
height: 100%;
max-height: 100%;
img{
margin: 0 auto;
width: auto;
max-height: 65%;
}
}
It's solve my problem & slider don't jump

Answer 4

div.partners div{
height:500px;width:500px;text-align:center; vertical-align:middle;display:table-cell;
}