Check out example codes for "position images in center of container". It will help you in understanding the concepts better.

Code Example 1

.image-container {
    width: 500px;
    height: 500px;
    position: relative;
}

.image-container img {
    position: absolute;
    right: 0;
    left: 0;
    top: 0;
    bottom: 0;
    margin: auto auto;
}

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